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Abstract: Olfactory Displays are devices used to generate and deliver scented air that is eventually smelled by the users. As the literature reports, their development and evaluation mostly rely on experimental activities based on a “trial-and-error” approach, which prevents a comparative analysis of designed solutions and their technical performances, thus leading to prototypes with low potential to become future products. In this paper, an innovative framework embedding Computational Fluid Dynamics (CFD) simulations for designing, prototyping and testing new Olfactory Displays is proposed. After presenting the framework, the paper illustrates the settings for a multi-phase CFD analysis based on Discrete Particles Modeling for simulating olfactory displays. The design of a new wearable olfactory display is presented, detailing all the steps of the framework. A first architecture is devised, and an initial set of simplified 2D multi-phase CFD simulations has been used to propose possible improvements. A new design has been developed, and a 3D CFD simulation has been run to predict its performance. A set of experiments has been conducted to test the real prototypes and compare the performance with the one predicted by the simulations. The experimental results are in good accordance with the simulations, which have proven their effectiveness in improving the design of the olfactory displays.
Keywords: CFD | Olfactory Display DOI: https://doi.org/ | Rapid Prototyping | Virtual and Physical Prototyping
Abstract: The aim of this work is to describe some experiences of additive manufacturing - AM - for nuclear fusion applications. In this paper, a first case study is introduced concerning the realization of a scale prototype of an in-vessel component for tokamak nuclear fusion reactors, a wishbone of the deflector made in Ti-6Al-4V alloy. The 3D model of the wishbone component was designed, optimized with simulation, and then fabricated using AM in collaboration with the Laboratory for Advanced Mechatronics - LAMA FVG - and researchers at the University of Udine. For the construction of the prototype, a SLM machine using powder bed metal laser melting was used. The design, simulation and fabrication activities of the AM mock-up are presented in this paper, discussing the main limitations and possibilities arising from the 3D printing of titanium alloy. In addition, a further scale prototype of the wishbone was produced using conventional milling techniques, allowing an economic comparison and evaluation of the two manufacturing processes. The prototypes will then be used for a future evaluation of the mechanical properties of this material (Ti-6Al-4V), first on material samples and then on the mock-ups, under irradiations conditions, due to nuclear fusion applications.
Keywords: Additive Manufacturing | Cost evaluation | DEMO divertor | Nuclear fusion | SLM | Ti-6Al-4V alloy
Abstract: Lattice structures are receiving a renewed interest in many areas such as biomedical and industrial fields, due to the capabilities of additive manufacturing technologies which allow for the fabrication of very complex shapes. Currently, several methods and tools are described in the scientific literature and some commercial software are introducing dedicated packages to reduce designer efforts for lattice structure design and optimization. However, by using commercial CAD/CAM tools in the fabrication of components filled by lattice structure, several critical issues remain and need to be taken into consideration. This work aims at manufacturing variable-density lattice structures via fused deposition modeling deriving the density map from a grayscale or color image. In the proposed approach, the shell-based lattice model is not achieved by CAD tools, but only during the CAM process, while the lattice relative density is computed by editing the G-code, modifying the extrusion flow according to the local grayscale of a volumetric CAD model, defined from an image. The main advantages are related to the absence of a graded lattice geometric model and the consistency of the toolpath. The method is tested on various images and patterns, and can find applications in artworks, embedded information on components, and functional 3D printed parts, such as the replication of the density map of a bone derived from a DICOM grayscale image.
Keywords: Additive manufacturing | Fused deposition modeling | Graded lattices | Heterogeneous objects
Abstract: Additive manufacturing allows the creation of highly customized and complex objects that could not be achieved with traditional methods. These characteristics of the production method make the products perfectly suitable for the design of orthotics, where the customization of the device and the speed of production are essential. For example, it may be necessary to create locally more or less rigid orthose depending on the anatomic area or its local function. The 3D printing of objects can be performed with variable properties within their domain by means of the so called Functionally Graded Additive Manufacturing (FGAM). This article presents a new method for the production of reticular orthoses which begins with the acquisition of the area of interest using a 3d scanner, followed by the generation of the reticular structure locally densified according to ergonometric models, and the finalization of the model with truss thickening and application of a closure system. Some models were then reproduced with AM techniques such as SLA and MJF and tested in daily use.
Keywords: Additive manufacturing | Custom manufacturing | Functionally graded materials | Orthotics
Abstract: This work aims to propose a novel geometric modeling method to obtain lattice structures with internal walls and external skins that can be selectively activated. Internal walls can separate two adjacent cells, locally increase the stiffness of the component, and generate internal ducts; external walls are used to strengthen the entire structure and create a division from the outside. The proposed approach models a beam-based cellular structure with the introduction of internal walls according to an activation pattern that indicates whether a cell is communicating with the adjacent one through their connecting faces or not. The data structure describes the topology of the subdivision surface control polygon. The proposed method is then applied to a case study based on the hydraulic manifold applications. The possibility of building custom internal channels is exploited, with the advantage of obtaining smooth surfaces at the direction changes, with lower pressure drops, and a lightweight component due to the lattice structure that surrounds the channels. The resulting structure has a complex geometry that perfectly suits the manufacturing capabilities of additive manufacturing technologies.
Keywords: Additive manufacturing | Closed cells | Geometric modeling | Hydraulic manifold | Lattice structures
Abstract: Compliant Mechanisms, Topology Optimization and low-cost 3D printing technologies have been exploited in a combined design approach aimed at the development of a Flapping Wing Micro Air Vehicle’s wing actuation mechanism. A series of topology optimization analysis was implemented to explore four different design domains, each with a specific supports’ positioning. Subsequently, the obtained topologies were geometrically remodeled and tailored to comply with the 3D printing process parameters, resulting in several monolithic Compliant Mechanisms. The different remodeled mechanisms were finally compared in terms of stress and range of movement, through non-linear transient Fem analysis. Although the designed compliant mechanisms move at high rotation frequencies (about 25 Hz) and undergo large deflections, the obtained results are interesting with regard to maximum stresses and rotation angle amplitudes, paving the way to a future design improvement both deepening fatigue issues and implementing size and shape optimization.
Keywords: Additive manufacturing | Compliant Mechanisms | Flapping Wing Micro Air Vehicles | Topology optimization
Abstract: In recent years, Additive Manufacturing (AM) proved to be extremely competitive in the production of small lots of pieces with high customization. Compared to subtractive production, AM allows to make less waste of material and reproduce highly complex components without increasing their costs. Some studies also assessed the environmental advantages of AM, which could be significant in the event of its future large-scale diffusion. However, an environmental assessment considering the aspects of hierarchical complexity that can be obtained with AM is missing in literature. This study bridges this gap by evaluating and comparing the environmental impacts resulting from the implementation of different design for AM options defined at different levels of detail, e.g. shape, cellular internal structure and infilling. For each option, the environmental impact arising from the mass and energy of manufacturing was calculated. The data were obtained through virtual simulations with commercial software for design for AM (i.e. nTopology) and experimentation with a 3D printer that produces pieces in polylactic acid (PLA). The obtained results highlighted the preponderant role of energy consumption deriving from the path of the print head in defining the environmental impacts, with respect to the quantity of material in the piece. In particular, we have seen how the shape and infill optimization (if the density is lower than 50%) reduce the environmental impacts, while the lattice structure optimization increases them, due to the more energy and time-consuming printing process.
Keywords: Design for Additive Manufacturing | Eco-assessment | Eco-design
Abstract: Additive manufacturing (AM) is currently one of the most promising industrial technologies that allow designers to operate with more degrees of freedom to create shapes without overthinking restrictive manufacturing constraints. Products must be conceived with the “AM on mind” to exploit AM potentialities. Design for AM (DfAM) methods and tools, such as topology optimization and generative design, are crucial for this aim. The present paper aims to understand how existing DfAM tools can effectively support the DfAM process. The study is based on the definition and application of a systematic evaluation protocol consisting of quantitative and qualitative metrics. The case studies involved four commercial DfAM tools tested on three mechanical components. Results confirmed that most of the tools lead to very similar solutions from the technical point of view since they are based on analogous optimization algorithms. The consideration of manufacturability constraints and the availability of advanced functionalities for geometry reconstruction after the optimization phase are relevant issues observed. Finally, regarding tools functionalities, notable differences have been registered
Keywords: Additive manufacturing | Design for Additive Manufacturing | DfAM tools | Generative design | Topology optimization
Abstract: Laser-Directed Energy Deposition (L-DED) is an Additive Manufacturing process in which focused thermal energy is used to fuse powder feedstock. The scientific literature concerning L-DED and cost estimation is not as comprehensive as Laser-powder Bed Fusion (L-PBF). Indeed, a robust and reliable cost model (in terms of the number of materials, machines, and process parameters managed) is not available. The paper aims to define an analytical cost model for L-DED, considering the material, machine, labour, consumables, energy and equipment cost items. The model seeks to evaluate the production cost from the machine setup to the removal of the part. Post-processing steps are not included. The cost model is based on a scientific review of journal papers, handbooks and datasheets from industrial partners. The cost drivers for this model are the overall 3-dimensions of the part, volume, material, accuracy and number of components in the build plate. The meaningful process parameters are the layer thickness, melt pool width and overlap, powder efficiency, laser power, linear energy density, scanning speed, and machine dimensions. The developed cost model was tested on two products: a heat exchanger and a landing gear analyzed in previous works. The comparison led to a deviation of about 10% for the manufacturing cost and printing time.
Keywords: Additive manufacturing | Cost model | Design to cost | Laser-directed energy deposition | Sensitivity analysis
Abstract: Lattice structures play an increasingly crucial role in Additive Manufacturing (AM) to enhance the performance of parts for industrial and biomedical applications. Among AM technologies, VAT photopolymerization is one of the most suitable in producing shapes characterized by a good resolution and fine details as required for lattice structures. High stiffness and strength photoresins are commonly adopted when strut-and-node lattice structures, based on stretch-dominated unit cells, are printed. However, this choice can lead to brittle and sudden structural failures, undermining the use of these structures due to safety reasons. This work evaluates the effect of chemical post-processing on the deformation behavior and the tensile properties of SLA strut-and-node-based lattice structures. FCC (Face-Centered Cubic) lattice structures with two different layer heights were tested, and a highly deformable UV resin was used as a coating product. Results evidenced an increase in specimen elongation up to 64% for coated FCC lattice structures with respect to as printed samples. Chemical post-processing based on resin coating demonstrated to be an effective solution to get additively manufactured strut-and-node-based lattice structures characterized both by high strength and high strain.
Keywords: Coating post-processing | Lattice structures | Tensile properties | VAT photopolymerization
Abstract: Additive Manufacturing (AM) is continuously increasing its appeal as a breakthrough production process due to well-established advantages compared to traditional manufacturing strategies based on chip removal or casting. The design of lightweight structures can exploit the AM advantages, thanks to the capability of shaping complex geometries where the constant level of stress can be achieved through Topology Optimization. Moreover, in transportation engineering and lightweight structures in general, thin-shell or thin-walled components are widely used for frames, fuselages, wings, car bodies, coaches, tanks or recipients. However, the application of topology optimization routines on thin-walled structures is not exempt from difficulties. This is true especially in the case of a distributed pressure load coming from fluid-structure interaction analysis. Coupling the benefits of TO methodology with the already good performances of thin-walled structures may lead to mechanically efficient shapes. This research addresses strategies to apply topology optimization on thin-walled structures. The effect of the local concentration of distributed load in a cloud of control points distributed along the surface of interest is considered and tested. Two case studies coming from industrial engineering have been carried out to show the capabilities of the proposed approach.
Keywords: Additive Manufacturing | Design for Additive Manufacturing | Distributed load | Thin-walled structure | Topology Optimization
Abstract: Additive Manufacturing (AM) technologies theoretically allow the production of complex products without any geometrical restriction. Nevertheless, production process delineates some limitations on the resulting dimensional and geometrical precision. This is a critical issue mainly for Metal Binder Jetting (MBJ) process, on the reason of anisotropic dimensional change and distortion on sintering. Literature reports fairly reliable models for predicting the deformation on sintering. However, the application of such methods might be time consuming from industrial perspective, because of the extensive experimental analysis required to assemble a robust material database. For that reason, this work aims at proposing an alternative approach for compensating dimensional and geometrical change on sintering. Two complex geometries, having similar geometrical features with different sizes, were printed and measured by a coordinate measuring machine before and after sintering process. The analysis of cylindricity form errors reveals an excellent geometrical stability of smaller geometry. Therefore, dimensional change along printing direction was derived in order to obtain a precise scaling factor for improving the dimensional and geometrical precision. By contrast, bigger samples encountered a dramatic distortion, which required a complete redesign. The shape of the distorted cylinder was approximated with an ellipse and a corrective function has been proposed for compensating green geometry.
Keywords: Additive manufacturing | Binder jetting | Design for AM | Distortion
Abstract: The orbital walls and floor are common sites of facial bone fracture and may cause severe functional impairment. The complex geometry of the bony orbit makes anatomical reconstruction extremely challenging, with main issues related to the implant’s correct shaping, positioning, and orientation inside the orbital cavity. This study proposes an innovative medical device to place patient-specific implants in fractured eye sockets properly. The device must be used with the developed improved version of a tailored implant shaping mould. The design of the orbital implant positioner followed specific clinical and technical requirements and specifications investigated through the Quality Function Deployment method. The device has been conceived to be simple, economical, capable of managing deantigenated bones or titanium meshes for orbital floor and wall, and reusable multiple times. The positioner consists of two handles hinged together and adequately coupled by a spring to allow the grasping and placing of the implant. Positioner and mould have been manufactured in polyamide using the Selective Laser Sintering technique. The system accuracy assessment resulted in promising outcomes. The mould can precisely shape the implant with a lower than 0.1 mm deviation. The implant positioner can place the implant with a rotation angle around the orbital rim of barely 7.1° and 1.2 mm deviation in the mediolateral direction (no deviations in the anteroposterior and superior-inferior directions occur)
Keywords: Computer-aided design | Craniomaxillofacial surgery | Implant design | Medical devices | Rapid prototyping
Abstract: Multi-Material Additive Manufacturing technologies enable the fabrication of objects consisting of multiple materials. Among them, Material Jetting allows the designer to control the spatial distribution of the selected materials down to the size of microns, making it suitable for Functionally Graded Materials. Despite this great capability, governing the design complexity unleashed by this class of material is still limited to the current computer-aided tools. The paper aims at investigating how a traditional Boundary representation (B-rep) in the CAD domain, which has been conceived for homogeneous materials, can be adapted to integrate heterogeneous object specifications. A workflow to produce heterogeneous objects, with a focus on Functionally Graded Material Objects, is outlined, from the design of the object geometry with a CAD system to the generation of the machine instructions. The procedure to specify the desired material distribution and to generate the voxels has been embedded in a traditional CAD software, allowing the users to define the specifications of the heterogeneous object interacting with the B-rep entities. Once the material distribution has been defined, a solid voxelization is performed on the geometry and the material composition for each voxel is computed. Finally, the object is sliced and a set of images is generated, informing the printer which material should be deposited at the specific position. A case study to check the feasibility of the proposed workflow has been performed: different specimens varying the voxel size and the deposition pattern have been printed.
Keywords: Additive manufacturing | Heterogeneous objects | Voxel printing
Abstract: The current best-practice in the assembly process of aircraft skin panels involves several manual measurement-fit-adjust quality loops, such as loading part on the assembly frame, measuring gaps, off-loading parts, adding be-spoke shims and re-positioning parts ready for the fastening operation. The consequence is that the aircraft is re-assembled at least twice and therefore this process has been proved highly inefficient. This paper describes the framework developed under the “Integrated Smart Assembly Factory” (ISAF) project in the “Intelligent Factory” specialisation area in Italy. Taking advantage of the emerging tools brought by Industry 4.0 the ISAF framework spearheads innovation in the assembly process of aircraft skin panels by integrating smart and digital technologies such as in-line measurement systems with highly accurate sensors, large-scale physics-based simulations, multi-disciplinary process optimisation and additive manufacturing. ISAF implements a flexible alignment, which combines both rigid rotations/translations and local deformations to account part deformations. The proposed methodology allows predicting and fabricating shims using in-line measurement data with no need to iterate the measurement-fit-adjust quality loops. This will undoubtedly reduce inspection/measurement time and costs, enabling operators to virtually test assembly operations before installation in the field. The results were demonstrated during the assembly process of a vertical stabiliser for commercial aircrafts, and findings showed a significant time saving of 75%.
Keywords: Additive manufacturing | Digital twin | Flexible alignment | In-line measurement | Physical simulation | Shimming | Smart factory
Abstract: This article proposes a design framework for additive manufacturing (AM) to solve contradictory design problems. Different structural features are selected within different levels of detail (e.g., cellular structures, infill, porosity) to realize the conflicting requirements and properly combined within the structure of the product. To do this a multilevel interpretation and classification of the options present in a commercial software of Design for AM was provided. Then, criteria to combine the different structural features within the structure of the product were proposed, starting from some principles of the TRIZ (i.e., Russian acronym for “Theory of Inventive Problem Solving”) method. The method was applied to design a dental prosthesis and the results, obtained by testing a simplified plastic sample were analyzed. The contradictory problem deals with the realization of both the mechanical resistance, during the chewing, and the thermal resistance to prevent the thermal dilatation during the workpiece finishing operations on machine tools. The sample designed with the proposed method exhibited better performances in both the requirements compared to another sample, made with a microstructure chosen in a completely random way.
Keywords: Design for Additive Manufacturing | Hierarchical complexity | Multilevel design | TRIZ
Abstract: Additive manufacturing (AM) methods have a growing application in different fields such as aeronautical, automotive, biomedical, and there is a huge interest towards the extension of their use. In this paper, lattice structures for AM are analysed with regards to stiffness and printability in order to verify the suitability for applications where the main requirement of efficiency in terms of stiffness has to be balanced with other needs such as weight saving, ease of manufacturing and recycling of the material. At this aim, lattice structures with high porosity unit cells and large cell size made of a recyclable material were considered with a geometrical configuration allowing 3D printing without any supports. The lattice structures considered were based on body-centred cubic (BCC) and face centred cubic (FCC) unit cell combined with cubic cell. Finally, a multi-morphology lattice structure obtained by mixing different unit cells is also proposed. The lattice structures were modelled and structurally analysed by means of finite element method (FEM), manufactured with a Fusion deposition modelling (FDM) printer and evaluated in relation to printability and dimensional accuracy. The results show that the proposed structure with mixed cells is potentially advantageous in terms of weight saving in relation to the mechanical properties.
Keywords: Additive manufacturing | Geometrical configuration | High porosity | Lattice structure | Supportless 3D printing
Abstract: The demand for orthodontic and aesthetic treatments, aimed at having healthier teeth and more beautiful smiles, is increasingly growing. The devices on which these treatments are based must be rigorously bespoke for each patient. This is amplifying the need to develop digitized workflows, ranging from scanning to Additive Manufacturing (AM). The present work proposes an alternative workflow for designing and manufacturing orthodontic aligners, also known as clear aligners, starting from the intraoral scanning of the patient’s dentition. Orthodontic aligners are an alternative to metal brackets to correct dental malocclusions and they are often preferred by the patients because of their lower impact on facial aesthetics and for their higher comfort. The orthodontic treatments based on the aligners utilize a series of aligners, each one with a geometry slightly different from the previous one. The use of the single aligners is aimed to apply a force to the teeth and gradually aligning them until the end of the treatment. The workflow we propose in the present study is based on the following three main stages: intraoral scanning of the patient’s dentition, design of the aligners through a semi-automatic algorithm, and the direct additive manufacturing of the aligners through VAT photopolymerization technique. The possibility to directly additive manufacturing the aligners allows us to rethink the current orthodontic treatments. The aligners geometry can be re-designed, with the possibility of locally manipulating the thickness. This approach would allow the regulation of the amount of force applied locally to the tooth, thus optimizing the treatment and its duration. A feasibility study of the proposed workflow is reported in the present paper, with a focus on the semi-automatic design algorithm and on the additive manufacturing process of the aligners.
Keywords: Additive Manufacturing | Bespoke Medical Devices | Dental Appliances | Design Algorithms for Medical Applications | DfAM
Abstract: Considering a modern approach to design, one of the viable options for developing innovative projects is the possibility of integrating the effectiveness of the solutions offered by nature and living beings with the latest design methods. With this in mind, the following research exploits the idea of reproducing the natural flexibility inherent in biological structures by combining the advantages of compliant mechanisms with the adaptability of additive manufacturing processes. In the specific, the authors intend to highlight the potential and critical aspects of a possible approach for the application of compliant mechanisms in the development of single-component structures suitable for the actuation of bio-inspired Flapping Wing Micro Air Vehicles (FWMAVs), which can be produced via low cost 3D printing. Some designs conceived by interpreting the movement of insects’ wings have been developed with the aim of reproducing the functionality and morphology of their thorax through single-component flexible mechanisms. The results of this research demonstrate the high potentiality of realizing bio-inspired single-component compliant mechanisms through 3D printing.
Keywords: Additive manufacturing | Bio-inspired | Compliant mechanisms | Flapping wing micro air vehicles
Abstract: Lattice structures have many outstanding properties, and their use in diversified industrial and biomedical fields is widely studied. The advent of additive manufacturing (AM) technologies has further pushed the design of these cellular structures allowing for the fabrication of complex trusses and tailored local geometries. However, geometrical defects introduced by the AM process into printed lattice structures significantly affect their mechanical properties. In this work, the effect of chemical post-processing on the compressive properties of FDM-PLA strut-and-node-based lattice structures is evaluated. A UV resin has been used as a coating film on samples fabricated using Simple Cubic (SC) and Face-Centered Cubic (FCC) unit cells. Results demonstrated a 65% increase in compressive strength for SC unit cells and a 12% increase for FCC unit cells with respect to as-printed samples. Resin coating demonstrated to represent an effective approach to minimize defects of strut-and-node-based lattice structures, thus enhancing mechanical properties.
Keywords: Additive manufacturing | Coating post-process | Compressive properties | Lattice structures
Abstract: Background: Orthopaedic and Trauma surgery is expected to undergo profound trans-formation as a result of the adoption of 3D technology. Among the various applications, patient specific manufacturing of splints and casts would appear to be, particularly in children, an interesting implementation. This study aims to assess the safety of patient specific 3D casts obtained with a newly developed 3D-scanning devise in a small case series. We therefore conducted a clinical outcome and pre-marketing study in 10 consecutive patients with distal radius fractures treated at an Academic Level I Pediatric Trauma Center. After the application of the 3D cast, patients underwent three consecutive evaluations in the following 21 days. The main outcome measurements were: pain, skin lesions and general comfort, and acceptance of the cast. The three domains were measured with the Visual Analogue Scale (VAS), the NPUAP/EPUAP classification and the Positive affect-Negative affect Scale for Children (PANAS-C), the Self-Assessment Manikin (SAM) clinical psychology tests and a Likert-type five item questionnaire, respectively. A final mechanical analysis of the cast was carried out to confirm product integrity. Results: The results obtained were consistently positive in the investigated domains of general comfort, efficacy of contention and mechanical integrity of the 3D-printed cast as well as in the practicability of the supply chain. Conclusions: This study provides Level IV evidence that patient specific 3D printed casts obtained with a specifically designed software were safe in the management of “buckle” fractures of the distal radius in children. These results encourage to extend the technology to the treatment of more demanding fractures.
Keywords: 3D printing | customized implants | orthopedic device | orthosis modeling | pediatrics | personalized medicine | reverse engineering
Abstract: In the biomedical field, high-fidelity simulation plays a fundamental role for medical and surgical staff as it allows them to simulate real scenarios from everyday clinical practice. The availability of patient-specific pathological models allows doctors to simulate surgical procedures before entering the operating room, thus reducing the risks associated with surgery. Such models are also employed in medical training to enhance the experience of trainees by confronting them with possible real-life emergency scenarios. To obtain a strict correspondence between simulator and reality - both in terms of geometry and haptic feedback - important decisions must be taken from the beginning of the design phase. High fidelity is a fundamental requirement of the simulators, since the design phase of the anatomical model, for what concerns geometries and materials. In this paper, a preliminary study for the development of a paediatric tracheal simulator is presented. This study is focused on the definition of some general geometric parameters and of the material composing the simulator. Mechanical characteristics of the trachea are investigated to identify a set of materials able to reproduce a realistic haptic feedback of the simulator. Materials are chosen in relation with the technological process that will be used for the simulator manufacturing: additive manufacturing or mould casting. To test the various materials, specimens are created and submitted to the judgement of a specialized medical team. The results showed Shore 40A silicone with a 1.75 mm wall-thickness value to be the best compromise for reproducing the haptic feedback of the trachea.
Keywords: 3D printing | Airway simulation | Haptic feedback | Paediatric trachea | Soft tissue modelling
Abstract: The use of additive manufacturing (AM) has widespread over the years in different areas, including the biomedical field. In particular, the design of customized orthoses, external medical devices used in the treatment of specific pathologies, was proposed in different studies mainly concerning upper limbs, while few investigations are reported relatively to the cervical area. In this paper a new design of a bespoke neck orthosis is reported. The manufacturing of a light device with a good transpiration allows to increase the patient’s comfort and, compatibly with the structural requirements, is a main goal to pursue. With this aim, various aspects were considered in the design and manufacturing of the orthosis. At the design stage, the geometry was conceived with a ventilation pattern based on Voronoi cells, which generally allows a better performance in terms of breathability with respect to a pattern made with uniform geometrical features, keeping at the same time structural requirements, as assessed by numerical finite elements simulations. At the manufacturing stage, a new composite material was used, namely Hemp Bio-Plastic® (HBP) filament, composed by polylactic acid (PLA) and hemp shives which provided lightweight, improved superficial finish and antibacterial properties. In order to assess the thermal comfort, an experimental analysis was finally conducted on a prototype of the orthosis, worn by a volunteer subject, with a thermal imaging camera. The beneficial effect of the ventilation pattern considered in terms of temperature and, accordingly, for the patient’s comfort, was highlighted also in relation to a neck orthosis previously designed.
Keywords: Additive manufacturing | Bio-composite | Orthosis modeling
Abstract: In the Cultural Heritage field, the choice of materials and exhibit structures is essential to properly house and support artifacts without causing damage or deterioration. This problem is even more evident in the case of finds made of stone for which, due to their weight, a proper selection and dimensioning of the relative supports is required. In fact, without adequate support, this can result in stress concentrations that could compromise the artifact's state of conservation. As a consequence, more often such exhibition supports are customized items, that are designed and manufactured to meet specific functional and artistic setup needs. In this context, the paper presents a design approach that combines topology optimization and additive manufacturing techniques to develop customized support structures which undertake the twofold purpose of preserving the artifact and making it available for the exhibition in the museum. The proposed approach has been assessed through the case study of a sandstone Ionic capital hosted in the Brettii & Enotri Museum in Cosenza (Italy). The proposed approach is therefore meant as a guideline for the design of customized exhibit supports especially in the case of sandstone artifacts with a complex shape or a conservation condition that requires specific attention.
Keywords: Additive manufacturing | Cultural heritage | Design methods | Exhibit supports | Photogrammetry | Topology optimization
Abstract: The advent of Additive Manufacturing (AM) is uncovering the limits of the current CAD systems and, at the same time, is highlighting the potentials of the Topology Optimization (TO) and Generative Design (GD) tools that had not been fully exploited until now. Differently from the traditional design approach in which designers occupy a predominant role in each stage of the design process, the introduction of such tools in the product development process pushes toward simulationdriven design approaches which imply a significant change in the role of the designer. To this end, the paper presents a comparison of two different design methods for Additive Manufacturing based on the adoption of TO and GD tools. The comparison aims to offer a reflection on the evolution of the traditional approach when TO and GD tools are used, and to highlight the potential and limitations of these optimization tools when adopted in an integrated manner with the CAD systems. Furthermore, this comparative study can be a useful and practical source for designers to identify the most appropriate approach to adopt based on their needs and project resources. The comparative study is carried out through the design study of a prototype of a rocker arm and a brake pedal for the Formula Student race car. Their results, compared in terms of mechanical performances, show that both TO and especially GD tools can be efficiently adopted early in a design process oriented to AM to redesign components to make them lighter and stronger.
Keywords: Additive Manufacturing | CAD systems | Design methods | Generative design | Topology optimization
Abstract: Hepatic diseases are serious condition worldwide, and several times doctors analyse the situation and elaborates a preoperative planning based exclusively on the medical images, which are a drawback since they only provide a 2D vision and the location of the damaged tissues in the three-dimensional space cannot be easily determined by surgeons. Nowadays, with the advancement of Computer Aided Design (CAD) technologies and image segmentation, a digital liver model can be obtained to help understand the particular medical case; even with the geometric model, a virtual simulation can be elaborated. This work is divided into two phases; the first phase involves a workflow to create a liver geometrical model from medical images. Whereas the second phase provides a methodology to achieve liver prototype, using the technique of fused deposition modelling (FDM). The two stages determine and evaluate the most influencing parameters to make this design repeatable in different hepatic diseases. The reported case study provides a valuable method for optimizing preoperative plans for liver disease. In addition, the prototype built with additive manufacturing will allow the new doctors to speed up their learning curve, since they can manipulate the real geometry of the patient's liver with their hands.
Keywords: 3D printing | Convolutional neural network | FDM | Image segmentation | Liver disease
Abstract: Additive Manufacturing (AM) has become an established discipline in both research and education. However, to achieve its full potential AM requires a step-change in design thinking, which makes Design for AM (DfAM) education and training crucial. This paper reports results from the first attempt to investigate the uptake of DfAM in higher education. This research required the development and administration of an articulated online survey, in which educators worldwide who teach AM and DfAM have participated. The results show that DfAM is taught in a considerable number of courses. However, the survey revealed that DfAM is seldom recognised as a distinct course or topic and the relevance attributed and proportion of teaching dedicated to DfAM within wider AM is typically marginal. DfAM is being mostly taught in North America and Europe and is also typically taught in institutions that are research active in AM or specifically DfAM, suggesting the subject has not yet reached maturity or diffusion into mainstream design and engineering curricula. It was interesting to find that currently, the contents of courses do not differ significantly between engineering and design programmes.
Keywords: 3D printing | design education | Design for Additive Manufacturing | survey
Abstract: The diffusion of Fab Labs and the continuous development of Additive Manufacturing technologies are undoubtedly two relevant phenomena nowadays. The former fuels the latter and vice versa, but their mutual relationship has not been systematically explored so far. This paper presents an exploratory study based on a survey, in which various aspects of the use of 3D printers in Fab Labs are investigated. The results show how different scales of Fab Labs are present in terms of investments made in 3D printing, as well as work purposes are not negligible for many attendees. In addition, the outcomes of the survey show that 3D printers are considered easy to use, as well as manufactured parts are deemed satisfactory. Despite this, there are still some barriers to boosting the market of domestic 3D printers for Fab Lab visitors.
Keywords: 3D printers | CAD | Design for Additive Manufacturing | Fab Labs | Skills
Abstract: Several implant materials are used in cranial surgery. Still, each one has its drawbacks, such as the risk of infections, low mechanical strength, or low osseointegration. Implants with a porous surface are considered more effective than a smooth and rough coating. The porosity density and structure also influence the mechanical properties of the final implant. Moreover, the implant properties depend on the manufacturing method. This study aims to present a custom-made cranial scaffold composed of two distinct layers. A compact inner one guarantees adequate structural properties to the scaffold. In contrast, a porous outer one lightens the scaffold structure and assures the correct osseointegration. The customized scaffold has been designed through a 3D free-form modeling system. It can be manufactured by 3D printing techniques such as direct metal laser sintering in titanium or via selective laser sintering using PEEK. The advantages and limitations of the multi-layered custom-made scaffold and the related design process are qualitatively described.
Keywords: Additive manufacturing | Craniofacial reconstruction | Customized scaffolds | Multi-layered scaffolds | Porous scaffolds
Abstract: Well-established advantages as design freedom, acceleration of design-to-manufacturing cycle, decreased internal logistics reflect on the wider application of Additive Manufacturing as the main manufacturing process. However, its application to large-scale components manufacturing is still an open challenge, because of the limited printing volume available in off-the-shelf machines, slow manufacturing process, and low production volume. After a review of the available contributions, this paper proposes a methodology to handle large-scale 3D models, to be applied before the slicing process. The methodology is based upon the large-scale component subdivision into subparts within CAD environments, using an innovative approach tailored to the problem, and exploits the multi-head capability of collaborative large-scale AM machines. A UAV fixed-wing shows the positive effects in terms of speeding up the manufacturing process. The approach can significantly reduce the printing time of large parts, but a new generation of Additive Manufacturing machines is required to exploit the methodology.
Keywords: Additive Manufacturing | Aerospace | Automotive | Collaborative Manufacturing | Large-Scale Part | Multi-head Extruder
Abstract: One of the open issues in additive manufacturing is the design of conformal lattice structures, leading to an optimal layout of the struts in the design domain. This paper aims to compare different struts distributions in conformal lattices via low computational power methods in a CAD environment. Four approaches for a wireframe virtual model definition are presented for a simple cubic conformal lattice structure. An iterative variable diameter optimization method and two linear structural analyses based on mono-dimensional elements and different theories are compared. These verification methods widen the capability of checking the results so the user can compute the deformation of 3D periodic structures, or other visual results, without spending a huge amount of time and computational power. Results show that both the analysis methods give reliable results and the struts layout based on trivariate NURBS shows the most flexible solution allowing for a real-time variation of the boundary condition.
Keywords: Additive manufacturing | Conformal lattice structure | Design for additive manufacturing | Size optimization | Virtual modeling
Abstract: The Selective Laser Melting (SLM) is accelerating the adoption of Additive Manufacturing (AM) technologies in the industry. One of the most critical benefits concerns the possibility of manufacturing complex-shaped components, which are not feasible or too expensive using traditional processes. Recent studies are evaluating the SLM manufacturability of closed impellers through laboratory tests. The adoption of numerical simulation models for achieving this goal is still limited due to the complexity of the additive process and the number of phases to be considered. The paper presents a numerical model developed in the ANSYS workbench platform for simulating the SLM process of closed impellers. This work is one of the first studies available in the literature for such a particular kind of components. The paper describes the overall simulation model and the steps required for its definition. Furthermore, boundary conditions and process parameters are provided for a better understanding of the model. A case study illustrates its application to a specific part, intending to evaluate (i) impact between the recoater and the component, (ii) maximum von Mises stress and (iii) maximum displacement during the printing phase and following post-processing. These evaluations will support design and manufacturing engineers during product and process engineering. The promising results of this study are encouraging further research about the application of SLM for closed impellers.
Keywords: Additive manufacturing | Impeller | Numerical simulation | Selective laser melting
Abstract: Mitral regurgitation is a common valvular disorder. Transcatheter edge-to-edge repair (TEER) is a minimally invasive technique which involves holding together the middle segments of the mitral valve leaflets, thereby reducing regurgitation. To date, MitraClip™ is the only Food and Drug Administration (FDA)-approved device for TEER. The MitraClip procedure is technically challenging, characterised by a steep learning curve. Training is generally performed on simplified models, which do not emphasise anatomical features, realistic materials, or procedural scenarios. The aim of this study is to propose a novel, 3D printed simulator, with a major focus on reproducing the anatomy and plasticity of all areas of the heart involved and specifically the ones of the mitral valve apparatus. A three-dimensional digital model of a heart was generated by segmenting computed tomography (CT). The model was subsequently modified for: (i) adding anatomical features not fully visible with CT; (ii) adapting the model to interact with the MitraClip procedural equipment; and (iii) ensuring modularity of the system. The model was manufactured with a Polyjet technology printer, with a differentiated material assignment among its portions. Polypropylene threads were stitched to replicate chordae tendineae. The proposed system was successfully tested with MitraClip equipment. The simulator was assessed to be feasible to practice in a realistic fashion, different procedural aspects including access, navigation, catheter steering, and leaflets grasping. In addition, the model was found to be compatible with clinical procedural imaging fluoroscopy equipment. Future studies will assess the effect of the proposed training system on improving TEER training.
Keywords: 3D printing | MitraClip procedure | mitral valve regurgitation | Polyjet | segmentation | simulation-based training | transcatheter edge-to-edge repair
Abstract: Medical image segmentation, especially for biological soft tissues, is an issue of great interest. The aim of this study is to evaluate the segmentation performance of a commercial and an open-source software, to segment aortic root and coronary arteries. 3D printing stereolithography technology was used to generate ground truth models, which were then re-acquired by means of a micro-CT scanner. Measurements from the printed and reconstructed models with both the software were compared, in order to evaluate the level of agreement. In the second phase of this study, Computational Fluid Dynamics (CFD) simulations were conducted, to compare the outputs between the models segmented with the two software. The goal was to understand how differences in the segmentation process propagate in CFD results. Results showed that both software guarantee satisfactory segmentation performance, with average geometrical differences between reconstructed and physical models in the order of a few percentage points. However, when we consider thin details, as a sharp stenotic region, the commercial validated software seems to be more accurate in replicating the real anatomy. We also realized how apparently negligible geometrical differences, varying the employed software, can turn into enormous variations of hemodynamic parameters, such as velocity and wall shear stress, which place in the centre the delicate role the segmentation process holds. This evidence is crucial in the biomedical field and especially in a coronary arteries study, where CFD simulations can be exploited as a starting point for surgery considerations.
Keywords: Additive manufacturing | CFD | Coronary arteries | Digital twins | Segmentation
Abstract: Additive manufacturing technologies are increasingly taking place in the medical field, enabling the creation of graspable patient-specific anatomical models. Because of their potentiality in improving the understanding of complex anatomies and their shown effectiveness for residents' training, devices testing and planning of innovative surgical interventions, 3D printed models have been incorporated also into cardiac surgery and interventional cardiology. To offer valid and reliable support, however, these printed models are often required to be flexible, with an adequate mechanical response, especially when they aim at replicating soft tissues. The goal of this paper is to provide a high-quality and robust template of a patient-specific whole heart model, obtained starting from a Computed Tomography dataset and exploiting a material jetting printer. Due to the significant shape complexity and the variability in compliance featuring the human heart, the selection of the materials have been diversified, taking into account different model wall thicknesses. Thanks to the capability of the material jetting technology, the 3D model of the heart has been printed with two different material assignments, designed to get highly realistic feedback and reduce the gap between the real heart and the printed ones. Eventually, an accuracy evaluation of the printed model has been performed, by means of a laser 3D scanner. Some further considerations about time and costs required to produce the model are part of the paper, together with a discussion about potential areas of improvement, from materials characterization to the need of speeding up and automating the segmentation procedure.
Keywords: Additive Manufacturing | Heart | Material Jetting | Patient-specific Anatomy | Segmentation
Abstract: Innovative design methods and manufacturing technologies, such as lattice structures optimization and additive manufacturing, allow for the production of functional and extremely complex components. Recent literature shows limits in geometric modeling and data exchange, highlighting some improvements in the design of variable density lattice structures mainly for powder bed fusion technologies. Similar improvements are not available for material extrusion (MEX) technologies which show technological and numerical limits related to the computer numerical control programming language (G-code) generated by computer aided manufacturing (CAM) software. This work aims at overcoming the limits in fabricating graded density shell-based lattice structures for MEX technology by using the infill patterns available in the CAM software and editing the G-code based on a density map defined by volumetric models. Combining two usually separated phases, i.e., the geometric modeling and the CAM processing, several advantages are obtained, considering at the same time some of the technological constraints.The proposed approach is tested on a cubic sample and on a bracket fabricated by a fused filament fabrication technology. The results show that the method allows for the reduction of design efforts, amount of data exchanged, and processing time, obtaining an effective G-code and consistent components.
Keywords: Additive manufacturing | Functionally graded lattice structures | Material extrusion | Volumetric modeling
Abstract: Worldwide, stroke is the third cause of disability. The majority of people affected by this disease cannot perform activities of daily living. Bringing the therapy to the patients' home is complex, and in literature, there are still open challenges to face. Starting from therapists' and patients' needs, this paper describes a possible solution: HANDY, a rehabilitative active hand exoskeleton for post-stroke patients. With a desktop application, they perform three different types of exercises: passive, active and based on activities of daily living. They can also control the exoskeleton themselves in a serious-game approach with a leap motion controller. We evaluated our method with patients at the Villa Beretta rehabilitative center. Preliminary results from the session about comfort, usability and willingness to utilize the system are promising.
Keywords: Additive manufacturing | CAD modeling | Hand exoskeleton | Interactive applications | Stroke
Abstract: Recent research has been focused on the binder jetting (BJ) additive manufacturing technique due to the high potential possibilities in industrial applications. The actual limitation of BJ process can be attributed to the difficult control of the product quality. In fact, a high dimensional variation occurs on sintering, which can detrimentally affect dimensional and geometrical precision, when not properly considered in the design step. This paper aims at investigating the influence of sintering on the dimensional change of through holes, with different diameter size and different axis orientation with respect to the building direction. Samples were measured in the green and sintered state by means of a coordinate measuring machine in order to calculate the diameter shrinkage. The empirical data were successfully compared with the prevision of an analytical model demonstrating that diameter shrinkage is influenced by: the anisotropic dimensional change, the axis orientation and the position of the two diametral opposite points used to identify the diameter. A deep analysis of the results showed a non-negligible effect of the gravity-induced load and of the inhomogeneous shrinkage on sample geometry. This study highlighted that the analytical model may serve as a basis in the design step for improving the dimensional quality of BJ product.
Keywords: Binder jetting | Design for additive manufacturing | Dimensional and geometrical precision
Abstract: Recently, thanks to the evolution of rapid prototyping, the interest in designing topologically optimized components have grown, to maintain good mechanical characteristics while reducing their weight. This work proposes a new method of topological optimization that associates the information obtained through a finite element analysis and a grid of prefixed points in space. The software used for this study is a Rhinoceros plugin called Grasshopper, which is composed of a parametric environment schematized by graphic algorithms. The Finite Element analysis is carried out through the Ansys Workbench software. The obtained stresses are the basis for the algorithm to parameterizes the hollowing with a variation of the diameter of the holes. The ability of the algorithm to directly modify the CAD, avoiding post-processing and generating directly the CAD topologies, represents the true potential of the method. Furthermore, the method lends itself to being used for both additive and subtractive manufacturing. In the presented case study, once the beam model was designed, it was printed using a Fused Deposition Modeling 3D printing technique and then a 3-point bending test was carried out on it. Finally, a comparison was made between the original non-optimized beam and the optimized one by the algorithm, observing an increase in the strength/weight ratio of about 20% but, conversely an increase in printing time of about 50%.
Keywords: Additive Manufacturing | Hollowing | Lightweight design | Topology Optimization
Abstract: The present work describes an automotive component design optimization process through a systematic approach. The redesign aims to improve product performance by Powder Bed Fusion metal Additive Manufacturing. The approach allows to match Topology Optimization and Design for Additive Manufacturing by exploiting benefits provided by CAD platforms that integrate CAD, CAE and CAM tools. The Systematic Concept-Selection-Based Approach aims to make redesign simple and effective, allowing design solutions exploration while containing product design lead time. Topology Optimization is the key phase to achieve lightweight design by a double-level optimization approach. In particular, the technique is setup to produce different design variants, whose subsequently undergo a Trade-off study to perform the concept selection step. Finally, one final redesign occurs and a design refinement step is performed to achieve product optimization. The case study is a high performance internal combustion engine piston, which has been redesigned to be produced by Selective Laser Melting process with benefit of weight reduction.
Keywords: Automotive | Design for additive manufacturing | Design method | Re-design | Topology optimization
Abstract: During the emergency caused by COVID 19 evidence has been provided about the risk of easily getting the virus by touching contaminated surfaces and then by touching eyes, mouth, or nose with infected hands. In view of the restarting of daily activities in presence, it is paramount to put in place any strategy that, in addition to social distancing, is capable to positively impact on the safety levels in public buildings by reducing such risk. The main aim of this paper is to conceive a design methodology, based on a digital, flawless, and sustainable procedure, for producing human-building interfacing solutions that allow anybody to interact in a safer and more comfortable way. Such solutions are focused on the adaptation of existing buildings features and are thought to be an alternative to sensor based touchless technology when this is not applicable due to economic or time constraints. The process is based on the integration of digital technologies such as 3D Scanning, Generative Design and Additive Manufacturing and is optimised to be intuitive and to be adaptive, hence, to be replicable on different kinds of surfaces. The design concept is finalised to generate automatically different products that meet geometry fitting requirements and therefore adapt to the specific geometries of existing handles. A specific case on Hands Free Door Handles is presented and the results of manufacturing and preliminary validation process are provided and discussed.
Keywords: Additive Manufacturing | Covid 19 | Generative Design | Reverse Engineering
Abstract: Many industrial technologies are developed to optimize products and bring innovation. In particular, the automotive sector is renewing itself according to the rules of green energy and consumption. This huge change requires a reinterpretation of the models on the market updating them to the present and the future needs of automotive industry. In this paper the best compromise between innovation and tradition is found for the Ford brand that has not yet presented electric cars in the sedan segment. Following the SDE method enriched with Quality Function Deployment (QFD), Benchmarking (BM) and Top Flop Analysis (TPA), it is possible to carry out an innovative project. All these technologies must, however, be ordered according to a specific product allowing the best result for the design process. It is therefore necessary identifying the most common stylistic trends in order to draw the external styling of the vehicle using virtual prototyping techniques. To achieve an innovative result, Augmented Reality (AR) is considered to complete the method substituting the static and expensive procedure of making maquettes.
Keywords: Additive manufacturing | Augmented reality | Benchmarking | Car design | Design engineering | QFD | Stylistic design engineering (SDE)
Abstract: Laser Powder Bed Fusion is the most widespread additive manufacturing process for metals. In literature, there are several analytical models for estimating the manufacturing cost. However, few papers present sensitivity analyses for evaluating the most relevant product and process parameters on the production cost. This paper presents a cost model elaborated from previous studies used in a sensitivity analysis. The most relevant process parameters observed in the sensitivity analysis are the 3D printer load factor, layer thickness, raw material price and laser speed.
Keywords: additive manufacturing | cost estimation | design costing | design to x (DtX) | sensitivity analysis
Abstract: In this paper, industrial design structure (IDeS) is applied for the development of two new full-electric sports sedan car proposals that go by the names Blitz Vision AS and Retro. With a deep analysis of the trends dominating the automotive industry, a series of product requirements was identified using quality function deployment (QFD). The results of such analysis led to the definition of the technical specifications of the product via benchmarking (BM) and top-flop analysis (TFA). The product architecture was then defined by making use of a modular platform chassis capable of housing a variety of vehicle bodyworks. The structured methodology of stylistic design engineering (SDE) was used. This can be divided in six phases: (1) stylistic trends analysis; (2) sketches; (3) 2D CAD drawings; (4) 3D CAD models; (5) virtual prototyping; (6) solid stylistic model. The chassis of the CAD model was verified structurally by means of FEM analysis, whereas the drag coefficients of the two vehicle proposals were compared with one of the main competitor’s vehicles via CFD simulations. The resulting car models are both aesthetically appealing and can be further developed, leading eventually to the production stage. This proves the effectiveness of IDeS and SDE in car design.
Keywords: additive manufacturing | augmented reality | car design | design engineering | industrial design | quality function deployment (QFD) | stylistic design engineering (SDE) | vehicle virtual design | virtual product development
Abstract: Purpose: Among thoracic malformations, pectus deformities have the highest incidence and can result in a wide range of severe and mild clinical manifestations. Recently, the treatment of pectus deformities is shifting from traditional approaches toward customized solutions. This occurs by leveraging innovative rapid prototyping tools that allow for the design and fabrication of patient-specific treatments and medical devices. This paper aims to provide a comprehensive view of the growing literature in this area to analyze the progress made in this direction. Design/methodology/approach: The search was performed on major search engines through keywords inherent to reverse engineering (RE) and additive manufacturing (AM) technologies applied to pectus deformities and related treatments, selecting 54 papers. These were analyzed according to the addressed pathology, the hardware and software tools used and/or implemented and their integration within the clinical pathway. Findings: First, the analysis led to analyze and divide the papers according to how RE and AM technologies are applied for surgical and non-surgical treatments, pathological assessment and preoperative simulation and planning. Second, all papers were considered within the typical rapid prototyping framework consisting of the three phases of three-dimensional (3D) scanning, 3D modelling and 3D printing. Originality/value: To the best of the authors’ knowledge, to date, no survey has provided a comprehensive view of innovative and personalized treatment strategies for thoracic malformations; the present work fills this gap, allowing researchers in this field to have access to the most promising findings on the treatment and evaluation of pathology.
Keywords: 3D printing | Additive manufacturing | Pectus carinatum | Pectus excavatum | Reverse engineering
Abstract: Tissue engineering or tissue reconstruction/repair/regeneration may be considered as a guiding strategy in oral and maxillofacial surgery, as well as in endodontics, orthodontics, peri-odontics, and daily clinical practice. A wide range of techniques has been developed over the past years, from tissue grafts to the more recent and innovative regenerative procedures. Continuous research in the field of natural and artificial materials and biomaterials, as well as in advanced scaffold design strategies has been carried out. The focus has also been on various growth factors involved in dental tissue repair or reconstruction. Benefiting from the recent literature, this review paper illustrates current innovative strategies and technological approaches in oral and maxillofacial tissue engineering, trying to offer some information regarding the available scientific data and practical applications. After introducing tissue engineering aspects, an overview on additive manufacturing technologies will be provided, with a focus on the applications of superparamagnetic iron oxide nanoparticles in the biomedical field. The potential applications of magnetic fields and magnetic devices on the acceleration of orthodontic tooth movement will be analysed.
Keywords: 3D/4D printing | Dentistry | Design for additive manufacturing | Magnetism | SPIONs | Tissue engineering
Abstract: Lattice structures with triply periodic minimal surfaces (TPMS) built using flexible materials are soft porous solids applicable in various fields, including biomedicine and tissue engineering. Such structures are also relevant for material extrusion additive manufacturing (MEAM), whose wide diffusion is pivotal to fostering their spread. Although design approaches are available to exploit the potential of soft TPMS, there are still manufacturing constraints that lead to practical limits on the shape and size of the structures that can be produced due to the complexities related to printing flexible materials. Besides, the computational models investigating the effect of cell type, the surface-to-volume fraction, and the combination of different periodic surfaces (i.e., graded or hybrid) on the mechanical behavior of these lattices are design aspects still debated. Here, the capabilities of MEAM to produce tailored soft lattice structures are explored by combining a design tool, numerical analyses, and mechanical testing using thermoplastic polyurethane (TPU) as feedstock material. The study addresses design issues, delves into optimum printing parameters, and analyzes a set of numerical parameters, which can be used for designing specific structures with tunable mechanical behavior, useful for healthcare and bioengineering. The printing parameters of three lattices, i.e., schwartz-P, gyroid, and honeycomb, with unit cell sizes spanning from 3 to 12 mm were studied. Their mechanical behavior was investigated using FEM simulations and mechanical testing. Lastly, the printability of graded and hybrid lattices with enhanced bearing-load capabilities have been demonstrated. Altogether, our findings addressed multiple challenges associated with developing soft lattice scaffolds with MEAM that can be used to fabricate innovative-engineered materials with tunable properties.
Keywords: Design for additive manufacturing | Finite element analysis (FEM) | Fused filament fabrication (FFF) | Lattice structures | Thermoplastic polyurethane (TPU) | Triply periodic minimal surfaces (TPMS)
Abstract: Additive manufacturing processes, such as Laser Additive Manufacturing (LAM), has become increasingly established in metal-processing industry offering versatile possibilities for producing individualized components or lightweight structures. LAM machines offer ecological and economical potentials due to comparatively low power and material demand. In general, Additive Manufacturing (AM), has been considered an alternative to the traditional manufacturing techniques, such as Subtractive Machining (SM), because allows the creation of new, light and complex products with an innovative design and manufacturing. Sustainability assessment is essential to identify and select the best technology among the alternative candidates. Sustainability of LAM needs to be evaluated for finding an optimal compromise between technical development and sustainability performance. The Life Cycle Assessment (LCA) methodology is applied to investigate the sustainability of Laser Engineered Net Shaping (LENS) by comparing that of the Computer Numerical Control (CNC) machining. The aim of this research is to analyze and compare the environmental impact between additive and subtractive manufacturing. In particular, CNC (SM) and LENS (AM) technologies have been chosen. A common spur gear has been defined as a case study. Therefore, the analysis allows to define the ecological characteristics of a new production technology compared to a gold standard such as CNC machining. Hence, the advantages and disadvantages of the reviewed additive technology are exposed. The ReCiPe midpoint results, shows advantages in term of environmental impact for the LENS manufacturing process, in particular for the damage to resource indicator.
Keywords: Additive Manufacturing | Ecodesign | Environmental sustainability
Abstract: Abstract: The additive manufacturing technology offers new and incredible opportunities in the design of components. Nowadays, structural integrity assessment of additively manufactured components is a formidable challenge that needs to be faced out in order to allow such components to be launched in the market. One of the major drawbacks of additive manufacturing is poor surface finish and loose geometrical tolerance of built parts. In this scenario, hybrid manufacturing, which takes advantage of both subtractive and additive manufacturing, can be considered as a solution worthy of investigation in view of possible applications to save costs and time in the component production. The present work is aimed at assessing microstructural properties of Co-Cr-Mo specimens manufactured by the hybrid subtractive/additive technology, when the additive part is built over the machined one. The results show an excellent metallurgical coupling at the interface between the two differently processed parts.
Keywords: biomaterials | Co-Cr-Mo alloy | hybrid manufacturing | mechanical properties | microstructure | selective laser melting
Abstract: This paper reports upon the results of an initial test cycle using a bespoke testing rig designed expressly to examine additively manufactured auxetic components. Firstly, the key problems facing practical researchers in the field of auxetics is explored with the treatment of the boundary condition identified as a key issue. The testing setup that is then introduced utilises a novel method of part mounting and facilitates optical analysis and real-time force measurements. The study analyses three different auxetic structures (re-entrant, chiral, and semi-rigid), a set of samples of which were additively manufactured in TPU material. A range of parameters were varied across the three designs including interior geometry and wall thicknesses in order to demonstrate the effectiveness of the setup for the examination of different structures. Several key results were distilled from the tests that were then further analysed through numerical modelling and discussed with respect to future testing. Our investigation shows a close alignment between the physical testing results and the simulations, indicating that the testing configuration is rigorous and may be used to explore the mechanical behaviour of more complex auxetic componentry.
Keywords: Additive manufacturing | Auxetics | Mechanical analysis | Simulation
Abstract: In this work the performances of three different techniques for 3D scanning have been investigated. In particular two commercial tools (smartphone camera and iPad Pro LiDAR) and a structured light scanner (Go!SCAN 50) have been used for the analysis. First, two different subjects have been scanned with the three different techniques and the obtained 3D model were analysed in order to evaluate the respective reconstruction accuracy. A case study involving a child was then considered, with the main aim of providing useful information on performances of scanning techniques for clinical applications, where boundary conditions are often challenging (i.e., non-collaborative patient). Finally, a full procedure for the 3D reconstruction of a human shape is proposed, in order to setup a helpful workflow for clinical applications.
Keywords: 3D printing | 3D scanning techniques | customised orthopaedic brace | low-cost technology | multimodal approach | non-collaborative patient | non-contact measurement
Abstract: Austenitic stainless steels produced by laser powder bed fusion (L-PBF) are quite interesting materials owing to their specific microstructure consisting of dendrite walls built of dislocations pinned by many nano-oxides that involves significant strengthening without loss of ductility. In this work, different plasma treatments were performed to harden the surface of 316 L steel manufactured by L-PBF. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), light microscopy (LM) and micro-hardness tests. The experimental results show that all the plasma treatments enhance the hardness of the surface because a C-enriched layer of austenite (S-phase) forms with a thickness up to 25 μm. The plasma gas mixture, consisting of 2.5% (CH4) + 97.5% (H2), resulted in being the most effective and produced a surface hardness (547 ± 27 HV) more than double with respect to that of the untreated material. The treatment temperature was 475 °C, which represents a good compromise between the necessity to avoid the precipitation of M23C6 carbides and the compatibility of treatment time with the industrial practice. Moreover, it has been observed that a 2 μm-thick over-layer of amorphous C forms on the sample surface. The hardness of such over-layer, which depends on the specific treatment and is related to the degree of topological disorder, is generally greater than that of S-phase. The work demonstrates that plasma carburizing is quite effective in hardening the surface of 316 L steel manufactured by L-PBF and further improves its mechanical properties, which are basically superior to those of the same material prepared by conventional processes.
Keywords: 316 L steel | Additive manufacturing | Austenitic stainless steels | Laser powder bed fusion | Low temperature carburizing | Microstructural characterization | Plasma treatment
Abstract: Silicone resins, filled with phosphates and other oxide fillers, have been recently proposed as feedstock for the manufacturing of scaffolds with a composition resembling that of commercial Biosilicate® glass-ceramics. Silicones and engineered fillers enable the preparation of novel carbon-containing Biosilicate-based composites and, fundamentally, the easy application of additive manufacturing technologies. After successful demonstration of the applicability of direct ink writing of silicone-based pastes, the present paper is dedicated to preparation of highly porous scaffolds obtained by masked stereolithography, starting from a simple blend of silicone resin with commercial photocurable acrylates. Deviations in the desired phase assemblage were corrected by calibration of the silicone/fillers ratio. The more advanced printing technology, combined with ceramic transformation, allowed fabrication of scaffolds with a complex geometry and a distinctive control of overall porosity.
Keywords: Additive manufacturing | Biosilicate® glass-ceramic | Masked stereolithography | Polymer-derived-ceramics | SiOC
Abstract: The present study illustrates the manufacturing method of hierarchically porous 3D scaffolds based on åkermanite as a promising bioceramic for stereolithography. The macroporosity was designed by implementing 3D models corresponding to different lattice structures (cubic, diamond, Kelvin, and Kagome). To obtain micro-scale porosity, flame synthesized glass microbeads with 10 wt% of silicone resins were utilized to fabricate green scaffolds, later converted into targeted bioceramic phase by firing at 1100◦C in air. No chemical reaction between the glass microspheres, crystallizing into åkermanite, and silica deriving from silicone oxidation was observed upon heat treatment. Silica acted as a binder between the adjacent microspheres, enhancing the creation of microporosity, as documented by XRD, and SEM coupled with EDX analysis. The formation of ‘spongy’ struts was confirmed by infiltration with Rhodamine B solution. The compressive strength of the sintered porous scaffolds was up to 0.7 MPa with the porosity of 68–84%.
Keywords: Additive manufacturing | Bioceramics | Glass microspheres | Silicones | åkermanite
Abstract: Strokes can lead to the paralysis of one or more parts of the human body and so stroke survivors more than often require rehabilitation to regain muscle coordination, for instance when trying to perform finger movements. For such an objective, an external device like an exoskeleton can be used. This paper presents a low-cost 3D printed hand exoskeleton with high flexibility degree to fit different hand, wrist, and finger sizes.
Keywords: 3D Printing | Hand Exoskeleton | Post-Stoke Rehabilitation | Stroke
Abstract: The present paper describes a procedure for the development and production of a physical model for surgical planning of a Left Ventricular Aneurysm. The method is based on the general approach provided in Otton et al. (2017) and was customized to seek a reliable and fast procedure for the production of a specific type of cardiac model – i.e. chambers of the left side of the heart. The paper covers all the steps: processing of the data, segmentation, modelling and 3D printing; details are provided for all the phases, in order to allow the reproduction of the achieved results. The procedure relies on Computed Tomography - CT imaging as data source for the identification and modelling of the anatomy. Materialise Mimics was used as segmentation software to process the CT data. While its usefulness for the surgical needs was verified on a single clinical case (provided by the Careggi Hospital of Florence, Italy), the modelling procedure was tested twice, to produce a physical replica both ex-ante and ex-post surgical intervention. • The tools used for segmentation and generation of the printable model were customized to reduce modelling time for the specific type of desired model. • Detailed information on the use of modeling tools, not available in the literature, will be provided. • The procedure allows fabrication of a physical model representing the heart chambers in a short time.
Keywords: 3D printing | Left Ventricular Aneurysm | Method for the production of an anatomical replica of a human heart for surgical planning | Surgical planning
Abstract: Additive Manufacturing technologies have opened new perspectives for the realization of tissue and organs substitutes. The main advantages come from the possibility of using the same technology to produce artificial or biological substitutes in a wide range of outer shapes and inner reticular architectures, which may pave the way to their use to produce personalized substitutes. Additive manufacturing technologies are based on layer-by-layer material fusion and deposition. As such, they have intrinsic limitations which may hinder the possibility to produce substitutes that meet the requirements for safe clinical use. As an example, discontinuities between layers may make the outer surface of a substitute significantly uneven, rough, and may even weaken the substitute mechanical properties in such an aggressive environment as the human body. Moreover, repeated thermal cycles (fusion and solidification) drastically limit the choice of materials which can be used. Finally, the outcome of the production technology is affected by many variables that it is not trivial to control to deliver the necessary quality and repeatability of the production process for medical applications. Indeed, the surface roughness of an implantable prosthesis or organ substitute is key to modulate cell adhesion and the susceptibility to chemical attack by body fluids. Structural strength is a mandatory requirement for load-bearing prostheses (e.g., orthopedic and dental prostheses). Materials for biomedical applications must not only be 3D printable, but also biocompatible and/or possibly have to promote cells growth and to prevent inflammatory reactions. The performance of artificial, bio artificial and tissue-engineered organs needs also to be certified and guaranteed, a rather difficult task to define for devices which may be unique, being tailored on the specific needs of the patient. In this paper, it will be discussed whether this technology is sufficiently mature to replace more traditional techniques or, alternatively, whether it should be limited to a restricted range of emergency applications until the existing relevant technological gaps are filled.
Keywords: 3D printing | additive manufaturing | artificial organs | clinical | corrosion | fatigue | prostheses | strength | surface | surgical guides | wear
Abstract: In recent years, 3D printed scaffolds have been proposed as promising alternative to the conventional cell culture techniques. Scaffolds, indeed, allow the development of a higher number of cellular connections along the three dimensions favoring the cell regeneration, which make them particularly suitable in case of implants for deteriorate bones in old age patients. Besides the characteristics of biocompatibility and biodegradability fundamental for the integration of the scaffolds with the human body, the inner morphology, the permeability as well as the porosity are parameters of paramount relevance in the design of 3D-printed scaffolds influencing the flow of the blood through the cells and, thus, their metabolic functions. In the present work the influence of the internal geometry of 3D-printed scaffolds on the blood flow was investigated. Five cylindrical scaffolds having different internal geometry and different porosity were fabricated using parametric design technique. Numerical analysis of the blood flow within the designed structures was conducted by using CFD tool.
Keywords: additive manufacturing | blood flow simulation | bone scaffolds | parametric design | porous metal
Abstract: The escalating demand for torsion- and bending-resistant structures paired with the need for more efficient use of materials and geometries, have led to novel bio-inspired ingenious solutions. However, lessons from Nature could be as inspiring as they are puzzling: plants and animals offer an enormous range of promising but hierarchically complex configurations. Avian bones are prominent candidates for addressing the torsional and bending issue. They present a unique intertwining of simple components: helicoidal ridges and crisscrossing struts, able to bear flexural and twisting actions of winds. Here, it is set how to harmonically move from the natural to the engineering level to formalize and analyze the biological phenomena under controlled design conditions. The effect of ridges and struts is isolated and combined toward tailored torsion and bending-resistant arrangements. Then the biological level is revisited to extrapolate the avian allometric design approach and is translated into multiscale lightweight structures at the engineering level. This study exploits the complexity of Nature and the scalability that characterizes the evolutionary design of bird bones through the design and fabrication versatility allowed by additive manufacturing technologies. This paves the way for exploring the transferability of the proposed solution at multiple engineering scales.
Keywords: 3D printing | avian-inspired structures | bending resistance | scalability | torsion resistance
Abstract: Despite the large diffusion of additive manufacturing, and markedly fused filament fabrication, some quality aspects of the 3D printed parts have not been dealt with sufficiently. This applies particularly to geometric accuracy and the influence process parameters have on it. The paper describes an experiment in which 27 copies of a part were manufactured by means of a desktop fused filament fabrication device while manipulating layer thickness, printing speed, and number of contours. The effect of such process parameters on five typologies of geometric deviations and the duration of the printing process was assessed. While all the process parameters showed effects on both the printing time and some geometric deviations, the number of contours resulted as the most critical factor. The paper includes a proposal to optimize geometric accuracy and the rapidity of the process, which foresees the maximization of the number of contours, the minimization of the layer thickness, and the use of an intermediate value for printing speed.
Keywords: Coordinate measuring machine | Engineering design | Fused deposition modelling | Geometric tolerances | Process parameters | Rapid prototyping
Abstract: In recent years, many research studies have focused on the application of 3D printing in the production of orthopaedic back braces. Several advantages, such as the ability to customise complex shapes, improved therapeutic effect and reduced production costs place this technology at the forefront in the ongoing evolution of the orthopaedic sector. In this work, four different materials, two of them poly(lactic acid) (PLA) and two of them poly(ethylene terephthalate glycol) (PETG), were characterised from a thermal, mechanical, rheological and morphological point of view. Our aim was to understand the effects of the material properties on the quality and functionality of a 3D-printed device. The specimens were cut from 3D-printed hemi-cylinders in two different orientation angles. Our results show that PETG-based samples have the best mechanical properties in terms of elastic modulus and elongation at break. The PLA-based samples demonstrated typical brittle behaviour, with elongation at break one order of magnitude lower. Impact tests demonstrated that the PETG-based samples had better properties in terms of energy absorption. Moreover, 3D-printed PETG samples demonstrated a better surface finishing with a more homogenous fibre–fibre interface. In summary, we demonstrate that the right choice of material and printing conditions are fundamental to satisfy the quality and functionality required for a scoliosis back brace.
Keywords: additive manufacturing | advanced material selection | functional characterisations | orthopaedic back braces
Abstract: The use of components obtained through the additive manufacturing (AM) technique has become increasingly widespread in recent years, playing a central role in industrial production, and in particular in some fields such as automotive, biomedical, aerospace and electronics. Among all AM techniques, FDM (Fused Deposition Modelling) represents the most used printing technique to produce polymeric and composite components, thanks to the flexible printing process, the low cost and the diversity of the materials adopted. The aim of the present work concerns the comparison between the mechanical properties of three plastic materials printed with the FDM technique (polylactic acid PLA, polyethylene terephthalate glycol-modified PETG and Acrylonitrile-butadiene-styrene ABS) using an Original Prusa i3 MK3S, by varying the raster angle between 0°, 45° and 90° degrees. Infrared Thermography has been adopted to monitor the temperature evolution during static tensile tests and to assess stress level that can initiate damage within the material. Failure analysis was performed to correlate the mechanical behaviour with the microstructural characteristics of the materials.
Keywords: 3D printing | ABS | DfAM | Microstructure | PETG | PLA
Abstract: Additive manufacturing represents a great candidate to boost smart materials expansion in the Industry 4.0 era through 4 D printing technologies. However, to fully exploit the benefits of these technologies, increasing knowledge is needed on how internal defects condition the overall behavior of the component. In this work, the Representative Volume Element approach is presented to investigate, through Finite Element Analyses, how micro-voids influence the stress-strain behavior of an AlSi10Mg additively manufactured through the Selective Laser Melting technique. An in-house code on the commercial software ANSYS Parametric Design Language APDL was developed to model a random pore distribution inside the RVE and to apply the boundary conditions necessary for the RVE periodicity; comparison with reference case studies from the literature are reported.
Keywords: additive manufacturing | FEM | Porosity | RVE
Abstract: In the last decades, compliant mechanisms have been widely studied but their application has not been widespread due to their susceptibility to fatigue and the lack of systematic design methodologies. In this paper, the authors propose a new approach to be used in the automated machinery mechanism design (the mechanisms are usually subjected to predominant inertial loads) that exploits the capability of the compliant joints to store and release elastic energy in order to reduce the motor torque requirements. Thanks to the carbon-fiber reinforced 3D printing technologies, the compliant joint stiffness can be properly designed to obtain, for the considered mechanism, a resonant condition during its nominal functioning. Moreover, topology optimization can be successfully employed to reduce the mechanism component inertia (keeping the same overall mechanism stiffness) and thus, further diminish the torque requirements. In order to assess the quality of the proposed approach, a pusher mechanism used in a real automated machine has been considered. A prototype has been manufactured to evaluate the effect of the compliant joint introduction and the topology optimization on the motor torque reduction. To validate the results, an experimental campaign has been conducted. Comparison between the standard design approach and the new one emphasizes the superior contribution of compliant joint introduction on the motor torque reduction: a 97% and 96% reduction on the RMS and peak motor torque, respectively, is achieved resorting to the new design approach. Although a high repeatability is achieved, a slight deviation of the trajectory with respect to the ideal one is however registered.
Keywords: Additive manufacturing | Continuous fibre reinforced thermoplastics | Size optimization | Topology optimization
Abstract: In the last decades, the flourishing of Additive Manufacturing (AM) promoted innovative design solutions in many different sectors. Despite the numerous advantages of AM technology, there are still open challenges in the field. In Fused Deposition Modelling (FDM) structures the layer-by-layer manufacturing process induces anisotropy in the material properties of the structures. The correct characterization of the mechanical properties is fundamental in the design and development stages but at the same time difficult to achieve. The experimental approach can be extremely long and expensive. An alternative is the use of an accurate numerical approach and performing a Finite Element Analysis (FEA) of the geometry which is effectively printed. However, to the best of the authors' knowledge, there is not a common and well-established procedure to reconstruct the real geometry which is generated after the slicing process. In this paper, starting from the information provided by the G-CODE, an easy-to-use, and reproducible methodology to reconstruct the printed geometry is presented. The performance of the innovative approach is evaluated via qualitative observations by referring to several case studies. The results are thoroughly analysed, and future trends and research needs are highlighted.
Keywords: Additive Manufacturing | CAD | Fused Deposition Modelling | G-CODE
Abstract: Fused Deposition Modelling (FDM) technology allows to choose a large variety of materials and it is widely used by companies and individuals nowadays. The cost effectiveness of rapid prototyping is achievable via FDM, that makes this technology useful for research and innovation. The application of 3D printing to aid production is the most common approach. Moreover, the use of 3D printing in prototypes result in a waste of material since no reuse is considered. In the following manuscript, this technology is applied to mould fabrication by achieving a low surface roughness at a modest cost compared to conventional manufacturing methods. Moreover, the possibility to use a combination of thermoplastic materials is analysed by examination of the CAD model optimized for Additive Manufacturing (AM) from scratch and was verified using metrology tools. Several moulds were finally built and applied to the specific case study of carbon fibre laminated components. This manuscript aims to analyse the manufacturing process by comparing the mould surface geometry before and after the smoothing process. The achieved tolerance between the produced moulds is ±0.05 mm that ensures the repeatability of the process from an industrial point of view; whilst the deviation between CAD and mould is ±0.2 mm. To combine an accurate FDM process together with chemical smoothing proved to be a powerful strategy to produce high quality components that can be inserted in the production process by means of traditional manufacturing techniques. This will aid to reduce the cost of standard manufacturing for low production batches and prototypes of carbon fibre composites.
Keywords: Carbon fibre mould | Chemical smoothing | FDM | Multimaterial FDM | PLA | PVB | Vapor smoothing
Abstract: Additive manufacturing technologies allow for the direct fabrication of 3D scaffolds with improved properties for tissue regeneration. In this scenario, design strategies and 3D fiber deposition technique are considered to develop advanced scaffolds with different lay-down patterns, tailored mechanical and biological properties. 3D poly(ε-caprolactone) scaffolds are manufactured and surface-modified (i.e., aminolysis). The effect of surface modification on the mechanical and biological performances of the designed 3D scaffolds is assessed.
Keywords: computer-aided design | design for additive manufacturing | mechanical analysis | scaffold design
Abstract: A wide range of materials has been considered to repair cranial defects. In the field of cranioplasty, poly(methyl methacrylate) (PMMA)-based bone cements and modifications through the inclusion of copper doped tricalcium phosphate (Cu-TCP) particles have been already investigated. On the other hand, aliphatic polyesters such as poly (e-caprolactone) (PCL) and polylactic acid (PLA) have been frequently investigated to make scaffolds for cranial bone regeneration. Accordingly, the aim of the current research was to design and fabricate customized hybrid devices for the repair of large cranial defects integrating the reverse engineering approach with additive manufacturing, The hybrid device consisted of a 3D additive manufactured polyester porous structures infiltrated with PMMA/Cu-TCP (97.5/2.5 w/w) bone cement. Temperature profiles were first evaluated for 3D hybrid devices (PCL/PMMA, PLA/PMMA, PCL/PMMA/Cu-TCP and PLA/PMMA/Cu-TCP). Peak temperatures recorded for hybrid PCL/PMMA and PCL/PMMA/Cu-TCP were significantly lower than those found for the PLA-based ones. Virtual and physical models of customized devices for large cranial defect were developed to assess the feasibility of the proposed technical solutions. A theoretical analysis was preliminarily performed on the entire head model trying to simulate severe impact conditions for people with the customized hybrid device (PCL/PMMA/Cu-TCP) (i.e., a rigid sphere impacting the implant region of the head). Results from finite element analysis (FEA) provided information on the different components of the model.
Keywords: Composite bone cement for cranioplasty | Design for additive manufacturing | Finite element analysis | Reverse engineering | Temperature profile analysis
Abstract: The aim of this work is to implement a new process for the design and production of orthopaedic devices to realize entirely by Additive Manufacturing (AM). In particular, a generative algorithm for parametric modelling of flexible structures to use in orthopaedic devices has been developed. The developed modelling algorithm has been applied to a case study based on the design and production of a customized elbow orthosis made by Selective Laser Sintering. The results obtained have demonstrated that the developed algorithm overcomes many drawbacks typical of traditional CAD modelling approaches. FEM simulations have been also performed to validate the design of the orthosis. The new modelling algorithm allows designers to model flexible structures with no deformations or mismatches and to create parametric CAD models to use for the production of orthopaedic devices through AM technologies.
Keywords: Additive Manufacturing | Additively manufactured textiles | CAD modelling | Elbow orthosis | Generative algorithms
Abstract: Currently, there is a growing interest of industries in applying additive manufacturing (AM) technology for generating objects with high geometrical complexity and low weight, ensuring good performance, comparable to those ones of products realized by means of traditional techniques. Anyway, it is still usual to realize AM products without focusing on the morphology of the object, hence without exploiting all the advantages of the technique. Indeed, since the several suitable AM technologies, it should be useful to know the functional characteristics of the component for the best choice of the appropriate one and its constructive complexity. In this regard, the 3D modeling strategy is extremely crucial for a proper realization of AM products. The paper deals with a study of the geometrical complexity of dashboard components of a car, based on several techniques for evaluating the geometric complexity. The latter is a fundamental element for estimating the feasibility of AM in terms of production costs and the benefits with respect to traditional molding. In detail, the study focuses on comparing several geometrical complexity evaluation techniques in order to identify the one that simplifies the calculation and better approximates the most used in literature.
Keywords: additive manufacturing | CAD | geometrical complexity
Abstract: In the last decade composite materials, previously almost exclusively used in aerospace and automotive industries, are becoming widespread thanks to the introduction of the fused filament fabrication (FFF) process in the additive manufacturing technology. With respect to the standard and more widely used material subtractive technologies, the FFF layer-by-layer construction process is capable of manufacturing parts featuring very complex geometry. Moreover, the deposition of reinforcing filaments provides components with highperformance mechanical characteristics. Since FFF is a relatively new technology, studies are still needed to fully understand the mechanical behavior of composite materials realized with FFF and how all the process parameters (e.g., layer thickness, filament deposition direction, type of matrix and reinforcement, the interaction between matrix and reinforcement) affect the final result. This paper deals with the preliminary experimental analysis of straight beams realized in carbon-fiber-reinforced Nylon White composite material with the MarkForged MarkTwo threedimensional printer. Envisaged application of the considered straight beams is as flexible elements in compliant mechanisms. In particular, tensile and bending tests are performed on nine different straight beam specimens in order to provide a first understanding on how the filament disposition within the sample affects its mechanical response. From the results it is found that the proper position of the reinforcement filaments provides a very effective means to tune the selective compliance of beam flexures.
Keywords: Additive Manufacturing | Compliant Mechanisms | Composites | Continuous Fiber-Reinforced Thermoplastics | Straight Beam Flexures
Abstract: In the last decade, additive manufacturing technologies (AMT) have spread widely in the industrial field, mostly for fast prototyping but also for the production of finished parts that need a high level of customization. With respect to the well-established material subtractive technologies (MST), some limitations due to component shape can be overcome with AMT. Topology optimization (TO) combined with AMT is a powerful tool capable of realizing components characterized by similar stiffness but smaller inertia concerning those realized with MST. This tool can be very useful in automatic machinery design in order to reduce the required motor torque. In fact, in this realm, the mechanisms are usually subjected to predominant inertial loads. Moreover, since the introduction of fuse filament deposition modeling (FDM) of continuous fiber-reinforced thermoplastics (CFRT), mechanical characteristics comparable to highperformance metal materials can be reached. Thus, rigidity and precision can be achieved as well. In addition to TO, with FDM and size optimization (SO), the designer can easily realize components characterized by a proper stiffness to be included in mechanisms to tune their dynamic mechanical characteristics. In fact, due to their ability to passively store and release mechanical energy, elastic elements can be introduced in a mechanism in order to compensate for kinetic energy variations, which drastically reduce motor torque requirements. The required elasticity can be easily introduced in the mechanism by replacing standard kinematic pairs with Compliant Joints (CJ) in the form of flexible lamina, also assuring lightness, precision and ease of realization. This paper analyzes the potentiality of FDM in combination with TO and CJ design (CJD) for the realization of automated machinery mechanisms subjected to inertial loads. A pusher mechanism is considered: The pros and cons of adopting the procedure are shown with respect to the standard procedure.
Keywords: Additive Manufacturing | Continuous Fiber-Reinforced Thermoplastics | Size Optimization | Topology Optimization
Abstract: The potential of additive manufacturing to produce optimised and customized polymeric parts is often impaired by poor surface finish, low mechanical properties, and insufficient dimensional accuracy. Post-processing treatments are usually adopted to address these issues. Scientific community and industrial actors are engaged in the development and use of post-processing to enhance the performance and widen the range of application of polymeric components manufactured by additive technologies. The present work aims to provide an exhaustive classification and discussion of the post-processing treatments, as well as an extensive literature review of the approaches proposed within the scientific community. A holistic view of post-processing is provided, including a discussion of the benefits associated with each technique as well as its side effects. This work is intended to support the selection of the most appropriate post-processing by considering multiple aspects such as the material, part geometry, processing time, costs, and treatment specificity.
Keywords: Additive manufacturing | polymers | post-processing treatments
Abstract: Autologous ear reconstruction is the preferred treatment in case of partial or total absence of the external ear. The surgery can be very challenging to perform and the aesthetic result highly dependent on the surgeon’s “artistic skills”. In this context a preoperative planning and simulation phase based on the patient’s specific anatomy may result crucial for the surgical outcome. In this work, starting from a case study, the elements necessary for an effective simulation are identified and a strategy for their interactive design and customization is devised with a perspective of a semi-automatization of the procedure.
Keywords: Additive manufacturing | Autologous ear reconstruction | Microtia | Preoperative planning | Reverse engineering
Abstract: The article discusses the design of an acquisition system for the 3D surface of human arms. The system is composed by a 3D optical scanner implementing stereoscopic depth sensors and by an acquisition software responsible for the processing of the raw data. The 3D data acquired by the scanner is used as starting point for the manufacturing of custom-made 3D printed casts. Specifically, the article discusses the choices made in the development of an improved version of an existing system presented in  and presents the results achieved by the devised system.
Keywords: 3D printing | 3D scanning | Arm scanner | Body scanner | Orthoses
Abstract: On the one hand, many mechanical components manufactured through additive technologies are optimized in terms of stiffness/weight or strength/weight thanks to lattice structures. On the other hand, the high complexity of these components often impedes further finishing operations and, therefore, the fatigue strength can be compromised. The high surface to volume ratio together with the high roughness, typical of additive manufactured components, promote the crack nucleation. In this paper, the High-Cycle-Fatigue (HCF) behavior of the 17-4 PH stainless steel (SS) was characterized. Cylindrical samples, manufactured via Selective Laser Melting (SLM) with an EOS M280, were tested in the as-build condition through a STEPLab UD04 fatigue-testing machine. In particular, a preliminary quasi-static traction test was performed on a sample to obtain the yield strength (σY = 570 MPa) and the ultimate tensile strength (UTS = 1027 MPa). Fatigue tests were performed on samples at different stress levels in order to characterize the whole Stress-Number of cycles (S-N) curve (Wöhler diagram). More specifically, the stair-case method combined with the Dixon approach were exploited to calculate the fatigue limit (σF = 271 MPa). The obtained results were compared with those present in literature for the same material and they are coherent with previous researches.
Keywords: 17-4 PH | Additive manufacturing | HCF | SLM
Abstract: In this paper, the static and low-cycle-fatigue (LCF) behavior of wrought samples of 17-4 PH stainless steel (SS) manufactured via Selective Laser Melting (SLM) are presented. On the one hand, several scholars have studied SLM materials and literature reports a huge amount of data as for the high-cycle-fatigue (HCF) behavior. On the other hand, few are the data available on the LCF behavior of those materials. The aim of the present research is to provide reliable data for an as-build 17-4 PH steel manufactured via SLM techniques. Only with quantitative data, indeed, it is possible to exploit all the advantages that this technology can offer. In this regard, both quasi-static (QS) and low-cycle-fatigue tests were performed on Additive Manufacturing (AM) cylindrical samples. Through QS tests, the constitutive low has been defined. Strain-controlled fatigue tests on an electromechanical machine were performed on 12 samples designed according to the ASTM standard. Tests were continued also after the stabilization was reached (needed for the cyclic curve described with the Ramberg-Osgood equation) to obtain also the fatigue (ε-N) curve. Results show that the material has a softening behavior. The Basquin-Coffin-Manson (BCM) parameters were tuned on the basis of the ε-N combinations after rupture.
Keywords: 17-4 PH | Additive manufacturing | LCF | SLM
Abstract: Laryngoscopes are used as diagnostic devices for throat inspection or as an aid to intubation. Their blade must be geometrically compatible with patients’ anatomy to provide a good view to doctors with minimal discomfort to patients. For this reason, this paper was aimed to investigate the feasibility of producing customized blades. The customizable blade model was developed following a feature-based approach with eight morphological parameters. The thickness of such a blade was determined through numerical simulations of ISO certification tests, where the finite element mesh was obtained by morphing a ‘standard’ mesh. The following procedure was applied: the model was built from the selected parameters; the blade was tested in silico; finally, the blade was produced by additive manufacturing with an innovative biodegradable material (Hemp Bio-Plastic® -HBP-) claimed to feature superior mechanical properties. The procedure evidenced that the mechanical properties of current biodegradable materials are unsuitable for the application unless the certification norm is revised, as it is expected.
Keywords: Additive manufacturing | Biodegradable materials | Feature-based modeling | Laryngoscope blades | Mesh-morphing | Parametric drawing | Patient-specific design
Abstract: Cranioplasty is a procedure performed to repair defects in the human skull bone by surgically reconstructing the shape and function of the cranium. Several complications, both intraoperative and postoperative, can affect the procedure’s outcome (e.g., inaccuracies of the reconstructed shape, infections, ulcer, necrosis). Although the design of additive manufactured implants in a preoperative stage has improved the general quality of cranioplasties, potential complications remain significant, especially in the presence of critical skin tissue conditions. In this paper, an innovative procedure to improve the chances of a positive outcome when facing critical conditions in a cranioplasty is described. The proposed approach relies on a structured planning phase articulated in a series of digital analyses and physical simulations performed on personalized medical devices that guide the surgeon in defining surgical cuts and designing the implant. The ultimate goal is to improve the chances of a positive outcome and a fast recovery for the patient. The procedure, described in extenso in the paper, was positively tested on a cranioplasty case study, which presented high risk factors.
Keywords: Additive manufacturing | Cranioplasty | Patient-specific implant | Skull reconstruction
Abstract: An important issue when designing conformal lattice structures is the geometric modeling and prediction of mechanical properties. This paper presents suitable methods for obtaining optimized conformal lattice structures and validating them without the need for high computational power and time, enabling the designer to have quick feedback in the first design phases. A wire-frame modeling method based on non-uniform rational basis spline (NURBS) free-form deformation (FFD) that allows conforming a regular lattice structure inside a design space is presented. Next, a previously proposed size optimization method is adopted for optimizing the cross-sections of lattice structures. Finally, two different commercial finite element software are involved for the validation of the results, based on Euler–Bernoulli and Timoshenko beam theories. The findings highlight the adaptability of the NURBS-FFD modeling approach and the reliability of the size optimization method, especially in stretching-dominated cell topologies and load conditions. At the same time, the limitation of the structural beam analysis when dealing with thick beams is noted. Moreover, the behavior of different kinds of lattices was investigated.
Keywords: Additive manufacturing | Conformal lattice structure | Design for additive manufacturing | Size optimization | Virtual modeling
Abstract: The topology optimization methodology is widely applied in industrial engineering to design lightweight and efficient components. Despite that, many techniques based on structural optimization return a digital model that is far from being directly manufactured, mainly because of surface noise given by spikes and peaks on the component. For this reason, mesh post-processing is needed. Surface smoothing is one of the numerical procedures that can be applied to a triangulated mesh file to return a more appealing geometry. In literature, there are many smoothing algorithms available, but especially those based on the modification of vertex position suffer from high mesh shrinkage and loss of important geometry features like holes and surface planarity. For these reasons, an improved vertex-based algorithm based on Vollmer’s surface smoothing has been developed and introduced in this work along with two case studies included to evaluate its performances compared with existent algorithms. The innovative approach herein developed contains some sub-routines to mitigate the issues of common algorithms, and confirms to be efficient and useful in a real-life industrial context. Thanks to the developed functions able to recognize the geometry feature to be frozen during the smoothing process, the user’s intervention is not required to guide the procedure to get proper results.
Keywords: Additive manufacturing | Mesh processing | Structural manufacturing | Surface smoothing | Topology optimization
Abstract: Nowadays additive manufacturing is affected by a rapid expansion of possible applications. It is defined as a set of technologies that allow the production of components from 3D digital models in a short time by adding material layer by layer. It shows enormous potential to support wind musical instruments manufacturing because the design of complex shapes could produce unexplored and unconventional sounds, together with external customization capabilities. The change in the production process, material and shape could affect the resulting sound. This work aims to compare the music performances of 3D-printed trombone mouthpieces using both Fused Deposition Modelling and Stereolithography techniques, compared to the commercial brass one. The quantitative comparison is made applying a Design of Experiment methodology, to detect the main additive manufacturing parameters that affect the sound quality. Digital audio processing techniques, such as spectral analysis, cross-correlation and psychoacoustic analysis in terms of loudness, roughness and fluctuation strength have been applied to evaluate sounds. The methodology herein applied could be used as a standard for future studies on additively manufactured musical instruments.
Keywords: Additive manufacturing | Design of experiment | Musical instruments | Sound analysis | Stereolithography
Abstract: Within the context of modern industries, additive manufacturing (AM) plays a critical role. Design for AM (DfAM) requires defining design actions related to the product's geometry under development. DfAM affects design choices such as the type of process, the material, the geometry, and the model's features. Knowledge-based engineering (KBE) is promising for integrating DfAM principles in the early phases of product development. Still, few limitations are noticed, such as the real interoperability between DfAM and 3D CAD systems, leading to the application of proper DfAM rules downstream of the 3D modeling. This paper aims to describe a method to formalize AM engineering knowledge used as a repository to develop a CAD-integrated decision support tool by acknowledging the current gap. The method uses, as input, geometrical data retrieved by the feature analysis of the 3D CAD model (feature recognition approach) and manufacturing information related to AM processes. The method will allow closing the gap between the design and production departments by creating a knowledge-based system. The outcome of this system does not concern the possibility of predicting the AM process parameters. The system will support engineers in delivering product designs compliant with AM processes. Based on this system, a CAD-integrated DfAM tool can be developed in the future.
Keywords: Additive manufacturing | Am | Cad | Design for additive manufacturing | Design rules | Design tool | Feature recognition | Knowledge-based system
Abstract: The die manufacturing industry is widely based on the use of conventional machining tools. However, several studies have proposed Additive Manufacturing (AM) for molds and die inserts in the last ten years. The AM flexibility allows designing and manufacturing complex surfaces. This flexibility can be used to optimize the cooling channels of die inserts (conformal cooling). The research aims to evaluate whether Design for Additive Manufacturing commercial tools can be employed in redesigning die inserts. Besides, the paper describes a method to redesign a die insert for High-Pressure Die Casting using Selective Laser Melting. A test case is proposed to analyze an AM die insert's redesign process for improving the thermal exchange and the material distribution. The simulation of the AM process supports the drafting conclusions from the results.
Keywords: 3D Printing | Additive Design | Conformal Cooling | High Pressure Die Casting | Lattice Structure | Metal Additive Manufacturing | Rapid Tooling
Abstract: Many companies have been evaluating the feasibility and gain of using Additive Manufacturing in their own business. One of the main advantages of this technology is the possibility to produce a shape with complex geometry in a reduced time. Therefore, Additive Manufacturing is often applied in rapid prototyping, which is an essential activity for the evaluation and testing of the design concepts. Even if the advantages and drawbacks of 3D printing are well known in the literature, there is still a lack of tools and methodologies to support a rapid techno-economic analysis for selecting the key manufacturing process between traditional machining tools and 3D printing. A case study on a 3D part of moderate complexity, a gas burner head, fabricated by additive manufacturing, using selective laser melting, has been described in this paper. This test case is focused on the context of rapid prototyping. The 3D part is a gas burner head which has to be printed for testing activity. The analysis focuses on the cost, time, and quality of the built part. An analytical approach has been proposed to calculate the cost of the 3D printing process. The analytical cost is related to the results of the numerical simulations to support the techno-economic analysis. The paper shows a method to compare additive manufacturing and traditional machining processes in rapid prototyping. However, the paper also shows a simulation activity to analyze with more details the 3D printing process in terms of part orientation and deformation of the build.
Keywords: 3D printing simulation | Additive manufacturing | Cost analysis | Metal printing | Rapid prototyping
Abstract: Medical images do not provide a natural visualization of 3D anatomical structures, while 3D digital models are able to solve this problem. Interesting applications based on these models can be found in the cardiovascular field. The generation of a good-quality anatomical model of the heart is one of the most complex tasks in this context. Its 3D representation has the potential to provide detailed spatial information concerning the heart’s structure, also offering the opportunity for further investigations if combined with additive manufacturing. When investigated, the adaption of printed models turned out to be beneficial in complex surgical procedure planning, for training, education and medical communication. In this paper, we will illustrate the difficulties that may be encountered in the workflow from a stack of Computed Tomography (CT) to the hand-held printed heart model. An important goal will consist in the realization of a heart model that can take into account real wall thickness variability. Stereolithography printing technology will be exploited with a commercial rigid resin. A flexible material will be tested too, but results will not be so satisfactory. As a preliminary validation of this kind of approach, print accuracy will be evaluated by directly comparing 3D scanner acquisitions to the original Standard Tessellation Language (STL) files.
Keywords: 3D printing | Heart model | Patient-specific modeling | Segmentation | Stereolithography
Abstract: Additive Manufacturing (AM) brought a revolution in parts design and production. It enables the possibility to obtain objects with complex geometries and to exploit structural optimization algorithms. Nevertheless, AM is far from being a mature technology and advances are still needed from different perspectives. Among these, the literature highlights the need of improving the frameworks that describe the design process and taking full advantage of the possibilities offered by AM. This work aims to propose a workflow for AM guiding the designer during the embodiment design phase, from the engineering requirements to the production of the final part. The main aspects are the optimization of the dimensions and the topology of the parts, to take into consideration functional and manufacturing requirements, and to validate the geometric model by computer-aided engineering software. Moreover, a case study dealing with the redesign of a piston rod is presented, in which the proposed workflow is adopted. Results show the effectiveness of the workflow when applied to cases in which structural optimization could bring an advantage in the design of a part and the pros and cons of the choices made during the design phases were highlighted.
Keywords: Computational geometry | Design for additive manufacturing | Design workflow | DfAM | Geometric modeling | Size optimization | Topology optimization
Abstract: Thanks to the great diffusion of additive manufacturing technologies, the interest in lattice structures is growing. Among them, minimal surfaces are characterized by zero mean curvature, allowing enhanced properties such as mechanical response and fluidynamic behavior. Recent works showed a method for geometric modeling triply periodic minimal surfaces (TPMS) based on subdivision surface. In this paper, the deviation between the subdivided TPMS and the implicit defined ones is investigated together with mechanical properties computed by numerical methods. As a result, a model of mechanical properties as a function of the TPMS thickness and relative density is proposed.
Keywords: Additive manufacturing | Design for additive manufacturing | Lattice structures | Triply periodic minimal surfaces
Abstract: Additive manufacturing allows high complexity of manufactured structures, permitting entirely new design capabilities. In the context of complex design, lattice structures hold the most promise for high complexity, tailorable and ultra-lightweight structures. These unique structures are suitable for various applications including light-weighting, energy absorption, vibration isolation, thermal management amongst many others. This new complexity leads to new manufacturing quality control and metrology challenges. Traditional metrology tools cannot access the entire structure, and the only reliable method to inspect the inner details of these structures is by X-ray computed tomography (CT). This work highlights the challenges of this process, demonstrating a novel workflow for dimensional metrology of coupon lattice samples—using a combination of surface and internal metrology using tactile probe and CT. This dual combined approach uses traditional surface coordinate measurement on exterior accessible surfaces, which is followed by internal lattice measurements. The results show a clear method and workflow for combining these technologies for a holistic dimensional inspection. The confidence gained by inspection of such lattice coupons will support the application of these lattices in end-use parts.
Keywords: calibration | laser powder bed fusion | lattice structures | metal additive manufacturing | metrology | X-ray tomography
Abstract: Lattice structures made by means of Additive Manufacturing are more and more used in several fields of application. In particular, reticular Titanium alloy bodies are used in biomechanics as fusion devices, due to their biocompatibility and lightweight characteristics. Although these structures have been extensively investigated, it is currently not possible to predict their behavior easily. Indeed, due to the high number of degrees of freedom of the lattice structures, it is usually required to conduct extensive experimental campaigns in order to anticipate the mechanical behavior of complex components. The present study proposes a method to predict the run-out in an intervertebral cervical cage based on experimental tests conducted on a similar cage and using Finite Element simulations. The cages were made of Ti-6Al-4V ELI by means of Electron Beam Melting. The experimental tests were carried out in accordance with the appropriate ASTM standards. The numerical simulations were consistent with the experimental results and showed a very good agreement. This methodology helped to identify the most critical issues and to verify a new cage without a second test campaign, which allows both cost and time savings.
Keywords: Additive manufacturing | Computer aided engineering | Electron beam melting | Intervertebral cervical cage | Lattice structures
Abstract: Stochastic lattice structures are very powerful solutions for filling three-dimensional spaces using a generative algorithm. They are suitable for 3D printing and are well appropriate to structural optimization and mass distribution, allowing for high-performance and low-weight structures. The paper shows a method, developed in the Rhino-Grasshopper environment, to distribute lattice structures until a goal is achieved, e.g. the reduction of the weight, the harmonization of the stresses or the limitation of the strain. As case study, a cantilever beam made of Titan alloy, by means of SLS technology has been optimized. The results of the work show the potentiality of the methodology, with a very performing structure and low computational efforts.
Keywords: Additive Manufacturing | Lattice structures | Mechanical design | Topology Optimization
Abstract: The use of Topology Optimization techniques has seen a great development since the last decade. The principal contributor to this trend is the widespread use of Additive Manufacturing technologies to effectively build complex and performant structures over different settings. Nevertheless, the use of Topology Optimization in Design for Additive Manufacturing processes is not simple and research aims to fill the gap between theory and practice by evolving at the same time both approaches, workflows, and design software that allow their implementation. Since a strong connection between methodologies and tools exists, this work proposes a method to assess computer-aided design tools or platforms. This can be applied to sustain the key phase for selection and adoption of the computer-aided tools in industrial settings embracing Additive Manufacturing. The workflow for Topology Optimization implementation, the structure of the proposed evaluation approach, and its application, are presented to demonstrate effective usability. The automotive case study is the redesign of internal combustion engine piston to benefit of metal Additive Manufacturing based enhanced product performance. A preliminary finite element model is defined and a Topology Optimization based redesign is concurrently set up through four different commercial computer-based platforms. The method accounting for the assessment of required operations for the design optimization is applied to perform the tools selection phase.
Keywords: Automotive | Computer aided design tools | Design for additive manufacturing | Design methods | Topology optimization
Abstract: Additive Manufacturing (AM) is a key technology in current industrial transformations thanks to the significant benefits that can bring to high-level sectors. Nevertheless, AM-based design approaches require improvements that are fundamental to exploit the potentials of the technology and reduce the lack of process consistency. This work focuses on integrated Design for Additive Manufacturing (DfAM) approaches for product-process design, to meet both functional and technological targets. The key aspects of process design and issues are summarized and the design method to perform metal AM process optimization is presented. The aim is therefore to minimize process-induced defects and flaws of AM-based manufacturing of metal products, such as residual stress and distortions. The approach consists of industrialization task improvement based on modelling optimization and build optimization sub-phases supported by numerical process simulation. Integration of CAD platforms allows embedding these steps to be performed downstream of the product design, which can be achieved through functional or multifunctional optimization techniques as well (e.g. topology optimization, latticing, graded structures/materials). The design method is finally applied to perform the industrialization phase of a high-performance automotive component. The case study is a formula SAE topology optimized brake caliper to be produced by Selective Laser Melting (SLM) process. Process simulationdriven studies on modelling and build preparation subphases (i.e. orientation definition, supports generation, model distortion compensation) are conducted to support the process design. The study demonstrates the part scale level method's suitability to industrial context to improve industrialization in the redesign of components to be produced by metal AM.
Keywords: Additive manufacturing | Automotive | Design method | Powder bed fusion | Process optimization | Process simulation
Abstract: Improvements in software for image analysis have enabled advances in both medical and engineering industries, including the use of medical analysis tools to recreate internal parts of the human body accurately. A research analysis found that FDM-sourced elements have shown viability for a customized and reliable approach in the orthopedics field. Three-dimensional printing has allowed enhanced accuracy of preoperative planning, leading to reduced surgery times, fewer unnecessary tissue perforations, and fewer healing complications. Furthermore, using custom tools chosen for each procedure has shown the best results. Bone correction-related surgeries require customized cutting guides for a greater outcome. This study aims to assess the biopolymer-based tools for surgical operations and their ability to sustain a regular heat-sterilization cycle without compromising the geometry and fit characteristics for a proper procedure. To achieve this, a DICOM and FDM methodology is proposed for fast prototyping of the cutting guide by means of 3D engineering. A sterilization test was performed on HTPLA, PLA, and nylon polymers. As a result, the unique characteristics within the regular autoclave sterilization process allowed regular supplied PLA to show there were no significant deformations, whilst annealed HTPLA proved this material’s capability of sustaining repeated heat cycles due to its crystallization properties. Both of these proved that the sterilization procedures do not compromise the reliability of the part, nor the safety of the procedure. Therefore, prototypes made with a similar process as this proposal could be safely used in actual surgery practices, while nylon performed poorly because of its hygroscopic properties.
Keywords: 3D engineering | Cutting guide | FDM | HTPLA | Nylon FDM | Preoperative planning | Sterilization
Abstract: Fused Deposition Modeling (FDM) 3D printing is the most widespread technology in additive manufacturing worldwide that thanks to its low costs, finished component applications, and the production process of other parts. The need for lighter and higher-performance components has led to an increased usage of polymeric matrix composites in many fields ranging from automotive to aerospace. The molds used to manufacture these components are made with different technologies, depending on the number of pieces to be made. Usually, they are fiberglass molds with a thin layer of gelcoat to lower the surface roughness and obtain a smooth final surface of the component. Alternatively, they are made from metal, thus making a single carbon fiber prototype very expensive due to the mold build. Making the mold using FDM technology can be a smart solution to reduce costs, but due to the layer deposition process, the roughness is quite high. The surface can be improved by reducing the layer height, but it is still not possible to reach the same degree of surface finish of metallic or gelcoat molds without the use of fillers. Thermoplastic polymers, also used in the FDM process, are generally soluble in specific solvents. This aspect can be exploited to perform chemical smoothing of the external surface of a component. The combination of FDM and chemical smoothing can be a solution to produce low-cost molds with a very good surface finish.
Keywords: Carbon fiber mold | Chemical smoothing | FDM | PVB | Vapor smoothing
Abstract: Additive manufacturing processes have evolved considerably in the past years, growing into a wide range of products through the use of different materials depending on its application sectors. Nevertheless, the fused deposition modelling (FDM) technique has proven to be an eco-nomically feasible process turning additive manufacture technologies from consumer production into a mainstream manufacturing technique. Current advances in the finite element method (FEM) and the computer-aided engineering (CAE) technology are unable to study three-dimensional (3D) printed models, since the final result is highly dependent on processing and environment parame-ters. Because of that, an in-depth understanding of the printed geometrical mesostructure is needed to extend FEM applications. This study aims to generate a homogeneous structural element that accurately represents the behavior of FDM-processed materials, by means of a representative volume element (RVE). The homogenization summarizes the main mechanical characteristics of the actual 3D printed structure, opening new analysis and optimization procedures. Moreover, the linear RVE results can be used to further analyze the in-deep behavior of the FDM unit cell. Therefore, industries could perform a feasible engineering analysis of the final printed elements, allowing the FDM technology to become a mainstream, low-cost manufacturing process in the near future.
Keywords: Additive manufacturing | FDM | FEM | Linear analysis | Microstructure behavior | RVE
Abstract: The design of an E segment, executive, midsize sedan car was chosen to fill a gap in the market of the Ford brand and to achieve the goal of innovation looking towards the future. Ford has not owned an E-segment flagship sports sedan for years, since the historic 1960s Falcon. Starting from the latter assumption and considering that the major car manufacturers are currently investing heavily in E-segment cars, it is important to design a new model, which has been called the Eagle. This model proposed here is to fill the gap between Ford and other companies that are already producing sport cars for the electric sector and to complete Ford’s proposal. The presented methodology is based on SDE, on which many design tools are implemented, such as Quality Function Deployment (QFD), Benchmarking (BM), and Top Flop Analysis (TPA). A market analysis follows in order to identify the major competitors and their key characteristics considering style and technology. The results are used to design an innovative car. Based on the most developed stylistic trends, the vehicle is first sketched and then drawn in the 2D and 3D environments for prototyping. This result leads to the possibility of 3D printing the actual model as a maquette using the Fused Deposition Modelling (FDM) technology and testing it in different configurations in Augmented Reality (AR). These two final applications unveil the possibilities of Industry 4.0 as enrichment for SDE and in general rapid prototyping.
Keywords: Additive manufacturing | Augmented reality | Benchmarking | Car design | Design engineering | QFD | Stylistic design engineering (SDE)
Abstract: Three-dimensional printed custom cutting guides (CCGs) are becoming more and more investigated in medical literature, as a patient-specific approach is often desired and very much needed in today’s surgical practice. Three-dimensional printing applications and computer-aided surgical simulations (CASS) allow for meticulous preoperatory planning and substantial reductions of operating time and risk of human error. However, several limitations seem to slow the large-scale adoption of 3D printed CCGs. CAD designing and 3D printing skills are inevitably needed to develop workflow and address the study; therefore, hospitals are pushed to include third-party collaboration, from highly specialized medical centers to industrial engineering companies, thus increasing the time and cost of labor. The aim of this study was to move towards the feasibility of an in-house, low-cost CCG 3D printing methodology for pediatric orthopedic (PO) surgery. The prototype of a femoral cutting guide was developed for its application at the IOR—Rizzoli Orthopedic Institute of Bologna. The element was printed with an entry-level 3D printer with a high-temperature PLA fiber, whose thermomechanical properties can withstand common steam heat sterilization without bending or losing the original geometry. This methodology allowed for extensive preoperatory planning that would likewise reduce the overall surgery time, whilst reducing the risks related to the intervention.
Keywords: 3D printing | CAD surgery simulation | CASS | CT scan | Cutting guide | Orthopedic reproduction model
Abstract: The study of CAD (computer aided design) modeling, design and manufacturing techniques has undergone a rapid growth over the past decades. In medicine, this development mainly concerned the dental and maxillofacial sectors. Significant progress has also been made in orthopedics with pre-operative CAD simulations, printing of bone models and production of patient-specific instruments. However, the traditional procedure that formulates the surgical plan based exclusively on two-dimensional images and interventions performed without the aid of specific instruments for the patient and is currently the most used surgical technique. The production of custom-made tools for the patient, in fact, is often expensive and its use is limited to a few hospitals. The purpose of this study is to show an innovative and cost-effective procedure aimed at prototyping a custom-made surgical guide for address the cubitus varus deformity on a pediatric patient. The cutting guides were obtained through an additive manufacturing process that starts from the 3D digital model of the patient’s bone and allows to design specific models using Creo Parametric. The result is a tool that adheres perfectly to the patient’s bone and guides the surgeon during the osteotomy procedure. The low cost of the methodology described makes it worth noticing by any health institution.
Keywords: 3D Printing | CAD Modeling | Cutting guides | Pediatric orthope-dics | Preoperative simulation | Surgery and diagnostics
Abstract: Software for image analysis endorsed further developments in the medical area that would accept state of the art reengineering processes to reproduce actual internal organs and structures of the human body. Previous research on FDM produced elements in the medicine field shown important discoveries on orthopedics. Preoperative planning shown to be suitable for additive manufacturing solutions that could help to improve the efficiency on procedures lowering potential risks after surgery. Accurate and well thought planning is necessary to choose the best way for the practice and deliver the best results. Tooling customization has shown to help into achieving this result. Bone-related surgeries require customized cutting guides for better accuracy. The following work aims to deliver the opportunity to use variations of Polylactic acid (PLA) based cutting guides in actual surgery practices by means of sustaining a regular heat-sterilization procedure without compromising its tailor-made characteristics. This would be possible by means of a proved, reliable procedure for obtaining the prototype from traditional CT scan images. As a result, HTPLA material composition and crystallization properties allowed to sustain a sterilization procedure in a way that does not compromise the reliability of the part, nor the safety of the procedure, so prototypes made with a similar process as the proposed one, can be used in actual surgery practices with safety.
Keywords: 3D Engineering | Cutting Guide | FDM | HTPLA | Sterilization
Abstract: Nowadays there is a trend of development of a number of FDM-sourced elements that have improved the ways for fast prototyping. CAE software technologies enabled sharing of knowledge across different sectors in the industry, there are important research findings in the medical area in which FDM implies an interesting and a rather efficient option for surgical procedure assessment; mainstream PLA has been a matter of various studies trying to understand its behavior to its limits, a heat treatment on PLA materials could allow to have different, and more diverse applications. HTPLA is another variation that deserves attention due to its prospective. This material has proven to expand the availability of PLA to different sectors because of its rather ease printability and higher heat-resistance. This study would assess the properties of neat PLA and HTPLA printed with optimized parameters, in addition of an annealing process that would modify its internal structure. Results suggest that HTPLA can resist higher temperatures and stress changes whilst scoring lower elongation and tensile response degrading.
Keywords: Annealing | FDM | HT-PLA | Polymers | Tensile Testing
Abstract: The present paper is about a family car project that starts from a study of the characteristics of the type of car taken into consideration and from an analysis of the environment carried out through an historical research on the models on the market from the 30s to the mid-90s, and their classification. The market analysis was carried out by answering six questions from the QFD and by developing the tables of relative importance and interrelation through which the most important and the most independent requirements to be attributed to the innovative family project were obtained. The competitor analysis was made through a research on the models currently on the market, the development of the benchmarking, and the what/how matrix from which the final requirements and project objectives were determined. The brand was selected, the budget was drawn up over a 12-month period and the car’s product architecture was defined. The SDE was carried out through an aesthetic analysis of the existing models, the sketches for each type of style and the selection of the final sketches. The development of the product, instead, consisted in the prototyping of a 1:18 scale model of the car through 3D printing.
Keywords: 3D Printing | CAD | QFD | Rendering | SDE
Abstract: Since 3D printing was developed, it became the most promising technique to speed up prototyping in a wide variety of areas across the industry. Rapid prototyping allows the medical industry to customize the surgery procedures, thus predicting its result. Biomedical applications made by medical grade elastic thermoplastic polyurethane (TPU); a non-traditional plastic material which allows to obtain additional benefits in rapid 3D prototyping because of its flexibility and anti-bacteriological capabilities. The aim of this study is to assess the efficacy of TPU polymer, FDM objects sourced from CT scanned 3D surfaces for helping surgeons in preoperative planning and training for increasing environment perception, that is, geometry and feeling of the tissues, whilst performing standard procedures that require complex techniques and equipment. A research was performed to assess the physical and qualitative characteristics of TPU 3D developed objects, by developing a proper SWOT analysis against PLA, a widely used, and cost-effective option in FDM industry. Therefore, giving a proposition opposite to other known modern medical planning techniques and bringing out the benefits of the application of TPU-sourced, FDM parts on professional medical training. As a result, PLA is a reliable, wide-available process whilst TPU’s flexible capabilities improves realism in 3D printed parts. Surgical planning and training with rapid prototyping, would improve accurate medical prototyping for customized-procedures, by reducing surgery times, unnecessary tissue perforations and fewer healing complications; providing experience that other FDM materials like PLA cannot be reached.
Keywords: 3D Printing | 3D Scanner | QFD | Surgical Training | TPU
Abstract: Fused Deposition Modeling (FDM) 3D printing technology has widespread in a variety of scientific fields, since rapid prototyping and low-cost investments well meet flexibility of application. Mechanical engineering is taking an essential role in Orthopaedics and Traumatology. As a patient-specific approach and minimally invasive surgeries are progressively needed in today’s medical routines, highly-customized 3D printed devices and surgical instruments represent a milestone in medical equipment. Virtual preoperatory planning and computer aided surgical simulations (CASS) enhance 3D visualization of human anatomy, giving doctors full understanding of traumas and deformities. Custom cutting guides (CCGs) represent the cutting edge of patient-dedicated surgical routines, allowing for a sensible reduction of operative time and risk of human error. While maxillofacial surgery (MFS) has already adopted customized 3D printed tools, pediatric orthopaedics (PO) and general long bones surgery strive to put these devices into common practice. Limitations to a large-scale implementation rely on collaboration with the industrial world, as engineering and designing skills are inevitably demanded. Here displayed is the prototype for a femoral cutting guide designed for a pediatric application of the IOR - Rizzoli Orthopaedic Institute of Bologna. The device was printed in a High-Temperature PLA, supporting common steam heat sterilization and maintaining designed geometry.
Keywords: 3D printing | CAD surgery simulation | CT scan | Cutting guide | Orthopaedic reproduction model
Abstract: The present work is a case study about the application of the methodology named Stylistic Design Engineering (SDE), that is an approach to develop car design projects in the industrial world. For attending this goal, it was chosen the S-segment car products, category that identifies the sport car as today’s Lotus. The inspiration for the project started from the top model in the past years of the car manufacturer Audi, or the Audi Quattro (1980-1991). This model represented all the time the most advanced technology in the automotive world of the house, and the most important thing was the all-wheel drive, therefore with four-wheel drive. In the following pages will be illustrated the summary of the path that led to the final product following the “instructions” of SDE method.
Keywords: 3D Printing | QFD | SDE | Sportcar
Abstract: This work is the outcome of a partnership between the Department of Industrial Engineering of the University of Bologna and the Rizzoli Orthopedic Institute of Bologna. The aim of this collaboration is using medical engineering tools during orthopedic surgeries. This article focuses on the design and construction of a custom-made surgical guide for cubitus varus. The guides are special aids that allow surgeons to perform operations smoothly, to achieve the planned result and to reduce the risk of inaccuracy. They are obtained with an additive manufacturing process that starts from a 3D digital model of the patient's bone obtained from CT scans and allow designing patient-specific templates using specific software as the Creo Parametric CAD. For the proper functioning of the guide the internal shape must correspond to the external profile of the patient's bone. In this way, the tool obtained fits exactly to the bone and it is possible to direct the cutting during surgery in a very specific direction as identified in the preoperative planning phase.
Keywords: 3D Printing | Cutting guides | Pediatric Orthopedics | Surgery and Diagnostics
Abstract: Additive manufacturing represents one of the most promising and innovative technologies of the moment. In fact, it is considered among the nine technological pillars on which Industry 4.0 is based. In particular, it has received a lot of interest from industries, educational institutions and government agencies. For these reasons, it is necessary to develop and train a specialised workforce and to prepare it for these new opportunities. This work aims to investigate, through the completion of a survey based on a systematic review of the literature, the current state of education and dissemination of educational practices related to the training of young engineers at university on the issues of additive manufacturing and related to Industry 4.0. The results show that the introduction of additive manufacturing education represents an important leverage in the preparation of young engineers who benefit from it both in terms of personal preparation and in terms of learning and refining different skills. However, certain aspects, linked to the need to have adequate equipment and a properly trained teaching staff, should not be overlooked.
Keywords: 3D printing | Additive manufacturing | Engineering education | Industry 4.0 | Systematic literature review
Abstract: This paper aims to provide the study of a design strategy for 3D printing production process, given its recent development, as well as that of high-performance materials. In particular, we focus on the blade of a wind generator by evaluating new construction methods deriving from new design approaches. The strategies used for the present study are described as follows: firstly, it was necessary to proceed to redesign the blade, by CAD software in order to menage a 3D model for the study and to initialize the whole project; then, the FEM analysis to validate the study. Finally, the AM (Additive Manufacturing) theorization and simulation for both a scaled blade and a full-sized one. The motivation behind this paper draws on the predominance and the constant evolution of the 3D printing in recent years, as well as the continuous research on both development and improvement of costs and performance of composite materials used.
Keywords: Composite Materials | Design for Additive Manufacturing | Finite Element Analysis | Wind-turbine
Abstract: Autologous ear reconstruction is the preferred treatment in case of partial or total absence of the patient external ear. This kind of surgery can be really challenging since precise replication of complex three-dimensional structure of the ear is crucial to provide the patients with aesthetically consistent reconstructed anatomy. Therefore, the results strongly depends on the “artistic skills” of the surgeon who is in charge to carry out a three-dimensional sculpture, which resembles the shape of a normal ear. In this context, the definition of a preoperative planning and simulation process based on the patient's specific anatomy may help the surgeon in speeding up the ear reconstruction process and, at the same time, to obtain better results, thus allowing a superior surgical outcome. In the present work the main required features for performing an effective simulation of the ear reconstruction are identified and a strategy for their interactive design and customization is devised with the perspective of a semi-automatization of the procedure. In detail, the paper provides a framework which start from the acquisition of 3D data from both a healthy ear of the patient (or, if not available e.g. due to bilateral microtia of the ear of one of his parents or from a template) and of costal cartilage. Acquired 3D data are properly processed to define the anatomical elements of the ear and to find, using nesting-based algorithms, the costal cartilage portions to be used for carving the ear itself. Finally, 3D printing is used to create a mockup of the ear elements and a prototype of the ear to be reconstructed is created. Validated on a test case, the devised procedure demonstrate its effectiveness.
Keywords: Additive manufacturing | Autologous ear reconstruction | Microtia | Preoperative planning | Reverse engineering
Abstract: The advantages of additive manufactured scaffolds, as custom-shaped structures with a completely interconnected and accessible pore network from the micro- to the macroscale, are nowadays well established in tissue engineering. Pore volume and architecture can be designed in a controlled fashion, resulting in a modulation of scaffold’s mechanical properties and in an optimal nutrient perfusion determinant for cell survival. However, the success of an engineered tissue architecture is often linked to its surface properties as well. The aim of this study was to create a family of polymeric pastes comprised of poly(ethylene oxide therephthalate)/poly(butylene terephthalate) (PEOT/PBT) microspheres and of a second biocompatible polymeric phase acting as a binder. By combining microspheres with additive manufacturing technologies, we produced 3D scaffolds possessing a tailorable surface roughness, which resulted in improved cell adhesion and increased metabolic activity. Furthermore, these scaffolds may offer the potential to act as drug delivery systems to steer tissue regeneration.
Keywords: additive manufacturing | mechanical analysis | mesenchymal stem cells | microparticles | polymers | tissue engineering
Abstract: The concept of magnetic guidance has opened a wide range of perspectives in the field of tissue regeneration. Accordingly, the aim of the current research is to design magnetic responsive scaffolds for enhanced bone tissue regeneration. Specifically, magnetic nanocomposite scaffolds are additively manufactured using 3D fibre deposition technique. The mechanical and magnetic properties of the fabricated scaffolds are first assessed. The role of magnetic features on the biological performances is properly analyzed.
Keywords: bone tissue engineering | design for additive manufacturing | magnetic nanocomposite scaffolds | mechanical and functional properties
Abstract: Additive manufacturing (AM) is changing our current approach to the clinical treatment of bone diseases, providing new opportunities to fabricate customized, complex 3D structures with bioactive materials. Among several AM techniques, the BioCell Printing is an advanced, integrated system for material manufacture, sterilization, direct cell seeding and growth, which allows for the production of high-resolution micro-architectures. This work proposes the use of the BioCell Printing to fabricate polymer-based scaffolds reinforced with ceramics and loaded with bisphosphonates for the treatment of osteoporotic bone fractures. In particular, biodegradable poly(ε-caprolactone) was blended with hydroxyapatite particles and clodronate, a bisphosphonate with known efficacy against several bone diseases. The scaffolds’ morphology was investigated by means of Scanning Electron Microscopy (SEM) and micro-Computed Tomography (micro-CT) while Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) revealed the scaffolds’ elemental composition. A thermal characterization of the composites was accomplished by Thermogravimetric analyses (TGA). The mechanical performance of printed scaffolds was investigated under static compression and compared against that of native human bone. The designed 3D scaffolds promoted the attachment and proliferation of human MSCs. In addition, the presence of clodronate supported cell differentiation, as demonstrated by the normalized alkaline phosphatase activity. The obtained results show that the BioCell Printing can easily be employed to generate 3D constructs with predefined internal/external shapes capable of acting as a temporary physical template for regeneration of cancellous bone tissues.
Keywords: Additive manufacturing | Biocompatibility | Bone substitute | Clodronate | Composite scaffold design | Hydroxyapatite | Mechanical analysis | Poly(ε-caprolactone) | Thermal analysis | X-ray Photoelectron Spectroscopy
Abstract: Learning from Nature and leveraging 3D printing, mechanical testing, and numerical modeling, this study aims to provide a deeper understanding of the structure-property relationship of crystal-lattice-inspired materials, starting from the study of single unit cells inspired by the cubic Bravais crystal lattices. In particular, here we study the simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC) lattices. Mechanical testing of 3D-printed structures is used to investigate the influence of different printing parameters. Numerical models, validated based on experimental testing carried out on single unit cells and embedding manufacturing-induced defects, are used to derive the scaling laws for each studied topology, thus providing guidelines for materials selection and design, and the basis for future homogenization and optimization studies. We observe no clear effect of the layer thickness on the mechanical properties of both bulk material and lattice structures. Instead, the printing direction effect, negligible in solid samples, becomes relevant in lattice structures, yielding different stiffnesses of struts and nodes. This phenomenon is accounted for in the proposed simulation framework. The numerical models of large arrays, used to define the scaling laws, suggest that the chosen topologies have a mainly stretching-dominated behavior- A hallmark of structurally efficient structures-where the modulus scales linearly with the relative density. By looking ahead, mimicking the characteristic microscale structure of crystalline materials will allow replicating the typical behavior of crystals at a larger scale, combining the hardening traits of metallurgy with the characteristic behavior of polymers and the advantage of lightweight architected structures, leading to novel materials with multiple functions.
Keywords: 3D printing | bioinspired materials | lattice structure | lightweight structure | trabecular structure
Abstract: Purpose: This paper aims to investigate the feasibility of supportless printing of lattice structures by metal fused filament fabrication (MF3) of Ti-6Al-4V. Additionally, an empirical method was presented for the estimation of extrudate deflection in unsupported regions of lattice cells for different geometric configurations. Design/methodology/approach: Metal-polymer feedstock with a solids-loading of 59 Vol.% compounded and extruded into a filament was used for three-dimensional printing of lattice structures. A unit cell was used as a starting point, which was then extended to multi-stacked lattice structures. Feasible MF3 processing conditions were identified to fabricate defect-free lattice structures. The effects of lattice geometry parameters on part deflection and relative density were investigated at the unit cell level. Computational simulations were used to predict the part quality and results were verified by experimental printing. Finally, using the identified processing and geometry parameters, multi-stacked lattice structures were successfully printed and sintered. Findings: Lattice geometry required considerable changes in MF3 printing parameters as compared to printing bulk parts. Lattice cell dimensions showed a considerable effect on dimensional variations and relative density due to varying aspect ratios. The experimental printing of lattice showed large deflection/sagging in unsupported regions due to gravity, whereas simulation was unable to estimate such deflection. Hence, an analytical model was presented to estimate extrudate deflections and verified with experimental results. Lack of diffusion between beads was observed in the bottom facing surface of unsupported geometry of sintered unit cells as an effect of extrudate sagging in the green part stage. This study proves that MF3 can fabricate fully dense Ti-6Al-4V lattice structures that appear to be a promising candidate for applications where mechanical performance, light-weighting and design customization are required. Originality/value: Supportless printing of lattice structures having tiny cross-sectional areas and unsupported geometries is highly challenging for an extrusion-based additive manufacturing (AM) process. This study investigated the AM of Ti-6Al-4V supportless lattice structures using the MF3 process for the first time.
Keywords: Additive manufacturing | Deflection prediction | Finite element analysis simulation | Lattice structure | Metal fused filament fabrication | Titanium Ti-6Al-4V
Abstract: Additive Manufacturing (AM), allowing the layer-by-layer fabrication of products characterized by a shape complexity unobtainable with conventional manufacturing routes, has been widely recognized as a disruptive technology enabling the transition to the Industry 4.0. In this context, the design of a Portable Assisted Mobile Device (PAMD) prototype was considered as a case study. The best practices of the re-design for AM were applied to three of the main structural components, and the most sustainable manufacturing approach between AM processes and the conventional ones was identified with respect to cumulative energy demand, carbon dioxide emissions and costs. The paper aims to promote the debate concerning the correlation between design choices, process selection and sustainable product development.
Keywords: Cost assessment | Design for Additive Manufacturing | Energy efficiency | Portable Assisted Mobile Device (PAMD)
Abstract: Additive Manufacturing (AM) technologies have expanded the possibility of producing unconventional geometries, also increasing the freedom of design. However, in the designer’s everyday work, the decision regarding the adoption of AM for the production of a component is not straightforward. In fact, it is necessary to process much information regarding multiple fields to exploit the maximum potential of additive production. For example, there is a need to evaluate the properties of the printable materials, their compatibility with the specific application, redesign shapes accordingly to AM limits, and conceive unique and complex products. Additionally, procurement and logistics evaluations, as well as overall costs possibly extending to the entire life cycle, are necessary to come to a decision for a new and radical solution. In this context, this paper investigates the complex set of information involved in this process. Indeed, it proposes a framework to support and guide a designer by means of a structured and algorithmic procedure to evaluate the opportunity for the adoption of AM and come to an optimal design. A case study related to an ultralight aircraft part is reported to demonstrate the proposed decision process.
Keywords: Additive manufacturing | Design for additive manufacturing | Multi criteria decision‐making | Product design
Abstract: Purpose: To determine the targeting accuracy of brain radiosurgery when planning procedures employing different MRI and MRI + CT combinations are adopted. Materials and method: A new phantom, the BrainTool, has been designed and realized to test image co-registration and targeting accuracy in a realistic anatomical situation. The phantom was created with a 3D printer and materials that mimic realistic brain MRI and CT contrast using a model extracted from a synthetic MRI study of a human brain. Eight markers distributed within the BrainTool provide for assessment of the accuracy of image registrations while two cavities that host an ionization chamber are used to perform targeting accuracy measurements with an iterative cross-scan method. Two procedures employing 1.5 T MRI-only or a combination of MRI (taken with 1.5 T or 3 T scanners) and CT to carry out Gamma Knife treatments were investigated. As distortions can impact targeting accuracy, MR images were preliminary evaluated to assess image deformation extent using GammaTool phantom. Results: MR images taken with both scanners showed average and maximum distortion of 0.3 mm and 1 mm respectively. The marker distances in co-registered images resulted below 0.5 mm for both MRI scans. The targeting mismatches obtained were 0.8 mm, 1.0 mm and 1.2 mm for MRI-only and MRI + CT (1,5T and 3 T), respectively. Conclusions: Procedures using a combination of MR and CT images provide targeting accuracies comparable to those of MRI-only procedures. The BrainTool proved to be a suitable tool for carrying out co-registration and targeting accuracy of Gamma Knife brain radiosurgery treatments.
Keywords: 3D MR image distortion phantom | 3D printing | Brain phantom | MR/CT imaging quality control | Stereotactic radiosurgery accuracy
Abstract: The primary task of machine tools is simultaneously positioning and orienting the cutting tool with respect to the work piece. The mechanism must avoid positioning errors, and limit forces and torques required to the motors. A novel approach for combined design and control of manufacturing means is proposed in this work. The focus is on the optimization of the control logic of a redundant 6 axis milling machine, derived from the 5 axis milling machine by adding redundant degree of freedom to the work piece table. The new mechanism is able to fulfill a secondary task due to the introduction of redundancy. The proposed methodology sets as secondary task the minimization of the rotary motors torque, or the minimization of the norm of the positioning error. The control is based on the solution of a constrained optimization problem, where the constraints equations are the kinematic closure equations, and the objective function is the table motor torque or the positioning error of the tool tip. The implementation of this framework in the virtual machine model of the mechanism shows an improvement of the performances: actually, the introduction of a redundant axis allows the minimization of the torques and position errors.
Keywords: Additive manufacturing | Machine tool | Mechanism redundancy | Optimization
Abstract: The cooling of a melt corresponding to the eutectic between wollastonite (CaSiO3) and diopside (CaMgSi2O6) determines the synthesis of an interesting example of alkali-free bioactive glass, easily converted into glass-ceramics featuring two silicate phases, coupled also with åkermanite (Ca2MgSi2O7), by sinter-crystallization of fine glass powders at 1000°C. The fabrication of scaffolds by digital light processing of glass powders suspended in a photo-curable, sacrificial binder, is a well-established technique; the present paper aims at disclosing novel approaches, concerning the topology of scaffolds, offering components with remarkable strength, especially in bending conditions. As an alternative, glass-ceramic foams were fabricated by the firing of porous precursors derived from the gelation of suspensions of glass powders in alkali-free basic aqueous solution.
Keywords: additive manufacturing | alkali-free bioactive glasses | bioactive glass-ceramics | gel casting | scaffolds | sinter-crystallization
Abstract: Additive manufacturing technologies, compared to conventional shaping methods, offer great opportunities in design versatility, for the manufacturing of highly porous ceramic components. However, the application to glass powders, later subjected to viscous flow sintering, involves significant challenges, especially in shape retention and in the achievement of a substantial degree of translucency in the final products. The present paper disclosed the potential of glass recovered from liquid crystal displays (LCD) for the manufacturing of highly porous scaffolds by direct ink writing and masked stereolithography of fine powders mixed with suitable organic additives, and sintered at 950◦C, for 1–1.5 h, in air. The specific glass, featuring a relatively high transition temperature (Tg~700◦C), allowed for the complete burn-out of organics before viscous flow sintering could take place; in addition, translucency was favored by the successful removal of porosity in the struts and by the resistance of the used glass to crystallization.
Keywords: Additive manufacturing | Direct ink writing | Glass recycling | LCD glass | Scaffolds
Abstract: The introduction of digital workflows and their combination with miniscrew assisted appliances has opened new and enthusiastic perspectives in modern orthodontics. However, in all digital workflows currently in use for orthodontic tooth movement, the miniscrews are inserted first in the maxillary bone, often by means of a surgical guide, and then the appliance is fabricated and secured over the miniscrews with different fixation mechanisms. By doing so, some adaptation problems can be encountered while securing the appliance over the miniscrews, and the chairside time required can therefore be significant. In the present study, we introduce a digital workflow for the design and fabrication of a new appliance, customized on the individual morphology of maxillary bone by using patient Cone Beam Computed Tomography CBCT, for sagittal and vertical orthodontic tooth movement (DIVA, divergent anchors). Differently from the existing protocols, the appliance is cemented first intraorally, serving as a surgical guide for the subsequent insertion of miniscrews. In this way, the adaptation problems are avoided and the chair-side time is reduced.
Keywords: 3D printing | CAD/CAM | Digital orthodontics | DIVA | Laser melting | Miniscrew | Tooth anchorage
Abstract: Metal additive manufacturing is proposed as route for the manufacturing of moulds for expanded polymer parts. The traditional tools used in steam-chest moulding technologies can be replaced by lighter moulds accurately designed and produced by the laser-powder bed fusion technology, with significantly reduced thermal capacity and optimized ability to homogeneously deliver the steam throughout the part volume. The general design approach is described and the performance of the innovative tested solution is presented by the discussion of a case study. The experimental tests carried out on the moulds and moulding equipment prototypes showed remarkable reduction in cycle times and energy consumption when compared to a traditional steam-chest moulding used to print the same product.
Keywords: Additive manufacturing | Expanded polymers | Laser powder bed fusion | Mould design | Steam-chest moulding
Abstract: Recently, a variety of craniofacial approaches has been adopted to enter the skull base, including the endonasal endoscopic technique. An effective watertight technique, the reconstruction can be performed using different materials, both autologous and non-autologous, individually or combined in a multilayer fashion. The current study focuses on the development of new advanced devices and techniques that help to reduce the postoperative cerebrospinal fluid leak rate. Additive manufacturing allows the design of devices with tailored structural and functional features, as well as injectable semi-interpenetrating polymer networks and composites; therefore, specific mechanical/rheological and injectability studies are valuable. Accordingly, we propose new additive manufactured and injectable devices.
Keywords: Additive manufacturing | CSF leakage | Design of injectable systems | Endoscopic endonasal surgery | Reverse engineering | Skull base reconstruction
Abstract: It has been widely reported that breast reconstruction improves the quality of life of women who undergo mastectomy for breast cancer. This approach provides many psychological advantages. Today, different techniques are available for the breast oncoplastic surgeon that involve the use of breast implants and autologous tissues, also offering interesting results in terms of aesthetic and patient-reported outcomes. On the other hand, advanced technologies and design strategies (i.e. design for additive manufacturing, reverse engineering) may allow the development of customised porous structures with tailored morphological, mechanical, biological, and mass transport properties. For this reason, the current study deals with the challenges, principles, and methods of developing 3D additive manufactured structures in breast reconstructive surgery. Specifically, the aim was to design 3D additive manufactured poly(ε-caprolactone) scaffolds with different architectures (i.e. lay-down patterns). Preliminary mechanical and biological analyses have shown the effect of the lay-down pattern on the performances of the manufactured structures.
Keywords: Additive manufacturing | Breast reconstructive surgery | Fat grafting | Functional properties | Mechanical | Pore geometry and lay-down pattern | Reverse engineering | Scaffold design
Abstract: In the current research, an optimization design strategy for additive manufacturing processes based on extrusion/injection methods was extended to the fabrication of poly(ε-caprolactone) (PCL)/iron oxide (Fe3O4) scaffolds for tissue engineering. The attention was focused on four parameters: process temperature (PT), deposition velocity (DV), screw rotation velocity (SRV), slice thickness (ST). Specifically, PCL/Fe3O4 scaffolds were manufactured varying iteratively one parameter, while maintaining constant the other three parameters. A further insight into the influence of process parameters on the morphological features and mechanical properties of PCL/Fe3O4 scaffolds was provided.
Keywords: Design for additive manufacturing | Magnetic nanocomposite scaffolds | Mechanical and morphological properties | Tissue engineering
Abstract: Additive manufacturing is a technology for quickly fabricating physical models, functional prototypes, and small batches of parts by stacking two-dimensional layered features directly from computer-aided design data. One of the most important challenges in this sector relates to the capability to predict the build time in advance, since this is crucial to evaluating the production costs. In this paper, an accurate method for obtaining build-time is proposed. This method is based on an advanced GCode analyzer written in Python following an object-oriented paradigm for scalability and maintainability. Various examples are used to demonstrate the reliability of the algorithm, while its potential applications are also illustrated.
Keywords: Additive manufacturing | Build time estimation | Manufacturing costs | Process planning
Abstract: By additive manufacturing technologies, an object is produced deposing material layer by layer. The piece grows along the build direction, which is one of the main manufacturing parameters of Additive Manufacturing (AM) technologies to be set-up. This process parameter affects the cost, quality, and other important properties of the manufactured object. In this paper, the Objective Functions (OFs), presented in the literature for the search of the optimal build direction, are considered and reviewed. The following OFs are discussed: part quality, surface quality, support structure, build time, manufacturing cost, and mechanical properties. All of them are distinguished factors that are affected by build direction. In the first part of the paper, a collection of the most significant published methods for the estimation of the factors that most influence the build direction is presented. In the second part, a summary of the optimization techniques adopted from the reviewed papers is presented. Finally, the advantages and disadvantages are briefly discussed and some possible new fields of exploration are proposed.
Keywords: Build orientation factors | Cost analysis | Multi objective optimization | Part build orientation
Abstract: Additive manufacturing (AM) is a group of processes which manufacture a part by adding sequential layers of material on each other. In the last decade, these processes have been extensively applied in industry for constructing small volumes of complex, customized parts. Since parts are built layer-by-layer, the build orientation affects the surface quality and the total cost of the part. The search for optimal build orientation is not trivial since these factors are, typically, in conflict with each other. The major limitation of the methods described in the literature to choose the optimal build direction is in the insufficient accuracy of the estimates of the manufacturing cost and of the surface quality. These factors are very complex to be estimated, and accuracy in their evaluation requires methods that are very time-consuming. On the contrary, in practical use, a multi-objective optimization process requires an objective function that is reliable and easy to be evaluated. In order to overcome these problems, in this paper, original methods to estimate the manufacturing cost and surface quality as a function of build orientation are presented. They are implemented, for the fused deposition modeling (FDM) technology, in a multi-objective optimization problem that is solved by an S-metric selection evolutionary multi-objective algorithm (SMS-EMOA), obtaining an approximation of the Pareto front. The final selection of the recommended orientation is performed by the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Properly designed case studies are used to evaluate the reliability of the proposed method, and the results are compared with the state-of-the-art method to find optimal build orientation.
Keywords: Additive manufacturing | Build orientation | Multi-objective optimization | Surface quality
Abstract: Additive Manufacturing is a very time consuming technology. An estimation of the build time is fundamental to: Evaluate the production cost in budgeting process.Make use of optimization methods, which use as parameter the build time, for determining optimal build direction. In both these cases a fast and valid build time estimator, which can work with a few input data deducible from geometric model, is required. In the proposed paper a reliable parametric-based method to determine the build time for additive manufactured objects is provided. The implemented method is based on a back-propagation artificial neural network, which gives the possibility to implement the complex functions that elapse some driving build-time factors and the build time. The neural network training is based on data provided by a properly developed analyzer of the list of commands given to AM machines, which performs an analytical estimation of the build time. The implementation of the proposed methodology is illustrated and some comparisons between the real and estimated build-time are provided, then the results are critically analyzed.
Keywords: Adaptive model | Additive Manufacturing | Build time estimation | Process planning
Abstract: The aim of this work is the design of a new customised elbow orthosis completely realized by Additive Manufacturing and the development of generative algorithms for parametric modelling and creation of 3D patterns to be adapted to the CAD model. This work describes a method to perfect the design of a custom elbow orthosis. A reverse engineering approach has been used to digitalize the patient’s arm and the subsequent CAD modelling of the structure of the custom elbow orthosis has been performed. In particular, two algorithms have been implemented for the creation of 3D patterns and Voronoi tessellations. Subsequently, FEM analyses have been carried out to validate the design. Finally, a prototype of the elbow orthosis with Voronoi tessellation has been realized by means of the SLS technology. The results obtained have demonstrated that the implemented algorithm solved the problems found during CAD modelling with conventional software. Furthermore, the results of FEM analyses have validated the design choices. All this allowed realizing the prototype by AM technologies without problems. Moreover, the new proposed modelling approaches allows creating, in an interactive way, patterns on complex surfaces. The results of this research activity present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to the modelling for Additive Manufacturing. Furthermore, another innovative characteristic of the device is the use of torsion springs that simulate the action of physiotherapists during exercises for patient rehabilitation.
Keywords: Additive manufacturing | Computer aided design | Elbow orthosis | Generative design | Reverse engineering
Abstract: Purpose: The purpose of this paper is to implement a new process aimed at the design and production of orthopaedic devices fully manufacturable by additive manufacturing (AM). In this context, the use of generative algorithms for parametric modelling of additively manufactured textiles (AMTs) also has been investigated, and new modelling solutions have been proposed. Design/methodology/approach: A new method for the design of customised elbow orthoses has been implemented. In particular, to better customise the elbow orthosis, a generative algorithm for parametric modelling and creation of a flexible structure, typical of an AMT, has been developed. Findings: To test the developed modelling algorithm, a case study based on the design and production of an elbow orthosis made by selective laser sintering was investigated. The obtained results have demonstrated that the implemented algorithm overcomes many drawbacks typical of the traditional computer aided design (CAD) modelling approaches. The parametric CAD model of the orthosis obtained through the new approach is characterised by a flexible structure with no deformations or mismatches and has been effectively used to produce the prototype through AM technologies. Originality/value: The obtained results present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to modelling for AM in different application fields.
Keywords: Additive manufacturing | Additively manufactured textiles | AM technologies | CAD modeling | Elbow orthosis | Generative algorithms
Abstract: Planning prototyping strategies for conceptual design purposes is a crucial activity, which needs a clear understanding of the potentialities of the different typologies of prototype. Therefore, to prepare future designers, it is very important to provide the required information in design-related academic courses. However, prototypes and prototyping activities are often taught in specific courses with a major emphasis on the underpinning technologies, but with limited attention on design implications, especially about the fuzzy-front-end of the design process. The work presented in this paper aims at investigating about how students perceive the usefulness of prototypes during conceptual design activities, in order to provide first indications about the gap to be filled. To this purpose, two classes of students participated to an experimental session, and were asked to perform a conceptual design task individually. Subsequently, they participated to an on-line survey developed to gather information about the perceived usefulness of prototypes, in relation to the performed conceptual design activity. Several findings have been obtained from this work, but maybe the most impacting one concerns the different consideration that the two samples of students had about the fidelity of prototypes. Indeed, differently from what recently highlighted in current literature, it emerged that engineering students preferred low-fidelity prototypes. However, other unexpected evidences have been found, which highlight that at least for the considered institution, students still lack a comprehensive understanding of the design-related potentialities of prototypes.
Keywords: Additive manufacturing | CAD | Design | Design education | Engineering education | Prototyping
Abstract: The interest in developing customized external orthopaedic devices, thanks to the advent of Additive Manufacturing (AM), has grown in recent years. Greater attention was focused on upper limb casts, while applications to other body’s parts, such as the neck, were less investigated. In this paper the computer aided design (CAD) modelling, assessment and 3D printing with fused deposition modelling (FDM) of a customized neck orthosis are reported. The modelling, based on anatomic data of a volunteer subject, was aimed to obtain a lightweight, ventilated, hygienic and comfortable orthosis compared to the produced medical devices generally used for neck injuries. CAD models with different geometrical patterns, introduced for lightening and improving breathability, were considered, specifically, a honeycomb pattern and an elliptical holes pattern. These models were structurally assessed by means of finite elements analysis (FEA). Furthermore, an innovative composite material was considered for 3D printing. The material, Hemp Bio-Plastic® (HBP), composed by polylactic acid (PLA) and hemp shives, offers different advantages including lightweight, improved superficial finish and antibacterial properties. The results obtained in terms of design methodology and manufacturing by 3D printing of a prototype have shown the feasibility to develop customized cervical orthoses, with potentially improved performance with respect to cervical collars available on the market also thanks to the use of the innovative composite material.
Keywords: Additive Manufacturing | Bio-composite | CAD | Neck orthosis
Abstract: The use of modeling and ergonomic analysis software is a widespread practice in the industrial sector to effectively improve the operator’s well-being and operating comfort within the workplace. In this context, the paper proposes a Mixed Reality system for the ergonomic assessment of industrial workstations. Specifically, the proposed system integrates motion capture tools, a head-mounted display device, and ergonomic analysis software to simulate and analyse the operations to be carried out within a virtual workplace where some physical components, with which the operator interact, are prototyped through 3D printing technology in order to make the simulation as realistic as possible. The proposed Mixed Reality system in fact increases the realism of the simulation and improves the effectiveness of the ergonomics analysis thanks to the haptic feedback that the user perceives when manipulating the physical objects.
Keywords: Ergonomics | Industry 4.0 | Mixed Reality | Rapid prototyping
Abstract: Autonomous Surface Vehicles are versatile marine vehicles that allow to fulfill a variety of offshore activities. Their versatility has been appreciated by the marine and aquatic science community, in fact, in the last years, a large number of ASVs have been developed in research projects and introduced in the market. In this paper, the design and simulation of a small-sized ASV for seabed mapping of shallow waters are described. The vehicle is characterized by catamaran shape, low draft, jet-drive propellers that allow its deployment from the shore, and a payload of 20 kg. The design process has been carried out with the aim to realize a vehicle characterized by ease of transportability and deployment, available payload and performance in terms of speed and endurance. Three hull types have been modelled in a computer-aided design environment and then optimized through fluid dynamics analysis for a cruise speed of 1.5 kN. The results of these simulations have been used to choose the best hull shape in terms of resistance, in order to comply with the constraints of autonomy and available payload. Finally, a scaled model of the best hull shape has been then tested in a circulating water channel to validate simulation data.
Keywords: Additive manufacturing | Autonomous Surface Vehicle | Modeling and simulation | Shape design
Abstract: This paper describes an innovative 3D-printed beam-based lightweight structure that is used to increase the adhesion strength of metal-composite joints without damaging the composite fibers. It is conceived as the interface between the two parts to be joined: by filling the voids of this structure with resin, a mechanical interlocking effect can be generated to enhance the mechanical properties of the junction. A dedicated design workflow was defined to explore different types of 3D beam-based structures, starting from the analysis of the main failure modes of this type of junction. Tensile tests were performed on both polymeric and metal samples to validate the effectiveness of this interlocking strategy. Results demonstrated an increase in the adhesion strength relative to standard adhesive joints. A possible practical implementation is also discussed: a new type of insert is presented for application in metal-to-polymer composite joints. Finally, such a beam-based joining approach also represents an innovative application in the field of design for additive manufacturing.
Keywords: 00-01 | 99-00 | Design for additive manufacturing | Lattice structures | Material extrusion | Metal-composite junctions | Powder bed fusion
Abstract: The recent interest in human-robot interaction requires the development of new gripping solutions, compared to those already available and widely used. One of the most advanced solutions in nature is that of the human hand, and several research contributions try to replicate its functionality. Technological advances in manufacturing technologies and design tools are opening possibilities in the design of new solutions. The paper reports the results of the design of an underactuated artificial robotic hand, designed by exploiting the benefits offered by additive manufacturing technologies.
Keywords: 3D printing | additive manufacturing | design for additive manufacturing | mechatronics
Abstract: A considerable part of the design literature focuses on creativity and puts forward means to enhance creativity. It is assumed that boosting creativity results in product improvements and benefits for many stakeholders, starting from the recipients of design deliverables. However, the actual outcomes of creative endeavors and, especially, creative products have never been assessed systematically. Within this overall goal, the present paper compares the results of two experiments in which the same participants were involved. Both experiments were meant to evaluate according to multiple dimensions couples of products, where an element of the pair was subjected to some variations. The experiments foresaw the use of eye-trackers to achieve additional behavioral information. As creativity or variations thereof (novelty, unusualness) were assessed, it is possible to infer dimensions of value that are affected by creativity in multiple settings. The outcomes show that creative products significantly give rise to increased exploration time and efforts to make sense out of objects, but this process leads nevertheless to difficulties in understanding the products and to the identification of some disadvantages. According to these preliminary results, the relationship between creativity and perceived value, as well as their measurement, is overall dubious and highly depending on circumstances. While the authors support the relevance of design creativity, the paper urges to consider value at the same time.
Keywords: Design creativity | Eye-tracking | Fused Deposition Modelling | Perceived value | Product evaluation
Abstract: This paper presents a methodological procedure, based on the anatomical reconstruction and constrained deformation, to design custom-made implants for forehead augmentation in people affected by Apert syndrome, experiencing a frontal bone deficiency. According to the anthropometric theory, a cranial landmarks identification procedure was applied to retrieve, from a repository, a healthy skull, used as reference geometry for implant modelling. Then, using constrained deformation and free-form modelling techniques, it was possible to design a patient-specific implant. At last, the implant was realised using a custom mould, specially designed according to the patient’s needs to provide an accurate fit of the defect site. The design procedure was tested on a patient suffering from Apert syndrome. Three implants were virtually modelled and 3D-printed for pre-surgical evaluation. Their shapes were 3D compared with a reference one (handcrafted by a surgeon) to test the accuracy. Deviations are negligible, and the customised implant fulfilled the surgeon’s requirements.
Keywords: Computer-aided design | Craniomaxillofacial surgery | Implant design | Medical devices | Rapid prototyping
Abstract: The availability of advanced tools able to model complex geometries along with the relaxing of the constraints related to the manufacturing technologies are heavily transforming the design approach in many fields, including healthcare. The focus of this paper is on the optimization of porous lightweight cellular geometries in the orthopedic implants design: lattice structures have proven to fulfill the biological, mechanical, and technological constraints required in designing load bearing devices. The aim is to collect the information provided by the related literature to describe the effects induced by the selection of parameters designing lattice gyroid structures for orthopedic implants.
Keywords: custom metal implant | design for additive manufacturing | gyroid | metallic lattice structures | triply periodic minimal surface
Abstract: Computer Numerical Control (CNC) milling is still today the elective process for the production of single-piece impellers, as it can reliably produce complex geometries, removing the need for additional manufacturing processes. Nevertheless, Additive Manufacturing is winning more and more ground due to its ability to make components of any geometry that cannot be produced using subtractive techniques. As a result, the use of this technology can eventually be seen as the key to develop high-performance rotor components. In this scenario, the design of 3D impellers does not make an exception. Accordingly, the present paper proposes a general framework for engineered re-design and manufacture of 3D impellers installed on centrifugal compressors by exploiting Topology Optimization and Additive Manufacturing's potential. The procedure investigates also the rotoric component's best configuration for both static and dynamic behavior. Finally, the topology-optimized component is produced with AM through the use of suitable materials that can ensure efficient mechanical efficiency to prove the manufacturability of the entire procedure. To validate the proposed framework, the complete re-design of a 3D impeller of a major Italian-based Oil Gas company is carried out, demonstrating that the re-thinking of the component in terms of Topology Optimization is a straightforward approach to increase the overall performance of the produced rotoric part.
Keywords: 3D impellers | additive manufacturing | design | topology optimization | turbomachinery
Abstract: Purpose: The purpose of this study is the evaluation of advantages and criticalities related to the application of addtive manufacturing (AM) to the production of parts for musical instruments. A comparison between traditional manufacturing and AM based on different aspects is carried out. Design/methodology/approach: A set of mouthpieces produced through different AM techniques has been designed, manufactured and evaluated using an end-user satisfaction-oriented approach. A musician has been tasked to play the same classical music piece with different mouthpieces, and the sound has been recorded in a recording studio. The mouthpiece and sound characteristics have been evaluated in a structured methodology. Findings: The quality of the sound and comfort of 3D printed mouthpieces can be similar to the traditional ones provided that an accurate design and proper materials and technologies are adopted. When personalization and economic issues are considered, AM is superior to mouthpieces produced by traditional techniques. Research limitations/implications: In this research, a mouthpiece for trombone has been investigated. However, a wider analysis where several musical instruments and related parts are evaluated could provide more data. Practical implications: The production of mouthpieces with AM techniques is suggested owing to the advantages which can be tackled in terms of customization, manufacturing cost and time reduction. Originality/value: This research is carried out using a multidisciplinary approach where several data have been considered to evaluate the end user satisfaction of 3D printed mouthpieces.
Keywords: Additive manufacturing | Dental materials | Fused deposition modelling | Musical instruments | Stereolithography
Abstract: The interest of industrial companies for the Additive Manufacturing (AM) technology is growing year after year due to its capability of producing components with complex shapes that fit industrial engineering necessities better than traditionally manufactured parts. However, conventional Computer-Aided Design (CAD) software are often limited for the design and representation of complex geometries, especially when dealing with lattice structures: these are bio-inspired structures composed of repeated small elements, called struts, which are combined to shape a unit cell that is repeated across a domain. This design method generates a lightweight but stiff component. The scope of this work is to analyse the problem of the lattice structures representation in 2 D technical drawings and propose some contributions to support the development of Standards for their 2 D representation. This work is focused on the proposal of rules useful to represent such hierarchic structures. Python language and the open-source software FreeCad™ are used as a software platform to evaluate the suitability and usability of the proposed representation standard. This is based on simplified symbols to describe complex lattice structures instead of representing all the elements which constitute the lattice. The standard is thought to be used in technical 2 D drawings where assemblies are represented and lattice components are used (e.g. parts assembly, maintenance, parts catalogues). A case study is included to describe how the proposed standard could be integrated into a 2 D assembly drawing, following technical product documentation production typical workflow.
Keywords: Additive manufacturing | design | drawing standards | ISO standards | lattice structures
Abstract: Additive Manufacturing is becoming a suitable production process for many industries: it is based on the idea of adding material layer by layer, in opposite to traditional manufacturing processes. This technology shows advantages as design flexibility, internal logistics minimization and product customization that make it perfect to produce customized parts and all the applications where low production rates occur. The production of spare parts for classic or luxury cars is a field where Additive Manufacturing can be adopted because of low demand and relevant costs to manage stocks keeping several different parts in the after-sales inventory. The photogrammetry technique has been investigated to obtain the 3D model of the component to be replaced and send it to decentralized production centers equipped with 3D printers. This approach can enhance by far the supply chain management for automotive spare parts.
Keywords: Additive Manufacturing | Automotive | Maintenance | Photogrammetry | Supply chain management
Abstract: A significant growth of Additive Manufacturing technology has been noticed in the last few decades due to its well-established advantages. This production process based on the idea of adding material layer by layer, instead of removing it, has several advantages such as: time reduction in the design-to-manufacturing cycle, capability to produce complex shapes in a single piece thus reducing the connections, and weight saving just to mention the main significant. On the same wave of enthusiasm, the research community is significantly focused on this technology and many contributions that are focused on the whole range of aspects connected to this manufacturing way are already available. However, Additive Manufacturing is in a development phase, and the design tools, the material portfolio and the production methodologies are still far from the optimum typical of mature technologies. This paper critically reviews the Additive Manufacturing advantages and weaknesses which nowadays limits its wider application; a discussion about how these problems could be solved is included, together with an outlook of the challenges the practitioners must face off from nowadays up to a time window of ten years.
Keywords: Additive Manufacturing | Design tools | Future challenges | Technology review | Topological optimization
Abstract: In recent years, 3D printing gained considerable attention in the orthopedic sector. This work evaluates the feasibility of producing orthopedic scoliosis braces by 3D printing, comparing performance and costs with classical thermoforming procedures. Critical parameters, such as manufacture time, mechanical properties, weight, and comfort are carefully considered. Polyethylene terephthalate glycol-modified (PETG) was selected among the several filaments materials present on the market. Printed samples were analyzed with electronic microscope, tensile, and impact tests and compared with thermoformed polyethylene (PE) and polypropylene (PP) samples. Moreover, a cost analysis was carried out for the specific application. The thermoformed brace of a volunteer patient affected by scoliosis was reproduced using reverse-engineering techniques. The model was then printed as a single piece and postprocessed by an expert orthotist. Subsequently, the patient wore the brace in a pilot case to compare comfort and mechanical effectiveness. Results show that the 3D printing fabrication method is able to provide a valid alternative to the current fabrication methods, being also very competitive in terms of costs. The morphological analysis does not show critical defects in 3D printed samples, while the mechanical tests highlighted their anisotropy, with an overall brittleness of PETG samples in the direction orthogonal to the fibers. However, in terms of mechanical stresses, a back brace should never reach the polymer yield stress, otherwise the shape would be modified and the therapeutic effect could be compromised. Finally, the patient reported the perception of improved support and no significant comfort differences compared with the thermoformed brace.
Keywords: 3D printing | FDM | Manufacturing process | Mechanical characterization | Orthopedic scoliosis brace | PETG
Abstract: The present work aims to present the current virtual design process of scoliosis braces and propose an improvement by considering the internal geometry. Starting from the external scanning it is possible to apply only corrections that do not consider the interaction with the human body. For this reason we propose to embed the 3D model reconstruction of the skeleton of the patient from the medical images. This would bring to a better virtual design process that could help avoiding the current need for a physical positive mold. The final goal of such a change is to pass from the current thermoforming production to the use of additive manufacturing. In the paper, we briefly analyze the choice of the most convenient 3D printing technology and the selection of a proper material that can be comparable to the ones used for thermoforming. Finally, a case study is presented to test the assumptions regarding both the design and manufacturing processes.
Keywords: 3D printing | Scoliosis brace | Virtual design
Abstract: Additive manufacturing technology offers new design possibilities compared to traditional casting processes applied to metallic materials. Not only there are no limits in shape, but a higher microstructure control is allowed compared to traditional processes. Irrespective of the sample dimensions, the solidification defects induced by SLM process depend only on process parameters and do not vary from zone to zone of the component like in a casting component: the higher the casting dimensions and thickness variations, the lower the microstructure homogeneity resulting from different cooling conditions inside the casting itself. The effect of process parameters on porosity, in selective laser melted AlSi10Mg aluminium alloy, is carefully analysed with the aim to find optimal conditions that guarantee the maximum material density and the best mechanical properties.
Keywords: Additive manufacturing | Aluminium alloy | Mechanical properties | Porosity | Selective laser melting
Abstract: The freedom in geometry given by additive manufacturing allows to produce cellular materials, also called lattice structures, with unit cells and mesoscale features that are impossible to obtain with traditional manufacturing techniques. The geometric modeling of lattice structures still presents issues such as robustness and automation, but, with a novel modeling approach based on subdivision surface algorithm, these troubles were limited. Furthermore, the subdivision method smooths surfaces, avoiding sharp edges at nodal points and increasing performances in fatigue properties. The aim of this work is twofold; a. The subdivision surface method is validated through fatigue tests on specimen additively manufactured by selective laser melting technology in SS316L stainless steel; dynamic tests were carried out on two types of lattice structures based on cubic cell: one obtained with a traditional modeling method, one obtained with a subdivision surface approach. b. Additional tests on bulk cylindrical samples, allowed to propose a preliminary model that describes the fatigue behaviour of additively manufactured lattices as a function of the bulk material properties, considering the shape and scale effects coming from stress concentration factor, increased area, surface roughness and porosity of the part. Results show that the subdivision surface approach improves the fatigue life of lattice structures, as expected. More, the lattices have a worse fatigue life compared to the bulk samples due to the scale and shape effects, that results in a higher sensibility to surface and internal defects related to the manufacturing process.
Keywords: Additive manufacturing | Fatigue behaviour | Lattice structure | Scale effect | Shape effect
Abstract: The objective of this study is to demonstrate the possibility of obtaining a completely customized orthosis through the use of multi-material 3-D printing technique. Additive manufacturing with multi-material enables to print objects with two different materials at the same time. Two immiscible materials Polylactic Acid (PLA), Thermoplastic Polyurethane (TPU) are chosen to give the orthosis a good trade-off between flexibility and rigidity. Results show that with this innovative technology it is possible not only create complex functional geometries but also to overcome some of the issues associated with traditional immobilization techniques (plaster of Paris splints). Tensile and impact tests are performed on 3D printed specimens to analyze their toughness, rigidity and flexibility. Three different prototypes are developed varying the composition and the organization of the materials used. Results show that the proposed approach is capable of addressing all the issues associated with conventional plaster casts.
Keywords: 3D printing | Impact test | Multi-material printing | Orthosis | Polylactic Acid (PLA) | Tensile test | Thermoplastic Polyurethane (TPU)
Abstract: The work proposes a method of Topological Optimization of 3D surfaces using an algorithm that works by considering the distribution and intensity of stress on the studied component. Rather than acting on the mesh, this algorithm modifies directly the CAD, allowing its direct use avoiding any subsequent intervention. The algorithm has been developed using Rhino – Grasshopper. The FEM analyses have been performed using the Nastran solver within the Siemens NX environment. With this method the original non-optimized model is hollowed through a Voronoi tessellation that is managed through several parameters. Through an iterative process, the algorithm performs the hollowing on the original CAD, varying the size and distribution of the holes in function of the stresses. As case study, the authors considered a safety device that helps to prevent injuries to the necks of pilots of various high-speed motorsports (Head and Neck Support, HANS). The results of this work show the potentiality of this methodology, with which it is possible to obtain a much lighter device with the same mechanical performance.
Keywords: Additive Manufacturing | Mechanical design | Selective Laser Sintering | Topology Optimization
Abstract: Additive Manufacturing based on Powder Bed Fusion processes enables the construction of end-use functional metal components, making it feasible to design several level of geometrical complexity. Nevertheless, the printing process leads to material and shape defects, residual stress and induced distortions on final components that mainly are caused by the high thermal gradients associated to the intense and nonuniform power energy sources used to selectively melt metal powders. In this paper, techniques to reduce or prevent these effects are summarized. The more broadly Design for Additive Manufacturing approach based on the use on CAD platforms for product-process design is the backbone upon this research is based on. Specifically, the work presents a design method to predict drawbacks and improve the industrialization subphase. Laser-based Powder Bed Fusion technique is considered and the implementation and validation of the Selective Laser Melting process simulation is performed in order to support the method. Two case studies are presented. The former demonstrates the simulation implementation feasibility through a CAD platform. The latter validates the simulation results compared to experimental data for further method application.
Keywords: CAD platforms | design for additive manufacturing | industrialization | powder bed fusion | process simulation | selective laser melting
Abstract: The development of additive manufacturing allows the transformation of technological processes and the redesign of products. Among the most used methods to support additive manufacturing, the design can be optimised through the integration of topology optimisation techniques, allowing for creating complex shapes. However, there are critical issues (i.e., definition of product and process parameters, selection of redesign variants, optimised designs interpretation, file exchange and data management, etc.) in identifying the most appropriate process and set-ups, as well as in selecting the best variant on a functional and morphological level. Therefore, to fully exploit the technological potentials and overcome the drawbacks, this paper proposes a systematic redesign approach based on additive manufacturing technologies that integrate topology optimisation and a tool for selecting design variants based on the optimisation of both product and process features. The method leads to the objective selection of the best redesigned configuration in accordance with the key performance indicators (KPIs) (i.e., functional and production requirements). As a case study, the redesign of a medical assistive device is proposed, previously developed in fused filament fabrication and now optimised for being 3D printed with selective laser melting.
Keywords: Assistive device | Design for additive manufacturing | Design method | Design optimisation | Design variants selection | Redesign | Selective laser melting | Topology optimisation
Abstract: Collaborative robotics and additive manufacturing are two enabling technologies of the Industry 4.0 manufacturing paradigm. Their synergic integration requires novel and effective design approaches, aiming to the development of new reconfigurable solutions for customised processes and products. This work presents an integrated approach that exploits the capabilities of Cobots to mimic the repetitive and exhausting operator’s movements as well as the competitive advantages offered by additive manufacturing to realize tailored equipment. In particular, the case study shows the development of a customised device for the manipulation of biomedical components by means of a Cobot, which is introduced in a workstation to replace manual operations. Moreover, the flexibility and the effectiveness of a Cobot can be improved thanks to customised devices for gripping and pick-and-place operations based on a specific application. During the development phase, we simulated the assembly process, and tested different options. The final configuration, with conformal circuits and suction cups, can pick, manipulate and assembly the biomedical components, and thanks to a Fused Filament Fabrication technology is additively manufactured. In conclusion, this developed prototypal solution proves the real capabilities offered by integrating Cobots and additive manufacturing for the lean automation of a biomedical workstation.
Keywords: Additive manufacturing | Biomedical components | Collaborative robot | Design approach | Industry 4.0
Abstract: The presented paper suggests a design method which seeks to identify the best scheduling of human robot collaborative (HRC) operations with respect to a required safety level. The human behavior along manufacturing scenarios is effectively forecasted through dedicated computer-aided tools. Consequently, this method stresses the usage of virtual environment to replicate both human postures and robot encumbrances over the manufacturing operations. Moreover, it proposes a safety index formulation for HRC systems based on the minimum distance between human and robot (H-R). As results, the approach returns the safety index for every possible combination of H-R operations. Subsequently, a scheduling algorithm suggests the operations sequence depending on the expected value of the safety index, providing an evaluation of the time needed to complete the process. The method is validated on surface control phase involved in post-processing of parts produced by laser powder bed fusion (L-PBF) Additive Manufacturing.
Keywords: Additive Manufacturing | CAD-based methods | Human Robot Collaboration | Safety index | Task scheduling
Abstract: Additive Manufacturing is a widespread technology that may enhance product customization based on specific users’ needs, as in the case of assistive devices. Many chronic physical progressively disabling diseases, but also ageing, may cause severe limitations in daily life, which can be overcome by highly customized aids. Literature shows that the active involvement of the patient in the development of assistive devices through co-design allows for their greater therapeutic effectiveness and acceptance. Therefore, this paper proposes a methodological approach for the development of inclusive assistive devices to support daily activities in persons with disabling diseases of the upper-limb. The approach integrates co-design, standardized tools, and low- and high-tech prototyping techniques and tools, which lead to significant feedbacks from patients. The patients are encouraged to interact with conceptual prototypes through direct 3D CAD modelling and touch screen devices. Assessment tests highlight the suitability of the method to achieve the expected goals.
Keywords: Additive Manufacturing | Assistive device | Co-design | Hand pathologies | Inclusive method | Occupational therapy | Parametric modelling
Abstract: The aim of this paper is to analyze some critical issues in the Design for Additive Manufacturing workflow and evaluate the introduction of CAD platforms as backbone tools to shorten product development time and raise its efficiency. It is focused on the design of components to be printed by Powder Bed Fusion metal Additive Manufacturing. Even though the use of additive technologies firmly joins a CAD mathematical model and the actually printed component, the workflow from the concept to the definitive job may result in many sequential steps which have complex and slow relationships. Currently, at the state of art for the production of components specifically designed to be produced by additive manufacturing, there are issues both with the adoption of STL as interchange files and the not reversible sequence of tasks. For example, if a problem occurs in the part re-design during component industrialization, usually one must restart the work from the beginning. Thus, an improvement of the design workflow that could shorten time to product and improve both product performances and process quality and reliability, is necessary. In particular, the use of CAD platforms that integrates CAD and CAE tools has been investigated. An automotive case study, originally made by traditional subtractive technology (CNC milling), has been re-designed with topology optimization in order to be printed by Selective Laser Melting process with benefit of weight reduction. Design and industrialization tasks have been tested with respect to the selected integrated CAD platform, and potential improvements have been evaluated.
Keywords: Automotive | CAD platform | Design for Additive Manufacturing | Topology optimization
Abstract: This work is focused on the study of 3D prints applied in the orthopedic-pediatric field. The focus is therefore on all the processes that lead to obtaining 3D bone printing starting from the three-dimensional digital CAD model. Specifically, the case study concerns patients with flat foot pathology from tarsal synostosis. The final result of the printing process is a three-dimensional bone model reflecting the original anatomical structure. This is a useful tool for surgeons who can carry out a preventive analytical evaluation of the relative intervention methods. 3D printing can be useful both in the preoperative planning phase and during the operation. Depending on the case, it may be more convenient to use one material than another. For this reason, another goal set by this work concerns the study of materials used for 3D printing of bones.
Keywords: 3D Printing | Diagnostics | Pediatric Orthopedics | Surgery
Abstract: As Industry 4.0 is the driving force behind the manufacturing industry in this period, increasing importance is being attached to its enabling technologies, formerly known as the nine pillars. In particular, within this context, interest in Additive Manufacturing – AM is constantly growing. For this reason, the authors have considered as appropriate to carry out a literature search to assess whether there is any relationship between AM processes and product design and development practices after 2011. Particularly, the authors were interested in considering the use of additive technologies in relation to the TRIZ – theory of inventive problem solving - and its tools. To this end, it has been decided to carry out a search among the publications contained in the Scopus Database. 115 potential papers have been identified for analysis. After a careful selection, 14 papers, containing information on AM and TRIZ useful for our survey, were selected. Reading these works, it was possible to identify current research trends related to the use of creative problem solving strategies such as TRIZ and its combined use with AM, ranging from the definition of particular integrated methodologies of product development to the definition of guidelines for Design for AM or technological predictions, the state of the art of current research, highlights possible levers of intervention and potential developments and future trends.
Keywords: Additive Manufacturing | Industry 4.0 | Research trends | TRIZ
Abstract: In brain tumor surgery, an appropriate and careful surgical planning process is crucial for surgeons and can determine the success or failure of the surgery. A deep comprehension of spatial relationships between tumor borders and surrounding healthy tissues enables accurate surgical planning that leads to the identification of the optimal and patient-specific surgical strategy. A physical replica of the region of interest is a valuable aid for preoperative planning and simulation, allowing the physician to directly handle the patient’s anatomy and easily study the volumes involved in the surgery. In the literature, different anatomical models, produced with 3D technologies, are reported and several methodologies were proposed. Many of them share the idea that the employment of 3D printing technologies to produce anatomical models can be introduced into standard clinical practice since 3D printing is now considered to be a mature technology. Therefore, the main aim of the paper is to take into account the literature best practices and to describe the current workflow and methodology used to standardize the pre-operative virtual and physical simulation in neurosurgery. The main aim is also to introduce these practices and standards to neurosurgeons and clinical engineers interested in learning and implementing cost-effective in-house preoperative surgical planning processes. To assess the validity of the proposed scheme, four clinical cases of preoperative planning of brain cancer surgery are reported and discussed. Our preliminary results showed that the proposed methodology can be applied effectively in the neurosurgical clinical practice both in terms of affordability and in terms of simulation realism and efficacy.
Keywords: 3D casting | 3D printing | Additive manufacturing | Brain | Cancer | Computer aided design | Neurosurgery | Physical simulation | Preoperative planning | Virtual planning
Abstract: Although the wide diffusion and technological development of Additive Technologies, it is still unclear to what extent the related potentialities are actually exploited. The work described in this paper aims at developing an on-line survey to be administered to industrial practitioners from different types of firm to elicit the information required to better understand the role of additive technologies and/or prototypes. In particular, we developed a preliminary version of the survey, and tested it with a limited sample of academic participants. The followed procedure, which includes the administration of a NASA Task Load Index questionnaire to participants, allowed to rapidly receive important feedbacks to support the development of a robust survey. Once administered to the expected final participants, the survey is expected to provide information about which are the main technologies used by different industrial sectors, how firms currently select 3D printers, and how they are currently used for design purposes.
Keywords: 3D printing | Additive Manufacturing | Prototypes | Survey
Abstract: Peripheral venous access is an extremely common procedure, crucial in delivering drugs and collecting blood samples. It is associated to high failure rates, especially when pediatric subjects are involved, due to reduced limb size and low cooperation. Ultrasound can sensibly increase success rates and reduce the time required to perform the procedure, though a specific training is necessary to acquire adequate hand-eye coordination and simultaneously handle needle and probe. Commercially available simulators lack of realistic devices that reproduce anatomy and kinematics of pediatric patients. In this work, an echogenic simulator integrating direct 3D printing and silicone casting is proposed. More specifically, it replicates a five years old upper limb’s anatomy comprising an articulated skeleton, muscle tissues, skin and an integrated blood circuit. The devised simulator shows its effectiveness in terms of acoustic properties, articular kinematics reproduction and haptic feedback. Furthermore, the simulator can be easily customized according to specific training needs thanks to a highly flexible manufacturing process.
Keywords: 3D printing | Echogenic soft phantom | Peripheral venous access trainer | Silicone casting
Abstract: Additive manufacturing represents a powerful tool for the direct fabrication of lightweight and porous structures with tuneable properties. In this study, a fused deposition modelling/3D fibre deposition technique was considered for designing 3D nanocomposite scaffolds with specific architectures and tailored biological, mechanical, and mass transport properties. 3D poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) nanocomposite scaffolds were designed for bone tissue engineering. An optimisation design strategy for the additive manufacturing processes based on extrusion/injection methods was at first extended to the development of the PCL/HA scaffolds. Further insight into the effect of the process parameters on the mechanical properties and morphological features of the nanocomposite scaffolds was provided. The nanocomposite structures were analysed at different levels, and the possibility of designing 3D customised scaffolds for mandibular defect regeneration (i.e., symphysis and ramus) was also reported.
Keywords: Additive manufacturing | Design of Experiments | Nanocomposites | Reverse Engineering | Scaffold Design and Analysis
Abstract: Background: In the case of a degenerated intervertebral disc (IVD), even though spinal fusion has provided good short-term clinical results, an alteration of the spine stability has been demonstrated by long-term studies. In this context, different designs of IVD prostheses have been proposed as alternative to spinal fusion. However, over the past few years, much of the recent research has been devoted to IVD tissue engineering, even if several limitations related to the complex structure of IVD are still presented.Purpose/Aim: Accordingly, the aim of the current paper was to develop a strategy in designing customised multiphasic nucleus/annulus scaffolds for IVD tissue engineering, benefiting from the great potential of reverse engineering, additive manufacturing and gels technology.Materials and Methods: The device consisted of a customised additive-manufactured poly(ε-caprolactone) scaffold with tailored architectural features as annulus and a cell-laden collagen-low molecular weight hyaluronic acid-based material as nucleus with specific rheological and functional properties. To this aim, injectability and viscoelastic properties of the hydrogel were analyzed. Furthermore, a mechanical and biological characterization of cell-laden multiphasic nucleus/annulus scaffold was performed.Results and Conclusions: Analyses on the developed devices demonstrated appropriate viscoelastic and mechanical properties. As evidenced by rheological tests, the hydrogel showed a shear-thinning behaviour, supporting the possibility to inject the material. The mechanical characterization highlighted a compressive modulus which falls in the range of lumbar discs, with the typical initial J-shaped stress–strain curve of natural IVDs. Furthermore, preliminary biological tests showed that human mesenchymal stem cells were viable over the culture period.
Keywords: additive manufacturing | gels | intervertebral disc | Polymers | reverse engineering | tissue engineering
Abstract: Additive manufacturing applied to polymeric as well as metallic materials offers a lot of advantages, today not yet fully explored. They can potentially enhance the structural efficiency of the components, which means, for a given loading condition, the section uses as little material as possible. As a matter of fact, the complete freedom in parts shape design could be exploited to increase the fatigue strength of structural components by crack arresters (CAs) design. From classical fracture mechanic theories, it is well known that when the fatigue crack meets a hole, the consequent sudden reduction of the stress concentration ahead of the crack tip promotes the arrest of the crack propagation itself. Using additive manufacturing, it is now possible to design structural components with CAs in the vicinity of crack initiation points like notches. This paper is aimed at exploring, with preliminary experiments supported by numerical analyses, this possibility. It was found that crack arresters effectively enhance the fatigue life of a notched component provided that their shape and position are designed properly.
Keywords: Additive Manufacturing | Crack arrester | Crack growth | Fatigue | Stop-hole | Stress concentration
Abstract: Soundness of additively manufactured parts depends on a lot of process and geometrical parameters. A wrong process design leads to defects such as lack of fusion or keyhole porosity that have a detrimental effect on the mechanical properties of the printed parts. Process parameter optimization is thus a formidable challenge that requires in general a huge amount of experimental data. Among the others, heat source power and scan speed are the most defects-affecting parameters to be optimized. The energy density is used in literature to quantify their combination. Unfortunately, in different works it was demonstrated that it fails if used as design parameter mainly because it does not take into account the material properties and the interaction between heat source and the powder bed. In this contribution, a modified volumetric energy density equation that takes into account the powder-heat source interaction to optimize the combination of power-scan speed values for porosity assessment in powder bed fusion process design is proposed and verified on both AlSi10Mg alloy and Maraging steel 300.
Keywords: Additive manufacturing | Aluminium alloy | Energy density | Maraging steel | Porosity | Selective Laser Melting
Abstract: Additive manufacturing is an emerging technique that is not only subjected to the interest of academic world because of its peculiar characteristics to obtain new material properties and optimized 3D geometries, but it also finds the interest of the industrial sector because of the possibility to build advanced components never realized until now. Among the additive manufacturing processes, Laser Powder Bed Fusion process is perhaps the most used in producing components out of metallic materials. In particular, thanks to its low density and its hypoeutectic favourable composition, AlSi10Mg alloy is particular suitable for the production of lightweight components by additive manufacturing. However, for safety reasons, their mechanical, static and cyclic, characteristics need to be well understood and predicted. Unfortunately, they are dramatically influenced by process parameters that in turn may promote killer defects dangerous for the fatigue strength of load bearing mechanical components. This contribution is aimed at highlighting the influence of defects on the fatigue resistance of AlSi10Mg samples produced by laser powder bed fusion. The combination of process parameters were obtained that maximizes the fatigue strength and reduces the scattering of the results.
Keywords: Additive manufacturing | ALSi10Mg | Fatigue strength | Fractography | Laser powder bed fusion | Porosity
Abstract: The interest in Phase Change Materials (PCMs) has been continuously growing, since they were identified as a suitable way to store large quantities of thermal energy. Despite many PCMs being available on the market, almost all present a relatively low thermal conductivity, which limits the efficiency and the convenience of their use inside Latent Thermal Energy Storage (LTES) units. This paper proposes a novel method to overcome the low thermal conductivity drawback: additive manufacturing was used to realize three innovative 3D metallic periodic structures, with different base pore sizes (10, 20, and 40 mm) and constant porosity, to be filled with a suitable PCM. The samples were experimentally tested by analyzing the temperature field in a paraffin wax, which has a melting temperature of around 55 °C. Furthermore, several videos and images were taken during the charging (i.e. heating and melting) process, obtained by electrical heating (three heat fluxes corresponding to 10, 20, and 30 W were applied) and the discharging (i.e. solidification and cooling) process, where the heat was only rejected by natural convection with ambient still air. The coupling of PCMs and aluminum structures was demonstrated to enhance both the charging and the discharging processes.
Keywords: Additive manufacturing | PCM | Periodic structures | Phase change materials | Thermal energy storage
Abstract: Abstract: Additive manufacturing techniques areknown for the unrivalled geometric freedom they offer todesigners. It is one of the mainstays of “metal 3D-printing”,compared to casting, which, in contrast, implies morerestrictions because some shapes do not cool evenly or may needmoulds or forms. Despite the possible presence of defects insideadditive manufactured components, such as oxide films, pores orunmelted powder, they can be strongly reduced or controlled byprocess parameters optimization. That seems not true for acasting component, in which defects can vary a lot from zone tozone according to the solidification conditions. Porosityinducing process parameters in selective laser melted AlSi10Mgaluminium alloy are carefully analysed with the aim to findoptimal conditions that guarantee the maximum material densityand the best mechanical properties. Finally, a model is proposedthat correlates the amount of pores with the alloy ultimatetensile strength.
Keywords: Additive manufacturing | Aluminium alloy | Mechanical property | Porosity | Selective laser melting
Abstract: Additive Manufacturing (AM) technologies have greatly extended design possibilities and freedom. However, in the designer everyday work, the decision regarding the adoption of AM for some components is not straightforward. There is a need to evaluate the properties of the available materials, their compatibility with the specific application, redesign shapes accordingly to additive rather than subtractive or deforming processes, conceive merging components in unique complex multifunctional parts. Indeed, economic, procurement and logistics evaluations, possibly extended to the entire life cycle, are necessary to come to a decision for a new and radical solution. In this context, the paper investigates the complex set of information involved in the process to guide a designer in a structured assessment and evaluation of opportunities for the adoption of AM. The approach includes the analysis of the design requirements to evaluate the applicability of additive technologies. Selected design questions are presented as attention points to help designers in the decision-making process along with a metric to merge the answers in an overall compliance index. Finally, some test cases from the literature and industry are reported to validate the proposed decision process.
Keywords: Additive manufacturing | Decision-making | Design for additive manufacturing | Design process
Abstract: In the last decades a variety of innovative craniofacial approaches has been adopted to entire skull base. The endonasal endoscopic route has emerged as a suitable methodology for several skull base lesions. An effective watertight closure is essential to isolate the intracranial cavity in order to restore the natural intra and extradural compartment division, necessary to prevent postoperative cerebrospinal fluid (CSF) leakage and complications such as meningitis, brain herniation, and tension pneumocephalus. The reconstruction can be performed using different materials, both autologous (autologous grafts) and non-autologous, individually or combined in a multilayer fashion. The harvesting a nasoseptal flap is one of the most effective techniques: it reinforces the skull base closure granting isolation of the surgical field. The current study was focused on the development of new advanced devices and techniques, aiding in reducing postoperative CSF leak, which is one of the most feared complication of this surgical procedure. Additive manufacturing allows to design devices with tailored structural and functional features, in order to satisfy all the requirements. On the other hand, the development of injectable semi-IPNs and composites clearly benefits from specific mechanical/rheological and injectability studies. Accordingly, starting from some basic concepts, innovative principles and strategies were also proposed towards the design of additively manufactured and injectable devices.
Keywords: additive manufacturing | CSF leakage | design of injectable systems | endoscopic endonasal surgery | reverse engineering | skull base reconstruction
Abstract: Many women with early breast cancer undergo mastectomy as a consequence of an unfavorable tumor/breast ratio or because they prefer this option to breast conservation. As reported, breast reconstruction offers significant psychological advantages. Several techniques are currently available for the breast oncoplastic surgeon and offer interesting results in terms of aesthetic and patient-reported outcomes, using both breast implants and autologous tissues. On the other hand, advanced methodologies and technologies, such as reverse engineering and additive manufacturing, allow the development of customized porous scaffolds with tailored architectures, biological, mechanical and mass transport properties. Accordingly, the current research dealt with challenges, design methods and principles to develop 3D additively manufactured structures in breast reconstructive surgery.
Keywords: additive manufacturing | breast reconstructive surgery | design | fat grafting | reverse engineering | scaffold design
Abstract: The current research reports for the first time the use of blends of poly(ε-caprolactone) (PCL) and poly(ester amide) (PEA) for the fabrication of 3D additive manufactured scaffolds. Tailor made PEA was synthesized to afford fully miscible blends of PCL and PEA using different percentages (5, 10, 15 and 20% w/w). Stability, characteristic temperatures and material's compatibility were studied through thermal analyses (i.e., TGA, DSC). Even though DMTA and static compression tests demonstrated the possibility to improve the storage modulus, Young's modulus and maximum stress by increasing the amount of PEA, a decrease of hardness was found beyond a threshold concentration of PEA as the lowest values were achieved for PCL/PEA (20% w/w) scaffolds (from 0.39 ± 0.03 GPa to 0.21 ± 0.02 GPa in the analysed load range). The scaffolds presented a controlled morphology and a fully interconnected network of internal channels. The water contact angle measurements showed a clear increase of hydrophilicity resulting from the addition of PEA. This result was further corroborated with the improved adhesion and proliferation of human mesenchymal stem cells (hMSCs). The presence of PEA also influenced the cell morphology. Better cell spreading and a much higher and homogenous number of cells were observed for PCL/PEA scaffolds when compared to PCL ones.
Keywords: Additive manufacturing | Biological properties | Image analysis | Poly(ester amide) | Scaffold design | Thermal and mechanical properties
Abstract: This paper deals with parenthood perception (maternal and paternal) after the visualization and interaction (touch) with a 3D printed facial fetal model. The model is created using Additive Manufacturing techniques, starting from the image elaboration of routine ultrasound data. In this study, the method used for the elaboration and construction of 3D printable models of fetal faces starting from routine ultrasound images is briefly described. In addition, we present the results of a new survey conducted with future parents at the Altamedica clinic (Rome, Italy) to verify whether there are any benefits derived from the use of 3D printing models with future parents, both regarding the improvement of the parenthood experience, and the improvement of the understanding and collaboration with the physicians in case of fetal malformations, using 3D models coupled with the data of routine ultrasound examinations.
Keywords: 3D ultrasound | Additive manufacturing | Fetal face | Image processing | Parenthood perception | Survey
Abstract: The current research was focused on a further insight into the mechanical properties of 3D parts printed with virgin and recycled polylactic acid (PLA). A first set of specimens was printed with virgin PLA lament and mechanically tested. Such specimens were then ground up and re-extruded into filament using a homemade extruder. The re-extruded filament was employed to manufacture a new set of specimens which were also analysed. Three recycling processes were performed to assess the effect on the mechanical properties. The obtained results suggested that 3D printing with recycled PLA may be a viable option.
Keywords: Additive Manufacturing | Mechanical properties | Recycled polymers
Abstract: Additive Manufacturing (AM) is a technology for quickly fabricating physical models, functional prototypes and small batches of parts, by stacking two-dimensional layered features, directly from computer-aided design (CAD) data. One of the most important challenges in this sector is represented by the capacity to predict in advance build time required for manufacturing a part because it's crucial to evaluate production cost. In this paper, an accurate method for obtaining build time is proposed. This method is based on an advanced GCode reader written in Python following an Object Oriented paradigm for scalability and maintainability. Some examples were used to demonstrate the reliability of the algorithm and possible uses of it are illustrated.
Abstract: Orthoses are additional devices that help people with disabilities. The focus of this work is the design and manufacture of a new customized elbow orthosis completely made by Additive Manufacturing (AM). One of the innovative characteristic of the device is the use of torsion springs that simulate the action of physiotherapists during exercises for patient rehabilitation. Parametric modeling approach based on generative algorithms was used to design the device. Finally, FEM analyses have been performed to validate the design.
Keywords: 3D acquisition | Additive manufacturing | Computer aided engineering
Abstract: In this paper, a novel concept of robotic manipulator is developed for direct additive manufacturing on non-planar surfaces. The application scenario is the metal coating of the internal surface of radome systems, using frequency selective surface patterns. The manipulator is presented from the design, modeling, and control point of view. It is developed following an application-driven approach, meaning that the requirements from the application and the additive manufacturing technology are translated into the design specifications of the robotic system. Simulation results demonstrate that the proposed control strategy based on a decentralized architecture is satisfactory to accurately control the motion of the robotic mechanisms along the trajectory foresees by the direct additive manufacturing task.
Keywords: Additive manufacturing | Aerosol jet printing | Design method | Robot control | Virtual prototyping
Abstract: The paper presents the third version of the hybrid leg-wheel ground mobile robot Mantis, a small-scale platform designed for inspection and surveillance tasks. The locomotion system is based on the cooperating action of a couple of actuated front legs and wheels, along with a passive rear carriage. The system performs wheeled locomotion on even grounds and hybrid locomotion in case of terrain irregularities or obstacles. This architecture combines high speed, energy efficiency, maneuverability and stable camera vision on flat terrains with good motion capabilities in unstructured environments. In the embodiment design presented hereafter, referred to as Mantis 3.0, the rear carriage has been equipped with four passive wheels, instead of two as in the previous versions, in order to improve the stability during steep stair climbing maneuvers; moreover, the legs, the main body and the rear carriage have been significantly redesigned in order to be realized by additive manufacturing techniques, with the final aim of obtaining a low-cost device suitable for Open Source distribution.
Keywords: Additive manufacturing | Ground mobile robot | Hybrid leg-wheel locomotion | Low-cost robotics | Step climbing
Abstract: Recent advances in Additive Manufacturing (AM) technologies have allowed a widespread diffusion of their use in different fields. 3D printing is becoming commonplace for biomedical applications requiring the custom fabrication of prostheses and appliances fitting patient-specific anatomies. In this work, the feasibility of a vat photopolymerization technology, based on Digital Light Processing (DLP), has been investigated for the manufacturing of polymeric orthodontic appliances. A custom DLP 3D printer has been developed by exploiting an off-the-shelf digital projector, with the aim at studying the influence of printing parameters on the surface roughness. The feasibility of using Dental LT Clear resin, a biocompatible photopolymer specifically designed for SLA technology, has been finally verified.
Keywords: Additive manufacturing | Custom DLP 3D printer | Orthodontic appliances
Abstract: Bamboo is one of the longest-used organic raw materials in the tropics for a large number of different purposes in the daily lives of human beings. Because of its excellent physical-mechanical properties, in many parts of the world it is widely used as a structural material, especially for the construction of scaffolding and the construction of buildings. The bamboo can be modelled as a composite material, consisting of a of a parenchyma cells matrix, similar to a foam, reinforced by bundles of fibers associated with vessels. The present work aimed to explore the possibility to design a 3D printed biomimetic composite material able of keeping advantages from the bamboo morphological structure. Samples made of PVA, ABS and PVA + ABS were manufactured using Fused Deposition Modelling and tested under compression and bending conditions. The behavior under compression has shown to depend mainly on the material used while in bending the structure has shown important effects leading the sample made of PVA + ABS to have the same performances of much expensive pure ABS.
Keywords: Additive manufacturing | Bamboo | Structure optimization
Abstract: Pectus Arcuatum, a rare congenital chest wall deformity, is characterized by the protrusion and early ossification of sternal angle thus configuring as a mixed form of excavatum and carinatum features. Surgical correction of pectus arcuatum always includes one or more horizontal sternal osteotomies, consisting in performing a V-shaped horizontal cutting of the sternum (resection prism) by means of an oscillating power saw. The angle between the saw and the sternal body in the V-shaped cut is determined according to the peculiarity of the specific sternal arch. The choice of the right angle, decided by the surgeon on the basis of her/his experience, is crucial for a successful intervention. The availability of a patient-specific surgical guide conveying the correct cutting angles can considerably improve the chances of success and, at the same time, reduce the intervention time. The present paper aims to propose a new CAD-based approach to design and produce custom-made surgical guides, manufactured by using additive manufacturing techniques, to assist the sternal osteotomy. Starting from CT images, the procedure allows to determine correct resection prism and to shape the surgical guide accordingly taking into account additive manufacturing capabilities. Virtually tested against three case studies the procedure demonstrated its effectiveness.
Keywords: Biomedical devices | CAD | Design for additive manufacturing | Medical imaging
Abstract: In these last years, with the advent of Additive Manufacturing, a deep review of the design methodologies has occurred. This is mainly due to two reasons: The technological progress and the new manufacturing capabilities that offer designers much greater freedom for the creation of complex geometries; the modern engineering optimization tools that are spreading widely in the industrial design field, and offer new opportunities for searching a compromise between form and function. On the basis of these two reasons, the paper presents some reflections and exemplifications on the changes that new AM technologies, together with the optimization tools, are bringing in the design process.
Keywords: Additive manufacturing | Design theory and methodology | Topology optimization
Abstract: The potentiality of the Fused Deposition Modeling (FDM) process for multi-material printing has not yet been thoroughly explored in the literature. That is a limitation considering the wide diffusion of dual extruders printers and the possibility of increasing the number of these extruders. An exploratory study, based on tensile tests and performed on double-material butt-joined bars, was thus conceived; the aim was to explore how the adhesion strength between 3 pairs of filaments (TPU-PLA, PLA-CPE, CPE-TPU) is influenced by the material printing order, the type of slicing pattern used for the layers at the interface, and the infill density of the layers below the interface. Results confirm the effectiveness of mechanical interlocking strategies in increasing the adhesion strength even when thermodynamic and diffusion mechanisms of adhesion are not robust enough. Besides, thermal aspects also demonstrated to play a relevant role in influencing the performance of the interface.
Keywords: design for additive manufacturing | fused deposition modelling (FDM) | multi-material adhesion | Multi-material printing | slicing parameters
Abstract: 3D printed heterogeneous lattice structures are beam-and-node based structures characterised by a variable geometry. This variability is obtained starting from a periodic structure and modifying the relative density of the unit cells or by combining unit cells having different shapes. While several consolidated design approaches are described to implement the first approach, there are still computational issues to be addressed to combine different cells properly. In this paper, we describe a preliminary experimental study focused on exploring the design issues to be addressed as well as the advantages that this second type of heterogeneous structures could provide. The Three-Point-Bending test was used to compare the behaviour of different types of heterogeneous structures printed using the Fused Deposition Modeling (FDM) technology. Results demonstrated that the possibility of combining multiple unit cells represents a valid strategy for performing a more effective tuning of the material distribution within the design space. However, further studies are necessary to explore the behaviour of these structures and develop guidelines for helping designers in exploiting their potential.
Keywords: 3D printing | Design for Additive Manufacturing (DfAM) | Heterogeneous lattice structures | Lightweight design
Abstract: Additive Manufacturing (AM) is a potentially revolutionary technique in industry with claims of high skills shortage in the recent days. It is assumed that full exploitation of AM capabilities can be made possible by a paradigm shift steered by engineering design. Future generations of engineers might benefit from Design for Additive Manufacturing (DfAM), which targets AM potential and enables design freedoms. In this context, the paper investigates AM education for a better understanding of the main AM-related subjects taught in universities. To this scope, the authors gathered 52 syllabi of courses taught in highly-ranked technical universities worldwide that relate to AM. From the investigation, it emerges that AM is the core discipline of the course in 42 out of 52 cases and considered widely as an independent domain to date. As for taught subjects, it was found that design aspects in AM and DfAM are poorly focused on, while manufacturing and process areas are the most popular. This poses a challenge especially to the design community, as the current situation might limit the exploitation of AM capabilities.
Keywords: Additive Manufacturing | Computer Aided Design (CAD) | Design education | Design for Additive Manufacturing (DfAM)
Abstract: The outreach of application domains for Additive Manufacturing (AM) is expanding and end-use products represent their next frontier. Contextually, design methods are developed for exploiting the unique AM capabilities. They largely benefit from the knowledge about peculiarities, constraints and technical performances of the various AM processes and devices. However, while the mechanical properties of objects created with AM are widely studied, there is lack of research on emotional and perceptual aspects. This is of great relevance in the mentioned perspective of employing AM for end-use products. The paper aims to elucidate which perceptual mechanisms are activated when a user observes an object generated with AM instead of traditional technologies. An experiment has involved 43 participants who have evaluated ten pairs of objects, constituted by a commercial product and a replica made with Fused Deposition Modelling. Testers have answered a questionnaire, as well as their visual behavior has been recorded with eye-tracking glasses. Based on results, replicas suffer from poor attractiveness and especially low perceived quality. They have also given rise to more careful exploratory behaviors because they likely require a lengthier examination for testers’ assessment or they arouse curiosity. It can be inferred that Fused Deposition Modelling does not exhibit sufficient accuracy to achieve acceptability with reference to everyday products. Nevertheless, it is also deemed that limited improvements might compensate for the perception of technical unsuitability this technology engenders. This can be verified by repeating the experiment with more sophisticated and precise AM devices.
Keywords: Design for additive manufacturing | End-use products | Eye-tracking | Fused deposition modelling
Abstract: This study defines a methodological procedure for the design and manufacturing of a prosthetic implant for the reconstruction of a midsagittal bony-deficiency of the skull due to the Apert congenital disorder. Conventional techniques for craniofacial defects reconstruction rely on the mirrored-image technique. When the cranial lesion extends over the midline or in case of bilateral defects, other approaches based on thin plate spline interpolation or constrained anatomical deformation are applied. The proposed method uses the anthropometric theory of cranial landmarks identification for the retrieval of a template healthy skull, useful as a guide in the successive implant design. Then, anatomical deformation of the region of interest and free-form modelling allow to get the customized shape of the implant. A full bulk and a porous implant have been provided according to the surgeon advises. The models have been 3D printed for a pre-surgical analysis and further treatment plan. They fulfilled the expectancies of the surgeon thus positive results are predictable. This methodology results to be reproducible to any other craniofacial defect spanning over the entire skull.
Keywords: Additive Manufacturing | Apert Syndrome | Biomedical design | Design process | Implant design
Abstract: Background: The integration of computer-aided design/computer-aided manufacturing (CAD/CAM) tools and medicine is rapidly developing for designing medical devices. A novel design for a 3D-printed patient-specific surgical template for thoracic pedicle screw insertion, using a procedure based on reverse engineering, is presented. Methods: The surgeon chooses the entry point on the vertebra. The optimal insertion direction and the size of the screws are defined via an algorithm on the basis of a patient-specific vertebra CAD model. The template features an innovative shape for a comfortable and univocal placement and a novel disengaging device. Results: Three spinal fusions were performed to test the template. Excellent results were achieved in terms of the accuracy of the screw positioning, reduction in surgery duration, and number of X-rays. Conclusions: A novel design for a customized, 3D-printed surgical template for thoracic spinal arthrodesis was presented, and improvements in terms of precision, duration, and safety were achieved without changing the standard procedure.
Keywords: 3D imaging | additive manufacturing | bone | computer-assisted surgery | imaged guided surgery | in vivo | modelling | pedicle screw fixation | screw direction optimization | spine | surgical template | thoracic | thoracic spinal arthrodesis | X-ray minimization
Abstract: The paper broadly addresses how Industry 4.0 program drivers will impact maintenance in aviation. Specifically, Industry 4.0 practices most suitable to aeronautical maintenance are selected, and a detailed exposure is provided. Advantages and open issues are widely discussed and case studies dealing with realistic scenarios are illustrated to support what has been proposed by authors. The attention has been oriented towards Augmented Reality and Additive Manufacturing technologies, which can support maintenance tasks and spare parts production, respectively. The intention is to demonstrate that Augmented Reality and Additive Manufacturing are viable tools in aviation maintenance, and while a strong effort is necessary to develop an appropriate regulatory framework, mandatory before the wide-spread introduction of these technologies in the aerospace systems maintenance process, there has been a great interest and pull from the industry sector.
Keywords: Additive Manufacturing | Aeronautical maintenance | Augmented Reality | Industry 4.0
Abstract: Additive manufacturing (AM) is becoming an important alternative to traditional processes. AM technology shows several advantages in literature, and its use increases in aerospace, automotive and biomedicine. Time reduction in design-to-manufacturing cycle, customization, capability to generate complex shapes in one piece and ability to imitate low-weight bio-inspired shapes are the strength of designs based on AM. Due to its potentials, major progresses were done in AM, thanks to technology evolution and increased computational power. With regard to AM, voxelization can be defined as part's discretization in hexahedral elements, as done with pixels in 2D image. Voxels are used to speed-up geometry and algebraic manipulation thanks to their inherent advantages. This paper analyses advantages and criticalities of AM and voxel manipulation through a systematic literature review methodology. The analyses are based upon the filtering of a huge amount of publications available in literature up to obtaining the most significant 25 studies published in the last 5 years. The study's main result is the technology gap's identification, i.e. where AM and voxelization still need improvements, thus providing the reader with suggestions about possible further studies. Computer elaboration power and voxel discretization algorithms are suggested being key issues in AM's further development.
Keywords: Additive manufacturing | Design | Systematic literature review (SLR) | Voxel
Abstract: Minimal surfaces are receiving a renewed interest in biomedical and industrial fields, due to the capabilities of additive manufacturing technologies which allow very complex shapes. In this paper, an approach for geometric modeling of variable thickness triply periodic minimal surfaces in a CAD environment is proposed. The approach consists of three main steps: the definition of an initial mesh, the adoption of a subdivision scheme and the assignment of a variable thickness by a differential offset. Moreover, the relationship between relative density and mesh thickness was established for two types of minimal surfaces: Schoen’s gyroid, Schwarz’ Primitive. The proposed method improves the main issues highlighted in literature in the modeling of cellular materials and allows to easily obtain a consistent polygonal mesh model satisfying functional requirements. Two test cases were presented: the first shows a gradient thickness gyroid; in the second the relative density obtained by topology optimization was adopted in our modeling approach using a Schwarz’ Primitive. In both cases, guidelines for selecting the geometric modeling parameters taking into account the specific additive manufacturing process constraints were discussed. The proposed method opens new perspectives in the development of effective CAD tools for additive manufacturing, improving the shape complexity and data exchange capacity in cellular solid modeling.
Keywords: Cellular materials | Design for additive manufacturing | Geometric modeling | Triply periodic minimal surfaces
Abstract: The diffusion of design tools suitable for regular lattice structures was recently stimulated by the spread of additive manufacturing technologies that enable the fabrication of complex geometries, exceeding the limits of traditional manufacturing methods. Fillet radii play a fundamental role in the design of lattice materials, reducing the stress concentration and improving fatigue life. However, only simplified beam and 2D models are available in the literature, which are unable to capture the actual stiffness and stress concentrations in the cell nodes of the 3-D beam based lattice structures with fillets. In this paper, four types of polyamide 12 cells, fabricated by selective laser sintering technology, based on cylindrical elements, are studied by finite element (FE) analysis, evaluating the influence of struts and fillet radii on the mechanical properties. In order to study a single cell, specific boundary conditions, simulating the presence of adjacent cells, were adopted in FE analysis. As a result, a model describing mechanical properties as a function of geometrical characteristics is obtained. By this model, it is possible to replace the complex shape of a lattice structure with its boundary, simplifying numerical analyses. This approach, called homogenization, is very useful in the design process of lightweight structures and can be adopted in optimization strategies. Numerical outcomes show that the effect of fillet radius is not negligible, especially in cells having a large number of struts. Moreover, experimental tests were also carried out showing a good agreement with the numerical analysis. Finally, an interactive design process for lattice structures based on experimental and numerical outcomes is proposed.
Keywords: Additive manufacturing | Finite element analysis | Homogenization | Lattice structures | Polyamide 12 | Tensile tests
Abstract: Nowadays, topology optimization and lattice structures are being re-discovered thanks to Additive Manufacturing technologies, that allow to easily produce parts with complex geometries. The primary aim of this work is to provide an original contribution for geometric modeling of conformal lattice structures for both wireframe and mesh models, improving previously presented methods. The secondary aim is to compare the proposed approaches with commercial software solutions on a piston rod as a case study. The central part of the rod undergoes size optimization of conformal lattice structure beams diameters using the proposed methods, and topology optimization using commercial software tool. The optimized lattice is modeled with a NURBS approach and with the novel mesh approach, while the topologically optimized part is manually remodeled to obtain a proper geometry. Results show that the lattice mesh modelling approach has the best performance, resulting in a lightweight structure with smooth surfaces and without sharp edges at nodes, enhancing mechanical properties and fatigue life.
Keywords: Additive Manufacturing | Case study | Lattice structures | Modeling approaches | Optimisation
Abstract: According to recent studies, a new paradigm in the geometric modeling of lattice structures based on subdivision surfaces for additive manufacturing overcomes the critical issues on CAD modeling highlighted in the literature, such as scalability, robustness, and automation. In this work, the mechanical behavior of the subdivided lattice structures was investigated and compared with the standard lattices. Five types of cellular structures based on cubic cell were modeled: struts based on squared or circular section, with or without fillets and cell based on the subdivision approach. Sixty-five specimens were manufactured by selective laser sintering technology in polyamide 12 and tensile and fatigue tests were performed. Furthermore, numerical analyses were carried out in order to establish the stress concentration factors. Results show that subdivided lattice structures, at the same resistant area, improve stiffness and fatigue life and reduce stress concentration while opening new perspectives in the development of lattice structures for additive manufacturing technologies and applications.
Keywords: Design for additive manufacturing | Fatigue | Geometric modeling | Lattice structures | Selective laser sintering | Subdivision surface
Abstract: The unique capabilities of additive manufacturing (AM) technologies highlight limits in commercial CAD tools. In this manuscript, after a synthetic description of the main AM technologies based on international standards classification, geometric modeling methods and data exchange file formats available in the literature are presented. Twelve geometric models have been studied to evaluate the effectiveness of the file format, noting the file dimension and the time to open and close the file. As a result, a roadmap in the development of new tools for design in AM is drawn, taking into account the new possibilities offered by AM technologies.
Keywords: Additive manufacturing | Data exchange | Design for additive manufacturing | Geometric modeling
Abstract: The work presents a stress-based algorithm developed for the topology optimization of 3D surfaces. The novelty of the proposed methodology consists in the fact that it acts directly on a CAD level, and not on the mesh as is more usual. This allows to obtain a CAD ready to be manufactured with Additive Manufacturing technologies, without any subsequent intervention by the designer. The CAD algorithm is written in Rhino-Grasshopper environment and it is suitable to any FEM software. The methodology consists in a hollowing of the surface, starting by a Voronoi tessellation, allowing the designer to set a lot of parameters, as the number of control points, the dimension of the holes and the thickness of the branches of the tessellation. An iterative process leads to redraw at each iteration the Voronoi scheme in order to add material where the stress is higher and to remove it where the stress is lower. As a case study, in order to show the characteristics of the methodology, a seat for powerboats applications has been tested and optimized. The results from the case study demonstrate the high performance of the method and the capability to obtain in easy way light weight structures oriented for the Additive Manufacturing new technologies.
Keywords: Additive Manufacturing | Mechanical design | Selective laser sintering | Topology optimization
Abstract: Topological optimization is a fairly innovative numerical technique that makes it possible to reduce the mass of mechanical components. It is an alternative to the optimizations of shape or geometry that allow to highly improve the efficiency of products. The recent development of metal additive manufacturing technologies allows the production of pieces that were not feasible before, permitting the use of topological optimization in many fields. In the biomedical field, for example, the reduction of prosthetic and orthotic materials allows to save weight, to the advantage of comfort, and to minimize the invasiveness of these systems. In this paper, an optimization of a system consisting of a femoral nail and two screws is carried out. The pieces were obtained by 3D scanning of prostheses, so as to obtain the true geometry. The femur is the standard one in literature. Following topological optimization, a new nail, with a mass of 60% of the previous one, was obtained, without limiting the functionality or the reliability of the product. Results and methodological problems are discussed.
Keywords: Additive manufacturing | Biomedical engineering | Femoral nail | Reverse engineering | Topology optimization
Abstract: Additive Manufacturing (AM) involves a set of production processes in which a layer-based material deposition approach to build parts is applied. These technologies are now extensively used in the industry in many cases as the main manufacturing process for making components with high shape complexity. The dimensional and geometric accuracy of the parts manufactured by means of AM are mostly determined by the specific type of additive process employed and the related process parameters. The part orientation in the build space is an important process parameter that has an influence on the stair-step effect and on the need of support structures and the subsequent post-processing refinements. In addition, the position of the part in the build volume may have an influence on the shape. These factors concur to the surface finish and to the dimensional and shape accuracy. In this paper, the flatness error on several surfaces, built on a test artefact ad hoc conceived, has been measured by means of a CMM-based setup in order to quantify the variation of the error in relation to: The orientation of the surfaces with respect to the platform, and the position of the part in the build volume of the AM machine. The test part has been produced by Direct Metal Laser Sintering (DMLS) process using the EOS Stainless Steel GP1. The test artifact has been designed with five flat surfaces at different angles with respect to the building platform. Two specimens were built in the same DMLS session with different position and alignment. The influence of the surface slope on the flatness error has been investigated. Flatness, 3D Roughness and orientation errors (parallelism, inclination, perpendicularity) have been measured and compared between both specimens.
Keywords: 3D surface roughness | Additive manufacturing | Flatness | Orientation error
Abstract: In an increasingly competitive business world, the “time to market” of products has become a key factor for business success. There are different techniques that anticipate design mistakes and launch products on the market in less time. Among the most used methodologies in the design and definition of the requirements, quality function deployment (QFD) and design for Six Sigma (DFSS) can be used. In the prototyping phase, it is possible to address the emerging technology of additive manufacturing. Today, three-dimensional printing is already used as a rapid prototyping technique. However, the real challenge that industry is facing is the use of these machineries for large-scale production of parts, now possible with new HP multi-fusion. The aim of this article is to study the entire product development process taking advantage of the most modern models and technologies for the final realization of a case study that involves the design and prototyping of an innovative multifunctional fan (lamp, aroma diffuser and fan) through the Multi Jet Fusion of HP. To begin with, issues related to the DFSS, the QFD and their application to identify the fan requirements are explored. Once the requirements have been defined, the modern CAD design systems and the CAE systems for the validation of the case study will be analyzed and applied. Finally, HP’s Multi Jet Fusion methodology and design rules for additive manufacturing will be analyzed in detail, trying to exploit all the positive aspects it offers.
Keywords: CAD | CAE | Design for additive manufacturing | Design for six sigma | FEA | Multi jet fusion | Product development | QFD | Rapid prototyping
Abstract: In an increasing number of aggressive enterprise world, “time to market” concerning products has come to be a solution element because of enterprise success. There are exceptional techniques so expect layout mistakes or open products concerning the need between much less time. Among the most used methodologies in the design and setting about stability the requirements, Quality Function Deployment (QFD) and Design for Six Sigma (DFSS) execute remain used. In the prototyping phase, such is feasible in imitation of tackle the rising science regarding additive manufacturing. Today, three-dimensional stamping is in the meanwhile used as a rapid prototyping technique. However, the actual challenge that enterprise is going through is the use of these machineries for large-scale production about parts, at last viable along current HP Multi fusion. The aim of this article is to study the interactive design and engineering applied to the entire product development process taking advantage of the most modern models and technologies for the final realization of a case study that involves the design and prototyping of an innovative multifunctional fan (Lamp, Aroma Diffuser and fan) through the Multi Jet Fusion of HP. To begin with, issues related to the DFSS, the QFD and their application to identify the fan requirements are explored. Once the requirements have been defined, the modern CAD design systems and the CAE systems for the validation of the case study will be analyzed and applied. Finally, HP’s Multi Jet Fusion methodology and design rules for additive manufacturing will be analyzed in detail, trying to exploit all the positive aspects it offers.
Keywords: CAD | CAE | Design for additive manufacturing | Design for Six Sigma | FEA | Multi jet fusion | Product development | QFD | Rapid prototyping
Abstract: This paper presents a a novel alghorithm of diagnosis and treatment of rigid flatfoot due to tarsal coalition. It introduces a workflow based on 3D printed models, that ensures more efficiency, not only by reducing costs and time, but also by improving procedures in the preoperative clinical phase. Since this paper concerns the development of a new methodology that integrates both engineering and medical fields, it highlights symmetry. An economic comparison is made between the traditional method and the innovative one; the results demonstrate a reduction in costs with the latter. The current, traditional method faces critical issues in diagnosing the pathologies of a limb (such as the foot) and taking decisions for further treatment of the same limb. The proposed alternative methodology thus uses new technologies that are part of the traditional workflow, only replacing the most obsolete ones. In fact, it is increasingly becoming necessary to introduce new technologies in orthopedics, as in other areas of medicine, to offer improved healthcare services for patients. Similar clinical treatments can be performed using the aforementioned technologies, offering greater effectiveness, more simplicity of approach, shorter times, and lower costs. An important technology that fits into this proposed methodology is 3D printing.
Keywords: 3D printing | Diagnostics | Orthopaedics | Paediatry | Surgery
Abstract: This paper presents the application of a low-cost 3D printing technology in pre-operative planning and intra-operative decision-making. Starting from Computed Tomography (CT) scans, we were able to reconstruct a 3D model of the area of interest with a very simple and rapid workflow, using open-source software and an entry level 3D printer. The use of High Temperature Poly-Lactic Acid (HTPLA) by ProtoPasta allowed fabricating sterilizable models, which could be used within the surgical field. We believe that our method is an appealing alternative to high-end commercial products, being superior for cost and speed of production. It could be advantageous especially for small and less affluent hospitals that could produce customized sterilizable tools with little investment and high versatility.
Keywords: 3D printing | Computed tomography | Diagnostic imaging | Mesh reconstruction | Rapid prototyping | Surgical planning
Abstract: Used in several industrial fields to create innovative designs, topology optimization is a method to design a structure characterized by maximum stiffness properties and reduced weights. By integrating topology optimization with additive layer manufacturing and, at the same time, by using innovative materials such as lattice structures, it is possible to realize complex three-dimensional geometries unthinkable using traditional subtractive techniques. Surprisingly, the extraordinary potential of topology optimization method (especially when coupled with additive manufacturing and lattice structures) has not yet been extensively developed to study rotating machines. Based on the above considerations, the applicability of topology optimization, additive manufacturing, and lattice structures to the fields of turbomachinery and rotordynamics is here explored. Such techniques are applied to a turbine disk to optimize its performance in terms of resonance and mass reduction. The obtained results are quite encouraging since this approach allows improving existing turbomachinery components’ performance when compared with traditional one.
Keywords: additive manufacturing | lattice structures | Topology optimization | turbomachinery
Abstract: Microtia is a congenital malformation affecting one in 5000 individuals and is characterized by physical deformity or absence of the outer ear. Nowadays, surgical reconstruction with autologous tissue is the most common clinical practice. The procedure requires a high level of manual and artistic techniques of a surgeon in carving and sculpting of harvested costal cartilage of the patient to recreate an auricular framework to insert within a skin pocket obtained at the malformed ear region. The aesthetic outcomes of the surgery are highly dependent on the experience of the surgeon performing the surgery. For this reason, surgeons need simulators to acquire adequate technical skills out of the surgery room without compromising the aesthetic appearance of the patient. The current paper aims to describe and analyze the different materials and methods adopted during the history of autologous ear reconstruction (AER) simulation to train surgeons by practice on geometrically and mechanically accurate physical replicas. Recent advances in 3D modelling software and manufacturing technologies to increase the effectiveness of AER simulators are particularly described to provide more recent outcomes.
Keywords: Additive manufacturing | Autologous ear reconstruction | Computer-Aided Design (CAD) | Costal cartilage | Image-processing | Microtia | Silicone rubbers | Simulation | Training
Abstract: 3D Printing and Additive Manufacturing technologies represent powerful tools for the direct fabrication of lightweight structures with improved and tunable properties. In current research, Fused Deposition Modeling (FDM)/3D fiber deposition technique was considered to design 3D multifunctional scaffolds with complex morphology, tailored biological, mechanical and mass transport properties. Polymeric and nanocomposite materials were used for scaffold design and optimization, with a particular focus on bone tissue engineering. As an example, poly(ϵ-caprolactone) (PCL), and PCL-based nanocomposite scaffolds were fabricated and analyzed. The effects of structural and morphological features (i.e., sequence of stacking, fiber spacing, pore size and geometry) as well as of nanoparticle inclusion on the mechanical performances were reported. Furthermore, the possibility to design 3D customized scaffolds for mandibular defect regeneration (i.e., symphysis and ramus) was also considered.
Keywords: Additive manufacturing | nanocomposites | reverse engineering | scaffold design
Abstract: Purpose: The purpose of this paper is to describe an innovative Parametric and Adaptive Slicing (PAS) technique to be used for generating material addition paths along three-dimensional surfaces. Design/methodology/approach: The method is grounded on the possibility to generate layers starting from multiple reference surfaces (already available in the model or created on purpose). These are used for mathematically deriving a family of parametric surfaces whose shape and spacing (the layer thickness) can be tuned to get the desired aesthetic, technical and functional characteristics. The adhesion among layers is obtained guaranteeing a smooth transition among these surfaces. Findings: The examples described in the paper demonstrate that the PAS technique enables the addition of the material along non-planar paths and, hence, the elimination of the staircase effect. In addition, objects printed using this technique show improved mechanical properties with respect to those printed using standard planar layers. Research limitations/implications: As the method allows a local control of the material addition/deposition, it can be used to design the mechanical behavior of the objects to be printed. Originality/value: The technique proposed in this paper overcomes the limitations of currently available adaptive and curved layer slicing strategies, by introducing the possibility to generate layers with a non-constant thickness whose shape morphs smoothly from one layer to another.
Keywords: Additive manufacturing | Computer aided design | Computer aided manufacturing | Curved layer | Design for additive manufacturing | Geometrical modelling
Abstract: The use of a Latent Thermal Energy Storage (LTES) system using suitable Phase Change Materials (PCMs) is an effective way of storing energy because of its high-energy storage density and isothermal nature of the storage processes. Unfortunately, PCMs present a few unfavorable thermophysical properties, among those the low thermal conductivity, which are limiting the development of efficient, reliable and convenient LTESs. However, LTES represents a promising technology, which can unlock unprecedented opportunities for multiple-sources energy integration, waste heat recovery, and efficient energy management. This paper aims at investigating new 3D periodic structures obtained via metallic additive manufacturing developed to enhance the phase change process during both loading and unloading processes of different paraffin waxes and sugar alcohols. The tests were run by imposing 20 W during the loading process and the monitoring the temperature distribution within the PCM.
Keywords: Additive manufacturing | PCM | Phase change | Renewable energy | Thermal energy storage
Abstract: Hybrid manufacturing is a new production strategy based on the combination of various processes to manufacture components more efficiently in terms of quality, productivity, and/or sustainability. Combinations of subtractive, forming, and additive manufacturing processes can follow one another to produce the desired parts. Hence, both part complexity and performance can increase significantly. The highlighted strategy has been tested by considering two different processes that are typically utilised for small batches of customised parts. Specifically, selective laser sintering has been used to thicken sheets locally, which are subsequently formed by single point incremental forming. This process combination can result in the development of a rapid prototyping technique that exploits the peculiarities of both the utilised processes, and thus allows for the manufacturing of more complex and/or higher quality parts, in a more flexible manner. In the research herein reported, various solutions have been tested to analyse the impact of the proposed hybrid manufacturing strategy on the a) dimensional accuracy, in terms of deviation from the nominal shape, b) quality, in terms of thickness distribution, and c) part complexity, in terms of the obtainable three-dimensional shape, of stainless-steel-formed sheets.
Keywords: Additive manufacturing | Hybrid manufacturing | SPIF
Abstract: PLA is an organic polymer that lends itself to multiple applications. It is commonly used in fused deposition modeling technology (FDM), which operates by depositing successive layers of material. The material extrusion, in the form of a wire, follows an imposed pattern, which influences the static and dynamic behavior of the final component. In the literature there are many works concerning the mechanical characterization of the PLA but, due to the natural orthotropy of the FDM process and, above all, to the ascertained influence of the particular technical system with which the operations are performed, it is necessary to characterize the extruded material through different metrological techniques. In order to allow the use of this technology for structural elements production, in the present work, quasi-static tests have been carried out to characterize the material and the process considering the three spatial growth directions (x, y and z). In particular, uniaxial tensile tests were performed for the determination of mechanical strength, modulus of elasticity and percentage elongation.
Keywords: 3D Printing | Acrylonitrile | Butadiene styrenepolylactic acid | FDM | Rapid prototyping | Tensile strength
Abstract: The purpose of this paper is to assess the main effects on the geometric errors in terms of flatness, circularity and cylindricity based on the size of the printed benchmarks and according to the position of the working plane of the 3D printer. Three benchmark models of different sizes, with a parallelepiped and cylinder shape placed in five different positions on the working plane are considered. The sizes of models are chosen from the Renard series R40. Benchmark models are fabricated in ABS (Acrylonitrile Butadiene Styrene) using RepRap Prusa i3 3D printer. A sample of five parts for each geometric category, as defined from the R40 geometric series of numbers, is printed close to each corner of the plate, and in the plate center position. Absolute Digimatic Height Gauge 0–450 mm with an accuracy of ± 0.03 mm by Mitutoyo is used to perform all measurements: flatness on box faces, and circularity/cylindricity on cylinders. Results show that the best performances, in terms of form accuracy, are reached in the upper-left printable area while they decrease with the sample size. Being quality a critical factor for a successful industrial application of the AM processes, the results discussed in this paper can provide the AM community with additional scientific data useful to understand how to improve the quality of parts which may be obtained through new generations of 3D printer.
Keywords: Additive manufacturing | Fused deposition modelling | GD&T | Geometric errors
Abstract: The use of intraoral scanners and Additive Manufacturing (AM) techniques in dentistry is increasing, and such technologies are integrated in daily workflows for the production of various types of dental restorations. Thus, it is clinically sensible to assess the accuracy of these systems. This in vivo study presents a comparison, in term of accuracy, among three commercially available AM systems, used to rapid prototype models obtained from intraoral scans data. Eight patients with a complete dentition were selected. Complete-arch scans of both upper and lower jaws were obtained using the 3Shape Trios 3 color intraoral scanner. The corresponding CAD models were created by means of the 3Shape Dental System software, and three AM systems, Photocentric LC10 (AM1), Zortrax M 200 (AM2) and Prusa I3 (AM3) were used to manufacture them. The manufactured fourty-eight models were scanned with the 3Shape Trios 3 color scanner, by the same operator. Scans of the manufactured models were aligned and compared to the reference intraoral scan by means of a Reverse Engineering software (Geomagic Studio). The comparison between the scans of the manufactured models and the reference intraoral scans, for the eight patients, shows a standard deviation (SD) in the range 0.11 – 0.27 mm for AM1, in the range 0.04 – 0.26 mm for AM2 and in the range 0.07 – 0.26 mm for AM3. The results of this research show that Prusa I3 and Zortrax M 200 are statistically more accurate than Photocentric LC10. Nevertheless, if we consider the amount of difference in accuracy, this may be not relevant from a clinical point of view. Thus, the three AM systems can be used in some dental applications which are compatible with the reported accuracy.
Keywords: Additive manufacturing | Dental models | Dentistry | Intraoral scans | Orthodontic appliances
Abstract: Additive Manufacturing technologies allow for the direct fabrication of lightweight structures with improved properties. In this context, Fused Deposition Modelling (FDM) has also been considered to design 3D multifunctional scaffolds with complex morphology, tailored biological, mechanical and mass transport properties. As an example, poly(ε-caprolactone) (PCL), surface-modified PCL and PCL-based nanocomposite scaffolds were fabricated and analysed. The effects of structural and morphological features (i.e., sequence of stacking, fiber spacing distance, pore size and geometry), surface modification and nanoparticles on the in vitro biological and mechanical performances were investigated.
Keywords: Additive Manufacturing | Design | Mechanical and Functional Analyses | Scaffolds
Abstract: Effective identification of the optimal design in the early stages of product development is critical in order to obtain the best chances of eventual customer satisfaction. Currently, the advancements in prototyping techniques offer unique chances to evaluate the features of different design candidates by means of product experts acting as assessors and/or customers enrolled as testers. In this paper, the candidate identification using virtual and physical prototypes is described and a practical fuzzy approach toward the evaluation of the optimal design is presented. The proposed methodology is tested on a full case study, namely the choice of optimal design for the traditional Neapolitan coffeemaker, inspired by the prototypes of the Italian designer Riccardo Dalisi. Several concepts are developed in a virtual environment and four alternatives among them are realized using Additive Manufacturing. By allowing experts to interact with virtual and physical prototypes, they were able to express their opinion on a custom fuzzy evaluation scale (i.e. they were freely choosing more or less coarse linguistic scales as well as the related shapes of fuzzy sets to adequately represent the level of fuzziness of their judgments). Once the opinions are collected, the set of best candidate(s) is easily identified and useful suggestion can be obtained for further developing the product.
Keywords: Additive manufacturing | Concept design | Concept selection | Design method | Fuzzy set | Virtual prototyping
Abstract: The effectiveness of custom-made prostheses or orthoses heavily depends on the experience and skills of the personnel involved in their production. For complex devices, such as lower limb prosthesis, a conventional manual approach affects the process at the point that the result is frequently not acceptable at the first trial. The paper presents a computer-aided environment, named socket modelling assistant2 (i.e., SMA 2) , to interactively design the socket of lower limb prosthesis by implementing a set of design rules extrapolated from the traditional development process. The new computer-aided environment has been implemented embracing a low-cost philosophy and using open source libraries to provide a solution affordable also by small orthopaedic laboratories. The system permits to modify and interact with the 3D model of residual limb to create the socket geometric model ready to be manufactured by means of additive manufacturing. SMA 2 embeds medical knowledge related to the device functioning, the conventional process and the way orthopaedic technicians work so that it can be much more reliable and repeatable compared to the conventional process, but still enough similar to it to be accepted by the involved personnel. In the paper, the new 3D design procedure is described in detail, from the acquisition of patient’s data to preliminary and customized modelling, and new geometric tools to perform context–related operations are shown. A case study is used to clarify the way the system works and to provide an example of the outcome.
Keywords: Additive manufacturing | Custom medical devices | Geometric modelling | Interactive design
Abstract: Microfluidic systems demonstrated to improve the analysis of biological and chemical processes by providing a more controlled fluid-handling environment. Typically, microfluidic systems are created in monolithic form by means of microfabrication techniques that constrain designers to work in a two-dimensional space. In this regard, Additive Manufacturing (AM) is a powerful set of technologies that can deal with the complexity of 3D structures producing flow paths with sections differing in size and direction. In this work, the use of a commercial laser-based stereolithography 3D printer has been firstly explored to fabricate transparent channels for flow reactors. A custom 3D printer, based on Digital Light Processing Stereolithography (DLP-SLA), has then been developed with the aim at gaining flexibility and overcoming typical limitations raised from standard commercial solutions. The effectiveness of the developed DLP-SLA 3D printer has been experienced by printing transparent fluidic devices with embedded channels with a specifically designed three-step printing process.
Keywords: Additive manufacturing | DLP 3D printing | fluidic reactor | laser-based stereolithograpy
Abstract: Orthodontic treatments are usually performed using fixed brackets or removable oral appliances, which are traditionally made from alginate impressions and wax registrations. Among removable devices, eruption guidance appliances are used for early orthodontic treatments in order to intercept and prevent malocclusion problems. Commercially available eruption guidance appliances, however, are symmetric devices produced using a few standard sizes. For this reason, they are not able to meet all the specific patient’s needs since the actual dental anatomies present various geometries and asymmetric conditions. In this article, a computer-aided design-based methodology for the design and manufacturing of a patient-specific eruption guidance appliances is presented. The proposed approach is based on the digitalization of several steps of the overall process: from the digital reconstruction of patients’ anatomies to the manufacturing of customized appliances. A finite element model has been developed to evaluate the temporomandibular joint disks stress level caused by using symmetric eruption guidance appliances with different teeth misalignment conditions. The developed model can then be used to guide the design of a patient-specific appliance with the aim at reducing the patient discomfort. At this purpose, two different customization levels are proposed in order to face both arches and single tooth misalignment issues. A low-cost manufacturing process, based on an additive manufacturing technique, is finally presented and discussed.
Keywords: additive manufacturing | eruption guidance appliance | finite element model | Orthodontics | temporomandibular joint
Abstract: Purpose: This paper aims to argue about the involvement of additive technologies (ATs) in the prototyping issues of designing. More precisely, it reviews the literature contributions focused on the different perspectives of prototyping activities for design purposes, searching for both available knowledge and research needs concerning the correct exploitation of ATs. Design/methodology/approach: A two-step literature review has been performed. In the first step, general information has been retrieved about prototyping issues related to design. In the second step, the literature searches were focused on retrieving more detailed information about ATs, concerning each of the main issues identified in the previous step. Extracted information has been analyzed and discussed for understanding the actual coverage of the arguments and for identifying possible research needs. Findings: Four generally valid prototyping issues have been identified in the first step of the literature review. For each of them, available information and current lacks have been identified and discussed about the involvement of AT, allowing to extract six different research hints for future works. Originality/value: This is the first literature review concerning AT-focused contributions that cover the complex and inter-disciplinary issues characterizing prototyping activities in design contexts.
Keywords: Additive technologies | Design | Engineering | Engineering design | Prototyping | Rapid prototyping
Abstract: Background and objective: The purpose of the present paper is to pave the road to the systematic optimization of complex craniofacial surgical intervention and to validate a design methodology for the virtual surgery and the fabrication of cranium vault custom plates. Recent advances in the field of medical imaging, image processing and additive manufacturing (AM) have led to new insights in several medical applications. The engineered combination of medical actions and 3D processing steps, foster the optimization of the intervention in terms of operative time and number of sessions needed. Complex craniofacial surgical intervention, such as for instance severe hypertelorism accompanied by skull holes, traditionally requires a first surgery to correctly “resize” the patient cranium and a second surgical session to implant a customized 3D printed prosthesis. Between the two surgical interventions, medical imaging needs to be carried out to aid the design the skull plate. Instead, this paper proposes a CAD/AM-based one-in-all design methodology allowing the surgeons to perform, in a single surgical intervention, both skull correction and implantation. Methods: A strategy envisaging a virtual/mock surgery on a CAD/AM model of the patient cranium so as to plan the surgery and to design the final shape of the cranium plaque is proposed. The procedure relies on patient imaging, 3D geometry reconstruction of the defective skull, virtual planning and mock surgery to determine the hypothetical anatomic 3D model and, finally, to skull plate design and 3D printing. Results: The methodology has been tested on a complex case study. Results demonstrate the feasibility of the proposed approach and a consistent reduction of time and overall cost of the surgery, not to mention the huge benefits on the patient that is subjected to a single surgical operation. Conclusions: Despite a number of AM-based methodologies have been proposed for designing cranial implants or to correct orbital hypertelorism, to the best of the authors’ knowledge, the present work is the first to simultaneously treat osteotomy and titanium cranium plaque.
Keywords: Additive manufacturing | CAD | Cranium surgery | Image processing
Abstract: The percutaneous interventions in the treatment of structural heart diseases represent nowadays a viable option for patients at high risk for surgery. However, unlike during the traditional open heart surgery, the heart structures to be corrected are not directly visualized by the physician during the interventions. The interpretation of the available medical images is often a demanding task and needs specific skills i.e. clinical experience and complex radiological and echocardiographic analysis. The new trend for cardiovascular diagnosis, surgical planning and intervention is, today, mutually connected with most recent developments in the field of 3D acquisition, interactive modelling and rapid prototyping techniques. This is particularly true when dealing with complex heart diseases since 3D-based techniques can really help in providing an accurate planning of the intervention and to support surgical intervention. To help the research community in confronting with this new trend in medical science, the present work provides an overview on most recent approaches and methodologies for creating physical prototypes of patient-specific cardiac structures, with particular reference to most critical phases such as: 3D image acquisition, interactive image segmentation and restoration, interactive 3D model reconstruction, physical prototyping through additive manufacturing. To this purpose, first, recent techniques for image enhancement to highlight anatomical structures of interest are presented together with the current state of the art of interactive image segmentation. Finally, most suitable techniques for prototyping the retrieved 3D model are investigated so as to derive a number of criteria for manufacturing prototypes useful for planning the medical intervention.
Keywords: 3D modelling | Cardiovascular diseases | Heart | Medical imagery | Rapid prototyping | Surgical planning
Abstract: Several models of FDM machines, characterized by different architecture and hardware components, have flooded the market in the last 5 years. As a result, given the high sensitivity of FDM to the specific machine characteristics, the search for optimal printing parameters is a renown problem. This two-parts paper proposes an easy-to-follow and low-cost procedure for the characterization of any given FDM machine. The method allows the evaluation of the effects of a wide selection of FDM process parameters on the quality of 3D printed parts. The first part focused on the definition of a series of metrics to be measured on a series of test prints to evaluate the quality of the produced parts. The evaluation of seven quality parameters on a single print is made possible thanks to: i) a specifically designed specimen that is made available to the user and ii) a rigorous and repeatable measurement procedure, which are both discussed in the first part of the paper. This second part presents the characterization procedure, the statistical tools used in the experimentation (DOE tools and principles are adopted throughout the experimentation) and provides guidelines to be used for the characterization of any FDM machine. The whole procedure is tested on a desktop FDM machine to demonstrate obtainable results, proving the efficacy of the proposed methodology and highlight strengths and drawbacks of the approach.
Keywords: 3D printing | Additive manufacturing (AM) | Design of experiments (DOE) | Fused deposition modeling (FDM) | Process optimization
Abstract: Several models of FDM machines, characterized by different architecture and hardware components, have flooded the market in the last 5 years. As a result, given the high sensitivity of FDM to the specific machine characteristics, the search for optimal printing parameters is a renown problem. This two-parts paper proposes an easy-to-follow and low-cost procedure for the characterization of any given FDM machine. The method allows the evaluation of the effects of a wide selection of FDM process parameters on the quality of 3D printed parts. The first part focuses on the definition of a series of metrics to be measured on a series of test prints to evaluate the quality of the produced parts. Specifically, several effects are considered: dimensional accuracy, small details, overhang surfaces, ability of printing small holes/thin extrusions and overall quality of the prints. The evaluation of seven quality parameters on a single print is made possible thanks to: i) a specifically designed specimen that is made available to the user and ii) a rigorous and repeatable measurement procedure, which are both discussed in the first part of the paper. The second part presents the characterization procedure, the statistical tools used in the experimentation and provides guidelines to be used for the characterization of any FDM machine. The whole procedure is tested on a desktop FDM machine to demonstrate obtainable results.
Keywords: 3D Printing | Additive Manufacturing (AM) | Design of Experiments (DOE) | Fused Deposition Modeling (FDM) | Process Optimization
Abstract: Lattice materials can overcome the need of light and stiff structures in the aerospace industry. The wing leading edge is one of the most critical parts for both on-board subsystem and structure features: it must withstand to the aerodynamic loads and bird-strike, integrating also the anti-ice system functions. Nowadays, this part is made by different components bonded together such as external skin, internal passageways, and feeding tubes. In the present work, a single-piece multifunctional panel made by additive manufacturing will be developed. Optimal design and manufacturing are discussed according to technological constraints, aeronautical performances and sustainability.
Keywords: Additive manufacturing | DOE | Metamodeling | Pareto optimality | Response surface | Virtual protyping
Abstract: This review focuses on the design process of additively manufactured mesoscale lattice structures (MSLSs). They are arrays of three-dimensional (3D) printed trussed unit cells, whose dimensions span from 0.1 to 10.0 mm. This study intends to detail the phases of the MSLSs design process (with a particular focus on MSLSs whose unit cells are made up of a network of struts and nodes), proposing an integrated and holistic view of it, which is currently lacking in the literature. It aims at guiding designers' decisions with respect to the settled functional requirements and the manufacturing constraints. It also aims to provide an overview for software developers and researchers concerning the design approaches and strategies currently available. A further objective of this review is to stimulate researchers in exploring new MSLSs functionalities, consciously considering the impact of each design phase on the whole process, and on the manufactured product.
Keywords: additive manufacturing | design for additive manufacturing | design process | mesoscale lattice structures | multifunctional lattice structures
Abstract: Abstract: In this study, the possibility of using a layered silicate-reinforced polylactic acid (PLA) in additive manufacturing applications was investigated. In particular, the aim of this work was to study the influence of printing temperature in the 3D printing process of PLA/clay nanocomposites. For this reason, two PLA grades (4032D and 2003D, D-isomer content 1.5 and 4, respectively) were melt-compounded by a twin screw extruder with a layered silicate (Cloisite 30B) at 4 wt %. Then, PLA and PLA/clay feedstock filaments (diameter 1.75 mm) were produced using a single screw extruder. Dog-bone and prismatic specimens were 3D printed using the FDM technique at three different temperatures, which were progressively increased from melting temperature (185-200-215 °C for PLA 4032D and 165-180-195 °C for PLA 2003D). PLA and PLA/clay specimens were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile tests. Moreover, the morphology of the 3D printed specimens was investigated using optical microscopy and contact angle measurements. The different polymer matrix and the resulting nanocomposite morphology strongly influenced 3D printed specimen properties. DMA on PLA/clay filaments reported an increase in storage modulus both at ambient temperature and above the glass transition temperature in comparison to neat PLA filaments. Furthermore, the presence of nanoclay increased thermal stability, as demonstrated by TGA, and acted as a nucleating agent, as observed from the DSC measurements. Finally, for 3D printed samples, when increasing printing temperature, a different behavior was observed for the two PLA grades and their nanocomposites. In particular, 3D printed nanocomposite samples exhibited higher elastic modulus than neat PLA specimens, but for PLA 4032D+C30B, elastic modulus increased at increasing printing temperature while for PLA 2003D+C30B slightly decreased. Such different behavior can be explained considering the different polymer macromolecular structure and the different nanocomposite morphology (exfoliated in PLA 4032D matrix and intercalated in PLA 2003D matrix).
Keywords: 3D printing | Clay | FDM | Nanocomposites | PLA
Abstract: In this article, the authors propose a novel procedure for designing a customized 3D-printed surgical template to guide surgeons in inserting screws into the sacral zone during arthrodesis surgeries. The template is characterized by two cylindrical guides defined by means of trajectories identified, based on standard procedure, via an appropriate Computer-Aided-Design (CAD)-based procedure. The procedure is based on the definition of the insertion direction by means of anatomical landmarks that enable the screws to take advantage of the maximum available bone path. After 3D printing, the template adheres perfectly to the bone surface, showing univocal positioning by exploiting the foramina of the sacrum, great maneuverability due to the presence of an ergonomic handle, as well as a break system for the two independent guides. These features make the product innovative. Thanks to its small size and the easy anchoring, the surgeon can simply position the template on the insertion area and directly insert the screws, without alterations to standard surgical procedures. This has the effect of reducing the overall duration of the surgery and the patient's exposure to X-rays, and increasing both the safety of the intervention and the quality of the results.
Keywords: Computer-aided surgery | Orthopaedic device | Patient-specific guide | Rapid prototyping | X-ray minimization
Abstract: The aim of this work was to study the influence of printing temperature in the 3D printing process of PLA/clay nanocomposites. For this reason, PLA 4032D was melt compounded in a twin screw extruder with a layered silicate (Cloisite 30B) at 4 wt%. Then, using a single screw extruder, PLA and PLA/clay filaments were produced so as to obtain the required diameter (1.75 mm). Finally, dog-bone specimens were 3D printed via FDM technique using three different temperatures (185, 200 and 215°C) and such specimens were mechanically tested in tensile mode. Dynamic mechanical analysis (DMA) on PLA/clay filaments reported an increase of storage modulus both at 35°C and 70°C (8 and 40 %, respectively) in comparison to the PLA filament. Differential scanning calorimetry (DSC) demonstrated the ability of nanoclay to act as nucleating agent because cold crystallization temperature decreased of about 10°C. Finally, nanocomposite 3D printed samples exhibited always higher elastic modulus than PLA specimens and it increases at increasing printing temperature.
Keywords: 3D printing | FDM | nanocomposites | PLA
Abstract: All over the world, and mainly in United States, since 1977 to 1991 the research centers of automotive companies have processed several statistical data on real accidents between vehicles and pedestrians taking care, obviously, to pedestrians' injury. In latest years, a research group of EEVC (European Enhanced Vehicle-Safety Committee) had realized some documents about "pedestrian test" procedures. In reference papers of period 1977 - 1997 and in EEVC documents, the scientists describe a proposed homologating test for child-head impact; it is represented by the impact of some standardized impactors on car bonnet, in order to evaluate the child-head injury as deceleration of its gravity center. Injury evaluation criteria is an energy criterion and is quantified by the HPC index (see below) calculated by acceleration resultant vector, measured by an accelerometer mounted in the head- impactor. Our research wants to propose a new potential-injury evaluation method based on virtual reconstruction of the surface that envelope all the deformation surfaces in internal part of the bonnet and on its rapid prototyping. This surface is so processed and rapid prototyped as a puzzle of shells with their support. This prototyped surface is super-imposed on the real under-bonnet layout of a car and allows to evaluate easily where and how much our deformed bonnet could hit the hard-parts of the engine layout. This paper shows the results of this research project.
Keywords: Additive manufacturing | Industrial benchmarking | Rapid prototyping | Vehicle design
Abstract: Rapid prototyping (RP) is a set of technologies that permits building a physical model directly from its design by implementing a single automatic process using a 3D model of the object to be printed. RP systems can be based on different Additive Manufacturing (AM) technologies, such as a Fused Deposition Modeling (FDM) machine that works by extruding and melting together fused plastic filaments, drawing the boundaries and filling the model thin layer by thin layer. Low-cost FDM 3d printers do not work well automatically but require of a calibration phase because the best configuration settings in the slicing software are unknown, and the number of parameters values that needs to be manually defined is very large. The scientific literature reports many interesting articles on this topic, describing how the process can be improved by choosing the correct values of various parameters. Internet websites such RepRap.org discuss 3D printers and ppost detailed FAQ sections where users described improvements in 3D printing with simple methods but with great effort in terms of costs and time. Yet not all questions are answered. This paper would introduces: a) a new method for the analysis of the slicing software parameters that can be done with easy models; b) a second method for improving the effects of the parameters that shows a higher influence in the signal-to-noise ratio analysis.
Keywords: Digital fabrication | FDM | NIST artifact | Rapid prototyping | RepRap
Abstract: The paper discusses how Industry 4.0 could impact practitioners performing maintenance in aviation. The attention has been on Augmented Reality and Additive Manufacturing, which can support maintenance tasks and spare parts production respectively. Advantages and open issues are widely discussed and couple of case studies dealing with realistic scenarios are presented to support what has been proposed by the authors. The intention is to demonstrate that AR and AM are viable tools in aviation maintenance, even if effort is necessary to develop an appropriate regulatory framework, required before the introduction of these technologies in the maintenance process. Once applied to real maintenance tasks by airline companies, the practitioning community can develop best practices and the necessary regulation pertaining to maintenance and repair of aerospace systems using AR and AM technologies.
Keywords: Additive Manufacturing | Aeronautical Maintenance | Augmented Reality | Industry 4.0
Abstract: Purpose: This paper aims to propose a consistent approach to geometric modeling of optimized lattice structures for additive manufacturing technologies. Design/methodology/approach: The proposed method applies subdivision surfaces schemes to an automatically defined initial mesh model of an arbitrarily complex lattice structure. The approach has been developed for cubic cells. Considering different aspects, five subdivision schemes have been studied: Mid-Edge, an original scheme proposed by the authors, Doo–Sabin, Catmull–Clark and Bi-Quartic. A generalization to other types of cell has also been proposed. Findings: The proposed approach allows to obtain consistent and smooth geometric models of optimized lattice structures, overcoming critical issues on complex models highlighted in literature, such as scalability, robustness and automation. Moreover, no sharp edge is obtained, and consequently, stress concentration is reduced, improving static and fatigue resistance of the whole structure. Originality/value: An original and robust method for modeling optimized lattice structures was proposed, allowing to obtain mesh models suitable for additive manufacturing technologies. The method opens new perspectives in the development of specific computer-aided design tools for additive manufacturing, based on mesh modeling and surface subdivision. These approaches and slicing tools are suitable for parallel computation, therefore allowing the implementation of algorithms dedicated to graphics cards.
Keywords: Cellular materials | Lattice structures | Mesh modelling | Subdivision surfaces
Abstract: An obstacle to the diffusion of additive technology is the difficulty of predicting the residual stresses introduced during the fabrication process. This problem has a considerable practical interest as evidenced by the abundant literature on residual stresses and distortion induced by the SLM (Selective Laser Melting) and EBAM (Electron Beam Additive Manufacturing). The purpose of this paper is to evaluate the effect of different process parameters on the heat distribution and residual stresses in components made with SLM technique. Three aspects are developed and illustrated: a) thermomechanical modeling of the growth process, based on Finite Elements (FE), which considers changes in the behavior of the material (powder→liquid→solid) through the finite element "birth" and "death" technique that enables the progressive activation of the elements as the component grows; b) sensitivity analysis of the model to the physical characteristics of the material (conductivity, specific heat capacity, Young's modulus). This is an important aspect allowing to focus on the most significant parameters to be determined experimentally with high reliability; c) evaluation of the effects of different process parameters (laser power, scan speed, overlap between adjacent paths) on the process. The article illustrates the theoretical thermal model and the detail of the strategy used in the FE analysis. The most influential characteristics of the material are highlighted and, finally, general criteria for choosing the optimal combination of process parameters to limit the residual stresses are provided.
Keywords: Additive Manufacturing | FE model | Residual stresses | Selective Laser Melting
Abstract: Considering the progressively expansive trade world, "time to market" of productions and goods has turned into a key element for business accomplishment. There are diverse practices that antedate design faults and unveil products on the market in minus time. Among the most used methods in the design and explanation of the necessities, quality function deployment (QFD) and design for Six Sigma (DFSS) can be used. In the prototyping stage, it is probable to address the emergent technology of additive manufacturing. Today, 3D printing is employed as a quick prototyping technique. Nevertheless, the tangible task which industry is fronting is the adoption of these machines for large-scale production of components, which is now possible with new HP multi fusion. The goal of this paper is to illustrate the entire product development process taking advantage of the most modern models and technologies for the final realization of a case study that involves the design and prototyping of an innovative multifunctional fan (lamp, aroma diffuser, and fan) through the multi jet fusion of HP. To begin with, issues related to the DFSS, the QFD and their application to identify the fan requirements are explored. Once the requirements have been defined, the modern CAD design systems and the CAE systems for the validation of the case study will be analyzed and applied. Finally, HP's multi jet fusion methodology and design rules for additive manufacturing will be analyzed in detail, trying to exploit all the positive aspects it offers.
Keywords: CAD | CAE | Design for additive manufacturing | Design for Six Sigma | FEA | Multi jet fusion | Product development | QFD | Rapid prototyping
Abstract: The purpose of this paper is to assess the main effects on the geometric errors in terms of flatness, circularity and cylindricity based on the size of the printed benchmarks and according to the position of the working plane of the 3D printer. Three benchmark models of different sizes, with a parallelepiped and cylinder shape placed in five different positions on the working plane are considered. The sizes of models are chosen from the Renard series R40. Benchmark models are fabricated in ABS (Acrylonitrile Butadiene Styrene) using Zortrax M200 3D printer. A sample of five parts for each geometric category, as defined from the R40 geometric series of numbers, is printed close to each corner of the plate, and in the plate center position. Absolute Digimatic Height Gauge 0-450mm with an accuracy of ±0.03mm by Mitutoyo is used to perform all measurements: flatness on box faces, and circularity/cylindricity on cylinders. Results show that the best performances, in terms of form accuracy, are reached in the area center printable while they decrease with the sample size. Being quality a critical factor for a successful industrial application of the AM processes, the results discussed in this paper can provide the AM community with additional scientific data useful to understand how to improve the quality of parts which may be obtained through new generations of 3D printer.
Keywords: Additive manufacturing | Fused deposition modelling | Geometric errors
Abstract: Additive manufacturing technologies produce objects which present a characteristic surface texture. This is an inevitable and systematic error and has a predictable shape feature which depends on certain process parameters. In order to reduce manufacturing costs and obtain the best results from the point of view of quality, it is essential to predict this error in advance and choose the process parameters which minimise it. For the purpose of measuring the surface quality, the index Ra (ISO 4287, 1997) is used in the related literature. In this paper, it is first demonstrated that the use of roughness parameters in FDM-manufactured surfaces is not adequate to quantify the surface error. The parameter Pa (ISO 4287) is proposed as a more appropriate index to evaluate the surface quality; it is investigated and critically analysed in comparison with the Ra index. A new original model to predict Pa for FDM-manufactured surfaces is presented. The model prediction is compared with experimental data and with the estimation performed by the models described in the literature, within the limits of their capability to predict Pa.
Keywords: Additive manufacturing | Fused deposition modelling | Surface quality
Abstract: Additive manufacturing is a rapidly expanding technology. It allows the creation of very complex 3D objects by adding layers of material, in spite of the traditional production systems based on the removal of material. The development of additive technology has produced initially a generation of additive manufacturing techniques restricted to industrial applications, but their extraordinary degree of innovation has allowed the spreading of household systems. Nowadays, the most common domestic systems produce 3D parts through a fused deposition modeling process. Such systems have low productivity and make, usually, objects with no high accuracy and with unreliable mechanical properties. These side effects can depend on the process parameters. Aim of this work is to study the influence of some typical parameters of the additive manufacturing process on the prototypes characteristics. In particular, it has been studied the influence of the layer thickness on the shape and dimensional accuracy. Cylindrical specimens have been created with a 3D printer, the Da Vinci 1.0A by XYZprinting, using ABS filaments. Dimensional and shape inspection of the printed components has been performed following a typical reverse engineering approach. In particular, the point clouds of the surfaces of the different specimens have been acquired through a 3D laser scanner. After, the acquired point clouds have been post-processed, converted into 3D models and analysed to detect any shape or dimensional difference from the initial CAD models. The obtained results may constitute a useful guideline to choose the best set of the process parameters to obtain printed components of good quality in a reasonable time and minimizing the waste of material.
Keywords: 3D printing | Additive manufacturing | Process parameters | Reverse engineering
Abstract: This paper concerns the design and manufacture of medical devices, such as lower limb prosthesis, integrating low cost industrial technologies. In particular, it focuses the attention on the custom-fit component of a lower limb prosthesis, i.e., the socket, that is the interface with the residual limb. The considered process starts from the 3D reconstruction of patients’ limb and ends with the manufacture of the socket with a 3D printer using a multi-material approach. The process counts three steps: 3D modeling, testing (both experimental and numer-ical) and manufacturing. For each step adopted solutions and tools are described. Finally, conclusions are drawn mainly concerning the challenge of multi-material 3D printing of the socket.
Keywords: 3D printing | Lower limb prosthesis | Socket Modelling Assistant
Abstract: Cardiovascular diagnosis, surgical planning and intervention are among the most interested in recent developments in the field of 3D acquisition, modelling and rapid prototyping techniques. In case of complex heart disease, to provide an accurate planning of the intervention and to support surgical planning and intervention, an increasing number of Hospitals make use of physical 3D models of the cardiac structure, including heart, obtained using additive manufacturing starting from the 3D model retrieved with medical imagery. The present work aims in providing an overview on most recent approaches and methodologies for creating physical prototypes of patient-specific heart and cardiac structures, with particular reference to most critical phases such as segmentation and aspects concerning converting digital models into physical replicas through rapid prototyping techniques. First, recent techniques for image enhancement to highlight anatomical structures of interest are presented together with the current state of the art of semi-automatic image segmentation. Then, most suitable techniques for prototyping the retrieved 3D model are investigated so as to draft some hints for creating prototypes useful for planning the medical intervention.
Keywords: 3D modelling | 3D printing | Cardiovascular diseases | Heart | Medical imagery | Rapid prototyping | Surgical planning
Abstract: This paper describes a part of the contribution of the CoMAS project (“In situ conservation planning of Underwater Archaeological Artifacts”), funded by the Italian Ministry of Education, Universities and Research (MIUR), and run by a partnership of private companies and public research centers. The CoMAS project aims at the development of new materials, techniques and tools for the documentation, conservation and restoration of underwater archaeological sites in their natural environment. This paper details the results achieved during the project in the development of an innovative electric tool, which can efficiently support the restorers’ work in their activities aimed to preserve the underwater cultural heritage in its original location on the seafloor. In particular, the paper describes the different steps to develop an underwater electric cleaning brush, which is able to perform a first rough cleaning of the submerged archaeological structures by removing the loose deposits and the various marine organisms that reside on their surface. The peculiarity of this work consists in a user centred design approach that tries to overcome the lack of detailed users’ requirements and the lack of norms and guidelines for the ergonomic assessment of such kind of underwater tools. The proposed approach makes a wide use of additive manufacturing techniques for the realization and modification of prototypes to be employed for insitu experimentation conducted with the final users. The user tests have been addressed to collect data for supporting the iterative development of the prototype.
Keywords: Additive Manufacturing | Product Design | Underwater Applications | User centred design
Abstract: Nowadays, the most updated CAE systems include structural optimization toolbox. This demonstrates that topological optimization is a mature technique, although it is not a well-established design practice. It can be applied to increase performance in lightweight design, but also to explore new topological arrangements. It is done through a proper definition of the problem domain, which means defining functional surfaces (interface surfaces with specific contact conditions), preliminary external lengths and geometrical conditions related to possible manufacturing constraints. In this sense, its applicability is possible for all kind of manufacturing, although, in Additive Manufacturing, its extreme solutions can be obtained. In this paper, we aim to present the general applicability of topological optimization in the design workflow together with a case study, exploited according to two design intents: the lightweight criterion and the conceptual definition of an enhanced topology. It demonstrates that this method may help to decrease the design efforts, which, especially in the case of additive manufacturing, can be reallocated for other kind of product optimization.
Keywords: Additive Manufacturing | Conceptual Design | Design Intent | Lightweight Design | Topological Optimization
Abstract: The design discipline is faced with radical changes related to new technologies and to an increasingly globalized world with more and more competitive markets. These factors are profoundly influencing methods and processes of design, and the knowledge and skills related to the designer's role. Consequently, the design educational models are radically changing. Today, one of the most impacting evolutions is related to rapid prototyping techniques, which are bringing design practice closer to the auto-production. This emerging trend cannot be anymore supported with traditional didactic approaches, but it is necessary to create spaces for allowing students to learn, design and experiment in a shared way. This paper presents the Polifactory Lab at Politecnico di Milano, an innovative makerspace established with the aim of creating a new research and teaching space. In this paper, the authors present the Polifactory Lab, its theoretical purposes, and some examples of didactic activities carried out in the lab.
Keywords: Design educational models | Innovation in education | Makerspace | Rapid prototyping
Abstract: In this paper, we discuss the possibilities available as well as the challenge to be faced when designing for metal additive manufacturing through the description of an application of the Selective Laser Melting technology within the professional sports equipment field. We describe the redesign activity performed on the cam system of a compound bow, starting from the analysis of the functional, manufacturing and assembly constraints till the strategies applied to guarantee the printability of the object. This activity has thus provided the opportunity to analyse the difficulties currently encountered by practitioners when designing for additive manufacturing due to the lack of integrated design approaches and the high number of aspects that need to be simultaneously taken into account when performing design choices.
Keywords: Design for Additive Manufacturing | Metal Additive Manufacturing | Selective Laser Melting | Sports Equipment
Abstract: One of the most fascinating possibilities of Additive Manufacturing technologies is their capability to realize objects that include various types of joints and moving parts. The research presented in this paper proposes to embed elastic elements in these joints in order to control their compliance. Two applications are also presented, in order to demonstrate, firstly, the practical feasibility of this innovative joint, and, secondly, the possibility to control joint elastic behavior in order to force the connected parts to automatically return to their initial positions when the actuating load is removed.
Keywords: Adaptive-Grip | Additive Manufacturing | Flexi-Hand | Fused Deposition Modelling | Multi-Material-Deposition | Print-in-Place
Abstract: The very rapid evolution of digital technologies and the "Internet of Things" phenomenon are today some of the most important issues that product designers have to face. Consequently, today designers need to understand and manage these new technologies in order to exploit their potential into innovative products. Therefore, it is recommendable that designers focus their activities on the design of the meaning and on the user interaction of products, in order to create smart products that are easy-to-use and enjoyable. In order to address all these issues, the authors set up an experimental workshop in which students with different backgrounds in design-related disciplines were asked to collaborate to the design of a domestic product that allows new tangible interaction with live-data streams. In addition, students were asked to develop the functioning prototype of their design solution, by using rapid prototyping and physical computing techniques. The students were able to develop working prototypes of products that are capable of communicating information derived from real-time data streams. Some of the most representative results of this workshop are presented in the paper.
Keywords: 3D printing | Design education | User centred design
Abstract: Background Additive manufacturing technologies are being enthusiastically adopted by the orthopaedic community since they are providing new perspectives and new possibilities. First applications were finalised for educational purposes, pre-operative planning, and design of surgical guides; recent applications also encompass the production of implantable devices where 3D printing can bring substantial benefits such as customization, optimization, and manufacturing of very complex geometries. The conceptual smoothness of the whole process may lead to the idea that any medical practitioner can use a 3D printer and her/his imagination to design and produce novel products for personal or commercial use. Aims Outlining how the whole process presents more than one critical aspects, still demanding further research in order to allow a safe application of this technology for fully-custom design, in particular confining attention to orthopaedic/orthodontic prostheses defined as components responding mainly to a structural function. Methods Current knowledge of mechanical properties of additively manufactured components has been examined along with reasons why the behaviour of these components might differ from traditionally manufactured components. The structural information still missing for mechanical design is outlined. Results Mechanical properties of additively manufactured components are not completely known, and especially fatigue limit needs to be examined further. Conclusion At the present stage, with reference to load-bearing implants subjected to many loading cycles, the indication of custom-made additively manufactured medical devices should be restricted to the cases with no viable alternative.
Keywords: Additive manufacturing | Fast prototyping | Fatigue resistance | Orthodontic implants | Orthopaedic implants | Prostheses
Abstract: The shipment of heritage artefacts for restoration or temporary/travelling exhibition has been virtually lacking in customised packaging. Hitherto, packaging has been empirical and intuitive which has unnecessarily put the artefacts at risk. So, this research arises from the need to identify a way of designing and creating packaging for artefacts which takes into account structural criticalities to deal with deteriorating weather, special morphology, constituent materials and manufacturing techniques. The proposed methodology for semi-automatically designing packaging for heritage artefacts includes the integrated and interactive use of Reverse Engineering (RE), Finite Element Analysis (FEA) and Rapid Prototyping (RP). The methodology presented has been applied to create a customised packaging for a small C3rd BC bronze statue of Heracles (Museo Civico “F.L. Belgiorno” di Modica-Italy). This methodology has highlighted how the risk of damage to heritage artefacts can be reduced during shipping. Furthermore, this approach can identify each safety factor and the corresponding risk parameter to stipulate in the insurance policy.
Keywords: Cultural heritage | FEM | Laser scanning | Packaging | Rapid prototyping
Abstract: In this study, the possibility to use a layered silicate reinforced polylactic acid (PLA) in additive manufacturing applications was investigated. In particular, after melt compounding in a twin-screw extruder a filament for 3D printing applications was produced using a single-screw extruder. The influence of nanoclay on mechanical, thermal and viscoelastic properties of the produced filaments was investigated. Differential scanning calorimetry (DSC) results reveal an increase in crystallinity for the nanocomposites and the presence of two crystalline forms (α and α'). Dynamic mechanical thermal analysis (DMA) results show that storage modulus increased for the nanocomposites when compared with neat PLA. Finally, the extruded PLA/clay filaments were successfully 3D printed using fused deposition modelling (FDM) technique. The printed nanocomposites showed a higher elastic modulus (15%) compared to printed samples of neat PLA. Moreover, PLA/clay printed samples present also a better shape stability, showing sharper edges.
Keywords: 3D printing | FDM | nanocomposites | PLA
Abstract: This work deals with the development, the application and the experimental validation of a procedure based on an algorithm, running in a finite element environment replacing the continuous mass of convex solids with a cancellous bone-inspired lattice structure showing curved beams oriented on the basis of the external forces, sharing with it border and boundary conditions. For the validation of the new lattice structure a cubic representative volume element, showing curved micro-beams, was chosen, implementing periodic boundary conditions. At the end, the algorithm created a. stl file to be printed by a 3D printer using an appropriate polymer. The numerical results were compared with experimental results obtained by compression tests. The experimental/numerical correlation confirmed the validity of the FEM “beam element – based” lattice structure that could be applied to different solid shapes.
Keywords: 3D printing | Directional orientation | Finite element analysis (FEA) | Mechanical testing | Microstructure
Abstract: This paper describes the beneficial impact of an augmented reality based technique on the 3D printing process monitoring within additive manufacturing machines. A marker is applied in a fixed point of the rapid prototyping machine, integral with the component being manufactured; as an alternative, a markerless approach can be followed too. A virtual model of the object to be printed is superimposed to the real one. In this way, the shape of the object in different printing stages can be viewed. An interactive comparison between real and virtual model can be carried out both in manual and automatic mode. If manufacturing errors are detected, the building process can be stopped. Augmented reality technique allows an intuitive shape check of a part being printed with rapid prototyping technologies. In case of complex objects it helps the operator in the detection of possible errors along the manufacturing process; stopping the machine as soon as an error appears avoids waste of machining time and material. The average precision of the augmented reality is useful to find significant geometrical errors; geometrical deviations less than 1 mm can hardly be assessed both in manual and in automatic mode, and further studies should be carried out to increase the technique precision and range of application. To the best of the authors’ knowledge it is the first time where experiments on the integration between augmented reality and rapid prototyping to interactively monitor 3D parts’ printing have been investigated and reported in literature.
Keywords: 3D printing | Additive Manufacturing | Augmented Reality | Design | Rapid Prototyping
Abstract: This paper presents the development of a CAD conceived to support the modelling of lightweight and lattice structures just from the initial stages of the design process. A new environment, called LWSM (acronym of LightWeight Structures Modelling), has been implemented in Python programming language in an open-source CAD software to allow the fast modelling of several sandwich structures or the filling of solid parts with cubic and tetrahedral lattice structures which can be produced by Additive Manufacturing (AM) techniques. Several tests have been carried out to validate the tool, one of which is included in the paper. The design of a bracket component inside LWSM using a traditional dense geometry and a lattice structure is described. The use of Design for Additive Manufacturing (DfAM) functions helps the user in the design of innovative structures which can produced only with AM technologies. A significant change in the shape of the part respect to traditional solutions is noticed after the use of DfAM functions by experimenters: FEM analysis confirms a strong weight reduction.
Keywords: Additive manufacturing | CAD | FEM analysis | Lattice structure | Lightweight structures
Abstract: Additive manufacturing technologies enable the fabrication of parts characterized by shape complexity and therefore allow the design of optimized components based on minimal material usage and weight. In the literature two approaches are available to reach this goal: adoption of lattice structures and topology optimization. In a recent work a Computer-Aided method for generative design and optimization of regular lattice structures was proposed. The method was investigated in few configurations of a cantilever beam, considering six different cell types and two load conditions. In order to strengthen the method, in this paper a number of test cases have been carried out. Results explain the behavior of the method during the iterations, and the effects of the load and of the cell dimension. Moreover, a visual comparison between the proposed method and the results achieved by topology optimization is shown.
Keywords: Additive Manufacturing | Cellular Structure | Computer-Aided Design (CAD) | Design Methods | Lattice Structures
Abstract: A feasibility study was performed in order to demonstrate the benefits of designing and manufacturing a customized foot orthosis by means of digital technologies, such as Reverse Engineering (RE), Generative Design (GD) and Additive Manufacturing (AM). The aim of this work was to define the complete design-manufacturing process, starting from the 3D scanning of the human foot anatomy to the direct fabricating of the customized foot orthosis. Moreover, this first methodological study tries to combine a user-friendly semi-automatic modelling approach with the use of low-cost devices for the 3D laser scanning and the 3D printing processes. Finally, the result of this approach, based on digital technologies, was also compared with that achieved by means of conventional manual techniques.
Keywords: Additive manufacturing | Computer aided design | Foot orthosis | Generative design | Reverse engineering
Abstract: The growing potential of additive manufacturing technologies is currently being boosted by their introduction in directly manufacturing of ready-to-use products or components, regardless of their shape complexity. Taking advantage from this capability, a full set of new solutions to be explored is related to the possibility to directly manufacture joints or mechanisms as a unibody structure. In this paper, the preliminary design of a robotic mechanism is presented. The component is designed in order to be manufactured as a unibody structure by means of an Additive Manufacturing technology. Fused Deposition Modelling technique is used to print the mechanic arm as a single component, composed by different functional parts already assembled in the CAD model. Soluble support material is commonly used to support undercuts: in this case it is also deposited in the space between two adjacent parts of the same component, in order to allow the relative motion and the kinematic connection between them. The design process considers component optimization in relation to both the specific manufacturing technique and both the interaction between the different parts of the same component, in order to guarantee the proper relative motions. The conceived mechanism consists in a robotic structure in which the mechanical arm is bounded to a base and connected to a plier on the opposite side. The effect of clearance between all the kinematic parts is evaluated in order to assess mechanism degree of mobility in relation to the manufacturing process and components tolerances and geometry.
Keywords: Additive Manufacturing | Clearance assessment | Design Methods | Fused Deposition Modeling technique | Unibody mechanism manufacturing
Abstract: Over the past few years, the influence of static or dynamic magnetic fields on biological systems has become a topic of considerable interest. Magnetism has recently been implicated to play significant roles in the regulation of cell responses and, for this reason, it is revolutionizing many aspects of healthcare, also suggesting new opportunities in tissue engineering. The aim of the present study was to analyze the effect of the application mode of a time-dependent magnetic field on the behavior of human mesenchymal stem cells (hMSCs) seeded on 3D additive-manufactured poly(ɛ-caprolactone)/iron-doped hydroxyapatite (PCL/FeHA) nanocomposite scaffolds.
Keywords: Additive manufacturing | Cell-material interaction | Magnetic field | Scaffold
Abstract: The success of Tissue Engineering (TE) based approaches is strongly dependent on the development of novel biomaterials for the design of 3D matrices with tailored biomechanical properties to promote the regeneration of human tissues and organs. This review covers the critical aspects related with the preparation of new unsaturated polyester (UP) resin formulations with suitable biological, chemical, thermal and morphological properties for the additive manufacturing (AM) of TE constructs. In this context, the basic principles of available AM technologies, with a special focus on novel stereolithography processes such as microstereolithography (micro-SLA), stereo-thermal-lithography (STLA), two-photon polymerization (TPP) and nanostereolithography (nano-SLA), are also presented and discussed. Ultimately, the present review will provide a better insight into the limitations and potential of combining UP and AM towards the rationale design/fabrication of complex artificial tissue substitutes.
Keywords: Additive manufacturing | Stereolithography processes | Structure/properties relationships | Tissue engineering | Unsaturated polyesters
Abstract: This work presents a photolithographic rapid prototyping process for producing thin films (“Rapid Phototyping”). This process allows a quick and cost-effective generation of scalable thermopile microstructures using commercial equipment and materials. Structural widths of 100x250μm can be produced reproducible in a lift-off process with an accuracy of 5 microns vertically and 30 microns horizontally.
Keywords: Bismuth | Foil | Laser | Lift Off | Optical power | Photolithography | Powersensor | Printer | PVD | Rapid phototyping | Rapid prototyping | Silver | Thermocouple | Thermopile | Thin film
Abstract: In the twenty-first century, meeting our technological challenges demands educational excellence, a skilled populace that is ready for the critical challenges society faces. There is widespread consensus, however, that education systems are failing to adequately prepare all students with the essential twenty-first century knowledge and skills necessary to succeed in life, career, and citizenship. The purpose of this paper is to understand how twenty-first century knowledge and skills can be appropriately embedded in engineering education finalised to innovative product development by using additive manufacturing (AM). The study designs a learning model by which to achieve effective AM education to address the requirements of twenty-first century and to offer students the occasion to experiment with STEM (Science, technology, engineering, and mathematics) concepts. The study is conducted using the quality function deployment (QFD) methodology.
Keywords: additive manufacturing | and mathematics | engineering | engineering education | learning/training model | Quality function deployment | science | technology | twenty-first century skills
Abstract: In the field of oral rehabilitation, the combined use of 3D imaging technologies and computer-guided approaches allows the development of reliable tools to be used in preoperative assessment of implant placement. In particular, the accurate transfer of the virtual planning into the operative field through surgical guides represents the main challenge of modern dental implantology. Guided implant positioning allows surgical and prosthetic approaches with minimal trauma by reducing treatment time and decreasing patient’s discomfort. This paper aims at defining a CAD/CAM framework for the accurate planning of flapless dental implant surgery. The system embraces three major applications: (1) freeform modelling, including 3D tissue reconstruction and 2D/3D anatomy visualization, (2) computer-aided surgical planning and customised template modelling, (3) additive manufacturing of guided surgery template. The tissue modelling approach is based on the integration of two maxillofacial imaging techniques: tomographic scanning and surface optical scanning. A 3D virtual maxillofacial model is created by matching radiographic data, captured by a CBCT scanner, and surface anatomical data, acquired by a structured light scanner. The pre-surgical planning process is carried out and controlled within the CAD application by referring to the integrated anatomical model. A surgical guide is then created by solid modelling and manufactured by additive techniques. Two different clinical cases have been approached by inserting 11 different implants. CAD-based planned fixture placements have been transferred into the clinical field by customised surgical guides, made of a biocompatible resin and equipped with drilling sleeves.
Keywords: Additive manufacturing | Biomedical imaging | Computer-assisted dental implantology | Freeform solid modelling | Oral rehabilitation
Abstract: Current researches on aircraft design aim to reduce airplanes and components weights, optimizing aircraft performances and contributing to the challenge of reducing fuel consumption and operational costs. In this perspective novel materials and technologies are developed, but also advances in design methods and tools. Generative Design is a novel approach to automatically optimize component design. The design process has to be designed itself to achieve the optimal solution, in relation to design parameters, requirements and limits. Which peculiar features justify considering this technique to be a substantial step forward with respect to classical MDO? Could Generative Design be only an important, but not particularly differentiated approach for the design of (aerospace) structures and possibly systems of a higher level? For example, when the design goal is to find the best configuration of a structure, does generative design lead to the discovery of new concepts, or types of structures, or it is a particular application of genetic algorithms to topological optimization? This paper aims to contribute to give an answer to the previous questions. Specifically, the generative design approach is expected to be able to select between basic concepts and use these as the basic instructions and ingredients of a recipe for the design of a new system. By these considerations, in this paper, we revised the improvements brought by Generative Design principles within the traditional design procedure in aeronautics, considering Additive Manufacturing technology.
Keywords: Additive manufacturing | Aircraft design | Design methods | Generative design | Materials and processes
Abstract: This study presents an approach based on Design of Experiment (DoE) technique for the optimization of an energy recovery ventilator (ERV). This system is one of the efficient ways to enhance the thermo-hygrometric comfort without increase excessively the thermal load in domestic kitchen. However, there is a major concern, which energy recovery cannot trade off ERV's fan power consumption. The goal of this study is to obtain the information about the relation between factors and response in an empirical way. This approach integrates three different levels of analysis: the virtual prototyping, Design of Experiment (DoE) and rapid prototyping. The virtual analysis allows to define the principal parameterization of a simplified model and to simulate the performance of each configuration at working condition. The proposed approach investigates the effect of the defined parameters and noise factor on the experimental results. In particular, the applied method for DoE analysis is based on virtual experiments in according to the necessity to reduce time and costs during the early design phase. The optimum parameters configuration, which is defined by the previous step, is useful to define the geometry and the working condition of a reliable virtual model. The final level is the realization of a 3D ERV with a rapid prototyping printer. The obtained component is now evaluable at the test bench to investigate the air flow rate and the electric power consumption.
Keywords: Design of Experiments | Energy Recovery Ventilator | Rapid Prototyping | Virtual Prototyping
Abstract: Patients undergoing mastectomy for breast cancer have nowadays many options for breast reconstruction, that will help in re-establishing patient's self confidence in her own body image. Implant-based reconstruction remains the most common form of post-mastectomy reconstruction, but it could also present some complications, the most common being capsular contracture. Accordingly, a novel breast mound may be perfectly designed using the reverse engineering approach and additive manufacturing methods combined with autologous fat grafting. A 3D hierarchical structure with autologous adipose-derived stem cells may be used as a construct for tissue regeneration. The 3D morphologically controlled scaffold may be placed in the subcutaneous position at the level of the conservative mastectomy side. The scaffold will be colonized with autologous fat tissue in some sessions. The biodegradable customized structure will help to maintain the breast shape and the natural consistency may be obtained with the fat grafting, also considering adequate enhancement techniques (Stromal Vascular Fraction derived growth factors). The principles of regenerative medicine may be combined and integrated with those of reverse engineering (3D image capture, 3D modelling and rapid prototyping) to design custom-made and high functional hierarchical structures with tailored properties and 3D complex geometry. The current study will focus on the basic principles and strategies in designing 3D advanced and complex structures for breast repair and regeneration.
Keywords: Additive Manufacturing | Breast reconstruction | Fat Grafting | Reverse Engineering | Tissue Regeneration
Abstract: In the past few years, researchers have focused on the development of three-dimensional (3D) advanced scaffolds and multifunctional hydrogel-based materials. As reported in literature, 3D polymer-based composite scaffolds for tissue engineering have been manufactured through conventional and advanced manufacturing techniques, and different injectable materials and hydrogel-based systems have been proposed and studied. The aim of the current research was to define an approach in the development of multifunctional tools spanning from 3D hierarchical scaffolds for soft tissue engineering to advanced hydrogel-based devices for in situ cell or drug release. The mechanical/rheological behaviour as well as the structural/functional features of the designed devices were discussed and analyzed.
Keywords: Additive Manufacturing | Hierarchical Scaffolds | Injectable Materials | Mechanical/Rheological Properties | Multilayer Hydrogels
Abstract: Patients undergoing mastectomy for breast cancer have nowadays many options for breast reconstruction, that will help in re-establishing patient's self confidence in her own body image. Implant-based reconstruction remains the most common form of post-mastectomy reconstruction, but it could also present some complications, the most common being capsular contracture. Accordingly, a novel breast mound may be perfectly designed using the reverse engineering approach and additive manufacturing methods combined with autologous fat grafting. A 3D hierarchical structure with autologous adipose-derived stem cells may be used as a construct for tissue regeneration. The 3D morphologically controlled scaffold may be placed in the subcutaneous position at the level of the conservative mastectomy side. The scaffold will be colonized with autologous fat tissue in some sessions. The biodegradable customized structure will help to maintain the breast shape and the natural consistency may be obtained with the fat grafting, also considering adequate enhancement techniques (Stromal Vascular Fraction derived growth factors). The principles of regenerative medicine may be combined and integrated with those of reverse engineering (3D image capture, 3D modelling and rapid prototyping) to design custom-made and high functional hierarchical structures with tailored properties and 3D complex geometry. The current study will focus on the basic principles and strategies in designing 3D advanced and complex structures for breast repair and regeneration.
Keywords: Additive Manufacturing | Breast reconstruction | Fat Grafting | Reverse Engineering | Tissue Regeneration
Abstract: In the field of reconstructive surgery, a great challenge is represented by bone injuries beyond the self-repair threshold. Autologous bone grafts may be considered the gold standard. Anyway, such approach is limited by the amount of tissue required for grafting and by donor site morbidity. To overcome these drawbacks, bone tissue engineering represents a promising solution. 3D fully biodegradable and nanocomposite scaffolds for bone tissue regeneration, consisting of poly(ϵ-caprolactone) (PCL) reinforced with hydroxyapatite (HA) nanoparticles, were developed using an additive manufacturing process. The effect of nanoparticles and architecture (i.e., lay-down pattern) on the mechanical/functional and biological properties was discussed.
Keywords: Additive Manufacturing | Bone | Nanocomposite Scaffolds | Tissue Regeneration
Abstract: Bone tissue engineered 3-D constructs customized to patient-specific needs are emerging as attractive biomimetic scaffolds to enhance bone cell and tissue growth and differentiation. The article outlines the features of the most common additive manufacturing technologies (3D printing, stereolithography, fused deposition modeling, and selective laser sintering) used to fabricate bone tissue engineering scaffolds. It concentrates, in particular, on the current state of knowledge concerning powder-based 3D printing, including a description of the properties of powders and binder solutions, the critical phases of scaffold manufacturing, and its applications in bone tissue engineering. Clinical aspects and future applications are also discussed.
Keywords: 3D printing | Additive manufacturing technologies | Binder | Bone | Depowdering | Powder | Scaffold | Sintering
Abstract: The saddle is one of the most complex bicycle components providing both comfort and support while pedalling. Several studies have been carried out on bicycle saddles in recent years including medical ones to identify any correlated pathologies, and others to optimize design and sports performance. There are various types of commercially available saddles but they are all fixed geometry. The main identifiers of these designs are their length, nose inclination and the geometry of the support of the ischial tuberosities and pubic rami (wide, narrow, flat, furrowed etc.). So as the literature suggests, the fixed-geometry saddle on today’s market has only partly resolved the anatomical pathologies related to extended saddle time. Consequently, the aim of this study is to develop, through interactive Re-design methodology, a variable geometry saddle (VGS) prototype for amateur cyclists capable of reducing the onset of saddle pathologies and improving pedalling comfort. The VGS was developed which can be adjusted to the physico-anatomical requirements of the rider as well as to various ride conditions (uphill, flat and downhill). The simple adjusters affect nose inclination and the width of the saddle back. In particular, the nose mechanism allows on-the-fly adjustment. The VGS developed could also allow the cyclist to identify the most congenial subjective geometry to help choose among commercial alternatives. An electroneurograph test on the pudendum nerve was also performed on five male amateur cyclists to see whether there were any effects with a variable saddle geometry compared to a fixed-geometry commercial saddle.
Keywords: Bicycle seat | Cycling | Interactive design | Rapid prototyping | Reverse engineering
Abstract: In recent years virtual anthropology has been carrying out investigations as an alternative to the traditional anthropological approach. Among various applications is the study of the death masks of historically famous people, to authenticate them and make facial reconstructions. This study describes a multidisciplinary approach applied to the only three death masks of the musician Vincenzo Bellini made from different materials in different periods. By applying virtual anthropology along with Reverse Engineering, the morphological and metrical relationships of the masks were able to be studied, a study uniquely enabled in virtual environment. So, the finds were investigated without compromising their integrity also thanks to the use physical models obtained through Rapid Prototyping. Integrated with traditional artistic techniques, these methodologies provided evaluations of the historical, technical and morphological relationships between the death masks. Nevertheless, to refer these faces to Bellini, the results were compared with Bellini's autopsy data from Prof. Dalmas.
Keywords: Additive manufacturing | Death mask | Laser scanning | Superimposition techniques | Vincenzo Bellini | Virtual anthropology
Abstract: The paper shows a research activity aimed at integrating low cost industrial technologies in the design, test and man- ufacture of medical devices. This work focuses on lower limb prosthesis and in particular on the custom-fit compo- nent interacting with the residual limb, i.e. the socket. The process going from the 3D reconstruction of patients' limb to the manufacture of the socket by means of a 3D printer has been designed. Moreover, this must be as automatic as possible and should not require the presence of a design and simulation expert. This implied a deep involvement of physicians and orthopaedic technicians in order to embed rules and procedures in the system. The process is divided in three steps: design, test and manufacture. For each step some details are shown and at last some conclusions are drawn mainly concerning the challenge of multi-material 3D printing of the socket.
Keywords: 3D printing | Lower Limb Pros-thesis | Socket Modelling Assistant
Abstract: Additive manufacturing technologies enable the fabrication of innovative parts not achievable by other technologies, such as cellular structures, characterized by lightness and good mechanical properties. In this paper a novel modeling and optimization method is proposed to design regular cellular structures. The approach is based on generative modeling of a structure by repeating a unit cell inside a solid model, obtaining a beam model, and on an iterative variation of the size of each section in order to get the desired utilization for each beam. Different structures have been investigated, derived by six cell types in two load conditions. Taxonomy of cell types as a function of relative density and compliance were proposed in order to support the design process for additive manufacturing of cellular structures.
Keywords: Additive manufacturing | Cellular structure | Computer aided design (CAD) | Design methods | Simulation
Abstract: Purpose - The purpose of this paper is to describe two different approaches for manufacturing pre-formed titanium meshes to assist prosthetically guided bone regeneration of atrophic maxillary arches. Both methods are based on the use of additive manufacturing (AM) technologies and aim to limit at the minimal intervention the bone reconstructive surgery by virtual planning the surgical intervention for dental implants placement. Design/methodology/approach - Two patients with atrophic maxillary arches were scheduled for bone augmentation using pre-formed titanium mesh with particulate autogenous bone graft and alloplastic material. The complete workflow consists of four steps: three-dimensional (3D) acquisition of medical images and virtual planning, 3D modelling and design of the bone augmentation volume, manufacturing of biomodels and pre-formed meshes, clinical procedure and follow up. For what concerns the AM, fused deposition modelling (FDM) and direct metal laser sintering (DMLS) were used. Findings - For both patients, a post-operative control CT examination was scheduled to evaluate the progression of the regenerative process and verify the availability of an adequate amount of bone before the surgical intervention for dental implants placement. In both cases, the regenerated bone was sufficient to fix the implants in the planned position, improving the intervention quality and reducing the intervention time during surgery. Originality/value - A comparison between two novel methods, involving AM technologies are presented as viable and reproducible methods to assist the correct bone augmentation of atrophic patients, prior to implant placement for the final implant supported prosthetic rehabilitation.
Keywords: CAD/CAM | Computed tomography | Implant surgery | Rapid prototyping | Titanium mesh
Abstract: In the past few years, researchers have focused on the design and development of three-dimensional (3D) advanced scaffolds, which offer significant advantages in terms of cell performance. The introduction of magnetic features into scaffold technology could offer innovative opportunities to control cell populations within 3D microenvironments, with the potential to enhance their use in tissue regeneration or in cell-based analysis. In the present study, 3D fully biodegradable and magnetic nanocomposite scaffolds for bone tissue engineering, consisting of a poly(ε-caprolactone) (PCL) matrix reinforced with iron-doped hydroxyapatite (FeHA) nanoparticles, were designed and manufactured using a rapid prototyping technique. The performances of these novel 3D PCL/FeHA scaffolds were assessed through a combination of theoretical evaluation, experimental in vitro analyses and in vivo testing in a rabbit animal model. The results from mechanical compression tests were consistent with FEM simulations. The in vitro results showed that the cell growth in the magnetized scaffolds was 2.2-fold greater than that in non-magnetized ones. In vivo experiments further suggested that, after only 4 weeks, the PCL/FeHA scaffolds were completely filled with newly formed bone, proving a good level of histocompatibility. All of the results suggest that the introduction of magnetic features into biocompatible materials may confer significant advantages in terms of 3D cell assembly.
Keywords: Bone tissue engineering | Experimental/theoretical analysis | Nanocomposite | Rapid prototyping | Scaffold
Abstract: Our goal is to allow the creators to focus on their creative activity, developing their ideas for physical products in an intuitive way. We propose a new CAD system allows users to draw virtual lines on the surface of the physical object using see-through AR, and also allows users to import 3D data and make its real object through 3D printing.
Keywords: 3D printing | AR/MR | CAD | Collaboration
Abstract: Purpose: The main purpose of this research work is to study the effect of poly lactic acid (PLA) addition into poly (e-caprolactone) (PCL) matrices, as well the influence of the mixing process on the morphological, thermal, chemical, mechanical and biological performance of the 3D constructs produced with a novel biomanufacturing device (BioCell Printing). Design/methodology/ approach: Two mixing processes are used to prepare PCL/PLA blends, namely melt blending and solvent casting. PCL and PCL/PLA scaffolds are produced via BioCell Printing using a 300-mm nozzle, 0/908 lay down pattern and 350-μm pore size. Several techniques such as scanning electron microscopy (SEM), simultaneous thermal analyzer (STA), nuclear magnetic resonance (NMR), static compression analysis and Alamar BlueTM are used to evaluate scaffold's morphological, thermal, chemical, mechanical and biological properties. Findings: Results show that the addition of PLA to PCL scaffolds strongly improves the biomechanical performance of the constructs. Additionally, polymer blends obtained by solvent casting present better mechanical and biological properties, compared to blends prepared by melt blending. Originality/value: This paper undertakes a detailed study on the effect of the mixing process on the biomechanical properties of PCL/PLA scaffolds. Results will enable to prepare customized PCL/PLA scaffolds for tissue engineering applications with improved biological and mechanical properties, compared to PCL scaffolds alone. Additionally, the accuracy and reproducibility of by the BioCell Printing enables to modulate the micro/macro architecture of the scaffolds enhancing tissue regeneration. © Emerald Group Publishing Limited.
Keywords: Biological analysis and testing | Fused deposition modelling | Polymers | Scaffolds
Abstract: Rapid-prototyping is usually considered as a powerful tool in geometric and functional optimization of a product. In such an approach, focus is exclusively on the real component, and not on the rapid prototype which represents it. This work takes part on a wider study which focuses on a rational, systematic approach in obtaining an "optimized rapid prototype", with particular regard to emptying strategies without loss of structural and geometric properties. In detail, a set of tensile tests have been performed on different types of specimen, which reproduce a set of corresponding emptying strategies: each type of specimen is characterized by a different percentage of porosity (40, 60 and 80%), obtained by the combination of particular values of two parameters: reticular structure and its density. As a result, the correlation between mechanical strength and geometric structure has been evaluated, allowing the identification of a profitable emptying strategy, in terms of cost and weight. © Springer-Verlag London 2013.
Keywords: Cellular structures | Light weight structures | Polyamide tensile properties | Rapid prototyping | Selective laser syntering
Abstract: The significantly growing use of Additive Manufacturing (AM) enables the fabrication of innovative parts, characterized by lightness and good mechanical properties. The biomedical field takes great advantage of these capabilities: in particular, the ability of producing porous or lattice structure-based parts allows to obtain prostheses with human bone like stiffness, with a positive influence in patient's lifestyle. The knowledge of the mechanical behavior of materials used in AM and producible geometries is an essential requirement to profit and improve this characteristic: in particular, recent studies focus on the correlation between strength parameters and relative porosity of the part. In a previous work a set of tensile tests have been performed on different types of specimens, reproducing a set of corresponding emptying strategies, with different resulting porosity rates, and a linear predictive model has been proposed. Aim of this work is to integrate the already acquired data, providing an interpretation on previous results by numerical simulations: the influence of porosity rate on mechanical properties was investigated by performing both global and local Finite Element Analyses, finding out an explanation on inverse proportionality between material strength properties and porosity rate. The methodology proved to be a profitable way in the optimization of lattice structures for Additive Manufacturing. © 2012 Elsevier Ltd.
Keywords: Additive Manufacturing | Cellular structures | Finite Element Analysis | Polyamide | Selective Laser Sintering
Abstract: In this paper we report the application of CAD/CAM based technologies for the innovative development of customized surgical devices to assist the mandibular rehabilitation in both primary surgery (resection and reconstruction) and secondary surgery (only reconstruction). Design and manufacturing of such customized surgical device are conducted according to the virtual pre-operative planning of the surgeon and with the aim to transferring this planning into the operating theatre. In the case of primary surgery, a cutting guide is developed to assist the resection step while a bone plate is developed to assist the reconstruction step. Instead, in the case of secondary surgery, in addition to the bone plate to support the reconstruction, also a repositioning guide is designed to bring back to the original position the resected stumps according to the original shape of the mandible. Finally, the components of the surgical devices are manufactured by DMLS in alloys suitable for biomedical applications. © 2012 Springer-Verlag France.
Keywords: 3D Reconstruction | Computed tomography | Computer aided design | Direct metal laser sintering | Rapid prototyping
Abstract: In this work a novel design and manufacturing procedure have been experimented in order to improve the production of implant-supported nasal prosthesis. The complete workflow was divided into three main steps: data capture, prosthesis design and prosthesis manufacturing. First, the data capturing of the patient's face was obtained by means of 3D laser scanning. Then, design and manufacturing phases were carried out through CAD-CAM procedures and Rapid Prototyping technologies to obtain the mold for the silicone processing and the substructure for the retention of the prosthesis. Moreover, to design the customized prosthesis based on real anatomic shapes, a novel "Ear&Nose Digital Library" was developed in the framework of a multidisciplinary project with the involvement of students from medicine and engineering faculties. Advantages in terms of improvement of retention and cost reduction are presented. © 2012 Springer-Verlag.
Keywords: Facial rehabilitation | Prosthesis design | Rapid Prototyping | Reverse Engineering
Abstract: The protocol presented here is intended to minimise the intervention in bone reconstruction surgery when severe atrophy or deformity is present in the maxillary arches. A patient underwent augmentation of an atrophic maxillary arch using titanium mesh and particulate autogenous plus bovine demineralised bone. After computed tomography data elaboration, computer-aided design and computer-aided machining were used to plan the augmentation of bone volume to improve the implant position needed to support the final dental prosthesis. The augmented maxilla was rapidly prototyped in plastic, and the titanium mesh was tested on this model before the surgical intervention. Then, the preformed titanium mesh was implanted in the maxillary arch with bone grafting. The bone was augmented relative to the position of the implants for the definitive fixed implant-supported rehabilitation. The protocol presented here is a viable, reproducible way to determine the correct bone augmentation for the final implant-supported prosthetic rehabilitation. © 2013 Copyright Taylor and Francis Group, LLC.
Keywords: bone augmentation | bone graft | computed tomography | dental implants | rapid prototyping
Abstract: Over the past years, polymer-based materials have attracted research interest in the field of tissue repair and regeneration. As reported in literature, different injectable systems have been proposed, trying to reduce surgical invasiveness. In a first step of the current research, the rheological and functional features of injecatble hydrogel-based materials for central nervous system applications or soft tissue regeneration (collagen/PEG semi-IPNs) as well as for hard tissue engineering (alginate/iron-doped hydroxyapatite) were evaluated. Then, the study was also devoted to the development of 3D nanocomposite poly(s-caprolactone)/iron-doped hydroxyapatite scaffolds for bone tissue engineering, providing a preliminary approach to assess magnetic attraction forces. © 2013 The Authors.
Keywords: Injectable Materials | Magnetic Scaffolds | Nanocomposites | Rapid Prototyping | Rheology
Abstract: An Additive Manufacturing technique for the fabrication of three-dimensional polymeric scaffolds, based on wet-spinning of poly(ε-caprolactone) (PCL) or PCL/hydroxyapatite (HA) solutions, was developed. The processing conditions to fabricate scaffolds with a layer-by-layer approach were optimized by studying their influence on fibres morphology and alignment. Two different scaffold architectures were designed and fabricated by tuning inter-fibre distance and fibres staggering. The developed scaffolds showed good reproducibility of the internal architecture characterized by highly porous, aligned fibres with an average diameter in the range 200-250 μm. Mechanical characterization showed that the architecture and HA loading influenced the scaffold compressive modulus and strength. Cell culture experiments employing MC3T3-E1 preosteoblast cell line showed good cell adhesion, proliferation, alkaline phosphatase activity and bone mineralization on the developed scaffolds. © 2012 Springer Science+Business Media, LLC.
Keywords: Additive manufacturing | Polycaprolactone | Scaffolds | Tissue engineering | Wet-spinning
Abstract: A correct prediction of build time is essential to calculate the accurate cost of a layer manufactured object. The methods presented in literature are of two types: detailed-analysis- and parametric-based approaches. The former require that a lot of data, related to the kinematic and dynamic performance of the machine, should be known. Parametric models, on the other hand, are of general use and relatively simple to implement; however, the parametric methods presented in literature only provide a few of the components of the total build time. Therefore, their performances are not properly suited in any case. In order to overcome these limitations, this paper proposes a parametric approach which uses a more complete set of build-time driving factors. Furthermore, considering the complexity of the parametric build time function, an artificial neural network is used so as to improve the method flexibility. The analysis of the test cases shows that the proposed approach provides a quite accurate estimation of build time even in critical cases and when supports are required. © 2011 Springer-Verlag London Limited.
Keywords: Artificial neural network | Build-time estimation | Rapid prototyping
Abstract: This study describes a protocol for the direct manufacturing of a customized titanium mesh using CAD-CAM procedures and rapid prototyping to augment maxillary bone and minimize surgery when severe atrophy or post-oncological deformities are present. Titanium mesh and particulate autogenous plus bovine demineralised bone were planned for patient rehabilitation. Bone augmentation planning was performed using the pre-op CT data set in relation to the prosthetic demands, minimizing the bone volume to augment at the minimum necessary for implants. The containment mesh design was used to prototype the 0.6 mm thickness customized titanium mesh, by direct metal laser sintering. The levels of regenerated bone were calculated using the post-op CT data set, through comparison with the pre-op CT data set. The mean vertical height difference of the crestal bone was 2.57 mm, while the mean buccal-palatal dimension of thickness difference was 3.41 mm. All planned implants were positioned after an 8 month healing period using two-step implant surgery, and finally restored with a partial fixed prosthesis. We present a viable and reproducible method to determine the correct bone augmentation prior to implant placement and CAD-CAM to produce a customized direct laser-sintered titanium mesh that can be used for bone regeneration. © 2011 International Federation for Medical and Biological Engineering.
Keywords: Bone augmentation | CAD-CAM | Implant surgery | Rapid prototyping | Titanium mesh
Abstract: Aim: To design a surgical template to guide the insertion of craniofacial implants for nasal prosthesis retention. Materials and methods: The planning of the implant position was obtained using software for virtual surgery; the positions were transferred to a free-form computer-aided design modeling software and used to design the surgical guides. A rapid prototyping system was used to 3D-print a three-part template: a helmet to support the others, a starting guide to mark the skin before flap elevation, and a surgical guide for bone drilling. An accuracy evaluation between the planned and the placed final position of each implant was carried out by measuring the inclination of the axis of the implant (angular deviation) and the position of the apex of the implant (deviation at apex). Results: The implant in the glabella differed in angulation by 7.78°, while the two implants in the premaxilla differed by 1.86 and 4.55°, respectively. The deviation values at the apex of the implants with respect to the planned position were 1.17mm for the implant in the glabella and 2.81 and 3.39mm, respectively, for those implanted in the maxilla. Conclusions: The protocol presented in this article may represent a viable way to position craniofacial implants for supporting nasal prostheses. © 2010 John Wiley & Sons A/S.
Keywords: CAD-CAM | Craniofacial implants | Nasal prosthesis | Rapid prototyping | Virtual surgery
Abstract: In this paper, the complete procedure to design and construct reusable moulds for implant-based ear prosthesis and manufacture substructures by means of a computer aided design-computer aided manufacturing (CAD-CAM) procedure and rapid prototyping (RP) technology is presented. The scan of the healthy ear, the virtual superimposition of its mirrored image on to the defective side, and the rapid manufacturing of the substructure and of the mould eliminate several steps of traditional procedures (wax, stone, try-in). Moreover, the precise design and customization of the substructure is presented, with the original and engineered shape for the retention of the silicone. The time and cost saving results of this protocol are presented together with a discussion of the main design features that make the prosthesis a stable and reproducible system to improve rehabilitation of patients with auricular defects or absence.
Keywords: CAD/CAM | facial rehabilitation | prosthetic rehabilitation | rapid prototyping | reverse engineering
Abstract: A basic approach toward the design of three-dimensional (3D) rapid prototyped magnetic scaffolds for hard-tissue regeneration has been proposed. In particular, 3D scaffolds consisting of a poly(ε-caprolactone) (PCL) matrix and iron oxide (Fe 3O 4) or iron-doped hydroxyapatite (FeHA) nanoparticles were fabricated through a 3D fibre deposition technique. As a first approach, a polymer to nanoparticle weight ratio of 90/10 (wt/wt) was used. The effect of the inclusion of both kinds of nanoparticles on the mechanical, magnetic, and biological performances of the scaffolds was studied. The inclusion of Fe 3O 4 and FeHA nanoparticles generally improves the modulus and the yield stress of the fibres if compared to those of neat PCL, as well as the modulus of the scaffolds. Micro-computed tomography has confirmed the possibility to design morphologically-controlled structures with a fully interconnected pore network. Magnetisation analyses performed at 378C have highlighted M-H curves that are not hysteretic; values of saturation magnetisation (M s) of about 3.9 emu/g and 0.2 emu/g have been evaluated for PCL/Fe 3O 4 and PCL/FeHA scaffolds, respectively. Furthermore, results from confocal laser scanning microscopy (CLSM) carried out on cell-scaffold constructs have evidenced that human mesenchymal stem cells (hMSCs) better adhered and were well spread on the PCL/Fe 3O 4 and PCL/FeHA nanocomposite scaffolds in comparison with the PCL structures. © 2011 Taylor & Francis.
Keywords: Biological and mechanical analyses | Hard tissue regeneration | Magnetic scaffold | Nanocomposite | Rapid prototyping
Abstract: The production methodology of 3D constructs for tissue regeneration is usually a complex discontinuous process involving three different stages: (1) production of 3D matrices; (2) matrix sterilisation and cell seeding; (3) in vitro dynamic cell culture. This paper presents a novel automated bench-top manufacturing system called BioCell Printing, designed for the integrated, continuous and fully automated production and in vitro dynamic culture of tissue engineering constructs. The BioCell aims at the rapid production of tissue-engineered substitutes with low risk of contamination, increasing the chances of direct clinical application. © 2011 CIRP.
Keywords: Biomedical | Extrusion | Rapid prototyping
Abstract: Accurately measuring an artefact of historical significance generally results in being able to extract information which is useful for evaluating what remains of the materials from a distant time. This allows scholars arrive at an exhaustive historical reading of the same artefact. Compared to the traditional measuring techniques, which can often be imprecise and complicated, 3D laser scanners measure the morphological characteristics of an artefact with extreme accuracy. Despite this, it is not always possible to choose the most appropriate sensors due to the geometric peculiarities, or indeed, the size of the object. The present work deals with two non-destructive analyses of an ancient stone sculpture, which for its morphology and size was scarcely compatible with the technical characteristics of either of the scanners used. Both scanners operate on the same technical principal, but are quite different from each other in terms of scale and precision. For these reasons, a complex 3D model (extremely appropriate given the original artefact) was draw out through a synergy of the two techniques. The virtual particularities of the model allowed it to be manipulated with the appropriate software. In fact, on the basis of qualitative parameters devised by researchers, it proved possible to reproduce the artefact's geometric form, both virtually and in the form of physical models, obtained through non-conventional restoration methods (R.P. techniques).It has also been possible to verify the state of degradation of the surface of the stone caused by the traditional methods of applying cataloguing or storage information to it.Finally, the results achieved provide opportunities for further research on certain geometrical characteristics of the stone which, as highlighted by the elaboration on the virtual model, seem to be traceable to non-manual, perhaps mechanical, processes. Therefore, the historical considerations which derive from this fact call certain scholars into play. © 2011 Elsevier Ltd.
Keywords: Arteafct | Rapid prototyping | Reconstructing | Scanner | Sculpture
Abstract: Web-based e-commerce of rapid prototyping services is going to be a widely diffused methodology used to compete in a global market. A competitive market imposes a very accurate estimation of prototyping price. Prototype costs depend on many factors, some of which may be easily deduced, while some others consist in a complex function of the geometric model properties and of the specific technology employed to build a physical model. Build time, which affects some components of the prototype's build cost, is a critical factor to deduce. Build time depends not only on the prototype dimensions but also on the complexity of the shape that, in turn, affects the movement of the tool to form the object. A parametric approach to build cost estimation, suited for web-based e-commerce, is presented in this paper. Significant cost driving factors of layer manufactured objects are identified and instruments to evaluate them are proposed. Special attention has been paid to define a parametric approach to build time estimation. The proposed parametric approach analyses the geometrical features, which typically affect the build time of the main layer manufacturing technologies. The method is verified in some test cases related to FDM technology. © 2010 Taylor & Francis.
Keywords: Cost estimating | E-commerce | Rapid prototyping
Abstract: The paper describes the development of a seating buck system for ergonomic evaluation of the driver's cab. Seating buck is a configurable structure that, thanks to the mixed reality technologies, allows us to simulate different driving seat and to perform different evaluation tests. In particular we are interested to evaluate the ergonomics of car's dashboard with its knobs, buttons, display and other control systems. For this reason, we studied and developed a seating buck system that addresses these issues. In particular, we investigated on the possibility of changing in real time the position of some components of the car dashboard with the aim of analysing different layouts. The effectiveness of the system has been subsequently validated through some test sessions with users. © Organizing Committee of TMCE 2010 Symposium.
Keywords: Ergonomic analysis | Haptic devices | Mixed reality | Rapid prototyping | Seating buck
Abstract: Ear defects in patients affected by Treacher Collins syndrome necessitate the replacement of the existing anatomic residuals of the ears with custom-made prostheses. This paper describes a multidisciplinary protocol involving both medicine and computer-aided design/computer-aided manufacturing for manufacturing ear prostheses. Using innovative prototyping technologies together with conventional silicone processing procedures, a step-by-step procedure is presented. The complete workflow includes laser scanning of the defective regions of a patient's face, the use of 3D anatomic models from an ear digital library and rapid prototyping of both substructures for bar anchoring and moulds for silicone processing. © 2010 Taylor & Francis.
Keywords: Computer-aided design | Ear prostheses | Maxillofacial rehabilitation | Rapid prototyping | Reverse engineering | Treacher Collins syndrome
Abstract: Restoration of a nasal defect after ablative surgery for squamous cell carcinoma necessitates replacing the missing volume and anchoring a prosthesis to the patient’s face. This report describes the failure of plastic reconstructive surgery after ablation of a squamous cell cancer of the nose and the esthetic and functional restoration of the patient with a nasal prosthesis. The process of making an implant-supported prosthesis using digital technology, including digitized anatomic models from a "nose library," and the rapid prototyping of the mesiostructure for bar anchorage and of the mold for silicone processing are presented. © 2010 by Quintessence Publishing Co Inc.
Keywords: Computer-aided design | Computer-assisted manufacture | Maxillofacial prosthesis | Nasal prosthesis | Rapid prototyping
Abstract: This paper describes the multi-disciplinary approach to reconstruct the face of Dante Alighieri (1265-1321). Since Dante's sepulchre will be opened in 2021, the reconstructive process is based on morphological and metric data collected on the poet's cranium during the formal identification of his remains in 1921 by the anthropologist Fabio Frassetto, as well as on the resulting plaster model. Starting from this plaster model and a morphologically compatible reference mandible, since the original mandible was never found, a 3D digital model of the complete skull was obtained by reverse engineering and virtual modelling techniques. The most important aspect in this work was the method of virtual modelling proposed for the ex novo generation of the mandible. The physical model of the skull (cranium + mandible) was then produced by means of a rapid prototyping system. This model was finally used to recreate Dante's face via traditional facial reconstruction techniques currently used in forensic anthropology. © 2008 Elsevier Ltd. All rights reserved.
Keywords: 3D digital models | Facial reconstruction | Rapid prototyping | Reverse engineering
Abstract: We developed a model to test new bone constructs to replace spare skeletal segments originating from new generation scaffolds for bone marrow-derived mesenchymal stem cells. Using computed tomography (CT) data, scaffolds were defined using computer-aided design/computer-aided manufacturing (CAD/CAM) for rapid prototyping by three-dimensional (3D) printing. A bone defect was created in pig mandible ramus by condyle resection for CT and CAD/CAM elaboration of bone volume for cutting and scaffold restoration. The protocol produced a perfect-fitting bone substitute model for rapid prototyped hydroxyapatite (HA) scaffolds. A surgical guide system was developed to accurately reproduce virtually planned bone sectioning procedures in animal models to obtain a perfect fit during surgery. © 2008 Elsevier Ltd. All rights reserved.
Keywords: Bone regeneration | CAD-CAM | Maxillofacial prosthesis | Rapid prototyping | Scaffold
Abstract: Tissue engineering represents an interesting approach which aims to create tissues and organs de novo. In designing scaffolds for tissue engineering applications, the principal goal is to mimic the function of the natural extracellular matrix, providing a temporary template for the growth of target tissues. For this reason, scaffolds should possess suitable mechanical properties and architecture to play their specific role. In this paper, limitations of conventional scaffold fabrication methods will be briefly introduced, and rapid prototyping techniques will be described as advanced processing methods to realize customized scaffolds with controlled internal microarchitecture. Among the rapid prototyping techniques, the potential and challenges of 3D fiber deposition to create multifunctional and tailor-made scaffolds will be reviewed. © Società Italiana Biomateriali.
Keywords: 3D fiber deposition | Bioplotter | Rapid prototyping | Scaffolds | Tissue engineering
Abstract: Applications are presented of the general shadow-projection moiré model described in the companion paper, "A general model for moiré contouring, part 1: theory." Two examples are discussed in detail. One example deals with the deflection of a large-size thin panel subjected to bending. The other example analyzes the accuracy that can be achieved in laser lithography rapid prototyping. The first example illustrates some theoretical aspects of the general contouring model proposed in this research and explains the reasons for differences between theoretical predictions and experimental results. In the second example, the whole process of data gathering and merging using geometric primitives and optimization techniques is demonstrated practically. Finally, a clear relationship between the measured standard deviations and moiré sensitivity values is obtained. The results show that the proposed methodologies lead to a quasi-quadratic correlation. © 2008 Society of Photo-Optical Instrumentation Engineers.
Keywords: contouring of surfaces | geometrical primitives | measurement of deflections | merging of different views | rapid prototyping | shadow/projection moiré
Abstract: Purpose - The purpose of this paper is to describe the method of virtually and physically reconstructing the missing part of a badly damaged medieval skull by means of reverse engineering, computer-aided design (CAD) and rapid prototyping (RP) techniques. Design/methodology/approach - Laser scanning data were used to create the 3D model of the damaged skull. Starting from this digital model, a virtual reconstruction of the missing part of the skull, based on the ideal symmetry with respect to the mid-sagittal plane, was achieved in a CAD environment. Finally, the custom-designed model was directly fabricated by means of the RP process. Findings - The result shows that the designed missing part of the skull fits very well with the existing skeletal remains. The final physical assembly of the prototyped element on the damaged skull was tested, restoring it to its whole original shape. Research limitations/implications - The entire process was time-consuming and may be applied just to the most representative skeletal remains. Practical implications - The method allows accurate fabrication of the missing part of the skull to be joined with the original skeletal remains. The advantage of using this technique is that the joining operation can be carried out without any need of supplementary connecting material, such as glue or plaster, to fix together the two parts. Originality/value - The reversible and non-invasive method improves the restoration process, reduces the risk of damage to the skeletal structure and allows reversion to the original repair as it was before. © Emerald Group Publishing Limited.
Keywords: Bones | Computer aided design | Rapid prototyping
Abstract: Computed tomography is a medical instrument that can be useful not only for diagnostic purposes, but also for surgical planning, thanks to the fact that it offers volumetric information which can be translated in three dimensional models. These models can be visualized, but also exported to Rapid Prototyping (RP) systems, that can produce these structures thanks to the rapidity and versatility of the technologies involved. The literature reports various cases of stereolithographic models used in orthopedic, neurological, and maxillo-facial surgery. In these contexts, the availability of a copy of the real anatomy allows not only planning, but also the practical execution of surgical operations, within the limitations of the materials. Nevertheless, the Rapid Prototyping model also presents some disadvantages that can be reduced if practical simulation is accompanied by virtual simulation, performed on a digital model. The purpose of this work is to examine and present the use of Virtual Reality (VR) and Rapid Prototyping for surgical planning in Maxillo-Facial surgery. ©2008Muntaz B. Habal, MD.
Keywords: Osteogenesis distraction | Rapid prototyping | Reverse engineering | Surgical planning | Virtual reality
Abstract: Tissue engineered scaffolds must have an organized and repeatable microstructure which enables cells to assemble in an ordered matrix that allows adequate nutriental perfusion. In this work, to evaluate the reciprocal cell interactions of endothelial and osteoblast-like cells, human osteoblast-like cells (MG63) and Human Umbilical Vein Endothelial Cells (HUVEC) were co-seeded onto 3D geometrically controlled porous poly(ε-caprolactone) (PCL) and cultured by means of a rotary cell culture system (RCCS-4DQ). In our dynamic co-culture system, the lack of significant enhancement of osteoblast ALP activity and ECM production indicated that the microgravity conditions of the rotary system affected the cells by favoring their proliferation and cellular cross-talk. These results emphasize how osteoblasts increase endothelial cell proliferate and endothelial cells amplify the growth of osteoblasts but decrease their differentiation. This dynamic seeding of osteoblasts and endothelial cells onto a 3D polymeric scaffold may represent a unique approach for studying the mechanisms of interaction of endothelial and osteoblast cells as well as achieve a functional hybrid in which angiogenesis, furnished by neo-vascular organization of endothelial cells may further support osteoblasts growth. Furthermore, this in vitro model may be useful in examining the applicability of novel material structures for tissue engineering. © SAGE Publications 2008.
Keywords: 3D scaffolds | Dynamic co-culture | Poly-ε- caprolactone | Rapid prototyping | Tissue engineering
Abstract: The present attention to production cost and time reduction has encouraged many factories to employ some non-conventional technologies instead of the conventional ones for mould production. These specific non-conventional manufacturing technologies, aimed at achieving a significant time reduction for tools manufacturing, are commonly called rapid tooling techniques. Among these rapid tooling methodologies, it is possible to find one of the most direct and flexible techniques which enables, by using a non-cured silicone, the manual shaping of a physical object obtaining directly the mould after some additional handmade refinements. In order to know how the process parameters influence the final shape of the cast object, this work develops an experimental analysis for the estimation of a preliminary model for the process characterization. © 2007 Elsevier B.V. All rights reserved.
Keywords: Rapid prototyping | Rapid tooling | Spin casting
Abstract: The work presented in this paper is focused on the finite element modelling (FEM) of the failure behaviour of lattice composite hollow structures that have been subjected to an external hydrostatic pressure. Furthermore, the development of an experimental procedure to measure the aforementioned resistance, and to test the FEM model is also presented. Carbon fibres composite hollow cylinders with a lattice structure and with different geometries were produced and tested. In order to develop a design tools for such structures, all the experiments performed were computer simulated using finite element modelling. The results obtained with FEM simulation provide further insight to analyze and investigate the failure mechanism. The elastic instability of the studied structures was therefore analyzed and the influence of element geometry on the collapsing resistance thereof was considered. As a result of the study it has been possible to locate three different failure modes which where strictly related to the length of the cylinders. Both the shape of the broken tube and the lever of failure stresses were correctly predicted by the FEM model. © 2005 Elsevier Ltd. All rights reserved.
Keywords: Buckling analysis | Composite tubes | FEM modelling | Lattice structures
Abstract: Product design and optimisation today involves so many fields of expertise, many of which are in rapid evolution, that it can be very difficult for the designer to manage them. This paper describes the development of the DGLs (Design Guidelines), a knowledge-based tool that could be of great help to designers and engineers in modifying their products to get compatibility with different manufacturing and verification technologies. The current release of the DGLs, heavily influenced by the adoption of some ISO-GPS (Geometrical Product Specification) concepts, has been validated using the Rapid Prototyping technique called FDM (Fluid Deposition Modelling) and the CMM (Coordinate Measuring Machine) verification technique. © Springer-Verlag London Limited 2007.
Keywords: Design Guidelines | Geometrical Products Specifications (GPS) | ISO Technical Committee 213 (ISO/TC 213) | Knowledge based systems (KBS) | Rapid Prototyping
Abstract: The paper presents an innovative approach totally based on digital data to optimize lower limb socket prosthesis design. This approach is based on a stump's detailed geometric model and provides a substitute to plaster cast obtained through the traditional manual methodology with a physical model, realized with Rapid Prototyping technologies; this physical model will be used for the socket lamination. The paper discusses a methodology to reconstruct a 3D geometric model of the stump able to describe with high accuracy and detail the complete structure subdivided into bones, soft tissues, muscular masses and dermis. Some different technologies are used for stump acquisition: non contact laser technique for external geometry, CT and MRI imaging technologies for the internal structure, the first one dedicated to bones geometrical model, the last for soft tissues and muscles. We discuss problems related to 3D geometric reconstruction: the patient and stump positioning for the different acquisitions, markers' definition on the stump to identify landmarks, alignment's strategies for the different digital models, in order to define a protocol procedure with a requested accuracy for socket's realization. Some case-studies illustrate the methodology and the results obtained. © 2006 SPIE-IS&T.
Keywords: 3D geometrical model | Human body scanning | Lower limb prosthesis | Medical imaging | Rapid prototyping | Reverse engineering
Abstract: Considering the whole product life-cycle, product model is usually defined during the design phase, given a set of requirements and constraints belonging to the same domain. The use of different manufacturing and verification technologies may, however, profoundly affect the characteristics of the product, so that a re-design phase is often necessary. In previous work, a Knowledge Based System named Design GuideLines (DGLs) was developed, aiming to help the designers make the product model compatible with the requirements and constraints of the specific manufacturing and verification domains. During the DGLs development, the possibility emerged to exploit them in order to identify possible relations among product features. This aspect seems very important, further helping the designer to better understand the consequences of the modifications suggested by the DGLs and applied to the product model during the re-design phase. The present work aims to identify these relations among product features. The result of DGLs exploitation has been critically analyzed to highlight the link between manufacturing characteristics and product features, and, further, among features themselves. Unpredictable relations among the product features, given a particular Rapid Prototyping technology as manufacturing technology, have been discovered and exploited. Copyright " 2006 by ASME.
Keywords: Fluid deposition modeling | Knowledge based systems | Process parameters | Product features | Rapid prototyping
Abstract: The aim of this study is to apply and validate a general-purpose working methodology, derived from the analysis of processes which come from two different domains (the field of medicine and the preservation of cultural heritage), in the investment casting process. CSCW methods and tools have proven to be the best 'gluing tool to bond the different activities, and thus heavily exploited during the customization of the general-purpose working methodology. This paper describes a case study performed in an industrial sector and related to the investment casting application field. It was chosen to test methodology and to demonstrate its wide applicability. The case study involved the realization of a centrifugal pump impeller, where the application of this CSCW-based methodology has delivered important results such as the reduction of product development time and the drastic reduction of production costs.
Keywords: CSCW | IDEF modelling | Rapid prototyping | Virtual team-working
Abstract: In a Design For Manufacturing context, Rapid Prototyping techniques are some way still considered as “new technologies”: the peculiar characteristics of the manufacturing processes are not widely known and may deeply affect the final product functionality. A Knowledge Based System, the Design Guidelines — DGLs, was developed by our Research Group at the University of Udine; it evaluated the products design, in order to verify its feasibility by DMLS (Direct Metal Laser Sintering) Rapid Prototyping technique. During the evaluation process, the DGLs also keep into consideration the aspects relating the verification step, according to the ISO-GPS principles, thus enhancing the completeness of the tool. Aim of this work was to customise the DGLs for design optimisation in FDM (Fused Deposition Modelling), also evidencing the critical aspects and proposing alternative solutions. The contents and structure of the customised version of DGLs are presented in this work.
Keywords: Fused deposition modelling | Knowledge-based systems | Rapid prototyping
Abstract: The purpose of the present work was to develop a tool for preoperatively planning the Total Hip Replacement (THR). Starting from the MR images, the 3D surface model of both the pelvis and the femur was built and the surgical operation was virtually performed. Data coming from gait analysis were added to visualize the physiologic movement of the hip joint. The resulting triangular mesh was sufficiently accurate to allow the building of the stereolithographic model of the joint by means of rapid prototyping technique. The plastic bones allow the user to have an enhanced vision of the surgical procedure to be performed. © 2005 CARS and Elsevier B.V.
Keywords: Magnetic resonance imaging | Rapid prototyping | Surgical planning | Total hip replacement
Abstract: The three-dimensional printing technology (3DP™) is a rapid prototyping process in which powdered material is deposited in layers and selectively joined with binder. The most common deposition method used in this rapid prototyping approach is the drop on demand. However, continuous jet deposition results in an order of magnitude increase in printing speed and that it is gaining popularity. A key component of a continuous deposition printhead is the catcher, which collects droplets that are not meant to hit the powder bed. Current catching systems face problems such as trapped air, and crystallisation that result in unwanted droplets hitting the powder bed. This work looks at redesigning the catcher, and addresses new control algorithms required for proper binder deposition. A mathematical model for binder flight trajectory is developed and validated by experiment. © 2004 Elsevier B.V. All rights reserved.
Keywords: Process simulation | Rapid prototyping | Three-dimensional printing
Abstract: This article presents the use of stereolithography in oral implantology. Stereolithography is a new technology that can produce physical models by selectively solidifying an ultraviolet-sensitive liquid resin using a laser beam, reproducing the true maxillary and mandibular anatomic dimensions. With these models, it is possible to fabricate surgical guides that can place the implants in vivo in the same places and same directions as those in the planned computer simulation. A 70-year-old woman, in good health, with severe mandibular bone atrophy was rehabilitated with an overdenture supported by 2 Branemark implants. Two different surgical planning methods were considered: 1) the construction of a surgical guide evaluating clinical aspects, and 2) the surgical guide produced by stereolithographic study. The accuracy of surgical planning can reduce the problems related to bone density and dimensions. Furthermore, the stereolithographic study assured the clinicians of a superior location of fixtures in bone. Surgical planning based on stereolithographic technique is a safe procedure and has many advantages. This technologic advance has biologic and therapeutic benefits because it simplifies anatomic surgical management for improved implant placement. Copyright © 2004 by Lippincott Williams & Wilkins.
Keywords: Anatomic models | Jaw atrophy | Rapid prototyping | Surgical planning
Abstract: Objectives: To create and to spread a new interactive multimedia instrument, based upon virtual reality technologies, that allows both the running simulation of machines and equipment and the reproduction via Web of complex three-dimensional (3D) anatomical models such as the skull. Methods: There were two main aspects of the project, one of design engineering and the other biomedical engineering, for the creation of "artificial" and anatomical objects. The former were made with 3D Studio Max R4 by Autodesk, San Rafael, CA, while the latter were created starting from real bones scanned with a CT system or a surface scanner and elaborated with different programs (3D Studio Max R4, Scenebuilder by Viewpoint, New York, NY and Spinfire by Actify, San Francisco, CA). The 3D models were to be integrated into web modules and had to respect file limits while preserving a sufficient definition. Two systems of evaluation were used, a questionnaire on a selected sample and an external evaluation by a different university. Results: The Viewpoint format offers the best interactivity and size reduction (up to 96% from the original 3D model). The created modules included production of radiological images, rapid prototyping, and anatomy. The complete "3D Distant Learning Prototype" is available at www.webd.etsii.upm.es. Conclusions: The software currently available permits the construction of interactive modules. The verification on the selected sample and the evaluation by the University of Naples show that the structure is well organized and that the integration of the 3D models meets the requirements.
Keywords: Distant learning | Rapid prototyping | Web 3D
Abstract: When considering the use of rapid prototyping (RP), there are many questions a designer might ask. One such question is "what build orientation should be used to minimise the adverse effects of surface roughness?" At present, this decision is often made in an intuitive way or sometimes overlooked completely. This paper describes a methodology and software implementation that provides the designer with a computer graphics based visualisation of RP model surface roughness. This enables the build orientation to be determined as a result of increased designer knowledge. The surface roughness values were obtained through an extensive empirical investigation of several RP techniques. These are used as the database for a visualisation algorithm that represents varying surface roughness of the RP model as colour shading within a CAD image. The nature of the empirical measurements is analysed and the functionality of the software algorithm is described. Examples are given that demonstrate the use and benefits of the methodology. Finally, conclusions are drawn as to the significance of the work and future research directions are outlined. © 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Material deposition | Rapid prototyping | Rapid technologies | Roughness visualisation | Surface roughness measurements
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