Geometric modeling and processing

Engineering design shows a growing interest in exploring cost analysis to anticipate manufacturing issues and integrate production aspects within the product development process. This research aims to highlight key elements (inputs, parameters, models) to accurately predict the cost of a forged part using a complete model, with important information that can be available during the design phase. For this purpose, a systematic literature review of existing engineering methodologies developed for cost analysis of forged parts (i.e., cost estimation, DtC, and ABC) was performed with characterizations of the different approaches for evaluating the most important topics related to this objective. As a result, the most important insights related to the aim of this review are provided: (i) among quantitative methods, analytical and parametric models are the most suitable approaches to develop a cost estimation, (ii) a cost model based on a linear equation supported by single or multiple variables seems to be the most accurate tool to establish a robust cost analysis in the design of forged components, and (iii) input parameters related to the material type and geometrical features are the most critical cost-drivers in the cost assessment. Moreover, this review contributes to identifying emerging applications and obsolete topics, providing the ground to investigate unexplored areas relevant to future research.

Keywords: CAD , CAE , Cost assessment , Cost model , Engineering knowledge , Forging , Material processing , Systematic literature review

Welding is a consolidated technology used to manufacture/assemble large products and structures. Currently, welding design issues are tackled downstream of the 3D modeling, lacking concurrent development of design and manufacturing engineering activities. This study aims to define a method to formalize welding knowledge that can be reused as a base for the development of an engineering design platform, applying design for assembly method to assure product manufacturability and welding operations (design for welding (DFW)). The method of ontology (rule-based system) is used to translate tacit knowledge into explicit knowledge, while geometrical feature recognition with parametric modeling is adopted to couple geometrical information with the identification of welding issues. Results show how, within the design phase, manufacturing issues related to the welding operations can be identified and fixed. Two metal structures (a jack adapter of a heavy-duty prop and a lateral frame of a bracket structure) fabricated with arc welding processes were used as case studies and the following benefits were highlighted: (i) anticipation of welding issues related to the product geometry and (ii) reduction of effort and time required for the design review. In conclusion, this research moves forward toward the direction of concurrent engineering, closing the gap between design and manufacturing.

Keywords: CAD , Design for manufacturing and assembly , DFMA , Engineering design , Feature recognition , Knowledge-based system , Rule-based system , Welded structure , Welding

The paper proposes a method to couple manufacturing knowledge in the context of casting with 3D CAD modelling and design. The approach allows formalizing tacit into explicit design knowledge, for aiding engineers during the development of metal casted components. It is based on three main pillars: (i) identification of geometrical features (3D CAD features) and parameters that can cause an issue during the manufacturing process, (ii) definition of a numerical threshold for feature parameters that guarantee the feasibility of the casting process, and (iii) representation of design rules within a CAD system to support product design review. The method is considered the starting point for future developing a software tool (CAD tool plug-in), here just presented. Two case studies are reported with the aim to show the advantages of the proposed method and tool in the identification of manufacturing issues early in the product development process. Results highlight how the CAD-based tool is a useful assistant to avoid design problems related to the metal casting process.

Keywords: CAD , Design for casting , Design rules , DFMA , Embodiment design , Mechanical products

The work carried out has the purpose of improving and optimizing various industrial technical operations, such as preventive maintenance, taken here as an example of application, using the Design for Disassembly (DfD) technique. Therefore, through four metaheuristic methods that have been chosen among the most widespread in the field (described below) to make a comparison between them, the optimal disassembly sequence is sought, if it exists, in terms of time and then costs in order to extract a target component without damaging the other mechanical parts of the assembly. The hypothesis that has been tested throughout this case study is “a responsible application of DfD, not only from the design process of a product but also during the disassembly procedure, can bring substantial benefits to the company”. Interaction with a hypothetical operator in charge of the work to be performed is implemented with the use of augmented reality. In fact, through an application programmed for an Android device (in this case, a mobile phone, hence a handheld device), the operator can be instructed step-by-step on the disassembly sequence in dynamics as an animation. Finally, two virtual buttons were added in augmented reality with which the operator can start and pause/resume the animation at any time to facilitate the understanding of the different steps established by the sequence.

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

This work shows a preoperative simulation procedure with Computer Aided Design (CAD) 3D software for a patient suffering from Ollier's disease. This pathology is very rare and occurs in extremely different ways depending on the case. Consequently, it is difficult to establish a correct surgical strategy that can be applied in a similar way to all patients. Computer Aided Surgical Simulation (CASS) process uses advanced modeling technologies to reproduce bony anatomy and simulate the surgery. The starting point is represented by the 3D digital model of the bone obtained from tomographic images. Through CAD modeling software such as Creo Parametric and following surgeons directives, engineers can provide doctors with orthopedic simulation and expectation of achievable surgical outcome. If virtual surgical prediction doesn't meet doctors requirements, model is regenerated and it is possible to seek for a better solution. CASS process allow for extensive surgical planning, enhancing accuracy in theatre and enriching the amount of medical information that is needed to perform complex orthopedic procedures. In conclusion, the possibility to recognize in advance the overall orthopedic situation and outcoming expectancy represent an extraordinary upgrade of current surgical state of the art, leading to minimally invasive surgeries and patient-specific solutions.

Keywords: 3D modeling , CAD , CASS , Parametric software , Preoperative planning

The influence of the grain angle on the cutting force when milling wood is not yet detailed, apart from particular cases (end-grain, parallel to the grain, or in some rare cases 45°-cut). Thus, setting-up wood machining operations with complex paths still relies mainly on the experience of the operators because of the lack of scientific knowledge easily transferable to the industry. The aim of the present work is to propose an empirical model based on specific cutting coefficients for the assessment of cutting force when peripheral milling of wood based on the following input: uncut chip thickness and width, grain angle (angle between the tool velocity vector and the grain direction of the wood), density and tool helix angle. The specific cutting coefficients were determined by peripheral milling with different depths of cut wood disks issued from different wood species on a dynamometric platform to record the forces. Milling a sample into a round shape (a disk) allows to measure the cutting forces toward every grain angle into a sole basic diameter reduction operation. Force signals are then post-processed to carefully clean the natural vibrations of the system without impacting their magnitudes. The experiment is repeated on five species with a large range of densities, machining two disks per species for five depths of cut in up- and down milling conditions for three different tool helix angles. Finally, a simple cutting force model, based on the previously cited parameters, is proposed, and its robustness analysed.

The increasing availability of 3D anatomical models obtained from diagnostic images exploiting Reverse Engineering techniques allows the application of statistical analysis in the quantitative investigation of anatomical shapes variability. Statistical Shape Models are a well-established method for representing such variability, especially for complex forms like the anatomical ones. Not by chance, these models are widely used for medical applications, such as guiding segmentation of the diagnostic image and virtual reconstruction of incomplete anatomic region. The application of a statistical analysis on a set of shapes representing the same anatomical region essentially requires that shapes must be in correspondence, i.e. constituted by the same number of points in corresponding position. This work aims to compare two established algorithms, namely a modified version of the Iterative Closest Point and the non-rigid version of the Coherent Point Drift, to solve the correspondences' problem in the construction of a Statistical Shape Model of the human cranium. The comparison is carried out on the models using the standard evaluation criteria: Generalization, Specificity and Compactness. The modified version of the Iterative Closest Point delivers a better Statistical Shape Model in terms of Generalization and Specificity, but not for Compactness, than the Coherent Point Drift-based model.

Keywords: Computer-Aided Technologies , Correspondences' problem , Reverse Engineering , Statistical Shape Analysis , Statistical Shape Model

The growing interest in the auricular anatomy is due to two different strands of research: 1) in the medical field it is associated with autologous ear reconstruction, a surgery adopted following trauma or congenital malformations; 2) in surveillance and law enforcement the ear is used for human detection and recognition. Alternative systems of ear analysis can be differentiated for the type of input data (two-dimensional, three-dimensional or both), for the type of acquisition tools (3D scanner, photographs, video surveillance, etc.) and finally for the adopted algorithms. Although the segmentation and recognition of the ear from the face is a widely discussed topic in literature, the detection and recognition of individual anatomical elements has not yet been studied in depth. To this end, this work lays the foundation for the identification of the auricular elements through image processing algorithms. The proposed algorithm automatically identifies the contours of the main anatomical elements by processing depth map images. The algorithm was tested qualitatively and quantitatively on a dataset composed of 150 ears. The qualitative evaluation was performed with the collaboration of medical staff and the quantitative tests were performed using manually annotated ground truth data.

Keywords: Depth map , Ear biometrics , Ear dataset , Ear reconstruction , Ear segmentation , Microtia

The major breakthroughs in the fields of reverse engineering and additive manufacturing have dramatically changed medical practice in recent years, pushing for a modern clinical model in which each patient is considered unique. Among the wide spectrum of medical applications, reconstructive surgery is experiencing the most benefits from this new paradigm. In this scenario, the present paper focuses on the design and development of a tool able to support the surgeon in the reconstruction of the external ear in case of malformation or total absence of the anatomy. In particular, the paper describes an appositely devised software tool, named G-ear, which enables the semi-automatic modeling of intraoperative devices to guide the physician through ear reconstruction surgery. The devised system includes 3D image segmentation, semi-automated CAD modelling and 3D printing to manufacture a set of patient-specific surgical guides for ear reconstruction. Usability tests were carried out among the surgeons of the Meyer Children's Hospital to obtain an assessment of the software by the end user. The devised system proved to be fast and efficient in retrieving the optimal 3D geometry of the surgical guides and, at the same time, to be easy to use and intuitive, thus achieving high degrees of likability.

Obstructive sleep apnoea syndrome is characterized by an obstruction in the upper airway due to the pharyngeal collapse during sleep. Mandibular advancement devices have gained success and large popularity as a non-invasive treatment for OSAS. Nevertheless, the effects of mandibular advancement devices were poorly investigated in literature. To this aim the paper proposes a procedure to achieve a numerical simulation model useful to assess the stress/strain distribution on the temporomandibular joint and periodontal ligaments caused by the mandibular advancement. The findings suggest that the mandibular roto-translation induced by the MAD provoke high stress on the molars and premolar teeth.

Keywords: Computer aided design , Finite element method , Mandibular advancement device , Periodontal ligaments , Temporomandibular joint

Obstructive sleep apnea syndrome (OSAS) is a sleep disorder that causes pauses in breathing or periods of shallow breathing during sleep. Mandibular advancement devices (MADs) represent a non-invasive treatment for OSAS that has had the highest development in recent years. Nevertheless, literature has not primarily investigated the effects of mandibular advancement. This paper presents a finite element method numerical simulation model for evaluating the stress/strain distribution on the temporomandibular joint (TMJ) and periodontal ligaments caused by advancement devices used for the treatment of OSAS. Results highlight that the mandible lift phase generates significant stress values on TMJ, which cannot be neglected for extended usage of MADs. Furthermore, mandible molar teeth are more loaded than incisor ones.

Keywords: Computer-Aided Design , Finite element method , Mandibular advancement device , Obstructive Sleep Apnea Syndrome , Virtual prototyping

This article reports on the results of research aimed to translate biometric 3D face recognition concepts and algorithms into the field of protein biophysics in order to precisely and rapidly classify morphological features of protein surfaces. Both human faces and protein surfaces are free-forms and some descriptors used in differential geometry can be used to describe them applying the principles of feature extraction developed for computer vision and pattern recognition. The first part of this study focused on building the protein dataset using a simulation tool and performing feature extraction using novel geometrical descriptors. The second part tested the method on two examples, first involved a classification of tubulin isotypes and the second compared tubulin with the FtsZ protein, which is its bacterial analog. An additional test involved several unrelated proteins. Different classification methodologies have been used: a classic approach with a support vector machine (SVM) classifier and an unsupervised learning with a k-means approach. The best result was obtained with SVM and the radial basis function kernel. The results are significant and competitive with the state-of-the-art protein classification methods. This leads to a new methodological direction in protein structure analysis.

Keywords: 3D face analysis , differential geometry , geometrical descriptors , machine learning , protein classification , support vector machine , tubulin

This work aims to identify people psychological stress through the capture of micro modifications and motions within their facial expression. Exogenous and endogenous causes of stress, from environment and/or psychological conditions that could induce stress, have been reproduced in the experimental test involving real subjects, and their face expressions have been recorded by 2D and 3D image capturing tools to create a sample of emotional database. Successively, 2D and 3D analyses have been performed on recorded data according to the respective protocols, by deep learning and machine learning techniques, and a data driven model of the databases has been developed by neural network approach, to classify the psycho-behavioral answers to the different kinds of stress conditions induced on tested people. The ultimate aim of the study is to demonstrate the possibility to analyze data collected on participants from 2D shooting and 3D scans in a consistent way by means of deep learning and machine learning techniques, so that to provide a methodology to identify and classify some of the subtle facial micro-expressions of people involved in stressing activities.

Keywords: Deep learning , Emotion detection , Image recognition , Machine learning , Neural networks

Facial Emotion Recognition (FER) is the automatic processing of human emotions by means of facial expression analysis[1]. The most common approach exploits 3D Face Descriptors (3D-FD)[2], which derive from depth maps[3] by using mathematical operators. In recent years, Convolutional Neural Networks (CNNs) have been successfully employed in a wide range of tasks including large-scale image classification systems and to overcome the hurdles in facial expression classification. Based on previous studies, the purpose of the present work is to analyze and compare the abstraction level of 3D face descriptors with abstraction in deep CNNs. Experimental results suggest that 3D face descriptors have an abstraction level comparable with the features extracted in the fourth layer of CNN, the layer of the network having the highest correlations with emotions.

Keywords: Abstraction , CNN , Deep learning , Explainable AI , Facial Emotion Recognition , FER

The ITER Radial Neutron Camera is a diagnostic whose objective is measuring neutron emissivity and fusion power density through an array of detectors placed in collimating structures. The RNC is composed of two subsystems (In-Port RNC and Ex-Port RNC), located in the Equatorial Port 01 of the ITER tokamak. Although the measurements from the RNC are required for ITER D-T phase, its In-Port components must be ready for Assembly phase 2. Consequently, the two subsystems will be delivered at different times. At the current status of the design the In-Port RNC interfaces must be defined, if not fully specified, in order to allow for the subsystem integration in the Port Plug. A thorough assessment of the interfaces of the subsystem with all the diagnostics, plants and services in the port has been made, taking into account the concurrent development of the Equatorial Port 01 and the progress in the design of some of the subsystem components that may affect the identification of interfacing Plant Systems. This paper deals with the process that led to definition of the internal and external interfaces of the In-Port RNC, highlighting the main issues and the solutions adopted to perform integration within the Equatorial Port Plug 01.

Keywords: Integration , Interfaces , Iter diagnostics , Radial neutron camera

The eutectic alloy Lithium Lead (LiPb) enriched at 90 % in 6Li is the breeder material for one of the candidate European Breeding Blanket (BB) concepts. Currently under investigation for DEMO reactor, the Water Cooled Lithium-Lead (WCLL), and for the WCLL Test Blanket Module (TBM) that will be qualified in the ITER reactor. The LiPb alloy is used as tritium breeder, neutron multiplier and tritium carrier. The design of the LiPb loops is currently under study and the conceptual design of the main loop components has been completed. For this reason, it becomes mandatory to proceed with the integration of the LiPb loops in the EU DEMO Tokamak building, checking the consistency of the different systems design to be integrated in DEMO reactor building. CAD design and integration of the entire LiPb loops are shown taking into account the building areas assigned, the interfaces with the other systems and the requirement related to the LiPb loop functions. An initial layout of the pipework and the position of the main components have been defined on the basis of the following design requirements: (I) gamma radiation shielding of the components and the pipework; (II) target flow velocity of the LiPb; (III) thermal expansion of the pipes; (IV) possibility to drain the entire loop; (V) redundancy of the loops; (VI) remote maintenance; (VII) position in the building and dimensions of the storage tanks. The 3D model of the entire loops has been provided and integrated in DEMO Tokamak building pointing out the issues related to the interfaces with the other systems and with the building itself.

Keywords: Breeding blanket , CAD , DEMO , Integration , Lithium lead , Piping design , Water cooled lithium lead

The Industry 4.0 framework is pushing the manufacturing systems towards a zero-defect production based on robot technologies. The increasing level of automation in the production lines is raising new challenges for designers that must face the latest requirements in terms of product quality and power consumption. Among the multitude of components of the industrial plants, Servo-Mechanisms (SMs) play a crucial role and govern important performance indices of both robots and automatic machines. During the execution of high dynamics tasks, the SMs performance is influenced by many factors, including motion law, acting load, temperature and degradation. The development of accurate models aiming at predicting and optimizing the SMs behavior may not be practicable without extensive experimental activities. Owing to these considerations, this work introduces a novel test rig for the accurate characterization of industrial SMs. The rig is designed by combining the advantages of the existing prototypes. It is equipped with high precision sensors and an active loading system that enable to test the SM in various working conditions. Also, the rig modularity facilitates the installation of newly commissioned components and the execution of static and dynamic experiments. The paper mainly focuses on the rig mechanical design and components selection criteria.

Keywords: Computer Aided Design , Design methods , High Precision Manufacturing , Industry 4.0 , Servo-Mechanism Test Rig

Mechanical assemblies are very complex structures, made of many parts of various shapes and sizes with different usages. Consequently, it is challenging to manage them during all the manufacturing processes, from the design to the assembly and the recycling. Aiming to simplify the assembly structure and reduce the number of parts to deal with simultaneously, in literature many works exist on subassemblies identification starting from the CAD assembly model. However, the methods provided loose sight of many details associated with the parts, as well as the fact that the treated model represents a real mechanical assembly which respects precise engineering rules. At this regard, this work introduces a novel methodology to detect meaningful clusters in CAD assembly models. The logic applied relies on engineering knowledge, both of mechanical assemblies' components and of assembling techniques, and on the leveraging of the semantics of components. In particular, referring to general design rules, we have identified some heuristics to exploit to partition the assembly into different types of clusters, such as the symmetry along an axis and the presence of fasteners or welds. It results that the assembly's parts are meaningfully grouped, considering, at the same time, their shape, functionality, and type of contact.

Keywords: Assembly cluster , CAD assembly model , Engineering knowledge , Heuristic method , Semantic component

In industrial manufacturing, both in the design and the production phase, the management of modern mechanical assemblies is becoming demanding due to their increasing complexity. The use of stable subassemblies concept constitutes a better alternative, which allows to independently treat smaller groups of the assembly's parts, also to achieve a parallel production. At this regard, several methods for automatic subassemblies identifi-cation, starting from the assembly CAD model, have been provided. However, most of the methodologies proposed rely on human intervention, especially in the model processing to make available essential data, while other details are ignored. After giving the definition of stable subassembly, this paper focuses on the application of stable subassemblies identification to industrial CAD models and highlights the issues arising. With the aim of ensuring a reliable CAD model analysis, starting point of the identification, the possible real engineering situations, both related to assembling methods and modelling techniques, are presented. Ap-proaches to algorithmically address them are then described, with the help of two examples of mechanical assemblies.

Keywords: Assembly analysis , Industrial CAD model , Stable subassembly , Subassembly identification

The miniscrew-assisted rapid palatal expansion approach has given new opportu-nities for the treatment of maxilla transverse deficiency by providing an alternative to the surgical approach for adult patients. However, the presence of a thin palatal bone can compromise the success of such approach. Recently, the digital planning of the miniscrew-assisted appliances has offered unique advantages in terms of safety and accuracy of the overall process. The aim of this study is to describe the digital planning and MSE fabrication with cad-cam technology using 6 mini-screws in cases with a palatal bone thickness of less than 2.5 mm.

Keywords: Digital orthodontics , MARPE , Maxillary transverse deficiency , MSE , Palatal expansion