Geometric modeling and processing

The design activities of an insulated Plasma Facing Components-Cassette Body (PFCs-CB) support has been carried out under the pre-conceptual design phase for Eurofusion-DEMO Work Package DIV-1 “Divertor Cassette Design and Integration” - Eurofusion Power Plant Physics & Technology (PPPT) program. The Eurofusion-DEMO divertor is a key in-vessel component with PFCs which directly interact with the plasma scrape-off layer. The PFCs have to cope with high heat loads, neutron irradiation and electromagnetic loads. The mechanical integrity of the PFCs and water cooling pipes can be jeopardized by high heat loads and by electromagnetic loads generated in a disruption event. In European-DEMO the possibility to estimate the heat load by measuring the relative thermocurrents is under investigation. In order to allow thermocurrents measurements, a divertor design option provides that PFCs are electrically insulated from CB. In this work authors aim to analyze the opportunity that the PFC-CB fixing system incorporates an electrical insulation system, thus acquiring also an important diagnostic role in the measurement of the thermocurrents and in the management of the current flows. The possible use of ceramic material (e.g. alumina) as the insulating layer between the support components is investigated.

Keywords: Divertor assembly , Divertor Plasma Facing Componentsfixation system , Eurofusion-DEMO

This paper reports about the virtual and physical prototyping of an antagonistic Variable Stiffness Actuator (VSA) to be used on robotic arms specifically realized for physical human-robot interaction. Such antagonistic actuation system, which comprises purposely conceived Compliant Transmission Elements (CTEs) characterized by a nonlinear relation between the deflection and the applied torque, allows to simultaneously control both the joint's position and stiffness. The CTE's beams geometry, namely slender spline beams, has been defined by means of an automatic routine leveraging on Matlab and ANSYS and allowing for the shape optimization of complex flexures. The synthesized springs are characterized by a predefined quadratic torque-deflection characteristic, which is shown to guarantee a precise stiffness modulation while avoiding the need for a joint's position sensor. After shape optimization, the CTE is fabricated via additive manufacturing and subsequently tested. The acquired data show a very good consistency with the numerical results, although highlighting a non-negligible hysteresis due to material damping. Therefore, in order to cope with such unavoidable effect along with other parameter uncertainties and unmodeled effects (e.g. static friction), a robust feedback controller is proposed, allowing for the simultaneous and decoupled regulation of joint position and stiffness. Finally, a VSA prototype is produced and tested. Experimental results confirm that the VSA behaves as expected.

Keywords: Compliant mechanisms , Multi software framework , Shape optimization , Sliding mode controller , Variable stiffness actuators

The paper describes a novel Clench-and-Release Device (CRD), which can be used to quickly replace the rear wheels of bikes equipped with disk brakes, while also being suitable for front wheels. Since a quick wheel replacement is a pressing demand during competitions, the CRD reduces time wasted in situations like flat tire replacement. At the same time, it can be useful also for amateur bikers, who desire a simple way to lock/release a wheel without the risk of getting dirty or being unable to properly align the brake's disk and pads. In fact, thanks to the CRD, both brake and pinion packs are kept in place at all times and the chain remains engaged with the gears, even after wheel removal. Although similar devices can be found on the market, the proposed CRD provides an improved design since: (i) pinions and brake are placed on the same side with respect to the wheel symmetry plane perpendicular to the wheel axis of rotation; (ii) the front and the rear wheel share the same hub; (iii) manual operations are definitely easier; (iv) the wheels are compatible with different types of transmission; (v) the brake discs are more protected in case of crashing. A patent for the Italian region has been filed.

Keywords: Computer-aided design , Through axle shaft , User centered design , Wheel quick release , Wheels' fast removal

This paper reports the design of a monolithic long-stroke constant force compliant mechanism (CM). The device is suitable for applications requiring a predefined force magnitude at the contact interface, such as manipulation systems. Starting from a compliant slider-crank mechanism providing a constant force within a rather limited deflection range, the paper describes the shape optimization carried out with the aim of extending the CM available stroke. In the first design step, the pseudo-rigid body (PRB) method is used to synthesize a sub-optimal lumped compliance solution. Secondly, two improved beam-based alternatives are evaluated by means of an integrated software framework, comprising Matlab and ANSYS. These new embodiments make use of a variable thickness beam, whose shape and dimensions have been optimized so as to provide a constant reaction force in an extended range. In particular, straight and spline segments are respectively used for the first and second prototype. With reference to the lumped compliance configuration, the available stroke has been increased of amounts equalling to 467% in the straight segments version (namely, from 3 mm to 14 mm) and to 833% in the spline segments version (namely, from 3 mm to 25 mm). All the predicted behaviors have been validated via physical experiments on 3D printed specimens. The proposed multi-step design flow may also be applied to a large variety of CMs, starting from their PRB model.

Keywords: compliant mechanisms , constant force mechanisms , pseudo-rigid body method , shape optimization , software integration

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

Background and objective:Tomographic sequences of biomedical images are commonly used to achieve a three-dimensional visualization of the human anatomy. In some cases, the number of images contained in the sequence is limited, e.g., in low-dose computed tomography acquired on neonatal patients, resulting in a coarse and inaccurate 3D reconstruction. Methods:In this paper, volumetric image interpolation methods, devised to increase the axial resolution of tomographic sequences and achieve a refined 3D reconstruction, are proposed and compared. The techniques taken into consideration are based on motion-compensated frame-interpolation concepts, which have been developed for video applications, mainly frame-rate conversion. Results: The performance of the proposed methods is quantitatively assessed by using sequences with a simulated low axial resolution obtained from the decimation of standard high-resolution computed tomography sequences. Real data with an actual low axial resolution have been used as well for a qualitative evaluation of the proposed methods. Conclusions:The experimental results demonstrate that the proposed methods enable an effective slice interpolation and that the achievable 3D models clearly benefit from the increased axial resolution.

Keywords: 3D reconstruction , Biomedical image sequences , Computer tomography , Optical flow , Registration , Volumetric interpolation

Pectus Arcuatum (PA) is a congenital chest wall deformity which produces a superior manubrial and sternal protrusion, particularly at the sternal angle. PA surgical correction to reduce the angle of the sternum always includes the removal of bone portion by means of horizontal sternal osteotomies, resection of deformed rib cartilage and finally stabilization of the anterior thoracic wall. Within this process an incorrect assessment of the sternotomy angle during the procedure may lead to the need for bone or cartilage grafts to fill the left voids. This problem has been addressed with a patient-specific cutting template, realized with Reverse Engineering and Additive Manufacturing techniques, which proved to be a key element to simplify the procedure and avoid the occurrence of this type of complications. In this work is presented and validated a procedure that, through common CAD operations, realizes in a completely automatic way the CAD model of the custom cutting template, so as to make non-expert users independent in the realization of the medical device.

Generative design tools have recently become an interesting solution to tackle design problems in several technical fields. This article takes into consideration the specific field of mechanical design and aims at describing available generative design solutions capable of dealing with structural optimization problems. The study provides a practical description on the workflow and performances of a specific software system implementing a generative approach for the generation of a set of alternative solutions for a static structural design problem. The software analyzed is Autodesk's Generative Design, hosted in Fusion 360. The article discusses the functioning of the software and its performances; an enhanced focus on the features oriented to the generation of manufacturable shapes is provided in the text. In order to provide a practical and effective procedure, a literature case study was selected to test the software.

Keywords: Biomimetic Design , CAD , Generative Design , Structural Optimization , Topology Optimization

Computer Aided reconstruction of mechanical parts nowadays heavily relies on dedicated RE software systems and highly skilled users to be carried out effectively. This paper investigates this scenario in order to identify most limiting factors in the current framework. With this respect, several considerations of general validity are drawn while presenting the problem from a theoretical perspective. A significant test case reconstruction, discussed in depth in the manuscript, is used to provide a practical point of view on real applications and help the reader acquire a hands-on comprehension of the current situation.

Keywords: CAD , CAD reconstruction , Reverse engineering

Total hip arthroplasty (THA) and total knee arthroplasty (TKA) have been recently heralded as the operations of the Century. Large improvements in mobility and patient-reported outcomes are typically observed compared with the small-to-moderate effects experienced with non-surgical interventions. Following surgery, physiotherapy-led exercise-based rehabilitation is often prescribed to yield better gait-related outcomes. Nevertheless, outpatient rehabilitation is expensive and heavily burden the national health service. When specific machines are not needed during the physiotherapy, patients, if assisted, can perform a home program. The purpose of this paper is to qualitatively investigate the applicability of a self-managed, home-based system for the automated evaluation of a home physiotherapy rehabilitation after TKA and THA. The system leverages the cost effectiveness and the versatility of a RGB-Depth camera system together with a commercial skeleton tracking system to analyse specific exercises. A novel computation of lower limb movements and related angles is proposed to evaluate the quality of the daily exercises. The laboratory experimental campaign, envisaged the analysis of the rotation angles of hips and knees; a lower limb schematic model is considered to estimate both knee and hip angles during ab/adductor and flex/extension movements. A novel real time calculation of the hip bone plane is proposed to assess the joint angles during specific exercises performance. A qualitative data analysis of each exercise has been performed. Results on the system usability in a domestic environment are reported as well as a visual comparison of the analysed output.

Keywords: 3D , Body tracking , RGB-D camera

In patients affected by craniosynostosis, i.e. a congenital cranial defect, diagnostic evaluation for a prompt surgical treatment is performed using low-dose three-dimensional computer tomography (CT), characterized by a poor spatial resolution (in terms of slice thickness). The limited number of CT images reduces the accuracy of the 3D reconstruction of the skull and leads to a coarser segmentation and modelling. In this paper, Motion Compensated Frame Interpolation (MCFI) techniques are applied for an effective axial interpolation of tomographic images sequences, with the main objective of obtaining a refined 3D reconstruction. The performance of the proposed method was assessed by using high-resolution CT sequences. After downsampling along the axial direction, the missing slices were recovered by using the proposed algorithm, to obtain an estimate of the original sequence. The experimental results show that the 3D models obtained from the downsampled/interpolated sequence are very close to those obtained from the original one thus providing a high-quality 3D skull reconstruction.

Keywords: 3D modeling , CT slices , Interpolation , Motion compensation

The present paper presents the study of a semi-automatic CAD technique for the generation of ventilation holes on ABS AM-manufactured arm orthoses. A lighter device, good air and water transpiration and an increased patient's comfort are the main advantages achievable by introducing openings on plastic casts. The proposed procedure relies on the adaptation of a reference pattern of holes, obtained integrating both structural and functional aspects, to each patient's cast. The adaptation procedure maps the original pattern, respecting its proportions, on each target orthosis, thanks to a set of reference points automatically extracted. The generation of holes is performed relying on an advanced CAD environment (i.e. Siemens NX), where a series of CAD modeling operations, based on the data extracted by the mapping algorithm, have been studied and tested. The whole procedure has been tested on 5 orthoses to validate its efficacy.

Keywords: Cad , Cast modeling , Orthosis modeling , Personalized medicine

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

In recent decades, increasing attention is being paid to the multidisciplinary approach that allows the performance of both a preventive conservation and a more invasive restoration action. In this context, the present study aims to acquire information and data from field surveys undertaken in San Domenico Church, Southern Calabria, in order to provide a tool for the recording and the inventory of damage and decay phenomena, and assess their causes and scale. The subsequent calculation of damage indices also provided useful information in order to allow the prioritization of conservation and preservation responses.

Keywords: Built heritage , Calabria , Computer graphics , Damage diagnosis , Decay , Italy , Photogrammetry

In this paper, we investigate the role of shape and texture features from 18F-FDG PET/CT to discriminate between benign and malignant solitary pulmonary nodules. To this end, we retrospectively evaluated cross-sectional data from 111 patients (64 males, 47 females, age = 67.5 ± 11.0) all with histologically confirmed benign (n = 39) or malignant (n = 72) solitary pulmonary nodules. Eighteen three-dimensional imaging features, including conventional, texture, and shape features from PET and CT were tested for significant differences (Wilcoxon-Mann-Withney) between the benign and malignant groups. Prediction models based on different feature sets and three classification strategies (Classification Tree, k-Nearest Neighbours, and Naïve Bayes) were also evaluated to assess the potential benefit of shape and texture features compared with conventional imaging features alone. Eight features from CT and 15 from PET were significantly different between the benign and malignant groups. Adding shape and texture features increased the performance of both the CT-based and PET-based prediction models with overall accuracy gain being 3.4–11.2 pp and 2.2–10.2 pp, respectively. In conclusion, we found that shape and texture features from 18F-FDG PET/CT can lead to a better discrimination between benign and malignant lung nodules by increasing the accuracy of the prediction models by an appreciable margin.

Keywords: Radiomics , Shape , Solitary pulmonary nodule , Texture

In injection molding production, automatic inspections are needed to control defects and evaluate the assigned functional tolerances of components and dies. With the “Smart Manufacturing” approach as a point of view, this paper resumes part of a wider research aiming the integration and the automation of a Reverse Engineering inspection process in components and die set-up. The paper compares two fitting approaches for recognition of portions of cylindrical surfaces. Therefore, they are evaluated in the respect of an automatic voxel-based feature recognition of 3D dense cloud of points for tolerance inspection of injection-molded parts. The first approach is a 2D Levenberg Marquardt algorithm coupled with a first guess evaluation made by the Kasa algebraic form. The second one is a 3D fitting based on the RANdom SAmple Consensus algorithm (RANSAC). The evaluation has been made according to the ability of the approaches of working on points associated to the voxel structure that locally divides the cloud to characterize planar and curved surfaces. After the presentation of the overall automatic recognition, the cylindrical surface algorithms are presented and compared trough test cases.

Keywords: Injection molding , RANdom SAmple Consensus algorithm , Tolerance inspection

The aim of this study is to understand if the shape of a cell can affect the characterization process of the mechanical properties via nanoindentation measurements. The characterization of the cell material by atomic force microscopy, in fact, traditionally implements the Hertz contact theory that is based on hypotheses not satisfied in the contact Atomic Force Microscope tip/cell and that do not take into account the actual cell morphology. In previous experimental studies, the mechanical properties of colorectal cancer cells differently shaped (rounded or elongated cells) and sized were determined via nanoindentation measurements. Implementing the Hertz theory, the authors found that differences in mechanical properties exist between the different cell lines with different shape. At this point, the question that can be raised is the following. Is it possible to state that this difference depends on the differences intrinsically existing between the mechanical properties of the investigated cells? Or, this difference can be justified with the difference in cells shape? In other words, the differences seen with the Hertz theory can depend on the fact that the cell shape was not taken into account. To respond to this question, the nanoindentation process of the different colorectal cancer cells was simulated via the finite element method. The finite element models reproducing the cells morphology were integrated into a numerical optimization algorithm that cyclically perturbs the cell mechanical properties until the difference between the force-indentation curve retrieved numerically and that obtained experimentally becomes smaller than an a priori fixed ε value. Once this occurs, the optimization algorithm stops and gives in output the optimal cell material properties. Interestingly, we found that the mechanical properties obtained via the Hertz contact theory are significantly different with respect to those computed with the proposed approach. Furthermore, we found that the material properties of the rounded cells are intrinsically different with respect to those of the elongated ones. The proposed approach provides new insights on the cell mechanobiology and on the effect of cell shape on the specific tasks in cancer growth and invasion.

Keywords: Cell material characterization , Cell modelling , Cell shape

During the concept phase of the industrial design process drawings are used to represent designer's ideas. More specifically, the designer's goal is to put the characteristics of ideas on paper so that they can later act as pivotal points in the development of a project. Sketching is also the ideal tool to continue developing an idea: because it is imprecise, the sketch guarantees a high degree of freedom, allowing for changes to made and new ideas to be added. Another possibility is to translate ideas into sketches on computer tools. This approach can allow the designer to use the created 3D model as the basis for further developing ideas. At the present moment, however, this type of solution is not extensively used by designers during the concept phase. Some researchers have identified technical problems as the reason why these instruments have been unsuccessful on the market, while for others this is related to systems still too rigid to be adapted to the often-diverse needs of designers. The research presented in this position paper aims at analyzing what has so far been understood with respect to the process of generating ideas, their initial representation in the concept phase and the tools that have been developed so far to support this phase. Consequently, a discussion on these themes and some hypotheses from which develop new research lines will be presented.

In Mass Customisation (MC), products are intrinsically variable, because they aim at satisfying end-users' requests. Modular design and flexible manufacturing technologies are useful strategies to guarantee a wide product variability. However, in the eyewear field, the current strategies are not easily implementable, due to some eyewear peculiarities (e.g., the large variability of the frame geometry and material, and the necessity to use specific manufacturing phases). For example, acetate spectacle-frames are bent through a thermoforming process. This particular phase requires dedicated moulds, whose geometry strictly depends on the frame model to be bent; consequently, changes of the frame geometry continuously require new moulds, which have to be designed, manufactured, used, and finally stored. The purpose of this paper is to propose a new strategy to transform a dedicated tool (i.e., a thermoforming mould) into a reconfigurable one, to optimise the tool design, manufacturing and use. First, how the frame features influence the mould geometry has been investigated, creating a map of relations. On the basis of this map, the conventional monolithic-metallic mould was divided into “standard” (re-usable) and “special” (ad-hoc) modules, where the “special” ones are in charge of managing the variability of the product geometry. The mapped relations were formalised as mathematical equations and then, implemented into a Knowledge Based Engineering (KBE) system, to automatically design the “special” modules and guarantee the mould assemblability. This paper provides an original example of how a reconfigurable thermoforming mould can be conceived and how a KBE system can be used to this aim.

Keywords: Eyewear , KBE system , Mass customisation , Thermoforming mould

The paper offers insights into people's exploration of creative products shown on a computer screen within the overall task of capturing artifacts' original features and functions. In particular, the study presented here analyzes the effects of different forms of representations, i.e., static pictures and videos. While the relevance of changing stimuli's forms of representation is acknowledged in both engineering design and human-computer interaction, scarce attention has been paid to this issue hitherto when creative products are in play. Six creative products have been presented to twenty-eight subjects through either pictures or videos in an Eye-Tracking-supported experiment. The results show that major attention is paid by people to original product features and functional elements when products are displayed by means of videos. This aspect is of paramount importance, as original shapes, parts, or characteristics of creative products might be inconsistent with people's habits and cast doubts about their rationale and utility. In this sense, videos seemingly emphasize said original elements and likely lead to their explanation/resolution. Overall, the outcomes of the study strengthen the need to match appropriate forms of representation with different design stages in light of the needs for designs' evaluation and testing user experience.

Keywords: Areas of interest , Creative products , Eye-Tracking , Human-computer interaction , Images , User experience , Videos