Additive manufacturing

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

Soft robots have gained significant interest due to their high flexibility and adaptability to various working conditions. Recent advancements in engineering and innovative materials have enabled the design and production of sophisticated soft robotic systems with enhanced capabilities. This study aims to evaluate the fatigue behavior of bellow-type pneumatic soft actuators fabricated through fused filament fabrication (FFF) using thermoplastic polyurethane (TPU), compared to silicone rubber cast actuators. The actuators were equipped with resistive flex sensors to monitor bending motion, and fatigue tests were performed with cycles of inflation and deflation until failure. Results showed that 3D printed TPU actuators could withstand a significant number of cycles before failure, with an average of 6410 cycles at 3 bar pressure, compared to 3439 cycles at 1 bar pressure for the silicone actuators. The study identified a set of fabrication parameters that positively affect the durability of TPU actuators, providing valuable insights for replicating these results. Additionally, the study established a plausible range of utilization for 3D-printed FFF actuators in terms of the number of cycles they can endure, offering critical data for engineers and designers to make informed decisions about the design and application of these actuators in various practical scenarios. The findings demonstrate the potential of FFF for producing durable, long-lasting pneumatic soft actuators.

Keywords: 3D printing , Fused filament fabrication , Pneumatic actuator , Soft actuator , Soft material

Technological advances have increased the use of plastic-based additive manufacturing for production in a variety of industries that require high mechanical properties while maintaining geometric precision. The Arburg Plastic Freeformer (APF) process, unlike other filament-based technologies, uses standard plastic granules used in mass production in injection moulding machines. This study focuses on optimising the interaction of three critical process parameters: layer thickness (LT), droplet aspect ratio (DAR) and discharge rate (DR). Previous studies have mainly varied individual parameters to evaluate mechanical and geometrical properties. In contrast, this work analyses these parameters as a whole and evaluates their combined effects on residual porosity and geometric accuracy. APF relies heavily on supports to sustain the printed part, with a smaller achievable self-supporting overhang angle compared to the Fused Filament Fabrication (FFF) printing process. For this reason, this study investigates two compatible materials, ABS Terluran GP35 and a water-soluble PVP compound named Armat11. Cylindrical and cubic samples were 3D printed using different combinations of LT, DAR and DR. A total of 150 cubic samples were printed to assess the geometric dimensional accuracy and repeatability of printing in the plate position using permutations in the printing plate. Subsequently, 30 cylindrical samples were printed for micro-CT analysis, reconstructed by CT file segmentation and compared with the ideal CAD model, in addition to the characterisation of residual porosity. The results show that optimal combinations of LT, DAR and DR produce high density parts with repeatable geometric properties. In addition, a quantitative analytical model was developed to optimise arbitrary parameter sets. This comprehensive investigation provides important insights into the APF process and increases its potential for wider industrial applications.

Keywords: Additive manufacturing , Arburg Plastic Freeforming (APF) , Geometric accuracy , Process optimisation , Residual porosity

Purpose: This study aims to examine the efficacy of 3D printing polymers to realistically mimic the fossa ovalis (FO) – a cardiac structure that is positioned in the interatrial septum – for simulating transseptal puncture (TP) procedures. Design/methodology/approach: Specimen of different materials and thicknesses were prepared and tested simulating the puncturing of the FO using a 12F ID/14F OD TP catheter. Force and tenting length results were compared with literature references. Scanning electron microscope images of the specimen were acquired to observe the perforated region as well as the structure of the specimen in the unaffected area. Findings: Significant changes in the properties of interest were registered for the same material on specimens tested at different moments after fabrication. Suturable vessel wall polyjet material offers the best characteristics to replicate FO anatomy and mimic its behavior to puncturing. Originality/value: The originality of the work lies in the test of different commercial materials. Similar works are already present in literature but specifically designed materials are used. Demonstrating that off-the-shelf materials could be viable for FO specimens would simplify the design of realistic TP simulators in the future.

Keywords: Additive manufacturing , Advanced manufacturing technologies , Fossa ovalis , Material testing , Mechanical properties of materials , Simulation training , Training devices , Transseptal puncture

This article presents a methodology for the design and production of custom prostheses for complex surgical interventions on long bones due to oncological surgical treatment. This type of intervention considers the complete or partial removal of bone tissue that might be affected by bone tumors. In this scenario it is important to limit the loss of functionality of the patients' joints. Accordingly, it is important to salvage, whenever possible, the original articulation surfaces of the joints; nevertheless, a complete evaluation of the tumor extension and of the state of bone tissue might be difficult to be performed in the preparation phase. The article presents an approach for geometrical modelling of a modular prosthesis for long bones, that leaves the surgeon free to tailor the resection according to their feedback in the operating theatre. Specifically, the devised methodology allows to salvage part of the original bone by switching modules of the prosthesis. The dissertation is tackled from a technical perspective, taking into account the constraints and key features that need to be considered in the design and production of a long bone prosthesis via additive manufacturing technologies. The methodology is presented with reference to a complex custom prosthesis design that was carried out with the support of T3Ddy's - Personalized pediatrics by inTegrating 3D aDvanced technologies research laboratory.

Keywords: Additive Manufacturing , Custom prosthesis , Design for Additive Manufacturing

Patients with spinal problems have difficulty when performing activities of daily living due to weakness or paralysis in the joints and muscular system, and this is a serious problem for people of all ages because it negatively affects their socio, physio, and economic lives. Traditional orthopedic corsets are a valuable support for these patients because these devices enable them to perform specific activities that require motor control, such as sitting, walking and other physical activities. However, they are often bulky, poorly ventilated and manufactured with non-biocompatible materials. This research focuses on the design and manufacturing of bespoke orthopedic corsets through a new organic bioplastic compound, optimizing the aspects of functionality, light weight, and small footprint. The developed orthosis offers design flexibility and improved porosity control, performing the functions of an exoskeleton, assisting patients with spinal problems who cannot be operated on because they have high risks during surgery, e.g., herniated disc, osteoporosis, injury, osteoarthritis, etc. It allows pain relief and the continuation of even the simplest activities of daily living making patients more independent. The most suitable materials, such as polymers and their composites, were evaluated to manufacture a customized and biodegradable orthosis. Future goals include automating the process of designing and printing the customized orthosis from a real-time scan of the patient's torso.

Keywords: Custom-made orthosis , Daily living activities , Orthopedic corset , Rehabilitation field , Wearable device

Amongst Additive Manufacturing (AM) processes, Powder Bed Fusion (PBF) technologies represent one of the most promising production methods for polymers and metals, and the laser-based systems are certainly the technology that currently guarantee the production of metal parts with complex geometries, shapes, and mechanical properties comparable to those of parts produced using traditional methods. A functionally graded material (FGM) or a multi-material (MM) component can be advantageously produced with several processes and laser-powder bed fusion (L-PBF) is one of the metal-based process for their production and design. In this scenario, the paper proposes a procedure to manufacture FGM or MM parts with standard L-PBF machines, that is equipped with only one powder deposition system, using the 2D multi-material approach, where the material transition occurs between the layers with a material change along the building direction. Joints between materials of common interest, such as AISI 316L & CuCrZr alloy, AISI 316L & 16MnCr5 steel, and Al-Sc & AlSi10Mg alloy, were considered. The joints were analysed by means of metallographic investigation, neutron tomography (NT) analysis and tensile tests. The results of metallographic and tomography analyses highlight the continuity of joints establishing the possibility and the effectiveness to manufacture FGM or MM. Also, the tensile tests showed interesting results, demonstrating that the mechanical properties of the joint depend on the bulk alloy properties and on the internal structural integrity.

Keywords: Functionally graded material , Laser-powder bed fusion , Mechanical properties , Microstructure , Neutron tomography

Background: Joint-sparing resection of juxta-articular knee tumors is challenging. With the development of 3D printing technology, custom-made cutting guides were introduced with the aim to improve the accuracy of tumor resection margins and to shape the allograft for adequate matching in biological reconstruction. Materials and Methods: Between December 2017 and July 2023, 13 patients underwent joint-sparing juxta-articular resection of the knee for a primary bone tumor at our institution. Resection was performed using a custom-made 3D-printed titanium alloy cutting guide and reconstruction was performed using a custom-shaped allograft. The mean follow up was 50 months (min 14–max 81). The study of cutting accuracy was performed by digital examination of CT images of the resection specimen in eight patients. Results: The average cutting error was 2.3 mm. Surgical margins were wide in all patients. Four patients developed postoperative complications that led to the removal of the allograft in one case. The average functional result according to the Musculoskeletal Tumor Society Score was 26 (min 14–max 30), and according to the Oxford Knee Score it was 44 (min 22–max 48). Conclusions: Custom-made titanium cutting guides resulted effective in improving the accuracy of joint-sparing juxta-articular resection of the knee and allograft matching.

Keywords: 3D printing , bone tumors , custom made , cutting guides , juxta-articular tumors

CAD-CAE software companies have introduced numerous tools aimed at facilitating topology optimization through Finite Element Simulation, thereby enhancing accessibility for designers via user-friendly interfaces. However, the imposition of intricate constraint conditions or additional restrictions during calculations may introduce instability into the resultant outcomes. In this paper, an algorithm for updating the design variables called Adaptive Variable Design is proposed to keep the final design space volume of the optimized part consistently under the target value while giving the main algorithm multiple chances to update the optimization parameters and search for a valid design. This algorithm aims to produce results that are more conducive to manufacturability and potentially more straightforward in interpretation. A comparison between several commercial software packages and the proposed algorithm, implemented in MATLAB R2023a, is carried out to prove the robustness of the latter. By simulating identical parts under similar conditions, we seek to generate comparable results and underscore the advantages stemming from the adoption and comprehension of the proposed topology optimization methodology. Our findings reveal that the integrated enhancements within MATLAB pertaining to the topology optimization process yield favourable outcomes with respect to discretization and the manufacturability of the resultant geometries. Furthermore, we assert that the methodology evaluated within MATLAB holds promise for potential integration into commercial packages, thereby enhancing the efficiency of topology optimization processes.

Keywords: discreteness , manufacturability , optimization software , performance optimization , topology optimization

Today, reducing vehicle energy consumption is a crucial topic. For electric vehicles, reducing energy consumption is essential to address some of the most critical issues associated with this type of vehicle, such as the limited range of electric powertrains and the long battery recharging times. To lower the environmental impact during the vehicle's use phase and reduce energy consumption, vehicle mass reduction (lightweighting) is an effective strategy. The objective of this work is to analyze the vehicle parameters that influence lightweighting outcomes on a real driving cycle, representative of the home-to-work travel in northern Italy. In particular, a previous work carried out on standard driving cycles is repeated in order to observe whether it is possible to draw the same conclusions regarding the variability in the lightweighting outcome. This study was conducted using two opposite vehicle models, a compact car and an N1 vehicle, simulated through a well-established vehicle simulation tool for energy consumption estimation. To conduct this analysis, several simulations with variable vehicle mass, and with different vehicle parameters, such as aerodynamics and rolling resistance, were performed to estimate energy consumption across a real-world driving cycle, acquired via GPS on board the vehicle during a home-to-work journey in northern Italy. This study reveals that even for the real driving cycle, as for the WLTC and US06 standards, the parameters that most influence the outcome of the lightening are the rolling resistance, the characteristics of the battery pack, the aerodynamic coefficients, and the efficiency of the transmission. Finally, the standard cycle that best fits with the real one considered in this study is the Artemis Urban Cycle.

Keywords: automotive , consumption analysis , energy consumption , energy reduction value (ERV) , fuel reduction value (FRV) , real data , real driving cycle , vehicle lightweighting

Global warming and air pollution are the main factors influencing international, national, and local strategies for the transition towards clean technologies to reduce polluting and climate-altering emissions. A further reduction of the latter can be achieved, with the same powertrain technology, by reducing vehicle consumption. One technique is to lighten the vehicle. The goal of this feasibility study is to act on the battery thermal management system to achieve vehicle lightweighting. Specifically, a sedan car with active-cooled batteries was considered as a reference case, and primary lightweighting was achieved through the use of passive cooling methods, i.e., air and Phase Change Material (PCM) cooling systems, followed by secondary lightweighting to re-establish the target range of the reference vehicle by downsizing the batteries. The air-cooled system leads to greater lightweighting, but its field of application is limited to vehicles operating in fleets; this obstacle can be overcome by using a PCM.

Keywords: Electric Vehicle; PCM (Phase Change Material) , Energy Consumption , Secondary Lightweighting , Traction Battery Thermal Management System , Vehicle Lightweighting

Metal Additive Manufacturing is an emergent production process that can realize geometries that are difficult to realize with traditional manufacturing techniques. The design rules and guidelines for Additive Manufacturing are different from the traditional approaches. One of the issues of Additive Manufacturing is the evaluation of the printability of the CAD model to be realized and the results in terms of residual stress and deformation. In the literature, there is a lack of tools and methods to rapidly evaluate the printability of the CAD models and predict the results in terms of residual stress and deformation. This paper proposes a Machine Learning-based method to confirm or not the printability of a 3D CAD model in the early design phase. This evaluation could reduce the errors during the printing phase. A Decision Tree classifier has been trained with virtual analysis. The dataset has been produced with CAD models, generated by a parametric approach, and numerical simulations used to evaluate the 3D printing output. A Knowledge-Based tool defines the list of parameters to be extracted from each CAD model. During the use of the proposed decision tool, the parameters are extracted from the CAD model and analyzed within the Decision Tree model.

Keywords: Additive Manufacturing , Decision Tree , Design for Additive Manufacturing , Knowledge-Based tool , Machine Learning

Extended Reality (ER) stands out as one of the major technology trends currently, with expectations of even further growth in the near future. The primary objective of this paper is to develop an ER application for the Sharebot One and Sharebot Next Generation 3D Printers, specifically designed to assist students with special needs. The application follows an inclusive design perspective based on the International Classification of Functioning, Disability, and Health (ICF) by the World Health Organization (WHO), enabling students to work and interact with the machine safely. To achieve this goal, three configurations have been developed and tested: a desktop version running on a PC, an Android tablet-based version, and a solution optimized for the Microsoft HoloLens device.

Keywords: Autism , Down Syndrome , Extended Reality , Inclusive Education , Neurodevelopmental Disorder , Special Education , Special Educational Needs , Training

Purpose: This study aims to provide understanding of the influence of external factors, such as gravity, during sintering of three dimensional (3D)-printed parts in which the initial relative density and cohesion between the powder particles are lower compared with those present in the green parts produced by traditional powder technologies. A developed model is used to predict shrinkage and shape distortion of 3D-printed powder components at high sintering temperatures. Design/methodology/approach: Three cylindrical shape connector geometries are designed, including horizontal and vertical tubes of different sizes. Several samples are manufactured by binder jetting to validate the model, and numerical results are compared with the measurements of the sintered shape. Findings: Simulations are consistent with empirical data, proving that the continuum theory of sintering can effectively predict sintering deformation in additively manufactured products. Originality/value: This work includes the assessment of the accuracy and limits of a multiphysics continuum mechanics–based sintering model in predicting gravity-induced distortions in complex-shaped additively manufactured components. © 2024, Elisa Torresani, Alberto Cabo Rios, Thomas Grippi, Andrii L. Maximenko, Marco Zago, Ilaria Cristofolini and Eugene A.

Keywords: Binder jetting , Deformation , Finite element methods , Sintering

This work collects as a whole the main results obtained in the Design for Sintering project, aimed at improving the effectiveness of a design procedure accounting for anisotropic dimensional change on sintering, through a deep investigation of the related phenomena and mechanisms. The project was developed in cooperation with the main European companies producing sintered components, and it is based on a huge experimental campaign. Ring-shaped parts with different characteristics were produced in different process conditions, and dimensional changes were derived from a careful reconstruction of geometry, measured in the green and sintered state. In the first part of the project, parts characterised by different geometrical parameters and different green densities were produced, using many different powder mixes, from highly shrinking to slightly swelling. The first part of the project highlighted the importance of anisotropic dimensional change in the compaction plane, and a new anisotropy parameter was proposed accordingly. In the second part of the project, the study was then focused on the anisotropy of dimensional changes in the compaction plane, as affected by different compaction strategies. The results were implemented in the design procedure, and process conditions were highlighted ensuring good agreement between real and predicted dimensions.

Keywords: anisotropy , cold compaction , design for sintering , dimensional changes , low alloyed steels

The safety of vessels at sea is crucial, given the potential presence of obstacles such as rocks, other vessels, or offshore structures. Impacts with such objects pose a significant risk to the integrity of ships and the safety of passengers. The present research activity explores safety in international nautical competitions, with a specific focus on races governed by the International Union of Motorboating (UIM). It analyzes the innovative design of the hull's sandwich construction of the XCAT racing catamaran, crucial for ensuring safety in the event of violent impacts, such as those from capsizing. The research activity involved four-point bending tests and impact tests to evaluate the mechanical performance and impact resistance of these sandwich specimens. Two types of sandwich structures were subjected to bending tests to determine their load-bearing capacity and to impact tests to assess their energy absorption characteristics. Through testing the effectiveness of structural innovations in enhancing the resilience of high-speed vessels is thus ensured, providing useful information for the development of theoretical and numerical prediction models.

Keywords: Four-point Bending Test , High-speed vessel , Impact Testing , Maritime Safety

Robotic Additive Manufacturing is an emerging trend thanks to effective advances compared to traditional machines based on Cartesian movements. Reduction of the volume of supports and the related “staircase effect” increased inaccuracy and surface roughness, large printing volumes, more flexibility on the printing strategy, and use of multiple materials are just some of the potential benefits returned by robotic additive manufacturing. Nevertheless, the selection of suitable strategies, planning of the printing trajectories and definition of the related code to drive the robot movements are still managed by different digital tools that make it challenging to identify the optimal process. This work describes a Design for Robotic Additive Manufacturing approach to support the development of the printing process driven by complex machines such as robotic arms. Based on an available computer-aided design platform, the digital replica of the robotic system is recreated, and additive process alternatives are applied to simulate the fabrication of an automotive part. A first assessment of the design integration by the approach suggested is evaluated by the simulation of fuse material deposition for a simplified version of the selected use case.

Keywords: Additive process simulation , Fused Filament Fabrication , Integrated Design Approach , Robot Programming , Robotic Additive Manufacturing

The integration of structural optimization into product design processes has been a focus of extensive research, leveraging advances in computing technology to embed numerical techniques within simulation-driven approaches. Topology optimization, particularly enabled by Additive Manufacturing, has emerged as a powerful tool for generating structurally efficient geometries. However, practical implementation poses challenges, often requiring manual redesign and interpretation of results. To address these issues, this study explores the potential of numerical optimization techniques, specifically parametric and shape optimization, to refine topology optimized structures automatically. The final aim is to develop a systematic workflow integrating these tools to produce ready-to-print geometries with minimal user intervention. The investigation, based on simple geometries resembling topology optimized structures, investigates the tools for simulation-driven design methods utilizing multi-step numerical optimization within an integrated CAD platform, aiming for a direct, efficient, and mathematically-driven design process. Advantages include faster iterations, reduced errors, and independence from user expertise, while challenges such as computational complexity, sensitivity to initial conditions, and need for specific design expertise are acknowledged. The potential further systematic approaches for broader applications, particularly in additive manufacturing and structural engineering, underscore the significance of further research in this area.

Keywords: Computer Aided Engineering , Design for Additive Manufacturing , Design Method , Design Optimization , Finite Element Method

Purpose: In this study, response surface methodology (RSM) is applied to a three-point bending stiffness analysis of low-cost material (PLA) specimens printed using FDM technology to analyze the performance of different internal lattice structures (Octet and IsoTruss principally). The purpose of this study is to extend the definition from a discrete (lattice) model to an analytical one for its use in subsequent design phases, capable of optimizing the type of cell to be used and its defining parameters to find the best stiffness-to-weight ratio. Design/methodology/approach: The representative function of their mechanical behavior is extrapolated through a two-variable polynomial model based on the cell size and the thickness of the beam elements characterizing it. The polynomial is obtained thanks to several tests performed according to the scheme of RSM. An analysis on the estimation errors due to discontinuities in the physical specimens is also conducted. Physical tests applied to the specimens showed some divergences from the virtual (ideal) behavior of the specimens. Findings: The study allowed to validate the RSM models proposed to predict the behavior of the system as the size, thickness and type of cells vary. Changes in stiffness and weight of specimens follow linear and quadratic models, respectively. This generally allows to find optimal design points where the stiffness-to-weight ratio is at its highest. Originality/value: Although the literature provides numerous references to studies characterizing and parameterizing lattice structures, the industrial/practical applications concerning lattice structures are often still detached from theoretical research and limited to achieving functioning models rather than optimal ones. The approach here described is also aimed at overcoming this limitation. The software used for the design is nTop. Subsequent three-point bending tests have validated the reliability of the model derived from the method's application.

Keywords: Additive manufacturing , Lattice structures , Lightweighting , Response surface method (RSM) , Stiffness optimization , Three-point bending

Adopting additive manufacturing in investment casting, known as rapid investment casting, can significantly reduce lead time and cost. Despite many publications on these technologies, no quantitative techno-economic analyses refer to rapid investment casting. The paper provides helpful insights and a decision-making approach for replacing conventional production technologies (i.e. wax injection) with additive manufacturing technologies. The study is based on a techno-economic analysis framework. It allows assessing key performance indicators (e.g. crossover points and payback periods) for stakeholders to decide the suitable VAT photopolymerisation processes (i.e. stereolithography, digital light processing, and material jetting) according to specific production scenarios (i.e. load factors). Analytical cost models were developed in the frame of this work to assess the time and cost of the overall manufacturing process of the resin model for investment casting, considering the post-processing stages for each of the technologies investigated. The cost models were used to assess the benefits introduced by additive manufacturing in rapid investment casting. A sensitivity analysis evaluated the impact of energy, material, and labour costs for both key performance indicators (crossover points and payback periods). The techno-economic analysis yielded the following results: (i) crossover points in terms of production costs vary, ranging from thousands of units for small components in the jewellery or fashion industries to a few dozen units for larger parts in the mechanical industry, and (ii) crossover points in terms of time are lower than those related to cost. Additionally, digital light processing is regarded as the most promising technology, offering the best crossover points and payback periods across various scenarios, mainly when 3D printers are used at a low utilisation rate.

Keywords: 3D printing , Additive manufacturing , Digital light processing , Material jetting , Rapid investment casting , Rapid tooling , Stereolithography , Techno-economic assessment