3D scanning

In this article, our aim is to underscore the importance of verifying that components produced through material extrusion additive manufacturing exhibit geometric and dimensional conformity with the STL (Standard Tessellation Language) model. Currently, the business world is heavily investing in additive technologies, but it is crucial to obtain feedback on the accuracy of the printed component without excessive economic expenditure. For this reason, we have opted to utilize a mid-range 3D scanner (Revopoint Mini with an accuracy of 0.02 mm) to investigate any disparities in print results using PLA material. Each model has been scanned and compared with the initial mesh to qualitatively and quantitatively assess the present errors. The analysis has revealed that the majority of features can be effectively controlled, while the remaining ones either fall within the tool's precision or necessitate a higher-quality scan. Particularly in the analysed case, flat surfaces, profiles of complex geometries, and holes have demonstrated dimensional and geometric controllability. However, details of reduced dimensions or those difficult to reach by the scanner do not allow for adequate comparison due to excessive standard deviation in the error. The analysed layer heights do not exhibit a significant impact on component accuracy.

Keywords: 3D scanning , Cost-effective , Dimensional accuracy , Material extrusion , Quality control

In recent years, additive manufacturing has been expanding rapidly in several sectors, including marine, aerospace and civil, offering broad design freedom and environmental/ecological advantages for the production of fully functional products. Particularly in the biomedical area, interesting manufacturing methods have recently been developed for the customisation of orthotic devices by automating the acquisition process and 3D printing. Today, in the development of complex geometries, it is necessary to meet certain design specifications, such as mechanical strength, surface finish, light weight, breathability and aesthetic appearance, which can potentially be met by manufacturing with 3D printers. This research deals with the development and implementation of organic bioplastic compounds based on polylactic acid (PLA) and organic by-products for additive manufacturing applications of customised orthotic parts. PLA, filled with reinforcements and additives, can be used to produce durable and functional parts for improved structural performance. By studying specific orthotic cases with CAD-CAE techniques, its potential mechanical properties will be evaluated and compared to highlight its performance comparable or even superior to that of classical PLA. The proposed methodology reduces production costs and environmental impact. Thanks to the presence of reinforcements and additives, the new organic bioplastic compounds are more biodegradable, while improving some of the functionality and comfort requirements of customised orthoses.

Keywords: biodegradability , biomedical orthosis devices , mechanical properties characterization , Organic bio-composite filament , Reverse Engineering

Pectus Excavatum is the most common form of thoracic deformity, characterized by the depression of the anterior chest wall. The most widely used non-surgical treatment involves the daily application of the Vacuum Bell, an external medical device that uses negative pressure to lift the sternum outwards. Nevertheless, the Vacuum Bell is only available in four sizes, making it difficult to apply to all possible cases of deformation. In addition, the variability of the surface to be treated and prolonged use can make the application uncomfortable, leading to decreased compliance and treatment discontinuation, thus compromising its effectiveness. In this context, the study was conducted with the aim of producing customized Vacuum Bell models. Starting with the 3D scanner acquisition of the patient, it was possible to reconstruct the three-dimensional model of the chest. Therefore, a specifically implemented MATLAB script enabled the identification of the surface to be treated and the semi-automatically drawing of the 3D curve outlying the deformation. Using this curve, via CAD software, it was then possible to proceed with the modelling of customized Vacuum Bells, whose profile adapts to the specific conformation of the patient's chest. Finally, a Vacuum Bell prototype was realized using additive manufacturing techniques.

Keywords: Additive manufacturing , Customized devices , Pectus Excavatum , Vacuum Bell

Retrievals of small and medium scale are one of the fundamental and most numerous parts of the entire museal heritage set. Their exposition represents an issue, looking for supporting structures that could be non-invasive, aesthetically pleasant, customized, and, last but not least, safe and stiff enough to avoid any damage to the artifacts. Through the usage of several engineering methods, starting from the retrieval and the exhibition requirements, optimized supporting structure can be developed. The procedure here reported and applied starts from the Reverse Engineering acquisition in order to obtain the 3D model of each retrieval, also comprehending color and texture information. After that, exhibition and preservation requirements, given by heritage experts, are translated into engineering requirements, with the usage of an immersive Virtual Reality environment. With these inputs, the developed Generative Design Method (GDM), using CAD, CAE and optimization tools synergically, can optimize the configuration of supporting interfaces with the artifact and then can generate a lightweight conceptual design through a generative design process. In this way, we can take into account all the given requirements, obtaining a lightweight support, topologically optimized, highly customized, non-invasive, possibly pleasant, able to resist in safety, and additively manufacturable. In this paper, the procedure is applied on different retrievals from Museo Civico dell'Agrocimino of Soriano nel Cimino, Italy, with different scales and materials, proving the robustness of the method.

Keywords: Cultural Heritage , Generative Design , Parametric Optimisation , Reverse Engineering , Virtual Reality

4D textiles are a specific class of 4D printed materials obtained by printing flat patterns on elastically pre-tensioned textiles and being able to switch from planar systems to complex 3D objects after the textile pre-stretch is released. The mechanical balance between textile recovering strain and printed structure stiffness determines the final shape. This study is carried out by coupling pre-stretched Lycra to PLA and explores ways to control 4D textile shape transformations by varying pre-stretch (10% ÷ 60%), printed structure geometry (bar-shaped and star-shaped elements; star-shaped patterns), printed element thickness (0.3 ÷ 3 mm) and mutual distance (2 ÷ 15 mm). By adjusting these parameters, a wide set of out-of-plane curvatures are obtained, ranging from flat, to dome-like and highly curved, wrapped or coiled shapes. Digital optical methods, including digital image analysis, 3D scanning, and digital image correlation, are used to evaluate the complexity of the final shape and strain state evolution during shape transformation. The geometry variation is measured in terms of height increase (maximum 45 mm for a star-shaped system, 30 mm for a multiple star pattern) and of area decrease (maximum 80% for a star-shaped system, 60% for a multiple star pattern). While most shape transformations occur immediately after printing (‘direct 4D printing'), further shape evolutions may be triggered by heating above the PLA glass transition, allowing for the creation of dynamic structures whose shape changes upon external stimuli. The adhesion between the 3D printed element and the stretched textile is also examined, with a focus on determining the role of interfacial strength and the conditions that could enhance it. This study provides an overview of the primary design variables and valuable maps of their impacts on shape transformations in this broad scenario of influencing parameters.

Keywords: 4D printing , 4D textiles , adhesion , self-assembly , thermally activated transformation

In the realm of cardiac health research, accurate fluid dynamics simulations are vital for comprehending the heart function and diagnosing conditions. Central to these simulations is the precision of ventricular wall meshes used to model heart geometry. However, segmenting the wetted surface, particularly in the right ventricle (RV) with its significantly thinner parietal thickness compared to the left ventricle, presents challenges. This study focuses on qualitatively evaluating an automated reconstruction model for the RV's outer wall using Radial Basis function (RBF) morphing. Two procedural criteria were compared, a random selection of control points and a curvature-based approach, which differ in terms of the identification of the control points of the RBF function. From these considerations, it emerges that a controlled use of the RBF function on the basis of the curvatures guarantees the greater controllability of the shape evolutions of the parietal structure of the RV, but it is more sensitive to any anomalies in the distribution of the vertices, as can be seen from the number of outliers, and its controllability is a function of the percentage of points chosen, exerting a greater impact on the required computational capacity. The definition of a strategic criterion for the selection of control points could represent a crucial aspect in the definition of an automatic reconstruction procedure of anatomical elements, which guarantees a morphological variability in line with the need to expand the pathological sample to be used for statistical formulations in the clinical field.

Keywords: morphing , radial basis functions , right ventricle

Three-dimensional acquisition and reproduction technologies are often exploited in cultural heritage field for a variety of applications such as conservation, restoration, and dissemination. Another valuable use of 3D data is to make exhibitions more accessible to visitors with impairments, allowing them to fully experience and enjoy the acquired objects. In this short paper, we explore the accessibility inherently provided by 3D representations of real-world objects, with a particular focus on the quality of the models and 3D printing, as well as the presentation aspects. To this end, we propose to apply a state-of-the-art saliency-driven process, generating a fixation map that identifies the object's salient areas that need to be reproduced with a higher definition during the 3D printing to improve the object accessibility. We present a case-study involving the full process of 3D scanning and printing the Coats of Arms in Palazzo Bo (Padova, Italy) to make them accessible to visitors with visual impairment. We employed different scanning techniques and applied the attention mechanism on acquired data to obtain the object salient areas and drive the printing process accordingly. Preliminary tests involving some participant feedback reveal that printing the objects with a variable detail level allows the visitors to have a better understanding of the object as a whole and to appreciate the relevant details.

Keywords: 3D printing , 3D reconstruction , Accessibility , Cultural heritage , Fixation prediction

RGB-D cameras have been widely used in various research fields and applications in recent years. With the growing availability of commercial products, choosing the most suitable sensor for a specific application has become more complex. The lack of tools to evaluate and compare the metrological performance of these sensors was addressed by the recent ISO 10360-13:2021 standard, which defines the standards for the metrological characterization of 3D optical coordinate measuring systems. This paper applies the ISO 10360-13 methodology to characterize and compare four RGB-D cameras: three Intel® RealSense™ (D415, D435i, D455) and one Microsoft® Azure Kinect DK. The procedures described in the standard were integrated with three tests: the analysis of systematic errors measured acquiring a planar surface at increasing distances; a test to analyze the resolution performances with a specifically devised artifact; the evaluation of 3D reconstruction performances on two objects with different geometric characteristics. The results highlighted the strengths and weaknesses of each device. The D415 showed better performance in reconstructions from close-range acquisitions. The Azure Kinect DK had the best results for systematic error and resolution. The D455 generally achieved the best performance in the standard tests, followed by the D435i.

Keywords: device characterization , Intel RealSense , ISO 10360-13:2021 standard , Microsoft Azure Kinect DK , performance evaluation

Autologous ear reconstruction is a surgical procedure aimed at total or partial reconstruction of the ear of patients with microtia, which is a malformation or absence of the anatomical element. This procedure involves harvesting cartilage material from the patient at the costal level, cut and sculpt the tissue to create the skeleton of the ear, which is then inserted into a subcutaneous pocket in the malformed region. The sculping procedure takes inspiration from the geometry of the patient's contralateral healthy ear and can be very complex given the particularity of the elements to be reconstructed. Taking advantage of Reverse Engineering and Additive Manufacturing technologies, the authors, in collaboration with hospital staff, proposed patient-specific three-dimensional cutting guides that can facilitate the surgeon in sculpting the ear structure. In this work, a fully automated procedure for creating the printable digital model of such guides is proposed: at first is performed the segmentation of ear elements, which represent the starting data for the automated CAD modelling of the surgical guides. The automatic CAD modelling procedure was tested and validated by medical personnel.

Keywords: CAD Modelling , Ear Reconstruction , Reverse Engineering , Surgical Guide

The growing attention of people to aesthetics has led to a greater demand for dental whitening treatments. Several solutions can be utilized to obtain the desired visual whiteness of teeth but, according to literature, at-home supervised treatments are the standard in dental bleaching. They require soft plastic trays to contain a whitening gel, with active chemical agents, and keep it in contact with the patient's teeth. The fitting, comfort, and tightness of trays play a fundamental role in the treatment. Any gel leakage can compromise the effectiveness of the treatment and damage soft tissues. Commonly, the trays are ready-made or based on physical dental impressions and manually modified by the dental technician. These procedures have low repeatability and do not always ensure high accuracy. This work presents an automatic digital algorithm to design customized whitening trays. Starting from a digital scan acquisition of the patient's dental arches, it generates the 3D models of the bespoke trays, in approximately two minutes per arch, ready to be produced by additive manufacturing and thermoforming technologies. The evaluation of the method involved 20 patients. The results emphasize that the custom trays were comfortable and ensured high levels of tightness and fitting.

Keywords: automatic product design , custom teeth trays , dental whitening , digital process

Purpose: Among thoracic malformations, pectus deformities have the highest incidence and can result in a wide range of severe and mild clinical manifestations. Recently, the treatment of pectus deformities is shifting from traditional approaches toward customized solutions. This occurs by leveraging innovative rapid prototyping tools that allow for the design and fabrication of patient-specific treatments and medical devices. This paper aims to provide a comprehensive view of the growing literature in this area to analyze the progress made in this direction. Design/methodology/approach: The search was performed on major search engines through keywords inherent to reverse engineering (RE) and additive manufacturing (AM) technologies applied to pectus deformities and related treatments, selecting 54 papers. These were analyzed according to the addressed pathology, the hardware and software tools used and/or implemented and their integration within the clinical pathway. Findings: First, the analysis led to analyze and divide the papers according to how RE and AM technologies are applied for surgical and non-surgical treatments, pathological assessment and preoperative simulation and planning. Second, all papers were considered within the typical rapid prototyping framework consisting of the three phases of three-dimensional (3D) scanning, 3D modelling and 3D printing. Originality/value: To the best of the authors' knowledge, to date, no survey has provided a comprehensive view of innovative and personalized treatment strategies for thoracic malformations; the present work fills this gap, allowing researchers in this field to have access to the most promising findings on the treatment and evaluation of pathology.

Keywords: 3D printing , Additive manufacturing , Pectus carinatum , Pectus excavatum , Reverse engineering

The huge possibilities generated by the introduction of rapid prototyping techniques in the medical field has paved the way for collaborations between physicians and engineers to produce personalized medical devices, tailored to the specific anatomy of the patient. Specifically, in the field of autologous auricular reconstruction, i.e. the reconstruction of the external ear using the patient's costal cartilage, the authors worked towards the development of new patient-specific intraoperative devices, to support the surgeon during the procedure. The surgical guide design was then supported by the development of automated techniques for their modelling. In this work, a new hybrid technique for the CAD modelling of surgical guides is proposed. The idea is not to totally eliminate the intervention of the physician in defining the shape of the surgical guides, but rather to simplify their interaction with design tools. The proposed method is based on the straightforward adaption of a two-dimensional template developed by evaluating various auricular biometric parameters to approximate ear structure. The template is coupled to a parametric automatic procedure that generates the surgical guides' CAD model. The template was created outside of commercial CAD modeling software packages to make the procedure more accessible, and it is managed using a well-designed graphical user interface. With specialized questionnaires to evaluate the surgeon's satisfaction, the interface was put to the test, and the results were positive.

Keywords: 3D Modelling , Autologous Ear Reconstruction , CAD , Microtia , Personalized Medicine , Reverse Engineering

Factory acceptance test is the inspection of equipment and components at the supplier's premises before delivery or final inspection. However, this control can represent a considerable cost for the customer, especially when the manufacturer's company is geographically far from the customer one and inspections must be frequent. In this paper, the authors present a framework to support the factory acceptance test based on augmented reality (AR) techniques and model-based definition aimed at dimensional checks that does not require the physical presence of the customer at the supplier's premises. The supplier must be previously equipped with an automatic measuring machine. Once the component under inspection is placed inside the machine, this reads the type and the position of the features to be measured along with the related specification limits directly from the annotated 3D model of the component. The results are automatically transmitted to the customer's site. Through a tablet, the supplier, guided by the customer, reads the results of the measures directly on the measured object through augmented or mixed reality techniques. Any out-of-specification dimension can be remeasured in real time with the customer's remote assistance using traditional measurement techniques. The proposed architecture, at an advanced stage of experimentation, is discussed with reference to an industrial case study proposed and using an entry level commercial 3D scanner.

Keywords: Augmented reality , Dimensional inspection , Factory acceptance test , Metrology

Preface and Acknowledgements (Editorial)

Keywords: Editorial

In this work a Reverse Engineering based approach has been implemented aiming to reconstruct the 3D shape of a strongly damaged and no longer usable impeller of a submersible centrifugal pump. After obtaining the 3D model, new designs of the impeller were investigated in terms of structural stability and corrosion resistance by changing the geometry and the material. Obtained results show the used approach can be very useful both to reproduce, by Additive Manufacturing, no longer available spare parts, so allowing to extend the useful life of old machineries and to reduce costs resulting from plant shutdowns, but also to improve the performances of old designs, making use of different materials and new manufacturing processes.

Keywords: CAD , Centrifugal pump , Impeller , Modal analysis , Reverse Engineering

The evaluation of hip implantation success remains one of the most relevant problems in orthopaedics. There are several factors that can cause its failure, e.g.: aseptic loosening and dislocations of the prosthetic joint due to implant impingement. Following a total hip arthroplasty, it is fundamental that the orthopaedist can evaluate which may be the possible risk factors that would lead to dislocation, or in the worst cases, to implant failure. A procedure has been carried out with the aim of evaluating the Range of Movement (ROM) of the implanted prosthesis, to predict whether the inserted implant is correctly positioned or will be prone to dislocation or material wear due to the malposition of its components. Leveraging on a previous patented methodology that consists in the 3D reconstruction and movement simulation of the hip joint, this work aims to provide a more effective visualization of the simulation results through Mixed Reality (MR). The use of MR for the representation of hip kinematics and implant position can provide the orthopaedic surgeon with a deeper understanding of the orientation and position of implanted components, as well as the consequences of such placements while looking directly at the patient. To this end, an anchoring system based on a body-tracking recognition library was developed, so that both completely automatic and human-assisted options are available without additional markers or sensors. An Augmented Reality (AR) prototype has been developed in Unity 3D and used on HoloLens 2, integrating the implemented human-assisted anchoring system option.

Keywords: Computer-aided surgery , HoloLens 2 , Mixed reality , THA assessment , Total hip arthroplasty

Post-processing pipeline for image analysis in reverse engineering modelling, such as photogrammetry applications, still asks for manual interventions mainly for shadows and reflections corrections and, often, for background removal. The usage of Convolutional Neural Network (CNN) may conveniently help in recognition and background removal. This paper presents an approach based on CNN for background removal, assessing its efficiency. Its relevance pertains to a comparison of CNN approaches versus manual assessment, in terms of accuracy versus automation with reference to cultural heritage targets. Through a bronze statue test case, pros and cons are discussed with respect to the final model accuracy. The adopted CNN is based on the U-NetMobilenetV2 architecture, a combination of two deep networks, to converge faster and achieve higher efficiency with small datasets. The used dataset consists of over 700 RGB images used to provide knowledge from which CNNs can extract features and distinguish the pixels of the statue from background ones. To extend CNN capabilities, training sets with and without dataset integration are investigated. Dice coefficient is applied to evaluate the CNN efficiency. Results obtained are used for the photogrammetric reconstruction of the Principe Ellenistico model. This 3D model is compared with a model obtained through a 3D scanner. Moreover, through a comparison with a photogrammetric 3D model obtained without the CNN background removal, performances are evaluated. Although few errors due to bad light conditions, the advantages in terms of process automation are consistent (over 50% in time reduction).

Keywords: Close range photogrammetry , CNN , Cultural heritage preservation , MobilenetV2 , Reverse engineering , U-Net

Tracheomalacia (TM) is a tracheal weakening that causes the cartilage structure to collapse during breathing. The term tracheobronchomalacia (TBM) is used when the bronchi are also implicated in the disease. This illness can be treated in a variety of methods, including the insertion of stents in the cartilage-restricted region. Stents are commercially available in numerous sizes (diameter and length), different shapes and materials. The shape of the stent is chosen based on where the disease is located, while the size is derived from measurements on CT images or by endoscopic investigations. This task is extremely critical for the patient's health since improper stent can have serious and even deadly repercussions for the patient. Therefore, it is necessary to choose a stent that fits the patient's anatomy as closely as possible. To this end, it is possible to employ a three-dimensional model of the investigated anatomy and choose the most suitable type of stent following measurements made on the model itself. In this work, a method to assist physicians in the choice of the stent to be used in TM or TBM patients, is proposed. By analyzing the tracheobronchial tree and measuring successive cross-sections along the centerline of the lumen, the automated procedure allows to localize the diseased area and to identify the optimal shape and size of the stent to be implanted. Four case studies of paediatric patients were performed and the results were validated by a team of physicians specialized in the treatment of upper and lower airways.

Keywords: 3D modelling , Airway obstruction , Reverse engineering , Stent

In this paper, a semi-automatic procedure to perform point clouds registration is presented. The method was developed for upper limb 3D scanning. During the acquisition, several frames are acquired from different points of view, to obtain a full 360° acquisition of the arm. Each frame stores both the point clouds coordinates and the corresponding RGB image. During post-processing, the RGB image is elaborated through a neural network, to detect relevant key points of the hand, which are then projected to the point clouds. The corresponding key points detected from different acquisitions are then used to automatically obtain a rough 3D rotation that aligns the point clouds corresponding to different perspectives in a common reference frame. Finally, the registration is refined through an iterative closest point algorithm. The method was tested on actual arm acquisitions, and the registration results are compared with the conventional fully manual 3-2-1 registration procedure, showing promising results of the proposed method.

Keywords: Neural network , Semi-automatic registration , Upper limb 3D scan

The optimization of a galvanic process is a crucial task for many manufacturers in the field of electro-deposition industry. This is true for companies operating in the high fashion field, in which expensive materials are used and reducing material waste is crucial. In this paper, the estimation of the wet surface of small metal parts is treated. In fact, considering a single piece, the amount of material required to guarantee a desired plate thickness is directly proportional to its outer surface. Starting with a rapid overview on other methods to come up with this task, the attention in principally oriented to surface estimation by means of optical scanning. A preliminary test session has been carried out and two main issues arose. The first one is related to resolution and accuracy: due to pieces small dimensions and details, high performances are required to achieve valid results. The second and principal issue is related to the high reflectivity of pieces, even before electroplating. With the aim of avoiding the use of matting paint (which is difficult to remove), the attention has been focused on commercial solution dedicated to jewellery and dentistry fields. Three devices (based on white and blue LED structured light) have been tested on high reflective and specular pieces. From the analyses, only the one based on blue LED technology was able to retrieve high reflective surfaces without matting. Minor issues arose in case of specular surface. The device has been considered suitable for the task.

Keywords: 3D optical scanners , 3D reconstruction , Blue LED structured light , Galvanic , Reverse engineering