Geometric modeling and processing

The paper investigates the relationship between the forms through which products are represented and the outcomes of evaluations made by observers. In particular, the study focuses on perceived affordances of creative designs, meant as the capability of capturing original elements and corresponding functions, for products presented through static images or videos. Also thanks to the use of Eye Tracking, the experimental results show how dynamic effects that involve salient aspects of products, as well as creative features, are critical to observers' capability of capturing design intentions.

Keywords: design affordance , design creativity , design evaluation , forms of representation , product design

High fidelity calculation tools are well established in the nautical design sector where advanced numerical simulations are adopted for the prediction of the interaction of boat parts with surrounding fluids. The capability to couple such tools with efficient shape parametrization procedures offers the possibility to further improve the performance speeding up the design process. Radial Basis Functions (RBF) Mesh Morphing (MM) allows to quickly modify the shape within numerical domains without the need of updating the underlying CAD representation. The validity of this approach, widely adopted in aeronautical and automotive fields, is demonstrated in this paper by applying the method to the analysis of the flying shape of a symmetric spinnaker also investigating the importance of panel arrangement on sail characteristics. The performance, in terms of drive and side forces, is evaluated for different morphed geometries by RANS (Reynolds Averaged Navier Stokes) analyses. The RBF setup proved to be efficient and robust in generating a good quality of the morphed domain within the full range of amplification from the undeformed to the flying shape geometry.

Keywords: Drive and side force , Geometric parametrization , Mesh morphing , Radial basis functions , RANS analysis , Symmetric spinnaker

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

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

Designing an acquisition system for 2D or 3D information, based on the integration of data provided by different sensors is a task that requires a labor-intensive initial design phase. Indeed, the definition of the architecture of such acquisition systems needs to start from the identification of the position and orientation of the sensors observing the scene. Their placement is carefully studied to enhance the efficacy of the system. This often coincides with the need to maximize the surfaces observed by the sensors or some other metric. An automatic optimization procedure based on the Particle Swarm Optimization (PSO) algorithm, to seek the most convenient setting of multiple optical sensors observing a 3D scene, is proposed. The procedure has been developed to provide a fast and efficient tool for 2D and 3D data acquisition. Three different objective functions of general validity, to be used in future applications, are proposed and described in the text. Various filters are introduced to reduce computational times of the whole procedure. The method is capable of handling occlusions from undesired obstacle in the scene. Finally, the entire method is discussed with reference to 1) the development of a body scanner for the arm-wrist-hand district and 2) the acquisition of an internal environment as case studies.

Keywords: 3D scanning , Body scanner , Computer graphics , Optical sensors , PSO , Sensor placement , Visibility analysis

In recent years, breakthroughs in the fields of reverse engineering and additive manufacturing techniques have led to the development of innovative solutions for personalized medicine. 3D technologies are quickly becoming a new treatment concept that hinges on the ability to shape patient-specific devices.Among the wide spectrum of medical applications, the orthopaedic sector is experiencing the most benefits. Several studies proposed modelling procedures for patient-specific 3D-printed casts for wrist orthoses, for example. Unfortunately, the proposed approaches are not ready to be used directly in clinical practice since the design of these devices requires significant interaction among medical staff, reverse engineering experts, additive manufacturing specialists and CAD designers. This paper proposes a new practical methodology to produce 3D printable casts for wrist immobilization with the aim of overcoming these drawbacks. In particular, the idea is to realize an exhaustive system that can be used within a paediatric environment. It should provide both a fast and accurate dedicated scanning of the hand-wrist-arm district, along with a series of easy-to-use semi-automatic tools for the modelling of the medical device. The system was designed to be used directly by the clinical staff after a brief training. It was tested on a set of five case studies with the aim of proving its general reliability and identifying possible major flaws. Casts obtained using the proposed system were manufactured using a commercial 3D printer, and the device's compliance with medical requirements was tested. Results showed that the designed casts were correctly generated by the medical staff without the need of involving engineers. Moreover, positive feedback was provided by the users involved in the experiment.

Keywords: CAD , Cast modelling , Orthosis modelling , Personalized medicine , Reverse engineering

The autologous ear reconstruction surgery, i.e. the reconstruction of the missing ear anatomy with autologous cartilage tissue in case of partial or complete absence of the auricular region, can be extremely complicated due to the unique shape and size of this anatomical region. Operations of sculpting and carving of the costal cartilage in order to realize the ear reproduction require a high degree of manual expertise and experience from the surgeon. The development of surgical aids that can provide the physician with guidelines during the reconstruction is being studied in the literature. However, state-of-the-art techniques do not represent the optimal solution and only partially help in the reconstruction process. They are based on two-or three-dimensional templates of the target anatomy, providing visual support, yet not helping in the actual reconstruction phase, or, in some cases, by providing active aid but not simplifying the procedure sufficiently. In this context, the option of creating custom cutting guides that could actively assist the surgeon both in the pre-operative planning phase and during the surgery was considered. The proposed approach involves the use of surgical guides adopted for the cutting and reconstruction of the individual anatomical elements involved. Through an iterative process carried out in collaboration with the surgeon the characteristics of the surgical guides have been defined. Subsequently, a method that can be applied systematically to model the cutting guides, ready to be printed with additive production techniques was defined. The procedure was designed with a view to a future semi-automatization of the entire process that could make the physician autonomous in the realization of the patient-specific guides.

Keywords: 3D Ear Templates , Autologous Ear Reconstruction , CAD modelling , Personalized Medicine , Reverse Engineering

Bone tumor resections have to be carefully planned in order to avoid intralesional cuts and thus lower the recurrence rate. Until the present-day bone resections have been performed freehand, using anatomical landmarks as reference points to retrieve planned resection planes over the very patient. Such method is highly prone to failure to the detriment of the patient's health, in fact survival rate for osteosarcomas is very low, ranging between 20% and 47%. The clinical outcome is highly dependent on the resections' accuracy; several emerging techniques proved to dramatically increase cutting accuracy, as well as survival rate, in particular Patient Specific Instruments (PSIs) and custom 3D printed metal prosthesis. The main limitation to a massive spread of this method is the large manufacturing time due to a lack of communication between surgeons and engineers about the surgical approach and the design constraints. This paper aims to compare several general-purpose low-cost software and to provide surgeons with an effective and easy to use platform to visually share information in a natural manner with engineers thus providing as many design constraints as possible, speed up the design process and avoid unfeasible results. Two surgeons from Azienda Ospedaliera Universitaria Careggi tested and evaluated a series of software. From this preliminary investigation Forger, a digital sculpting and texture painting application for iOS, resulted as the most user friendly and intuitive application among the test group.

Keywords: Computer aided surgery , Concurrent design , Digital surgical planning , Human computer interaction

Innovation on semiconductors technology requires enhancements of all actors like adhesion layers, barriers and metal stacks, beyond of semiconductor materials themselves. In general, metallic layers influence the whole die performances. The composition and the layout of these metal layers are fundamental for the signal transmission from the frame to the die and vice versa, and therefore their improvement contributes to the die development in terms of performances and reliability. In the present work, two pad structures have been benchmarked and analyzed under the structural strength standpoint. The experimental comparison among the different pads has been done through a flat punch nanoindentation to highlight the material strength and the crack propagation phenomena. Testing results have been compared to finite element models to analyze the stress through the different layers. The findings of the work demonstrate the validity of the methodology adopted and show the importance of the metallic connections layouts for the stress concentration and crack formation analysis.

Smoothing algorithms are used for mesh refinement and to remove undesired surface. This numerical procedure is recommended and applied on triangulated file coming from 3D scanners or Topology optimization designs based on voxel representation before the optimized structure is manufactured by Additive Manufacturing technologies. In literature, there are several available algorithms, but many of them suffer from mesh shrinkage and do not give to the designer easy procedures to select regions which do not need the application of the smoothing procedure as holes or flat surfaces. For this reason, an improved vertex-based algorithm is presented in this work along with a case study to prove its performances compared with existent algorithms. The algorithm confirms to be efficient and useful. However, user\'s intervention is required to guide the procedure to get proper results.

Keywords: mesh fairing , mesh smoothing , topology optimization , voxel

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

Nowadays, the contribution of the CAD modeling is not yet well exploited into the design of overhead lines. Even if some commercial tools are available, they are very similar to configuration tools with design rules related to reference normative. Sometimes, if 2D/3D CAD tools are employed, they are viewers or customized versions with specific features for the design of overhead lines. This situation limits the interoperability between the design of overhead lines and traditional software employed in the design of civil structures and infrastructures. Moreover, an information modeling approach is still lacking in current tools for the management of additional data about maintenance, cost, etc. In the context of overhead lines, the paper aims at showing an information modeling approach with a platform software which includes a configuration tool, a CAD module, an analytical-based solver, a costing tool, and a Finite Element Method solver. The CAD module is employed to define a 3D model including, as tag-objects, a set of information regarding the lifecycle design of overhead lines. Finally, a Finite Element Model solver enhances a second level of validation and enables advanced simulations.

Keywords: Computer-aided design , Configurations , Finite Element Model , Information Modeling , Overhead lines

Functionally Graded Materials (FGMs), initially conceptualized in the '80, have recently attracted a great research interest thanks to the advent of additive manufacturing (AM) technologies. AM permits to gradationally varying the spatial composition or porosity inside an object resulting in a corresponding spatial change in material properties. The data about this new class of materials are radically different from the traditional engineering materials and require information about the object geometry. Moreover, traditional methods for product design are not sufficient to represent heterogeneous objects. The full exploitation of these technologies requires the synergy of material science, product modeling and manufacturing domain. Ontologies can play a crucial role for the integration, making the information accessible and understandable to both experts from different domains and machines. In this paper, a prototypical ontology for the characterization of FGM objects is proposed. Firstly, an already existing FGM ontology is analyzed, highlighting shortcomings and possible improvements. Then, the new ontology is proposed, focusing on the classes and relationships for accommodating material knowledge and geometrical information. The core idea, retrieved from the literature on heterogeneous object representation and transposed in an ontological fashion, is based on the mapping between the geometrical 3D space and the n-dimensional material space. After presenting the new ontology, a benchmark case study is described to test the effectiveness of this approach along with some competency questions an engineer might be interested in. The proposed ontology represents a first, crucial building block for a more complex system aiming to support the communication and knowledge sharing among different actors in engineering..

Total Knee Arthroplasty is one of the most commonly performed orthopedic procedures and it is expected to grow in the next future . In the last past years, computer-assisted procedures represent one of the trends that are transforming the way of practicing medicine. Cornering the Total Knee Arthroplasty, digital models of the joints have been used to carry out simulation of their kinematics and mechanical performance. Whilst for the 3D digital reconstruction of the patient geometry several studies have been conducted, an approximated geometry of the prosthesis has been several times employed, with undeniable consequences on the final results. This paper aims at comparing two non-contact reverse engineering technologies to acquire the shape of femoral components employed for total knee arthroplasty. A high-level device (Konika Minolta Vivid 9i) and a mid-low cost laser (NextEngine) has been compared. For the comparison, a systematic procedure of acquisition and elaboration of the results has been adopted in order to have as unbiased as possible results. The procedure involves the use of the proprietary software of the scanners for the elaboration of the raw data and the meshing procedure has been kept the same for all the models. Since the as-is acquired mesh is of high-resolution, a decimation procedure has been carried out in order to make the 3D models lighter and easier to be handled. Once the decimation procedure has been evaluated comparing the original and the simplified models to one another, the digitalized models have been compared with the measurements taken from a coordinate measuring machines. As a preliminary result, the two lasers seem to be adequate to accomplish the reverse engineering process as required by this application. Of course, the mid-low cost laser would be preferable whether the performance will be confirmed to be (statistically) equal.

The present work shows how 3D models extracted from a computerised tomography (CT) scan can be processed to be 3D printed into 1:1 orthopedic scale models, which find unquestionable utility in pre-operative surgical planning. Relying on the CAT-CAD methodology, which produces a 3D surface called “mesh” from diagnostic images of body parts, the CAD-AM process elaborates a volumetric bone model which a cost-efficient FDM printer can work with. The suitable materials for these applications are PLA polymers, due to their thermo-mechanical properties, affordability and ecological sustainability; these anatomic 3D printed models allows surgeons to accurately see bones injuries and trauma, resulting in a minimisation of risk and a much more flowing doctor-patient communication. Furthermore these 3D printed objects can be manufactured with specific density in order to simulate bone tissues, resulting in a useful tool through which experienced surgeons can pass on their knowledge to medical students at a very reasonable cost, overcoming the glaring limitations of two-dimensional images provided by CT scans. Here represented is a 3D printed 1:1 scale model of a femur donated to the Bone Bank of IOR-Rizzoli Orthopaedic Institute in Bologna.

Keywords: CT scan , FDM printer , Orthopaedic Reproduction Model , PLA polymer

Design for Assembly is a strategy of design aimed at minimising product cost through design and process improvements. It led to a revolution in the manufacturing industry, resulting in reduced product costs, improved quality, shorter time to market, lower inventory, fewer suppliers and many other improvements. DFA is the method of design of the product for ease of assembly and in this context this paper presents an application of the strategy to a virtual case study represented by a two-way relief valve modelled by CAD. The aim of this paper was to test some DFA methods proposed by the literature and search for an efficient assembly of the virtual two-way relief valve reproduced by CAD, then verifying its assembly effectiveness. Some evaluation methods proposed by literature about the optimisation of design efficiency have been applied to the case study and this led to reconsider the design of some parts of the product. A final new design for the valve is proposed and the evaluation methods applied have been tested again on the new solution, in order to validate the results. A comparison between the original valve and the new version proposed by the authors has been made, in order both to check the feasibility of the new valve and in order to check the evaluation methods proposed.

Keywords: CAD , DfA , Optimization

The research presented in this contribution aims to investigate user preferences about how to convey information in Industrial Augmented Reality (IAR) interfaces to the user. Our interest is focused on the opinion of potential technical writers of IAR documentation for assembly or maintenance operations. Authoring of IAR interfaces imply a choice among various visual assets, that is influenced by the information type and the AR display used. There are no specific standards in the literature to follow and it is challenging to extract guidelines from the literature. This study gathers preferences of 105 selected users that have knowledge about IAR issues, graphical user interfaces (GUI) designing, and assembly/maintenance procedures. The results of this survey show a great preference for 3D CAD models of components (product model) for almost all the information types. However, some alternative visual assets have also been proposed, such as video and auxiliary models. Contrary to common practices in industry, text was the least preferred visual asset. The insights from this research can help other IAR technical writers in the authoring of their interfaces.

Keywords: Graphic Interface , Industrial Augmented Reality , Manual Assembly , Visual Asset

Environmental impact and recycling have been increasingly frequent topics in recent years. At the same time, the life cycle of products has increasingly become shorter, as the escalating competitive market requires new products in smaller pieces. From this perspective, the recovery of parts and products that are produced in this market system for subsequent reuse when they reach the end of their life cycle is essential. For these reasons, it has become critical that companies re-evaluate their product design with a view to the possible recovery of the parts that comprise their products and to create new products for the market. The following discussion was based on the study of design for disassembly (DfD), which is the analysis of industrial products aimed at optimizing disassembly in terms of time and costs. The application of the DfD to a case study of a gearbox has, among its main objectives, the search for the best disassembly sequence in terms of time and money. During the course of the study, augmented reality (AR) was used. Through the use of the Unity software and Vuforia package, it was possible to bring the gearbox back to AR and then simulate the disassembly sequence in AR.

Keywords: Augmented reality , Computer-aided design , Design for disassembly , Disassembly evaluation chart , Disassembly sequence planning , Gearbox , SolidWorks

The work here described aims to offer a starting point for improving and making a generic maintenance process more efficient, first of all thanks to the use of a cutting-edge technology such as augmented reality, as a key tool that makes it possible and immediate to communicate to operators which are the fundamental stages of the maintenance process to be followed in the working area. Furthermore, thanks to the use of two methods applied in the context of the Design for Disassembly (later described), we also propose to search for all the possible sequences to get to the removal of a target component to be adjusted—in particular the optimal one (if it exists, in terms of time and costs) to be subsequently applied in an augmented reality “self-disassembly” model that can be viewed and followed by the operator, in a way that is still very little used today.

Keywords: Augmented reality , CAD , DFD , Industrial maintenance , Optimization

This work aims to present an in-house low-cost computer-aided simulation (CASS) process that was recently implemented in the preoperative planning of complex osteotomies for limb deformities in children. Five patients admitted to the Unit of Paediatric Orthopaedics and Traumatology from April 2018 to December 2019, for correcting congenital or post-traumatic limb deformities were included in the study. Three-dimensional (3D) digital models were generated from Computed Tomography (CT) scans, using free open-source software, and the surgery was planned and simulated starting from the 3D digital model. 3D printed sterilizable models were fabricated using a low-cost 3D printer, and animations of the operation were generated with the aim to accurately explain the operation to parents. All procedures were successfully planned using our CASS method and the 3D printed models were used during the operation, improving the understanding of the severely abnormal bony anatomy. The surgery was precisely reproduced according to CASS and the deformities were successfully corrected in four cases, while in one case, the intraoperative intentional undersizing of the bone osteotomy produced an incomplete correction of a congenital forearm deformity. Our study describes the application of a safe, effective, user-friendly, and low-cost CASS process in paediatric orthopaedics (PO) surgery. We are convinced that our study will stimulate the widespread adoption of this technological innovation in routine clinical practice for the treatment of rare congenital and post-traumatic limb deformities during childhood.

Keywords: 3D modeling , Computer aided , Osteotomy , Paediatric orthopaedics , Preoperative planning , Surgery , Surgical simulation