Geometric modeling and processing

Background: – We aimed to describe a protocol and related surgical treatment for mentoplasty using virtual surgical planning (VSP) and piezosurgery. Methods: – Twelve patients requiring mentoplasty underwent VSP based on preoperative computed tomography. Virtual osteotomy was defined and the bone fragment was repositioned. Cutting and repositioning guides were exported as STL files and created using a 3-dimensional (3D) printer with biocompatible material. Plates were preblended on the printed model. Postoperatively, morphometric analysis was performed by comparing the planned and postoperative 3D models: distance between the apex of the cusp of 43 and 33 and lower edge of the chin; distance between the lower edge of the right and left mental foramen and osteotomy; and distance between the mandibular lingual fossa and pogonion. Results: – Six cutting guides were made composite and six were monobloc. The repositioning guides were all made monobloc. No adverse intraoperative events were observed. Postoperative transient hypoesthesia was reported in 1 case. The average distance between the planned and postoperative 3D models of the chin was recorded in translation (1.91 mm), rotation (right, 1.38 mm; left, 1.30 mm), and cranial-caudal repositioning (right, 1.39 mm; left, 1.23 mm). VSP and 3D printing have improved surgical precision and reproducibility; they help the surgeon decide the extent of chin movement and the most suitable type of surgical guide in advance. Conclusions: – Mentoplasty using 3D-printed guides and piezosurgery is simple, accurate, and safe. The costs of guide production are reduced using 3D printers by approximately €400–€800 per case compared with industrial printers.

The highly likely spread of autonomous vehicles has transformed the landscape of road travel, ushering in new opportunities and challenges in vehicle interior design. By removing the need for direct driver intervention, a wide array of Non-Driving-Related Activities (NDRAs) has become possible. These activities encompass working, studying, relaxing, and socializing during the ride, elevating the car from a mere instrument of transportation to an extension of our daily living space. In this context, this study aims to propose a new design for the Tesla Model 3, envisioning its evolution to SAE Level 5 autonomy, which denotes full autonomous driving capability under any conditions and in any location. We have selected the Tesla Model 3 for examination due to its compact size, posing a significant challenge for interiors' optimization. Starting with a critical review to identify the most pertinent activities for occupants, this study focuses on creating two virtual prototypes of the autonomous Tesla Model 3—one with 4 seats and another with 2 seats—to assess their spaciousness. 3D interiors model was created by CATIA V5 software, and the ergonomic evaluation was conducted using the Ergonomics Design & Analysis module, employing mannequins representing a 50 percentile French male and adopting REBA method for the virtual ergonomic assessment. The research question guiding this investigation is: “What should be the interior configuration of an autonomous vehicle to facilitate the execution of primary NDRAs?”.

Keywords: Autonomous vehicle , Comfort , Ergonomics , NDRAs , Self-driving car

No abstract

Purpose – In Wire Arc Additive Manufacturing, the size and shape of the deposited material are affected by heat input, material deposition rate, orientation with respect to gravity, substrate conformation and the sequence of beads. The paper aims to investigate the geometric behavior of adjacent overlapping beads and proposes a model to predict the shape assumed in case of multiple beads deposition according to the succession of accumulation. Design/methodology/approach – Geometric curves such as parabolas, circular arcs, cosines and ellipses have been proposed in the literature to represent the resulting cross-section bead profiles, even though multiple beads deposition scenarios have been scarcely explored and, in most cases, restricted to simplified situations, such as planar substrates. Therefore, a generic geometric model for the bead profile based on a closed curve composed of two Hermite spans is proposed. Findings – The algorithm reliability was tested on circular specimens realized with a Fronius TPS 320i welding generator and on a set of documented cases from the literature. The results demonstrate that the Hermite curve-based model and the proposed algorithm can accurately reproduce various bead profiles in multi-bead and multi-layer deposition sequences. Originality/value – Thanks to the positioning of its control points, the Hermite curve exhibits the necessary variability in bead height, width, shape and contact angles with the substrate, offering greater flexibility in geometric approximation compared to existing models.

Keywords: Bead geometric modeling , Multi-bead deposition , Multi-layer deposition , Weld deposition , Wire arc additive manufacturing

Biophilic design, which emphasizes integrating natural elements into built environments, is increasingly valued for its positive impact on workplace well-being and productivity. This study investigates how extended reality (XR) technologies can support biophilic design by incorporating digital representations of plants into immersive virtual and augmented workspaces. Central to this research is the evaluation of methods for generating realistic and adaptable digital plants suitable for XR integration, focusing on balancing visual quality, flexibility, and usability. Photogrammetry, a technique that creates detailed 3D models by combining photographs from multiple angles, is explored for its potential to quickly produce high-resolution digital plant assets. Despite its advantages, photogrammetry struggles with rendering fine details, such as delicate branches and leaves, limiting its effectiveness in XR settings. To address these shortcomings, the study compares photogrammetry with procedural modeling — a rapidly evolving approach supported by several tools. Procedural modeling offers enhanced precision, control, and adaptability, enabling dynamic, real-time modifications and interactions in virtual environments. The research highlights how technological innovations can advance biophilic design by enabling the seamless integration of natural elements into digital workspaces. Through comparative analysis, the paper identifies optimal strategies for creating immersive, well-being-focused environments that align with the principles of biophilic design. Ultimately, this study illustrates the potential of XR to transform workplace design by merging nature-inspired elements with cutting-edge digital tools, fostering environments that support both human and organizational productivity.

Keywords: Biophilic design , Digital plants , Extended reality (XR) , Photogrammetry , Procedural modeling

Nowadays, universities address topics like CAD modeling and additive manufacturing to teach students important aspects of engineering and design. However, the development of a prototype is an iterative process composed of different phases that range from the definition of the problem to the evaluation of the concept The paper describes how to integrate all these phases for active learning in the course Computer-Aided Design and Mechanical Prototyping, which is part of the Master's Degree in Mechanical Engineering program at Politecnico di Milano. The final project assigned as a case study to students consists in the development of a rehabilitative hand exoskeleton. The paper presents how students faced the different phases of the development process till the final prototype and its evaluation with healthy subjects and some post-stroke patients. The methodology applied to the course was really appreciated by students, in particular, the experience of designing different devices from scratch. They were challenged in different areas, like mechanics, electronics, informatics, and manual work, which allowed them to range widely during the design and manufacturing process and to extend considerably their knowledge.

Keywords: additive manufacturing , CAD modeling , engineering education , hand exoskeleton , interactive applications

Nowadays, robots hold crucial roles in an increasing number of different fields, highlighting an ongoing transition to ever-closer collaboration between humans and machines. In this context, this new technological era has brought out safety issues and, consequently, robots need to be monitored with an appropriate control architecture and human–machine interaction forces should be correctly estimated. For this purpose, friction, inertia, external perturbation, and the intrinsic dynamic of the robots should be monitored. This specific work starts from the need to monitor human–robot interaction forces to ensure safety for users. A successful case study concerning the integration of additional sensors on a wrist robot that directly interacts with humans is shown. Its limits have been the inability to directly measure forces applied by users and the impossibility to know accurately the end-effector position. Firstly, introducing a force/torque sensor, the detection of the forces applied by the user to the robot has been enabled. The user's force data have been used to measure force dissipation and, together with the smoothness of operation, to compare three different embeddable mechanisms. Moreover, the integration of a linear encoder allowed measuring the instantaneous end-effector position on a non-actuated linear guideway, consequently knowing the motor torque value and the force applied by the robot to the user. This has been compared to the interaction force estimated from the motor torques without the linear sensor. The error assessed between the force measured with the encoder and estimated without it is about 12.9%. These results demonstrate the importance of this new embedded system to detect human–machine interaction forces in an accurate way and prevent safety issues.

Keywords: CAD design , Human–robot interaction , Interaction forces , Mechanical design , Virtual prototyping

In this work, a procedure for modelling and simulating conformal biomimetic scaffolds for bone tissue engineering is presented. Starting from a three-dimensional biomedical model of a real human mandible presenting a severe damage, a conformal shape was modelled and filled with an irregular beam network mimicking human trabecular bone. The material considered for the realization of the scaffold was hydroxyapatite derived from fish industry by-products, a material that is highly biocompatible to human bone. Several simulations were conducted on a beam-based wireframe model by varying the radius of the trabeculae, until reaching a stiffness of the scaffold equal to that of human bone. This represents a good design practice to avoid the stress shielding effect on growing bone tissue and functionality losses during bone regeneration. The resulting porosity and the average pore size, which are fundamental properties to ensure a proper vascularization of the growing tissue, were measured and compared to literature data, showing an acceptable agreement. The proposed beam-based approach for modelling and simulating conformal irregular scaffolds appeared as an interactive, fast, and versatile procedure that can be applied in the design stage of conformal biomimetic scaffolds for bone tissue regeneration.

Keywords: Bone Tissue Engineering , CAD Modelling , Mechanical Simulation

Teaching technical contents related to product design and 3D modeling is a challenging task. Students enrolled in Master of Science courses often have different backgrounds and technical skills, due to their different educational paths at the bachelor's degree. From the student's perspective, one of the main difficulties concerns the definition of the 3D modeling procedure, understand technical drawings and figuring out the proper assembly sequence to get the final product. Over the years, some methods to fill these existing gaps have been experimented, such as tutoring and Massive Open Online Courses. Despite these passive approaches have been proven useful for students, digital technologies, such as Virtual Reality, can boost the implementation active learning sessions and hands-on experiences. In this paper, we present a Virtual Reality application for active learning developed to help students in the initial stage of the “Methods and tools for detailed design” course to acquire a set of lacking knowledge, which includes technical terminology related to mechanical parts and components, the ability to decompose mechanical systems into sub-parts, and to create a 3D model using a CAD tool given a 2D engineering drawing. To evaluate the effectiveness of the proposed approach, the application has been tested with a cohort of students with different backgrounds and knowledge about mechanical design and CAD.

Keywords: Active learning , hands-on experience , Virtual learning , Virtual Reality , Virtual Reality for education

The use of customized surgical guides for the removal of bone tumors is an increasingly common practice in advanced hospitals. These devices are modeled directly on the 3D model of the patient's anatomy and produced using additive techniques; therefore, they have the ability to perfectly anchor to the bone anatomy and allow the tissue of the tumor mass to be removed according to cutting paths predetermined by the physician during preoperative planning. This work proposes a semi-automatic framework for modeling custom surgical guides composed of two main modules: 1) a web application, called Precise, that allows the surgeon to visualize and manipulate 3D anatomical models and enter a set of cutting planes that determine the correct tumor resection paths and other useful information for modeling the surgical guide; 2) a fully automatic procedure that based on this information creates the guide's STL model. The entire procedure aims to create a specific type of cutting guide designed to guide an oscillating saw in a series of planar cuts, thus isolating the tumor. The cutting guides produced are composed of three main elements: a base, the blade slot, and pin's holes.

Keywords: Medical 3D Model , Medical Application , Rapid Prototyping , Surgical Planning

Autologous ear reconstruction is a surgical procedure which aims to restore the anatomy of the outer ear whenever there are malformations due to congenital defects (microtia) or as a result of trauma and burns. Reconstruction involves the cutting, carving, and modeling of a portion of costal cartilage harvested from the patient. The aesthetic results of the surgery are highly dependent on the manual skill of the surgeon, which therefore needs a wide range of surgical experience. Appropriate simulation and training tools are essential to acquire adequate familiarity with the procedure without compromising the patient's aesthetic appearance. In such a context, the present work aims to create replicas of the costal cartilage that allow a realistic simulation of the surgery, thus taking into account important characteristics of the cartilage tissue such as the behavior to cut and suture, hardness, etc. The problem is approached with well-established Additive Manufacturing and Reverse Engineering techniques, which are increasingly being used in the medical field, addressing both the problem of identifying the most suitable materials and the possibility of providing medical personnel with simple interactive procedures for the fabrication of multilayer replicas, without the need to turn to expert CAD modelers.

Keywords: CAD modeling , Costal cartilage mold , Ear reconstruction , Medical simulation

This study aims to evaluate the advantages and criticalities of applying additive manufacturing to produce climbing holds replicating real rocky surfaces. A sample of a rocky surface has been reproduced with a budget-friendly 3D scanner exploiting structured light and made in additive manufacturing. The methodology is designed to build a high-fidelity replica of the rocky surface using only minor geometry modifications to convert a 2D triangulated surface into a 3D watertight model optimised for additive manufacturing. In addition, the research uses a novel design and uncertainty estimation approach. The proposed methodology proved capable of replicating a rocky sample with sub-millimetre accuracy, which is more realistic than conventional screw-on plastic holds currently used in climbing gyms. The advantages can be addressed in terms of customisation, manufacturing cost and time reduction that could lead to real outdoor climbing experiences in indoor environments by coupling additive manufacturing techniques and reverse engineering (RE). However, operating the scanner in a rocky environment and the considerable size of the climbing routes suggest that further research is needed to extend the proposed methodology to real case studies. Further analysis should focus on selecting the best material and additive manufacturing technology to produce structural components for climbing environments.

Keywords: 3D scanning , Additive manufacturing , Climbing holds , Fused deposition modelling , Reverse engineering , Uncertainty quantification

To lower the cost of additive manufacturing of metallic components, the goal of this work is to investigate and optimize a multi-step process by material extrusion (MEX) of a polylactide filament loaded with bronze to remove the gas produced during the debinding and sintering steps. First, by adjusting the infill (10%, 50%, and 100%), and then by designing and constructing internal passages to aid in the expulsion of gases that occur during the debinding, a calibration cube is created. Additionally, the impact of the cooling period during the debinding is examined. To assess how the technique changes shape, sizes, and internal structure, all the samples are ultimately weighed, scanned, and cut. In order to reduce deformation occurred during the debinding and sintering gases, a new design method has been developed. The method consists of the generation of internal channels which connect the voids of the infill and allow gases to flow out through a central channel. As seen, samples with ejection channels and an intermediate infill (i.e., 50%) both exhibit better attributes.

Keywords: additive manufacturing , debinding , metal fused filament fabrication , optimised design , sintering

The supply of automotive spare parts, especially for historic vehicles, is not guaranteed by car manufacturers. Usually, car restorers look for original components at flea markets and fairs, but often they have to produce replicas from broken parts or, worse, without information about the original parts. A possible support in mechanical craftsmanship comes from digital tools commonly used in industry today. With the goal of replicating a component that no longer exists, this paper provides a workflow that integrates traditional manufacturing technologies with computer-based tools. The core is the digital model, which is used to prototype and test the replica for functionality as well as simulate its manufacturing process. An engine valve cover of a historic racing car was chosen as a case study, for which information sources were practically unobtainable. Firstly, a 3D model and a 3D printed prototype were developed. Sand casting was chosen based on the original process and computer simulations allowed to reconstruct the casting equipment and define the best part design. A faithful and functional replica is then manufactured and assembled with the original engine, respecting the original part in terms of form, materials and production. The proposed design approach can be further adopted in different contexts requiring on-demand, one-off or small-batch production.

Keywords: 3D modelling , Additive Manufacturing , Car restoration , Component reproduction , Computer-Aided Engineering , Sand casting

Background & objective: Human vertebrae are analysed and measured for various purposes, including to study anatomy, to diagnose illness, and to evaluate therapies. Achieving an accurate morphological and dimensional characterisation of three-dimensional (3D) vertebrae relies on the precise recognition of their features. Traditionally, these features, lacking defined edges, have been identified manually through a time-consuming, poorly repeatable, and poorly reproducible process. To the authors' knowledge, there is only one method published in the literature able to automatically recognise all the most important vertebral features: the algorithmic feature recognition method (AFRM). It requires a high-density point cloud as input, the presence of all morphological features, even if incomplete, and incurs high computational costs. This research aims to propose an improved version of the AFRM to overcome its limitations. Methods: The proposed approach combines the robustness of AFRM to provide the semantic segmentation of a 3D healthy human vertebra with the ability of the enhanced statistical shape model (eSSM) to transfer information among different models. Specifically, AFRM provides the semantic segmentation of the mean shape of the eSSM, while the latter transfers this information to target shapes. Results: The eSSM was developed using 20 training samples of healthy adult male L2 vertebrae. The test samples included five healthy vertebrae and four vertebras with large missing parts. None of the test shapes were included in the training set. The novel approach could accurately recognise morphological features without the constraints that affect the AFRM. Conclusion: The proposed method guarantees reliable and automated segmentation through AFRM, exploiting the eSSM's ability to provide results even when dealing with sparsely populated or partially incomplete target models, significantly reducing the computational load.

Keywords: 3D medical image analysis , Bio-informatics , Computer methods for vertebra analysis , Shape segmentation , Statistical Shape Analysis

In a digital world where technological development allows the implementation of computer-based methods that can objectively support human activities, it is no more conceivable that activities such as the analysis, classification, and reconstruction of archaeological ceramics are made manually. This determines that expert operators are involved in time-consuming, tedious, poorly repeatable, and reproducible activities whose results depend on his/her experience. This problem concerns the need for robust and reliable automatic methods supporting the operator in these activities. To address these problems, in the last years, the University of L'Aquila research group published robust and reliable methods based on the codification of archaeologists' knowledge in recognizing the most significant geometric and morphological features of sherds. With such tools now available, producing more objective knowledge referring to a huge amount of sherds, the need arises to develop computer-based systems capable of sharing this knowledge. For this purpose, in this paper, a dedicated database is proposed. Particular efforts were made to implement an intuitive and interactive web interface with commands that co-determine the essential interaction of the archaeologist with the fragments in the traditional method.

Keywords: Automatic features recognition , Computer methods in archaeology , Innovative representation scheme , Semantic annotations , Web-based application

The Divertor Tokamak Test (DTT) facility needs a large amount of heating power to study the problem of power exhaust in reactor-relevant conditions. Among the additional heating systems, the ion cyclotron resonance heating (ICRH) is characterized by radio frequency (RF) components based on standard technology and well-assessed solutions due to the tight schedule of the DTT construction. Considering the harsh fusion operating conditions, the ICRH antenna design involves different and interacting physical fields to be managed by the systems engineering (SE) approach. Therefore, following step by step this methodology, the design started with the definition of the main requirements of the whole system. Then, the main functions have been identified with the aim to define the logical architecture of the whole antenna structure. In the end, a preliminary 3-D parametric model of the ICRH antenna with its subsystems has been developed adopting a top-down modeling approach in the CATIA V5 environment provided by Dassault Systemes. Key aspects of the 3-D model are the clear definition of the position in the available space of all subsystems and of their interfaces, and its parametrization. They allow to quickly implement the modifications required by the multiple iterations between the geometrical modeling environment and several multiphysics simulation environments to check the compliance with mechanical, electrical, thermofluid dynamics, and remote handling requirements.

Keywords: 3-D parametric modeling , Antenna accessories , Antenna feeds , Antennas , ion cyclotron resonance heating (ICRH) antenna , Loaded antennas , Plasmas , Radio frequency , Solid modeling , systems engineering (SE) , virtual prototyping

Hygienic design requires the definition of rules allowing the correct development of food processing systems. The knowledge collection in this field would certainly help designers and engineers in developing hygienic-compliant systems. This paper aims to provide a knowledge-based (KB) system for gathering hygienic design guidelines for the design of food processing machinery and equipment. The KB system is based on a specific ontology that has been used to collect 78 hygienic design rules from different sources. The rules repository can be considered a backbone for the subsequent development of a CAD-based tool for an automatic search and detection of non-compliant design features. Starting with a CAD model, the KB system was used to check the compliance of a fish stick production machinery. Results highlight how the adoption of the KB system in the early design phase would anticipate hygienic design issues avoiding several design reviews.

Keywords: Design for manufacturing , Engineering design , Food equipment , Food industry , Hygienic design , Knowledge-based system

The paper focuses on the application of 3D printing technology in the medical field, particularly in cardiac surgery. Unlike traditional imaging techniques such as CT, MRI, and ultrasound, 3D printing offers a more detailed understanding and analysis of clinical cases. By using 3D printing, it becomes possible to study a patient's specific cardiac anatomy, manipulate objects before surgery, and accurately determine the surgical site. This reduces both the time required for the operation and the patient's recovery period. This study presents a methodology for creating 3D-printed models of aortic arch sections affected by aortic dissection. The aim is to produce anatomical models with varying levels of quality and accuracy. The research goal is to assess the differences in 3D printing materials and technologies for creating complex anatomical models like the aorta. The process involves segmenting medical images obtained from Computed Tomographic Angiography (CTA) and then 3D printing digital models using different materials (such as PLA, TPU, and resin) and technologies (like FDM and SLA). The resulting 3D printed models are low-cost and demonstrate good accuracy in reproducing human anatomy.

Keywords: 3D Printing , CAD , Cardiac surgery , Engineering method

The Reverse Total Shoulder Arthroplasty (RTSA) is a complex surgical procedure also due to the difficulty in correctly positioning all the components of the prosthesis. Malpositioning of the prosthesis, in fact, can lead to various complications such as scapular notching, early mobilization, instability and reducing of the range of movement (ROM). Preoperative planning with 3D imaging and patient specific instruments can be very useful tools to help surgeon in selecting the optimal position of implant components. Aim of this work is to develop a procedure based on a fully parametric CAD system that simulates the shoulder joint to identify the optimal positioning of the humeral and glenoid components of the prosthesis. In particular, the proposed system allows to find the optimal cutting angles of the humerus head and the glenoid cavity so to best fit the patient's bone structure and the prosthesis components and, consequently, to improve the range of movement. The system allows to create, in a semi-automatic way, CAD assembly models composed of the patient shoulder bones and different reverse shoulder prostheses. For each assembly different positions of the components of the prosthesis can be evaluated and various scenarios of movements can be simulated. In this way it is possible to identify the optimal positioning of the prosthesis for each patient in the preoperative stage. The proposed procedure has been tested with two types of prosthesis and two patients. Obtained results demonstrated that an optimal positioning of prosthesis an improve ROM up to 27%.

Keywords: CAD , Preoperative planning , Reverse engineering , Reverse total shoulder arthroplasty