Abstract: 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

Abstract: 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

Abstract: The current context is characterised by the speed of change in the technological sphere and in particular by the interconnection—to the point of overlaying—between physical and digital space. This stimulates consideration on the opportunities to explore the new frontiers of knowledge through advanced technologies and unprecedented cognitive-sensory perceptions, both from the user’s viewpoint and from that of the researcher. The chapter provides a critical-analytical reflection on accessibility and multisensory issues as fundamental tools for transferring multilevel knowledge between physical and digital. Based on this study, it proposes the configuration of immersive knowledge-sharing environments where cultural heritage and scientific research intersect, placing the user at the centre of experience. The augmented, multilevel fruition, the tracking within the multisensory environment of psycho-physiological and behavioural users’ data, together with the assessment of experience itself, have guided the design experimentations undertaken for the new layout of the Museum of Contemporary Mediterranean Ceramics in Cava de’ Tirreni. This was conceived as a multisensory and accessible phygital laboratory of inclusion and dialogue, a dynamic and adaptive space for sharing and experiencing knowledge.

Keywords: Accessibility | Immersive experience | Multilevel knowledge | Multisensory adaptive fruition | Phygital | Physical-digital relationship

Abstract: Variation Simulation (VS) allows early validation and certification of the assembly process before parts are built. State-of-the-art VS models of assembly systems with compliant sheet-metal parts are based on Finite Element Method (FEM) integrated with statistical approaches (i.e., Monte Carlo simulation). A critical technical barrier is the intense computational cost. This paper proposes a novel real-time physics-based VS model of assembly systems with compliant sheet-metal parts based on Reduced-Order Model (ROM). Compared to the literature on the topic, this study reports the first application of a ROM, developed for VS by using both intrusive and non-intrusive techniques. The capability of the proposed method is illustrated in a case study concerning the assembly process of the vertical stabiliser for commercial aircrafts. Results have shown that the accuracy of ROM (based on proper orthogonal decomposition) depends on the sampling strategy as well as on the number of reduced modes. Whilst a large CPU time reduction by several orders of magnitude is achievable by non-intrusive techniques (based on radial basis functions for interpolation), intrusive models provide more accurate results compared to the full-order models.

Keywords: Compliant assembly | Proper orthogonal decomposition | Radial basis functions | Real-time physics-based simulation | Reduced-Order Models | Sheet metals | Variation simulation analysis

Abstract: The current best-practice in the assembly process of aircraft skin panels involves several manual measurement-fit-adjust quality loops, such as loading part on the assembly frame, measuring gaps, off-loading parts, adding be-spoke shims and re-positioning parts ready for the fastening operation. The consequence is that the aircraft is re-assembled at least twice and therefore this process has been proved highly inefficient. This paper describes the framework developed under the “Integrated Smart Assembly Factory” (ISAF) project in the “Intelligent Factory” specialisation area in Italy. Taking advantage of the emerging tools brought by Industry 4.0 the ISAF framework spearheads innovation in the assembly process of aircraft skin panels by integrating smart and digital technologies such as in-line measurement systems with highly accurate sensors, large-scale physics-based simulations, multi-disciplinary process optimisation and additive manufacturing. ISAF implements a flexible alignment, which combines both rigid rotations/translations and local deformations to account part deformations. The proposed methodology allows predicting and fabricating shims using in-line measurement data with no need to iterate the measurement-fit-adjust quality loops. This will undoubtedly reduce inspection/measurement time and costs, enabling operators to virtually test assembly operations before installation in the field. The results were demonstrated during the assembly process of a vertical stabiliser for commercial aircrafts, and findings showed a significant time saving of 75%.

Keywords: Additive manufacturing | Digital twin | Flexible alignment | In-line measurement | Physical simulation | Shimming | Smart factory

Abstract: Preface and Acknowledgements (Editorial)

Keywords: Editorial

Abstract: Over the years, high attention has been paid to Reverse Engineering (RE) as a methodological approach for reconstructing 3D models of existing objects to carry out analyses aimed to estimate accurate products performance and to conduct accurate inspections and quality controls. Although these techniques are widely used, RE has limitations related to both the user’s operations and the range of high-quality acquisition. Consequently, large objects exclude the possibility of preserving scanning accuracy, unless alternative solutions are found, and require high repeatability, making necessary well-trained personnel. For these purposes, Extended Reality (XR) could pave the way for the development of advanced training systems and the implementation of optimized interfaces for testing the adopted design solutions. This research deals with the development of an XR application for simulating the 3D scanning process of the vertical stabilizer torque box of an airplane and providing both an effective virtual training tool for the operators and a supporting tool for testing design solutions.

Keywords: 3D scanning | Extended Reality | Virtual training

Abstract: Modern industries are experiencing radical changes due to the introduction of high technological innovations. In this context, even more highly complex and customized products are required, increasing the need of tending towards the concept of complexity for free. In addition, new products are conceived with the circular economy in mind, considering possible multi life-cycle at the early design stage to reduce time and costs while ensuring high quality standards. To evaluate the overall product complexity, this research combines geometrical, manufacturing, assembly, and disassembly complexity features, typically treated separately in the literature. The research is divided into two parts and proposes a novel methodological framework for assessing product complexity with an overall view, integrating many aspects of product life cycle. The framework aims to create a rank of product configurations, on the base of complexity. Making complexity assessment procedures objective is essential to effectively support decision-making processes, especially when introducing advanced manufacturing technologies such as Additive Manufacturing (AM). Additionally, it is necessary to know the complexity of the individual components before the overall assembly. This paper deals with the first part of the research, proposing the aforementioned novel methodological framework, with a great focus on geometrical complexity. A geometrical complexity index is defined through experimental and numerical surveys, involving CAD modeling experts and considering numerous metrics found in the technical literature. The proposed methodological framework and the geometrical complexity metric can provide useful tools for businesses looking to evaluate their product complexity and identify areas for improvement.

Keywords: CAD | Geometrical complexity | Methodological framework | Product complexity | Survey

Abstract: 3D printing, including the widely used technique of Fused Filament Fabrication (FFF), offers several benefits, such as freedom in design, faster production times, customization, and lightweight. In fact, it has the potential to serve a variety of sectors, from the everyday products market to the industry. However, the properties of FFF parts, in terms of mechanical strength and geometrical accuracy, are strongly influenced by printing process parameters, necessitating thorough investigations. This preliminary study proposes a comparison between data-driven Machine Learning (ML) models, i.e. Quadratic Regression (QR), Regression Tree (RT), and Neural Network (NN), to predict the impact of printing process parameters on both mechanical (tensile properties) and aesthetical (bending angle, thickness, and flatness tolerance) behavior of additively manufactured tough-Polylactic Acid (PLA) specimens. The investigated models were trained by using experimental data obtained from Design of Experiment (DoE) where the building orientation on plate, the infill percentage and the pattern were varied. An additional dataset was used to test the accuracy of the prediction. The results suggest that ML models perform well in predicting the tensile properties, particularly the Ultimate Tensile Stress (UTS). At the same time, further investigation is necessary to improve the prediction for aesthetical features.

Keywords: 3D measurements | Additive Manufacturing | Design for AM | experimentation | Machine Learning | Mechanical behavior | predictive model

Abstract: Additive manufacturing technology allows producing objects layer-by-layer starting from three-dimensional (3D) digital models. These 3D models can be drawn using CAD software or can be obtained starting from a real-world object, through reverse engineering (RE) techniques. RE process is today widely used in numerous industrial applications. It is a powerful tool for additive manufacturing, and their combination can greatly enhance product design as well as shorten the product development cycle. This chapter describes the main reverse engineering techniques – contact and noncontact active and passive systems – and the main phases that allow obtaining a 3D CAD model starting from a physical object.

Keywords: Active and passive methods | Contact and noncontact systems | Industrial CT scanning | Point cloud | STL format

Abstract: A leading challenge in the assembly process of aircraft skin panels is the precise control of part-to-part gaps to avoid excessive pre-tensions of the fastening element which, if exceeded, impair the durability and the response under dynamics loads of the whole skin assembly. The current practice is to measure the gap in specific points of the assembly with parts already at their final location, and then be-spoke shims are machined and inserted between the mating components to fill the gap. This process involves several manual measurement-fit-adjust quality loops, such as loading parts on the assembly frame, measuring gaps, off-loading parts, adding be-spoke shims and re-positioning parts ready for the fastening operation—as a matter of fact, the aircraft is re-assembled at least twice and therefore the current practice has been proved highly cost and time ineffective. Additionally, the gap measurement relies on manual gauges which are inaccurate and unable to follow the actual 3D profile of the gap. Taking advantage of emerging tools such as in-line measurement systems and large-scale physics-based simulations, this paper proposes a novel methodology to predict the part-to-part gap and therefore minimise the need for multiple quality loops. The methodology leverages a physics-driven digital twin model of the skin assembly process, which combines a physical domain (in-line measurements) and a digital domain (physics-based simulation). Central to the methodology is the variation model of the multi-stage assembly process via a physics-based simulation which allows to capture the inherent deformation of the panels and the propagation of variations between consecutive assembly stages. The results were demonstrated during the assembly process of a vertical stabiliser for commercial aircraft, and findings showed a significant time saving of 75% by reducing costly and time-consuming measurement-fit-adjust quality loops.

Keywords: Aircraft skin panels | Digital twin | Morphing mesh | Multi-stage assembly simulation | Physics-based modelling | Virtual shimming

Abstract: Emerging production technologies, in particular Additive Manufacturing (AM), nowadays are extremely suitable for creating highly complex products, tending towards the concept of ‘complexity for free’, which is often associated with AM. However, there are no adequate guidelines to provide decision support for the correct selection of the most economically appropriate technology. Indeed, from literature it has been highlighted the need to develop a technology selection methodology based no longer on production volume but on product complexity. This paper investigates this need by presenting an approach to determine the geometrical (or shape) complexity index of a part, which, combined with the assembly complexity, represents the driver for helping to decide the best production technology (traditional or additive). The geometrical complexity index has been determined based on complexity judgments, provided by CAD modelling experts, for a sample of CAD models. In this way, it has been possible to define a preliminary complexity index model, strictly linked to the CAD model information. The results showed that the geometrical complexity metrics from the literature, if individually considered, are not comprehensive. However, a combination of them makes it possible to obtain an index that best reflects the subjective judgement of the experts. In addition, by combining the geometrical and assembly complexity with a cost analysis it is possible to obtain convenience zones for better selecting the production technology.

Keywords: CAD | Geometrical complexity | Survey | Technology selection

Abstract: Image registration has widespread application in fields like medical imaging, satellite imagery and agriculture precision as it is essential for feature detection and extraction. The extent of this paper is focussed on analysis of intensity and feature-based registration algorithms over Blue and RedEdge multispectral images of wheat and cauliflower field under different altitudinal conditions i.e., drone imaging at 3 m for cauliflower and handheld imaging at 1 m for wheat crops. The overall comparison among feature and intensity-based algorithms is based on registration quality and time taken for feature matching. Intra-class comparison of feature-based registration is parameterized on type of transformation, number of features being detected, number of features matched, quality and feature matching time. Intra-class comparison of intensity-based registration algorithms is based on type of transformation, nature of alignment, quality and feature matching time. This study has considered SURF, MSER, KAZE, ORB for feature-based registration and Phase Correlation, Monomodal intensity and Multimodal intensity for intensity-based registration. Quantitatively, feature-based techniques were found superior to intensity-based techniques in terms of quality and computational time, where ORB and MSER scored highest. Among intensity-based methods, Monomodal intensity performed best in terms of registration quality. However, Phase Correlation marginally scored less in quality but fared well in terms of computational time.

Keywords: Control points (CP) | Feature transform (SIFT) | Feature-based | Intensity-based | KAZE | Maximally Stable Extremal Regions (MSER) | Modified difference local binary (MDLB) | Monomodal | Multi spectral (MS) | Multimodal | Mutual information (MI) | Normalized cross correlation | Oriented Fast and Rotated Brief (ORB) | Phase correlation | Scale-invariant (SI) | Speeded Up Robust Features (SURF) | Sum of squared differences (SSD)

Abstract: Building information modelling (BIM) plays a prominent role in a good deal of architecture, engineering and construction (AEC) works, envisaging a full transition to digitalization for the construction industry. This is also due to a number of national and international regulations regarding the design, erection, and management of civil engineering constructions. For this reason, full interoperability of software environments such as computeraided design (CAD) and computer‐aided engineering (CAE) is a necessary requirement, particularly when the exchange of information comes from different disciplines. Users, throughout the years, have faced CAD–CAE interoperability issues despite following the IFC neutral open file format. This inability to share data (CAD to CAD, CAD to CAE) often generates model-interpretation problems as well as a lack of parametric information and a disconnection of elements. This paper addresses issues and mapping mechanisms in the exchange of data for the purpose of defining a baseline for the current status of bidirectional data exchange between AEC CAD/CAE software via the IFC format. A benchmark study, covering three years of software releases is illustrated; the assessment of the software performance was made with reference to criteria associated with the software’s level of suitability for use of the structural models. Four classes of performance, depending on the accuracy of the data transfer and on the associated corrective actions to be taken, were adopted. This confirmed that at the moment, the implementation of the IFC standard by software manufacturers is geared towards an expert class of users. Further efforts are needed in order to ensure its application is adopted by a wider class, thus extending and regulating its use by national, regional, and local authorities.

Keywords: BIM interoperability | Building information modelling (BIM) | Computer‐aided design (CAD) | Computer‐aided engineering (CAE) | Data exchange | Industry Foundation Classes (IFC)

Abstract: The protection of artistic and cultural heritage is a major challenge due to its peculiarities and its exposure to significant natural hazards. Several methodologies exist to assess the condition of artistic heritage and to protect it from exceptional actions. Moreover, novel digital technologies offer many solutions able to deliver a digital replica of artifacts of interest, so that a reduction in the uncertainties in the analysis models can be achieved. A rational approach to the preservation and protection of artistic heritage is based on traditional approaches supported and integrated by novel technologies, so that qualitative and quantitative indicators of the current condition of artistic heritage can be defined and validated in an interdisciplinary framework. The present paper reports the results of an approach to the maintenance and preservation of art objects housed in a museum complex based on a comprehensive digital path towards a Historical Digital Twin (HDT). A workflow aimed at estimating the stress regime and the dynamic properties of two sculptures, based on the detailed three-dimensional model resulting from a laser scanner survey, is illustrated and dis-cussed. The results highlight the great advantages resulting from the integration of traditional and novel procedures in the field of conservation of artistic assets.

Keywords: 3D simulation | Conservation | Cultural heritage | Digital twin | Laser scanning | Maintenance

Abstract: Currently, there is a growing interest of industries in applying additive manufacturing (AM) technology for generating objects with high geometrical complexity and low weight, ensuring good performance, comparable to those ones of products realized by means of traditional techniques. Anyway, it is still usual to realize AM products without focusing on the morphology of the object, hence without exploiting all the advantages of the technique. Indeed, since the several suitable AM technologies, it should be useful to know the functional characteristics of the component for the best choice of the appropriate one and its constructive complexity. In this regard, the 3D modeling strategy is extremely crucial for a proper realization of AM products. The paper deals with a study of the geometrical complexity of dashboard components of a car, based on several techniques for evaluating the geometric complexity. The latter is a fundamental element for estimating the feasibility of AM in terms of production costs and the benefits with respect to traditional molding. In detail, the study focuses on comparing several geometrical complexity evaluation techniques in order to identify the one that simplifies the calculation and better approximates the most used in literature.

Keywords: additive manufacturing | CAD | geometrical complexity

Abstract: Background: In this study, we promote a global approach to occupational risk perception in order to improve occupational health and safety training programs. The study investigates the occupational risk perception of operating room healthcare workers using an Analytic Hierarchy Process approach. Methods: A pilot study was carried out through a cross-sectional survey in a university hospital in Southern Italy. An ad hoc questionnaire was administered to enrolled medical post-graduate students working in the operating room. Results: Fifty medical specialists from seven fields (anaesthetists, digestive system surgeons, general surgeons, maxillofacial surgeons, thoracic surgeons, urologists, and gynaecologists) were questioned about perceived occupational risk by themselves. Biological, ionizing radiation, and chemical risks were the most commonly perceived in order of priority (w = 0.300, 0.219, 0.210). Concerning the biological risk, gynaecologists unexpected perceived this risk as less critical (w = 0.2820) than anaesthesiologists (w = 0.3354), which have the lowest perception of the risk of ionizing radiation (w = 0.1657). Conclusions: Prioritization methods could improve risk perception in healthcare settings and help detect training needs and perform sustainable training programs.

Keywords: Analytic hierarchy process | Healthcare workers | Occupational risk perception | Prioritization risk methodology

Abstract: The measurement of geometric and dimensional variations in the context of large-sized products is a complex operation. One of the most efficient ways to identify deviations is by comparing the nominal object with a digitalisation of the real object through a reverse engineering process. The accurate digitalisation of large geometric models usually requires multiple acquisitions from different acquiring locations; the acquired point clouds must then be correctly aligned in the 3D digital environment. The identification of the exact scanning location is crucial to correctly realign point clouds and generate an accurate 3D CAD model. To achieve this, an acquisition method based on the use of a handling device is proposed that enhances reverse engineering scanning systems and is able to self-locate. The present paper tackles the device's locating problem by using sensor data fusion based on a Kalman filter. The method was first simulated in a MatLAB environment; a prototype was then designed and developed using low-cost hardware. Tests on the sensor data fusion have shown a locating accuracy better than that of each individual sensor. Despite the low-cost hardware, the results are encouraging and open to future improvements.

Keywords: Handling device | Large-scale metrology | Position measurement | Product design | Sensor data fusion

Abstract: Within the era of smart factories, concerning the ergonomics related to production processes, the Digital Twin (DT) is the key to set up novel models for monitoring the performance of manual work activities, which are able to provide results in near real time and to support the decision-making process for improving the working conditions. This paper aims to propose a methodological framework that, by implementing a human DT, and supports the monitoring and the decision making regarding the ergonomics performances of manual production lines. A case study, carried out in a laboratory, is presented for demonstrating the applicability and the effectiveness of the proposed framework. The results show how it is possible to identify the operational issues of a manual workstation and how it is possible to propose and test improving solutions.

Keywords: Digital Twin | Ergonomics | Manufacturing | Production process

Abstract: Assembly process of aeronautical skin panels deals with large, thin and compliant components, which are usually joined with rivets. A leading challenge is the control of part-to-part gaps prior to riveting operation, which must be maintained below tight design specification limits to avoid excessive pretensions of the rivets which, if exceeded, impair the durability of the whole skin assembly. Gaps are compensated by number of time consuming and costly manual inspection-repair quality loops, which involve measuring gaps, disassembling parts, adding be-spoke shims, re-assembling parts. This paper proposes a novel methodology to support the inspection-repair quality loops with the aim to model and optimise the shape of the shims with the ultimate goal of reducing/eliminating manual and trial-and-error measurements as per today best practice. The methodology will be discussed in two steps: (1) physics-based variation simulation to model generation and propagation of dimensional and geometrical variations (by using scanning data o morphing mesh model) during multi-stage assembly operations; (2) virtual shimming simulator to model and optimise shimming condition between parts being assembled. The proposed methodology is presented and validated using the assembly process of the vertical stabiliser for commercial aircrafts.

Keywords: Aircraft Skin Assembly | Morphing Mesh | Physics-based Modelling | Scanning Data | Virtual Shimming Simulator

Abstract: The research described in this paper shows the results of preliminary analyses carried out on an artwork housed in a museum complex. A three-dimensional model of the sculpture, resulting from a laser scanner survey, has been analysed to understand its current state and seismic response, from a quantitative and qualitative point of view. The results highlight the great advantages resulting from integration of traditional and novel procedures in the field of conservation of artistic assets.

Keywords: 3D analysis | Conservation | Documentation of cultural heritage | Laser scanning | Seismic risk

Abstract: Collaborative robotic solutions, where humans and robots share a common workspace performing tasks concurrently without physical safety barriers dividing them, are entering the 4.0 manufacturing market. Some proven and tested use cases of Human-Robot Collaboration have been implemented, but their identification process is often just based on the intuition of planning engineers. The purpose of this work is to propose a systematic approach for the identification of potential collaborative workstations within an industrial production plant. In order to do this a multi-layer modelling approach was used and enriched. The multi-layer approach defines the overall goal of the industrial process, the sub-processes that made it possible, the activity models that enables a flow of activities and, finally, a set of methods to carry out the activities. A morphological box of methods that can be used to achieve the specific goal of identifying suitable collaborative workplaces in an industrial plant, through a process of HRC potential analysis is, therefore, ready to be deeply investigated and used.

Keywords: Collaborative workplaces | Evaluation criteria | Multi-layer approach

Abstract: The optimization of production processes has always been one of the cornerstones for manufacturing companies, aimed to increase their productivity, minimizing the related costs. In the Industry 4.0 era, some innovative technologies, perceived as far away until a few years ago, have become reachable by everyone. The massive introduction of these technologies directly in the factories allows interconnecting the resources (machines and humans) and the entire production chain to be kept under control, thanks to the collection and the analyses of real production data, supporting the decision making process. This article aims to propose a methodological framework that, thanks to the use of Industrial Internet of Things—IoT devices, in particular the wearable sensors, and simulation tools, supports the analyses of production line performance parameters, by considering both experimental and numerical data, allowing a continuous monitoring of the line balancing and performance at varying of the production demand. A case study, regarding a manual task of a real manufacturing production line, is presented to demonstrate the applicability and the effectiveness of the proposed procedure.

Keywords: Internet of Things—IoT | Methodological framework | Production line performance | Simulation | Wearable devices

Abstract: Unfortunately, the affiliation of one of the authors “Salvatore Gerbino” was incorrect in the original publication, and the correct version is updated here.

Abstract: This paper presents an interactive design method aimed at improving workplace health and safety. Human performances and anthropometric variability are carefully considered to make the workplace “robust” from a safety point of view. This topic is of increasing interest to industries that plan to make safer workplaces without renouncing to their productivity targets. A challenging issue concerns the evaluation of the effects of sources of anthropometric variability in the process by using just a small sample of real or digital humans. The adoption of a discretization technique helps to solve this problem and saving time and resources. Through real industrial case studies, the authors investigate the main ergonomic and safety issues faced during the development of both manual and human–robot hybrid workcells.

Keywords: Design methods | Digital human modelling | Human–robot interaction | Robust design | Virtual ergonomics | Virtual safety

Abstract: This paper introduces a novel hybrid finite element (FE) formulation of shell element to enable assembly process simulation of compliant sheet-metal parts with higher efficiency and flexibility. Efficiency was achieved by developing both new hybrid quadrilateral and triangular elements. Quadrilateral element (QUAD+) was formulated by combining area geometric quadrilateral 6 (AGQ6) nodes and mixed interpolated tensorial components (MITC) to model membrane and bending/shear component respectively. Triangular element (TRIA+) was formulated by merging assumed natural deviatoric strain (ANDES) for membrane and MITC for bending/shear component. Flexibility was addressed by developing an open-source C++ code, enhanced by the OpenMP interface for multiprocessing programming. Tests and benchmarks were compiled and executed within Matlab using the MEX API interface. Extensive benchmark studies were accomplished to evaluate the performance of the proposed hybrid formulation and the shell formulations used in three FEM packages - ABAQUS, ANSYS and COMSOL- under static linear elastic condition with small strain assumption. It was observed that the proposed QUAD+ and TRIA+ elements performed better amongst the FE packages, especially when there was in-plane mesh distortion, with errors below 3%. It was also identified that the best efficiency is obtained by adopting dominant QUAD+ elements compared to the TRIA+ when working on complex geometries. This paper also contributes to present a wide set of benchmark studies required to verify new release of FE packages using shell element or evaluate the performance of new shell formulations.

Keywords: Benchmark study | Finite element modelling | Flexibility and efficiency | Sheet metal | Shell elements

Abstract: The measurement of geometric deviations within large-size products is a challenging topic. One of the most applied technique compares the nominal product with the digitalization of real product obtained by a reverse engineering process. Digitalization of big geometric models is usually performed by means of multiple acquisitions from different scanning locations. Therefore, digitalization needs to correctly place the acquired point clouds in 3D digital environment. For this purpose, it is very important identifying the exact scanning location in order to correctly realign point clouds and generate an accurate 3D CAD model.The present paper faces the locating problem of a handling device for reverse engineering scanning systems. It proposes a locating method by using sensor data fusion based on Kalman filter, implemented in Matlab environment by using a low-cost equipment.

Keywords: Kalman filter | Position measurement | Product design | Prototypes | Reverse Engineering | Sensor data fusion

Abstract: Biomechanical overload is a critical issue for the health of workers employed in manufacturing production systems, and so far it has been analysed by applying conventional observational methods. This research aims to introduce a procedure for quantitative biomechanical overload risk assessment in which surface electromyography integrates with a motion capture system, enhancing the use of Internet of Things (IoT) devices directly in the factory. A case study concerning an experimental session in a Fiat Chrysler Automobiles (FCA) assembly line is described in order to demonstrate how these devices, worn in actual working conditions, can be integrated to provide reliable data, despite possible influences of electromagnetic noise in the measures.

Keywords: biomechanical overload | IMU | IoT | manufacturing | risk assessment | surface electromyography

Abstract: A critical point for manufacturing companies has always been the optimization of their production processes to increase the productivity and minimize the related costs, chasing an efficiency principle. Thanks to advent of Industry 4.0 (I4.0) era, some technologies, perceived as far away few years ago, now can be reached by everyone. The use of these technologies allows factories to acquire and evaluate their production data (and much more) and carry out complex analyses in short time making possible the improvement of the production processes. Aim of this paper is to propose a methodological framework in which, starting from an existing process, where workers and machines have already been assigned to each station of a production line, the use of Industrial Internet of Things (IIoT) devices, such as wearable ones, allows to carry out analyses of the performance parameters of the production lines by means of an event-based simulation. In this way it is possible to evaluate if improvements are possible by re-balancing or re-scheduling the line. A case study, regarding a manual task of a real manufacturing production line, is presented to demonstrate the applicability and the effectiveness of the described framework.

Keywords: Internet of Things | Line balancing | Methodological framework | Wearable devices

Abstract: Light activated composites are the most popular choice in the field of dental restoration. They generally show internal stress even after a prolonged time period. The knowledge of mechanical properties and residual stress should provide interesting information on the clinical performance of such materials. Accordingly, in the current research experimental analyses were carried out to assess the effect of the curing process on the properties of one of the most commonly employed light activated dental composites (Gradia Direct—GC Corporation, Japan). At 10 min, 1 h and 24 h after light curing, the bending modulus (4.7–6.2 GPa) as well as the punching performance (peak load of 12.1–17.5 N) were evaluated for the micro-hybrid composite. Scanning electron microscopy also allowed to analyze the fracture surface. Residual stresses ranging from 0.67 ± 0.15 MPa to 1.12 ± 0.17 MPa were measured by means of the thin-ring-slitting approach reported in the literature, according to measurement time and cutting time.

Keywords: CAD/CAM system | Dental materials | Mechanical and morphological properties | Residual stress

Abstract: Meeting the demands of Industry 4.0 and Digital Manufacturing requires a transformative framework for achieving crucial manufacturing goals such as zero-defect production or right-first-time development. In essence, this necessitates the development of self-sustainable manufacturing systems which can simultaneously adapt to high product variety and system responsiveness; and remain resilient by rapidly recovering from faulty stages at the minimum cost. A Closed-Loop In-Process (CLIP) quality control framework is envisaged with the aim to correct and prevent the occurrence of quality defects, by fusing sensing techniques, data analytics and predictive engineering simulations. Although the development and integration of distributed sensors and big data management solutions, the flawless introduction of CLIP solutions is hindered specifically with respect to acquiring and providing in-process data streams at the required level of: (1) veracity (trustworthiness of the data); (2) variety (types of data generated in-process); (3) volume (amount of data generated in-process); and, (4) velocity (speed at which new data is generated in-process) as dictated by rapid introduction and evolution of coupled system requirements. This paper illustrates the concept of the CLIP methodology in the context of assembly systems and highlights the need for a holistic approach for data gathering, monitoring and in-process control. The methodology hinges on the concept of “Multi-Wave Light Technology” and envisages the potential use of light-based technology, thereby providing an unprecedented opportunity to enable in-process control with multiple and competing requirements. The proposed research methodology is presented and validated using the development of new joining process for battery busbar assembly for electric vehicles with remote laser welding.

Keywords: Battery busbar assembly | Closed-loop in-process quality control | Multi-level requirements | Multi-wave light technology | Remote laser welding

Abstract: The current research was focused on a further insight into the mechanical properties of 3D parts printed with virgin and recycled polylactic acid (PLA). A first set of specimens was printed with virgin PLA lament and mechanically tested. Such specimens were then ground up and re-extruded into filament using a homemade extruder. The re-extruded filament was employed to manufacture a new set of specimens which were also analysed. Three recycling processes were performed to assess the effect on the mechanical properties. The obtained results suggested that 3D printing with recycled PLA may be a viable option.

Keywords: Additive Manufacturing | Mechanical properties | Recycled polymers

Abstract: The purpose of this paper is to assess the main effects on the geometric errors in terms of flatness, circularity and cylindricity based on the size of the printed benchmarks and according to the position of the working plane of the 3D printer. Three benchmark models of different sizes, with a parallelepiped and cylinder shape placed in five different positions on the working plane are considered. The sizes of models are chosen from the Renard series R40. Benchmark models are fabricated in ABS (Acrylonitrile Butadiene Styrene) using RepRap Prusa i3 3D printer. A sample of five parts for each geometric category, as defined from the R40 geometric series of numbers, is printed close to each corner of the plate, and in the plate center position. Absolute Digimatic Height Gauge 0–450 mm with an accuracy of ± 0.03 mm by Mitutoyo is used to perform all measurements: flatness on box faces, and circularity/cylindricity on cylinders. Results show that the best performances, in terms of form accuracy, are reached in the upper-left printable area while they decrease with the sample size. Being quality a critical factor for a successful industrial application of the AM processes, the results discussed in this paper can provide the AM community with additional scientific data useful to understand how to improve the quality of parts which may be obtained through new generations of 3D printer.

Keywords: Additive manufacturing | Fused deposition modelling | GD&T | Geometric errors

Abstract: The paper deals with the problem of tolerance specification and, in particular, proposes a graph-based method and a preliminary software tool: (i) to accomplish the tolerance specification for a mechanical assembly; (ii) to verify the consistency of the specification and, (iii) to allow the tracing of relationships among parts and features of the assembly. The method adopts Minimum Reference Geometric Elements (MRGE), directed graphs (di-graphs) and a set of dedicated algorithms to tackle the problems of consistency that occur during an interactive tolerance specification activity. Finally, an application illustrates the proposed method and its actual implementation.

Keywords: Datum | GD&T | graph theory | MRGE | tolerance specification

Abstract: In the field of movement disorders, each disabled person is different for both motor performance for functional requirements and expectations. This paper describes the development of a personalized device for a student with spastic quadriplegia at Federico II. This device is an Alternative Augmentative Communication system and it consists of hardware and software, which have been adapted to the individual characteristics of the student. According to participatory design and using the task analysis, we proceed to the hardware prototyping and to the software interface improving. An approach based on Analytic Hierarchy Process and Multiple-Criteria Decision Analysis is used. Tests under laboratory conditions are performed for evaluating the usability index of the device. Considering the data analysis, some critical issues are identified. The knowledge acquired in the case study is a point of strength of the proposed paper because it can be re-used for other persons with severe motor disabilities to improve their inclusion, integration and participation and to carry out tasks in different areas of application with minimum stress and maximum efficiency and effectiveness.

Keywords: Alternative augmentative communication | Participatory design | Spastic quadriplegia | Usability assessment

Abstract: In this chapter, authors provide a description of boundary element method (BEM) applications in biomechanics, with a focus on advantages and limitations of BEM versus other numerical methods such as finite element method, finite difference method, and meshless methods. In addition to a general overview, the chapter focus on how the BEM approach can be advantageous in those biomechanical problems involving fracture mechanics and contact modeling. To this aim, its preprocessing flexibility to tackle sharp geometric changes and complex remeshing is highlighted. The comparison among BEM and other numerical approaches proceeds through the evaluation of inherent accuracy, preprocessing and postprocessing efforts, and run times. Bio-CAD models with complex shapes are usually created from medical images acquisition, computer tomography or magnetic resonance scan, with different modeling techniques, which result in different accuracy and usability of the generated tessellated or surface computer-aided design (CAD) geometry. Special attention must be drawn to the mathematical reconstruction of bio-CAD model to facilitate the meshing process in the BEM environment and reduce the geometrical imperfections generated during the CAD to computer-aided engineering translation phase. BEM is best suited to reproduce accurately high surface stress gradients that are generally a modeling issue (e.g., in bone-implant contact simulations). Working with 3D models, the mesh refinement in the neighboring areas where high stress gradients are expected is much facilitated when using BEM, also because it is possible to use discontinuous elements and circumvent the constraint of a continuous mesh. BEM approach is certainly more accurate for linear analysis but, on the other hand, less versatile in some areas like those of highly nonlinear material behavior. A short description of some case studies showing the described advantages of BEM approach is reported.

Keywords: Bio-CAD | Biomechanics | Boundary element method | Dual boundary element method | Fracture

Abstract: Design team belonging to powertrain divisions can speed up the process of managing information, within gearbox design activities, by adopting digital pattern tools. These tools, belonging to a knowledge-based engineering (KBE) system, can assist engineers in re-using company knowledge in order to improve time-consuming tasks as retrieval and selection of previous architectures and to modify and virtually test a new gearbox design. A critical point in the development of a KBE system is the usability of user’s interface to demonstrate effective reduction of development time and satisfaction in its use. In this paper, the authors face the problem of usability improvement of the graphical user interface (GUI) of the tool belonging to the KBE system and previously proposed. An approach based on analytic hierarchy process and multiple-criteria decision analysis is used. A participatory test is performed for evaluating the usability index of the GUI. Taking into account the data analysis, some changes are carried out and a new GUI release is validated through new experimentations.

Keywords: Gearbox design | Graphical user interface | Participatory design | Usability assessment

Abstract: The purpose of this paper is to assess the main effects on the geometric errors in terms of flatness, circularity and cylindricity based on the size of the printed benchmarks and according to the position of the working plane of the 3D printer. Three benchmark models of different sizes, with a parallelepiped and cylinder shape placed in five different positions on the working plane are considered. The sizes of models are chosen from the Renard series R40. Benchmark models are fabricated in ABS (Acrylonitrile Butadiene Styrene) using Zortrax M200 3D printer. A sample of five parts for each geometric category, as defined from the R40 geometric series of numbers, is printed close to each corner of the plate, and in the plate center position. Absolute Digimatic Height Gauge 0-450mm with an accuracy of ±0.03mm by Mitutoyo is used to perform all measurements: flatness on box faces, and circularity/cylindricity on cylinders. Results show that the best performances, in terms of form accuracy, are reached in the area center printable while they decrease with the sample size. Being quality a critical factor for a successful industrial application of the AM processes, the results discussed in this paper can provide the AM community with additional scientific data useful to understand how to improve the quality of parts which may be obtained through new generations of 3D printer.

Keywords: Additive manufacturing | Fused deposition modelling | Geometric errors

Abstract: Modern engineering systems are getting complex and integrate multi-physical objects. The Model-Based System Engineering (MBSE) seems to be the best way to manage complex system design and the Systems Modeling Language (SysML) may be considered one of the computer languages to perform the designing of a complex system. MBSE also seems to be a valid solution to integrate tolerance specification into design process. In particular, in the present work SysML is used to create a set of libraries containing simple and complex volumes, primary datum and tolerance zones, according to ASME Y14.5M and ISO 1101 standards. The generation of these libraries is based on the Technologically and Topologically Related Surfaces (TTRS) model and uses the set of thirteen positioning constraints able to represent every condition between assembly features. The paper summarizes the characteristics of the created SysML objects, able to represent Datum, Datum Reference Frame (DRF) and tolerance zones. In particular, the Datum included in ASME Y14.5-M are modelled. Then, all the tolerance zones included in both standards are modelled. Finally, a three-step procedure is summarized to preliminary illustrate the way of use the developed set of SysML objects.

Keywords: Assembly tolerance specification | Model-based Systems Engineering | SysML | TTRS model

Abstract: 3D inspection process is getting more and more interest for manufacturing industries as it helps to carefully check the expected quality of the released products. Much more attention is oriented to optical devices able to quickly capture the whole shape of the product providing many useful information on the process variability and the deliverability of the key characteristics linked to the quality of the product/process. Although the optical control of 3D scanners is mature enough, many factors may influence the quality of the scanned data. These factors may be strictly related to internal elements to the acquisition device, such as scanner resolution and accuracy, and external to it, such as proper selection of scanning parameters, ambient lighting and characteristics of the object surface being scanned (e.g. surface colour, glossiness, roughness, shape), as well as the sensor-to-surface relative position. For the 3D laser-based scanners, the most common on the market, it would be of great industrial interest to study some scanning factors mainly affecting the quality of the 3D surface acquisitions and provide users with guidelines in order to correctly set them so to increase the massive usage of these systems in the product inspection activities. In this context, by using a commercial triangulation 3D laser scanner, the effects of some scanning factors that may affect the measurement process were analysed in the present paper. Working on a sheet metal test part, more complex than the ones commonly used in laboratory and documented in the literature, the scanner-to-object relative orientation and the ambient lighting, as well as an internal scanner parameter, were tested. Through a Design of Experiments (DoE) approach, and setting root mean square error (RMSE) as response function, the outcomes of the tests mainly pointed out that the scanner-to-object relative orientation as well as its position within the field of view of the measurement device are the key factors mostly influencing the accuracy of the measurement process.

Keywords: 3D inspection process | 3D laser scanner | Design of Experiments | Surface acquisition

Abstract: This paper introduces the novel concept of fixture capability measure to determine fixture layout for the best assembly process yield by optimizing position of locators and reference clamps to compensate stochastic product variations and part deformation. This allows reducing the risk of product failures caused by product and process variation. The method is based on three main steps: (i) physics-based modelling of parts and fixtures, (ii) stochastic polynomial chaos expansion to calculate fixture capability, and (iii) fixture capability optimisation using surrogate modelling. The methodology is demonstrated and validated using the results of an aerospace wing sub-assembly joined by riveting technique.

Keywords: Fixture Capability | Fixture Layout Optimisation | Polynomial Chaos | Surrogate Model

Abstract: The paper deals with the relationship between geometrical or topological entities of complex systems and the physics in which the systems are involved. In particular, the paper deepens the integration of thermal physics with geometrical constraints. Therefore, the results of the work could be used within the development of a 3D-multiphysical sketcher viz., a tool for the preliminary design of complex systems, characterized by the presence of one or more overlapping physics. Firstly, the model of Topologically & Technologically Related Surfaces (TTRS) is used and related Minimal Reference Geometrical Elements (MRGEs) and constraint conditions are implemented by means of Modelica language. Then, the implementation of new objects for MRGEs and constraint conditions are applied to a mechanical assembly. Finally, the integration of TTRS model within thermal physics is applied to the case of the layout designing for electronic boards.

Keywords: Modelica language | Multiphysics | preliminary design | TTRS

Abstract: Remote Laser Welding (RLW) is a joining technique more recent than the most known and widely adopted (mainly in the automotive field) resistance spot welding technique (RSW). While RLW offers much more benefits than RSW (higherprocess speed, less number of operating robots, decreased factory floor footprint, reduced overall process costs), it also adds issues related to process planning and quality control of welded joints. The European Commission, under the ICT-Factories of the Future programme of FP7, funded a project, starting from January 2012 and just ended on June 2015, titled "RLW Navigator - Remote Laser Welding System Navigator for Eco Resilient Automotive Factories" which aims at developing an innovative Process Navigator for planning, integrating, testing and validating applications on the use of RLW in the automotive assembly addressing today's critical needs for frequently changing operating conditions and product-mix provisions. The project results are a set of toolboxes able to offer very useful tools to plan and control the RLW joining process. The key word that mainly describes the provided ICT-based solutions is Optimisation: from the optimisation of the working cell, by analysing several layout configurations, to the optimisation of robot path and weld sequencing for assigned product and process constraints; from the fixture optimisation (involving the best clamp configuration) starting from real/non-ideal shape parts, to the optimisation of process laser parameters to guarantee higher welded join quality. The applicability of these software tools goes beyond the automotive field and this makes the provided solutions much more interesting for the industry.

Abstract: In the present work the structural behaviour of a mandible with a dental implant, considering a unilateral occlusion, is numerically analysed by means of the Finite Element Method (FEM) and the Boundary Element Method (BEM). The mandible, whose CAD model was obtained by computer tomography scans, is considered as completely edentulous and only modelled in the zone surrounding the implant. The material behaviour of bone is assumed as isotropic linear elastic or, alternatively, as orthotropic linear elastic. With reference to the degree of osteo-integration between the implant and the mandibular bone, a partial osteo-integration is considered; consequently a nonlinear contact analysis is performed, with allowance for friction at the interface between implant and bone. A model of a commercial dental implant is digitised by means of optical 3D scanning process and fully reconstructed in all its geometrical features. Special attention is drawn to the mathematical reconstruction of the CAD model in order to facilitate the meshing process in the BEM environment and reduce the geometrical imperfections generated during the CAD to CAE translation process. The results of FEM and BEM analyses in terms of stress distribution on the mandible are compared in order to benchmark the two methodologies against accuracy and pre-processing efforts.

Keywords: BE modelling | Dental implant | FE modelling | Non-linear contact analysis

Abstract: One of most demanding tasks in the manufacturing field is controlling the variability of parts as it may affect strongly the deliverability of key characteristics defined at the final (product) assembly level. Current CAT systems offer a good solution to the tolerance analysis/synthesis task, but to handle flexible objects with shape errors more effort is needed to include methods able to capture the elastic behaviour of parts that adds more variability on the final assembly. Usually, sheet metal assemblies require dedicated fixtures and clamps layout to control the gap between parts in the specific location where a join must be placed. Due to the variability of parts the position of clamps can also be varied. The paper describes a FEM-based method able take into account part flexibility and shape error to parametrically analyse sheet metal assemblies by acting on some key parameters to look for the optimal clamp layout that guarantee the gap between parts to be under control after joining parts together. This method offers, with respect to commercial solutions, the ability to model fixtures, clamps and different joint types with no matter on the node positions of the mesh. Locations of such elements are based on the shape functions defined at element (shell) mesh level and modelled as local constraints. So the user can generate a mesh without a previous knowledge of the exact positions of clamps, for example. This allows to conduit a parametric analysis without remeshing the surfaces and with no need to physically model the clamps. An aeronautic case study is described with a four-part assembly riveted on a quite complex fixture by using several clamps.

Keywords: Clamp layout optimisation | Compliant assemblies | Free shape variability | Sheet metal parts | Shell.

Abstract: The present paper proposes a novel general approach to automatically calculate the variational parameters for planar or cylindrical features for a given set of tolerance specifications, according to ANSI or ISO Standards. Variational parameters correspond to those directions along/around which variation, in terms of small translation and rotation, may propagate for a given feature with tolerance specifications. A graph representation of these tolerance specifications is adopted and it is used along with screw theory and Davies's laws to automatically calculate the variational parameters, and then the net variational space of each toleranced feature, by capturing nominal geometries directly from a CAD environment (SolidWorks). From screw theory, twist matrices, able to capture the motion properties of any kinematic joint in mechanical assemblies, are here adopted at part level and collected for every feature-to-datum relationship. Davies's laws are then recalled to put those matrices together to calculate the variational parameters. In this way, both single-datum and multi-datum tolerance specifications can be handled. The proposed approach for the automatic calculation of variational parameters could be successfully implemented in a more general expert system for designing mechanical assemblies where an added-value interaction could allow user to detect relationships between geometric features. In this way, the leading of activities aimed to tolerance analysis could be accomplished both during the preliminary design stages and throughout the manufacturing and reviewing sessions. © 2012 Springer-Verlag France.

Keywords: CAD automation | Graph representation | Mechanical networks | Screw theory | Tolerance analysis | Variational parameters

Abstract: Objectives: Aim of the research is to compare the orthodontic appliances fabricated by using rapid prototyping (RP) systems, in particular 3D printers, with those manufactured by using computer numerical control (CNC) milling machines. 3D printing is today a well-accepted technology to fabricate orthodontic aligners by using the thermoforming process, instead the potential of CNC systems in dentistry have not yet been sufficiently explored. Materials and methods: One patient, with mal-positioned maxillary central and lateral incisors, was initially selected. In the computer aided virtual planning was defined that, for the treatment, the patient needed to wear a series of 7 removable orthodontic appliances (ROA) over a duration of 21 weeks, with one appliance for every 3 weeks. A non-contact reverse engineering (RE) structured-light 3D scanner was used to create the 3D STL model of the impression of the patient's mouth. Numerical FEM simulations were performed varying the position of applied forces (discrete and continuous forces) on the same model, simulating, in this way, 3 models with slice thickness of 0.2 mm, 0.1 mm (RP staircase effect) and without slicing (ideal case). To define the areas of application of forces, two configuration "i" and "i-1" of the treatment were overlapped. 6 patients to which for three steps (3rd, 4th and 5th step) were made to wear aligners fabricated starting from physical models by 3D printing (3DP-ROA) and afterwards, for the next steps (6th, 7th and 8th step), aligners fabricated starting from physical models by CNC milling machine (CNC-ROA), were selected. Results: For the 6 patients wearing the CNC-ROA, it was observed a best fitting of the aligner to the teeth and a more rapid teeth movement than the 3DP-ROA (2 weeks compared to 3 weeks for every appliance). FEM simulations showed a more uniform stress distribution for CNC-ROA than 3DP-ROA. Conclusions: In this research, 6 different case studies and CAD-FEM simulations showed that, to fabricate an efficient clear and removable orthodontic aligner, it is necessary to consider a compromise of several factors. A lower staircase effect (lower layer thickness) and a higher physical prototype accuracy allow a better control of tooth movement. © 2012 Academy of Dental Materials.

Keywords: 3D printers | CNC milling machine | FEM analysis | Modeling and simulation | Non-contact reverse engineering systems | Orthodontic appliances

Abstract: In the variational modeling of assemblies it is important to define the location of a part both in absolute terms and with respect to the position/orientation of other assembled parts. The present paper proposes a programming optimization approach to solve this problem. The algorithm, by using the heuristic Nelder-Mead technique - combined with a penalty function - simulates and solves sequential assembly strategies to find the optimal geometric configuration of a rigid part with variational features satisfying all the assembly constraints in the given sequence. The algorithm best aligns mating features avoiding, at the same time, feature-to-feature interferences, and automatically calculating the amount of movement the part being assembled must obey to satisfy assembly constraints, at that state of the assembly process. Thus, different assembly sequences can be simulated also including variational features. © 2013 The Authors.

Keywords: Assembly simulation | Constrained optimization | Rigid assemblies | Sequential constraint solver | Tolerance analysis

Abstract: In automotive and aeronautic fields, controlling the final shape of flexible assemblies (with sheet metal parts) is a key issue. Even assuming as known the shape errors in single manufactured parts, the assembly process can cause wide variability due to their flexibility and to the choice of fixtures and clamps as well as to the fastening technique adopted. Here it is strategic to analyse different assembly configurations at the beginning of the design phase and chose the one that assures less variability on the key characteristics to be achieved. This paper presents a FEM-based computer tool able to statistically analyse variations occurring in assembly processes of flexible parts. After assigning fixtures, clamping points, fastening joints and assembly sequence, the tool quickly outputs the statistical variability of the key characteristics. It is so possible to span a variety of design solutions predicting failures and controlling final variations. A case study will show how it works. Copyright © 2013 Inderscience Enterprises Ltd.

Keywords: Computer aided tolerancing | Finite element analysis | Fixture configurations | Flexible assembly

Abstract: It was reported that next to style, comfort is the second key aspect in purchasing footwear. One of the most important components of footwear is the shoe sole, whose design is based on many factors such as foot shape/size, perceived comfort and materials. The present paper focuses on the parametric analysis of a shoe sole to improve the perceived comfort. The sensitivity of geometric and material design factors on comfort degree was investigated by combining real experimental tests and CAD-FEM simulations. The correlation between perceived comfort and physical responses, such as plantar pressures, was estimated by conducting real tests. Four different conditions were analyzed: subjects wearing three commercially available shoes and in a barefoot condition. For each condition, subjects expressed their perceived comfort score. By adopting plantar sensors, the plantar pressures were also monitored. Once given such a correlation, a parametric FEM model of the footwear was developed. In order to better simulate contact at the plantar surface, a detailed FEM model of the foot was also generated from CT scan images. Lastly, a fractional factorial design array was applied to study the sensitivity of different sets of design factors on comfort degree. The findings of this research showed that the sole thickness and its material highly influence perceived comfort. In particular, softer materials and thicker soles contribute to increasing the degree of comfort. © 2012 IPEM.

Keywords: CAD-FEM modeling | Comfort assessment | Fractional factorial design | Numerical-physical correlation | Pressure map | Shoe sole

Abstract: Variation analysis of assemblies is a strategic task in many industrial applications. Parts manufactured through plastic deformation processes exhibit appreciable shape deviations from the nominal geometry due mainly to spring-back phenomena. When these parts are assembled, initial shape deviations at part level highly influence the final assembly shape. This work focuses on the modeling and simulation of shape errors in order to perform variation analysis of compliant assemblies. The aim is to simulate variational shape of parts according to a small number of control points chosen on the part geometry through a morphing mesh procedure. These points are typically related to measurement or inspection points of manufactured parts. From the mesh model of parts, mesh nodes are moved by applying the morphing procedure. In particular, in order to assure control points belong to the "perturbed" shape, a linear-constrained approach is adopted. The so-morphed parts are used to accomplish the variational assembly analysis following the classical place, clamp, fasten, and release cycle. In order to achieve statistical results, Monte Carlo simulation is performed: a set of control points driving the perturbed parts is generated at each iteration; these parts are then assembled and results are stored. Numerical results are compared with ones coming from commercial software that uses a linear approach based on the sensitivity matrix.

Keywords: Geometric covariance | Monte Carlo FEA | Morphing mesh | Shape errors | Variational assemblies

Abstract: In this paper, a general methodology to do tolerance analysis of rigid assemblies is proposed. Firstly, tolerance specification sets, according to GD&T or ISO specifications, are translated into variational features by using 4∈×∈4 homogenous transformation matrices. In particular, planar and cylindrical features are considered. Then, once all variational features are modeled, assembly constraints among parts are introduced. To solve assembly constraints, an assembly transformation matrix is evaluated. By using point, line, and plane entities and their combinations, kinematic joints are modeled. A numerical procedure is proposed to solve fully and over-constrained assemblies. The best-fit alignment among variational mating features is performed by using optimization algorithms. The proposed method for tolerance analysis of rigid part assemblies allows to simulate different assembly sequences. Finally, in order to show the effectiveness of the proposed methodology, three case studies are described and analyzed. © 2009 Springer-Verlag London Limited.

Keywords: Assembly constraints | Assembly simulation | Feature modeling | GD&T/ISO specifications | Tolerance analysis | Variational features

Abstract: The need for a designer to have a tool able to do motion and constraint analysis, to check for the under-constrained and/or over-constrained status of an assembly, is strategic in a design contest where several changes are made during the design process by using CAD. Traditional kinematic tools provide little information on over-constraints at 3D level. Screw theory has been already used in mechanical assemblies, in a top-down design, to do motion and constraint analysis. This theory is here used to analyze mechanical assemblies in the contest of a feature-based CAD system. The structure of the CAD assembly is captured and described as assembly graph, similar to Datum Flow Chain, through which the motion or constraint status of any part (in terms of twist and wrench matrices), can be obtained. The underlying algorithm is based on the Kirchoffs rules successfully applied by Davies to mechanisms. How to automatically create the assembly graph, detect the useful loops and then write the loop kinematic equations is described. Three case studies are presented related to CAD assemblies of mechanisms built up in SolidWorks® CAD system by Dassault Systèmes from which assembly constraints have been acquired. Copyright © 2010 by ASME.

Abstract: The paper represents the contribution to the PUODARSI (Product User-Oriented Development based on Augmented Reality and Interactive Simulation) research project in the development of a design environment which integrates modeling tools and CAE simulation capabilities. Typically, aerodynamic and mechanical performances of the object shape are in contrast with the stylistic requirements. Integrated tools and numerical simulations are then needed to support designers during the conceptualization of a new shape or when re-designing a product. This work combines Reverse Engineering methodologies and CAE tools to easily analyze the interaction between the aerodynamic behavior and the stress-strain state, due to viscous and pressure loads, of a physical object. A friendly interactive tool, based on MatLAB® and linked to Comsol Multiphysics®, was developed to drive user during the simulation and the visualization of results. © Springer-Verlag 2009.

Keywords: CAE | Design review | Meshing control | Reverse engineering

Abstract: A new method for tolerance/variation analysis of multi-station assemblies of compliant parts is presented. Based mainly on the 'unit displacement' and 'sensitivity matrix' method, it allows for the use of statistical variations in key points to predict the final shape variation of multi-station assemblies. 'Linear contacts' between parts are included to avoid part-to-part intersections. The evaluation of what happens at the end of the assembly process enables users to analyse different assembly configurations in the early design phase. Implemented in the Matlab environment, it requires two linear FEA runs for each assembly station. Two case studies are presented and discussed. Copyright © 2008 Inderscience Enterprises Ltd.

Keywords: Compliant parts/assemblies | Contact modelling | FEA | Finite element analysis | Linear static analysis | Multi-station assemblies | Statistical variations | Tolerance analysis

Abstract: In the paper the design process, from the idea to the manufacturing aspects, with all the technical and technological problems, to develop a new competitive hard antitheft is described. The integrated use of the CAD/CAE and RP techniques made possible to analyse three different solutions in a very short time. The new model has completely designed, developed and patented (patent n. NA2005A000037) at the University of Naples and Cassino, Italy. It has weight and size very limited and some important features such as easiness to handle, high strength and high versatility; all this makes it an exclusive product of its type. The final product, made in AISI 1040 steel, is going to be manufactured and distributed in Europe by BULLOCK® in 2006.

Keywords: Antitheft | CAD | CAE | Lock system | Patent | PhD Researcher | RP Massimo Martorelli

Abstract: This article presents the use of stereolithography in oral implantology. Stereolithography is a new technology that can produce physical models by selectively solidifying an ultraviolet-sensitive liquid resin using a laser beam, reproducing the true maxillary and mandibular anatomic dimensions. With these models, it is possible to fabricate surgical guides that can place the implants in vivo in the same places and same directions as those in the planned computer simulation. A 70-year-old woman, in good health, with severe mandibular bone atrophy was rehabilitated with an overdenture supported by 2 Branemark implants. Two different surgical planning methods were considered: 1) the construction of a surgical guide evaluating clinical aspects, and 2) the surgical guide produced by stereolithographic study. The accuracy of surgical planning can reduce the problems related to bone density and dimensions. Furthermore, the stereolithographic study assured the clinicians of a superior location of fixtures in bone. Surgical planning based on stereolithographic technique is a safe procedure and has many advantages. This technologic advance has biologic and therapeutic benefits because it simplifies anatomic surgical management for improved implant placement. Copyright © 2004 by Lippincott Williams & Wilkins.

Keywords: Anatomic models | Jaw atrophy | Rapid prototyping | Surgical planning

Abstract: In the mechanical transmission field, shaft-hub couplings with polygonal profiles play an interesting role because of their characteristics of self-alignment, lack of projecting elements (responsible for high stress concentration) and constructive compactness. Other characteristics, like transmission of static/oscillating torque load, even with small overall dimensions, and easy hub interchangeability, make such couplings competitive with the traditional ones based on keys and splined shafts. This work concerns a study on steel made polygonal couplings, with trochoidal three-lobe profile, and is aimed to highlight the contact stress and strain state of shaft-hub interface, with reference to particular profile geometric parameters. From Mechnik's and Kollmann's works, in which the analysis was performed by the Finite Element Method, this work develops a CAD/CAE methodology for coupling design, oriented to an efficient integration between CAD systems and BEM solvers. The stress analysis is carried out with a Boundary Element code (BEASY) well suited for this kind of contact problems while coupling geometric model is made by Pro/Engineer, a solid parametric modeller.

Abstract: Screw Theory is well known to do kinematic computations. Recently it has been used to create kinematic models of assembly features so allowing to do assembly analysis. Motion Limit Analysis uses the mathematics of screw theory to model the ability of mechanical assembly features to allow or constrain rigid body motions in six degrees of freedom. A user of this theory is able to determine the directions and quantitative amounts of possible finite rigid body motions of a part that is being added to an assembly via calculation applied to a defined set of assembly features. The ability to calculate rigid body motions of a part is important for enabling in-process adjustment during assembly to precisely establish key assembly dimensions. MLA software is a part of a suite of software programs used to do assembly analysis.