Additive manufacturing

To lower the cost of additive manufacturing of metallic components, the goal of this work is to investigate and optimize a multi-step process by material extrusion (MEX) of a polylactide filament loaded with bronze to remove the gas produced during the debinding and sintering steps. First, by adjusting the infill (10%, 50%, and 100%), and then by designing and constructing internal passages to aid in the expulsion of gases that occur during the debinding, a calibration cube is created. Additionally, the impact of the cooling period during the debinding is examined. To assess how the technique changes shape, sizes, and internal structure, all the samples are ultimately weighed, scanned, and cut. In order to reduce deformation occurred during the debinding and sintering gases, a new design method has been developed. The method consists of the generation of internal channels which connect the voids of the infill and allow gases to flow out through a central channel. As seen, samples with ejection channels and an intermediate infill (i.e., 50%) both exhibit better attributes.

Keywords: additive manufacturing , debinding , metal fused filament fabrication , optimised design , sintering

This paper presents a computer-based methodology to support the design for additive manufacturing of metal components. Metal additive manufacturing, and in particular powder bed fusion systems, are playing a prominent role in the industry 4.0 scenario. The state of the art concerning design methods and tools to support design for additive manufacturing is reviewed by the authors. The key phases of product design and process design to achieve lightweight functional designs and reliable processes are deepened, and the computer-aided technologies to support the approaches implementation are described. Indeed, the state of the art design for additive manufacturing general workflow can be enriched by holistic approaches, use of numerical simulation, and integration and automation between the required tasks. The paper provides a methodology based on the systematic use of numerical simulation to achieve the optimization of both products and associated processes. To take advantage of the holistic perspective, the approach relies on the use of integrated product-process design platforms, allowing to streamline the digital process chain. Product design is based on the systematic integration of topology optimization and automatized tools for concept development and selection and subsequent product simulation driven design refinement. Process design is based on a systematic use of process simulation to prevent manufacturing flaws related to the high thermal gradients of metal processes and minimize residual stress and deformations. This is achieved by working on both the build cycles layouts and the 3D models' distortion compensation. An automotive use case of product and process design performed through the proposed simulation-driven integrated approach is provided to assess the actual method suitability for effective re-designs of additive manufacturing high-performance metal products. The bridged gaps are systematically outlined, and further developments are discussed.

Keywords: Computer-aided engineering , Design method , Design optimization , Finite element method , Integrated design , Process simulation

The supply of automotive spare parts, especially for historic vehicles, is not guaranteed by car manufacturers. Usually, car restorers look for original components at flea markets and fairs, but often they have to produce replicas from broken parts or, worse, without information about the original parts. A possible support in mechanical craftsmanship comes from digital tools commonly used in industry today. With the goal of replicating a component that no longer exists, this paper provides a workflow that integrates traditional manufacturing technologies with computer-based tools. The core is the digital model, which is used to prototype and test the replica for functionality as well as simulate its manufacturing process. An engine valve cover of a historic racing car was chosen as a case study, for which information sources were practically unobtainable. Firstly, a 3D model and a 3D printed prototype were developed. Sand casting was chosen based on the original process and computer simulations allowed to reconstruct the casting equipment and define the best part design. A faithful and functional replica is then manufactured and assembled with the original engine, respecting the original part in terms of form, materials and production. The proposed design approach can be further adopted in different contexts requiring on-demand, one-off or small-batch production.

Keywords: 3D modelling , Additive Manufacturing , Car restoration , Component reproduction , Computer-Aided Engineering , Sand casting

Additive Manufacturing (AM) Powder Bed Fusion (PBF) metal processes enable significant design freedom, addressing design complexity in high-end sectors. To build performant products, several Design for Additive Manufacturing guidelines must be considered. Nevertheless, it is still noticeable a lack of reliability for AM processes, which is a key factor to guarantee both the expected enhanced product requirements and the manufacturability. Even though few rules and best practices to mitigate defects are provided either by standards or equipment suppliers, they are still missing approaches to predict build failures and process flaws, and therefore achieve faultless build processes. This work suggests a concurrent product and process design approach, in which Computer Aided Engineering tools are involved in both product and process design to identify the components' shapes that match the expected performance and a feasible PBF build layout. An automotive component is the use case, whose design based on topology optimization and product validation is enriched by integrating the associated process simulation. The build process is modeled by (a) the additive manufacturing simulation to identify flaws and resources usage, and (b) the thermo-mechanical finite element -based simulation to predict residual stress and distortions. The approach based on CAD platforms integrates product and process design to reduce design iterations, trial-error practices, and build failures.

Keywords: Design for Additive Manufacturing , Finite Element Analysis , Laser Powder Bed Fusion , Process simulation , Product-process design

Additive manufacturing (AM) of load-bearing metal implants allows sustainable production of personalized implants with complex shapes and inner architectures. Implants must meet strict requirements to not harm patients, and production technique must certify their performance. Available materials, many production parameters and implant personalization on patient's needs represent limits of AM. Layer-by-layer material deposition and repeated thermal cycles typical of AM may also cause discontinuities between layers affecting implant mechanical features, and its match to the host body. In this paper the mechanical challenges that AM must overcome to replace traditional manufacturing techniques are discussed, in order to better understand whether AM has to be limited to implant personalization for exceptional cases.

Keywords: Additive manufacturing , Conventional manufacturing , Geometric accuracy , Implants , Mechanical properties

Additive manufacturing (AM) permits sustainable production of personalized load-bearing metal implants with complex structures. Regulations prescribe that implants have to meet strict requirements to not harm patients, and production technique should allow the certification of their performance. Process, materials, operating parameters, and customization to patient's needs could limit AM. Layer-by-layer material deposition and repeated thermal cycles may make outer surface of AM implants chemically and physically uneven and rough, eliciting biological response of host tissue and hindering therapeutic success. In this paper, we discuss the clinical challenges that AM must overcome to replace traditional techniques in implant and prostheses design.

Keywords: Additive manufacturing , Clinical performance , Conventional manufacturing , Implants , Surface properties

FDM (Fused Deposition Modelling) is the most popular 3D printing technology worldwide due to its simplicity and low costs. One of the key points of FDM is the need for supporting material to realize the overhanging features. In general, however, both in the case of printing supports with the same material as the part and in the case of printing with soluble supports, there is a high waste of material and a significant increase in the printing time to get the finished part. One of the fundamental parameters for generating supports within the slicer software is the so-called “support overhang angle”, which consists of the maximum achievable angle beyond which the slicer generates supports. The other key parameter in FDM printing is the “layer height”, which directly determines both the quality of the final part, its strength, and the printing time itself. This paper will therefore attempt to investigate the relationship present between “layer height” and “support overhang angle”, bringing some examples of how with proper layer height one can significantly reduce support generation, wasted material and in some cases also printing time.

Keywords: FDM , Layer Height , Overhangs

Additive manufacturing presents unique opportunities for developing patient-specific medical devices and tools in orthognathic surgery. Devices used in maxillofacial surgery present several constraints which refer to the specific characteristics of the patient and the stress conditions that are in place during the surgery. This paper describes an integrated workflow used for the identification, design, optimization, and production of patient-specific devices while promoting synergy among specialists of vastly different backgrounds. Medical specialist interprets Computed Tomography scans with three-dimensional reconstruction of the patient and, supported by a CAD specialist design the required tools to restore the patient functionality. Preliminary tooling designs are checked for strength and stiffness by a structural engineer considering the mechanical properties of the perspective AM materials and passed in digital form to the AM technologist who will be responsible of the 3D printing. The medical specialist uses the devices through physical prototypes to assess effectiveness and usability. The integrated workflow allows to increase accuracy while reducing surgical time and costs.

Keywords: additive manufacturing , orthognathic surgery , reverse engineering , topology optimization

The paper focuses on the application of 3D printing technology in the medical field, particularly in cardiac surgery. Unlike traditional imaging techniques such as CT, MRI, and ultrasound, 3D printing offers a more detailed understanding and analysis of clinical cases. By using 3D printing, it becomes possible to study a patient's specific cardiac anatomy, manipulate objects before surgery, and accurately determine the surgical site. This reduces both the time required for the operation and the patient's recovery period. This study presents a methodology for creating 3D-printed models of aortic arch sections affected by aortic dissection. The aim is to produce anatomical models with varying levels of quality and accuracy. The research goal is to assess the differences in 3D printing materials and technologies for creating complex anatomical models like the aorta. The process involves segmenting medical images obtained from Computed Tomographic Angiography (CTA) and then 3D printing digital models using different materials (such as PLA, TPU, and resin) and technologies (like FDM and SLA). The resulting 3D printed models are low-cost and demonstrate good accuracy in reproducing human anatomy.

Keywords: 3D Printing , CAD , Cardiac surgery , Engineering method

Lung cancer is the second neoplasia for incidence and the leading cause of death from neoplasia in the world. A consolidated practice for lung cancer early diagnosis and staging is EBUS TBNA (EndoBronchial UltraSound-guided TransBronchial Needle Aspiration). Despite being a low-risk procedure, its success highly depends on the medical staff's skills, who therefore require appropriate training. With the future aim of developing a novel realistic EBUS TBNA simulator that also allows tissue sampling, in this paper, the authors propose a simplified representation of the mediastinum to define a suitable layout. As far as the authors know, the physical commercially-available simulators have poor echogenic properties, do not allow tissue sampling, and can be quite expensive. The project was carried out within Custom3D, a joint laboratory between Careggi Hospital of Florence and the Department of Industrial Engineering of the University of Florence, under the request of the interventional pneumology ward. The model was validated by an expert medical doctor who assessed its anatomical accuracy and the suitability of its mechanical and acoustic properties. Moreover, the possibility of performing lymph node needle aspiration is an added value that promises to bring the EBUS TBNA simulation to a new level of realism.

Keywords: EBUS TBNA , echogenic , mannequin , simulation

This research investigated on the tensile properties of Additive Manufacturing (AM) PolyEther Ether Ketone (PEEK) under different printing and post processing conditions, with a focus on providing insights for future fatigue tests. PEEK is a high-performance thermoplastic material with excellent mechanical properties that is widely used in many industries. In this study, the miniFactory Ultra 3D printer, based on Fused Filament Fabrication (FFF) technology, was used to fabricate PEEK specimens so as to assess the influence of printing parameters on the mechanical performances. Three key factors were considered: layer height, infill pattern and annealing as possible post-processing treatment. The variation of layer height and infill pattern aimed at evaluating their effects on the tensile properties, whereas annealing treatment was performed to assess the influence of residual stresses. The results indicated that infill pattern significantly affected the tensile properties, whereas annealing did not improve properties of specimens with triangular infill pattern. This research provides valuable insights for industries such as aerospace, automotive, and healthcare, where AM PEEK components are increasingly utilized.

Keywords: Design for AM , Experimental tests , Fused Filament Fabrication , PEEK

Polyether Ether Ketone (PEEK) is a high-performance polymer widely used in several fields due to its excellent material and chemical strength properties also at high operating temperatures. The processing conditions used to fabricate PEEK parts can significantly influence the crystallinity and, hence, mechanical properties. Manufacturing difficulties are further amplified when PEEK is produced by Additive Manufacturing (AM), since it requires high processing temperatures, which only a few 3D printers available on the market can guarantee. In this paper, a Design of Experiment (DoE) was employed to investigate the mechanical properties of PEEK produced by Fused Filament Fabrication (FFF). Nozzle Temperature (390 ℃ and 420 ℃), Chamber Temperature (80 ℃ and 100 ℃) and Infill orientations (0° and 45°) were involved in the experiment through a 2-level full factorial DoE. Young's modulus, Yield Stress, Ultimate Tensile Stress and elongation at fracture were investigated. Through ANOVA analysis it was found that the three parameters do not influence Young modulus (2.6 ÷ 3.2 GPa), while their combinations influence yield stress (36 ÷ 46 MPa), tensile strength (45 ÷ 74 MPa) and elongation at fracture (2.1 ÷ 16%). As expected, the optimal values for the best mechanical properties are the highest levels of nozzle and chamber temperatures and 0° infill orientation.

Keywords: Design for AM , Design of Experiment , Fused Filament Fabrication , PEEK , Tensile Test

The design of advanced devices is a paramount goal in the biomedical field. Current challenges include the development of customized devices with improved and tailored properties according to the specific application. Accordingly, the aim of the study was to report some recent efforts in the design of advanced biomedical devices, especially focusing on dental implants and hybrid structures for cranioplasty.

Keywords: Additive Manufacturing , Biomedical Applications , Design for Additive Manufacturing

Additive manufacturing (AM) allows to create complex shapes and to improve the performance of critical components in different fields. The characteristics of the as-built parts can be an obstacle in terms of satisfaction of the parts' quality requirements. Concerning the manufacturing process, the relationship among the process parameters, microstructure and mechanical properties is crucial in different areas and involves innovative and traditional fabrication techniques. Fused Deposition Modeling (FDM) is widely employed to fabricate devices with tailored and enhanced properties. In this context, the process parameters clearly influence the quality of devices fabricated from different polymer-based materials, according to the specific AM technology. As reported in the literature, many theoretical models for the prediction of the surface quality focus on the concept of roughness. Furthermore, several parameters have also been proposed to assess the surface quality. Benefiting from advances in design strategies and methodologies of analysis, the aim of the current research was to provide further insight into the development of models for surface roughness prediction in FDM. The relationship among the layer height, printing speed, flow rate and extrusion width was considered and implemented in the model. Preliminary experimental analyses were also performed.

Keywords: Additive Manufacturing , Prediction Model , Surface Roughness

Liquid crystal elastomers (LCEs) are deformable materials that can be programmed to respond to physical stimuli such as light, heat, and electricity. In order to achieve controllable macroscopic deformation in LCEs, it is important to design the orientation of the liquid crystal molecules. Capillary infiltration of LCEs between two coated laboratory glasses with microscopic grooves along one direction created by rubbing with a velvet-like cloth is a commonly used fabrication method. During infiltration, the desired orientation is influenced by the intermolecular shear force between the liquid crystal monomers and the material of the coated glasses, as well as the glasses surface rubbing direction. It is also important to ensure a constant thickness in the LCE. To address these issues, the authors propose a 3D printed prototype for LCE fabrication that can provide a repeatable procedure and uniform layer thickness. The paper describes the steps involved in the fabrication process, including rubbing, LCE infiltration, and photopolymerization. The results demonstrate that the implemented system can improve the reliability of LCE fabrication by ensuring consistent film thickness and alignment.

Keywords: 3D Print Design , Liquid Crystal Elastomer , Rubbing , Smart Material

This study investigates the synergy between additive manufacturing (AM) technologies and computational design strategies in jewellery and how that synergy can be successfully exploited to extend innovation in that field further. A case study called Ecdysis, a bioinspired jewellery collection, is presented. A dedicated computational algorithm has been developed and is described in detail. This algorithm allows for the exploitation of the shape and functional complexity dimensions allowed by AM and the control of the printability of the generated concept. Shape and functional complexity are exploited to mimic the beauty and dynamism of snakes' slithering mechanism. At the same time, starting from the developed algorithm, multiple digital models and physical prototypes have been fabricated, leveraging material extrusion, vat photopolymerisation, and powder bed fusion processes. This further development step of the collection thus confirms the versatility of both the proposed approach and AM technologies for jewellery. Therefore, the paper demonstrates how unique wearing experiences can be created and how uniqueness can be simultaneously preserved and democratised in jewellery by deepening the synergy between AM technologies and computational strategies.

Keywords: Bioinspired design , Computational design , Design for additive manufacturing , Interaction design , Jewellery

Purpose: This study evaluates the potential of using the material extrusion (MEX) process for recycling waste tire rubber (WTR). By investigating the process parameters, mechanical behaviour and morphological characterisation of a thermoplastic polyurethane-waste tire rubber composite filament (TPU-WTR), this study aims to establish a framework for end-of-life tire (ELT) recycling using the MEX technology. Design/methodology/approach: The research assesses the impact of various process parameters on the mechanical properties of the TPU-WTR filament. Hysteresis analysis and Poisson's ratio estimation are conducted to investigate the material's behaviour. In addition, the compressive performance of diverse TPU-WTR triply periodic minimal surface lattices is explored to test the filament suitability for printing intricate structures. Findings: Results demonstrate the potential of the TPU-WTR filament in developing sustainable structures. The MEX process can, therefore, contribute to the recycling of WTR. Mechanical testing has provided insights into the influence of process parameters on the material behaviour, while investigating various lattice structures has challenged the material's capabilities in printing complex topologies. Social implications: This research holds significant social implications addressing the growing environmental sustainability and waste management concerns. Developing 3D-printed sustainable structures using recycled materials reduces resource consumption and promotes responsible production practices for a more environmentally conscious society. Originality/value: This study contributes to the field by showcasing the use of MEX technology for ELT recycling, particularly focusing on the TPU-WTR filament, presenting a novel approach to sustainable consumption and production aligned with the United Nations Sustainable Development Goal 12.

Keywords: Additive manufacturing , Circular economy , Design for additive manufacturing , Recycling , Sustainability , Sustainable Development Goals , Triply periodic minimal surface , Waste tire rubber

Additive manufacturing (AM) is a flexible technology allowing designers to produce highly customized and complex shapes. The design phase can be supported by Design for AM (DfAM) tools in order to reduce material waste, design time and economic resources. This paper aims to evaluate the functionality of four commercial tools for simulating the powder bed fusion (PBF) deposition process using quantitative and qualitative evaluation metrics. An AM process simulation workflow has been defined to facilitate the tools evaluation. For a complete evaluation, three different case studies were analyzed. Simulation carried out with the tools have the same critical zones relative to the three mechanical components, but with different maximum distortion values. Qualitative metrics show differences in workflow complexity and support provided by tools during the simulation setup phase. In the industrial field, these aspects can affect the choice of one tool over another.

Keywords: Additive Manufacturing , Design for Additive Manufacturing , DfAM tools , PBF deposition process , Simulation

The use of CAD and 3D printing of surgical guides (SGs) for osteotomies is a widely developed practice in orthopaedic surgery, and particularly in maxillo-facial interventions, but validation studies rarely occur in literature. The present study defines a methodology to validate SGs dimensionally and mechanically through geometrical analysis, tensile testing, contact simulations, and abrasion testing. Distortions between the 3D printed SGs and the CAD model are quantified and an average deviation error for each production process step is obtained. Mechanical analysis identifies a way of applying the load on the SG to measure their equivalent linear stiffness (N/mm), maximum displacement (mm) and corresponding tolerable load (N) by varying some dimensional parameters. The stress state was assessed by finite element method (FEM) analysis, then the numerical results were compared with experimental ones using tensile tests: stiffness, maximum displacement and the corresponding loads were evaluated. The distribution of contact pressure on soft tissues was obtained numerically by FEM analysis. Finally, an ad hoc machine has been specially built to engrave discoidal specimens with typical operating room conditions. The methodology has been validated using 11 SG fibular and mandibular specimens and reporting the obtained results of each procedure step.

Keywords: CAD , Cutting guides , FEM , Maxillo-facial surgery , Surgical guides

Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various fields, from aerospace to medical applications, due to its exceptional mechanical and thermal properties. Nonetheless, the mechanical behavior of 3D-printed PEKK still deserves to be more thoroughly investigated, especially in view of its production by 3D printing, where mechanical properties measured at different scales are likely to be correlated to one another and to all play a major role in determining biomechanical properties, which include mechanical strength on one side and osteointegration ability on the other side. This work explores the mechanical behavior of 3D-printed PEKK through a multiscale approach, having performed both nanoindentation tests and standard tensile and compression tests, where a detailed view of strain distribution was achieved through Digital Image Correlation (DIC) techniques. Furthermore, for specimens tested up to failure, their fractured surfaces were analyzed through Scanning Electron Microscopy (SEM) to clearly outline fracture modes. Additionally, the internal structure of 3D-printed PEKK was explored through Computed Tomography (CT) imaging, providing a three-dimensional view of the internal structure and the presence of voids and other imperfections. Finally, surface morphology was analyzed through confocal microscopy. The multiscale approach adopted in the present work offers information about the global and local behavior of the PEKK, also assessing its material properties down to the nanoscale. Due to its novelty as a polymeric material, no previous studies have approached a multiscale analysis of 3D-printed PEKK. The findings of this study contribute to a comprehensive understanding of 3D-printed PEKK along with criteria for process optimization in order to customize its properties to meet specific application requirements. This research not only advances the knowledge of PEKK as a 3D-printing material but also provides insights into the multifaceted nature of multiscale material characterization.

Keywords: anisotropy , digital image correlation , lattice structure , mechanical properties , micromechanical characterization , multiscale mechanics , nanoindentation , PEKK , viscous behavior