Additive manufacturing

The growing use of additive manufacturing (AM) processes pushes research towards studying methods to reduce their environmental impact. The part build orientation is a significant process variable, which can be chosen through the Energy Performance Assessment (EPA), a straightforward method. The paper presents a method for identifying the best part build orientation considering energy consumption. The EPA has been adapted for this purpose, resulting in an approach based on four steps. The method was employed to determine the best printing direction for three parts and two AM technologies.

Keywords: 3D printing , additive manufacturing , ecodesign , energy efficiency , sustainable design

(1) Background: Orthopedic surgery has been transformed by 3D-printed personalized instruments (3DP-PSIs), which enhance precision and reduce complications. Hospitals are adopting in-house 3D printing facilities, using cost-effective methods like Fused Deposition Modeling (FDM) with materials like Polylactic acid (PLA) to create 3DP-PSI. PLA's temperature limitations can be overcome by annealing High-Temperature PLA (ann-HTPLA), enabling steam sterilization without compromising properties. Our study examines the in vivo efficacy of ann-HTPLA 3DP-PSI in pediatric orthopedic surgery. (2) Methods: we investigated safety and efficacy using ann-HTPLA 3DP-PSI produced at an “in-office” 3D-printing Point-of-Care (3DP-PoC) aimed at correcting limb deformities in pediatric patients. Data on 3DP-PSI dimensions and printing parameters were collected, along with usability and complications. (3) Results: Eighty-three ann-HTPLA 3DP-PSIs were utilized in 33 patients (47 bone segments). The smallest guide used measured 3.8 cm3, and the largest measured 58.8 cm3. Seventy-nine PSIs (95.2%; 95% C.I.: 88.1–98.7%) demonstrated effective use without issues. Out of 47 procedures, 11 had complications, including 2 infections (4.3%; 95% CI: 0.5–14.5%). Intraoperative use of 3DP-PSIs did not significantly increase infection rates or other complications. (4) Conclusions: ann-HTPLA has proven satisfactory usability and safety as a suitable material for producing 3DP-PSI in an “in-office” 3DP-PoC.

Keywords: 3D-printing , annealing , Fused Deposition Modeling , high-temperature polylactic acid , in vivo , orthopedic surgery , patient-specific instrument , pediatrics , polylactic acid , sterilization

Background: In recent years, the treatment of wrist fractures has been the focus of numerous studies, particularly in the development of casts modeled on the patient's anatomy using additive manufacturing techniques. A 3D printed cast offers several advantages over traditional treatment methods, including washability, lightness, and ventilation. Objective: This work introduces an automatic procedure for designing patient-specific wrist orthoses from a 3D scan of the arm using open-source mesh-processing libraries. Methods: The procedure consists of seven steps that generate a customized orthosis model. Due to the absence of a single library capable of completing the entire modeling process, we defined the best execution strategy for each step and established a communication flow between the various blocks. Results: The resulting orthosis comprises two halves, secured by three appropriately positioned bands and perforated with ventilation holes. The modeling procedure takes approximately 5 min to complete and was evaluated on 20 scans of arms of different shapes and sizes. The process proved to be fast, reliable, and suitable for direct use by medical personnel. Conclusions: The developed automatic procedure for designing patient-specific wrist orthoses is efficient and effective, facilitating the use of 3D printed casts in medical practice.

Keywords: 3D modelling , 3D printed orthosis , Personalized medicine , Reverse engineering , Wrist orthosis

In remanufacturing, Reverse Engineering (RE) tools and techniques could become essential in the rapid creation of digital 3D models of existing components, especially when drawings are no longer available. These models can be used to investigate potential remanufacturable parts, identify damages or defects and assist in the decision-making process for as-is rebuilding or redesigning of the part to improve performance. In this context, Additive Manufacturing (AM) technology is particularly well suited due to its capability to rapidly produce parts with minimal geometry constraints and at relatively low cost. This study proposes a methodological procedure based on the combined use of RE-AM to facilitate the remanufacturing decision-making process for better part performance and strategy. Moreover, through the use of Machine Learning (ML) algorithms, damages can be automatically and objectively identified and quantified. An application case is used to demonstrate the effectiveness of the proposed approach.

Keywords: Additive manufacturing , Machine learning , Methodological procedure , Remanufacturing , Reverse engineering

Additive Manufacturing (AM) has seen a massive growth in engineering applications in recent years. Fused Filament Fabrication (FFF), probably the most widespread technology, is nowadays capable of producing polymeric components for all kinds of need: from common use to advanced engineering applications, thanks to the usage of a wide range of polymer materials. Some of them (such as PEEK, PEI and others so-called ultra-polymers) offer very good mechanical properties and sometimes can be even capable of replacing metals. In addition, they are stable at relatively high temperatures and thermally re-processable and recyclable, showing good biocompatibility in most of cases. The distinct advantages of AM have facilitated the rapid development of polymer products with complex customized structures and functionalities, thereby enhancing their applications in various fields. In this work, the mechanical behaviors of FFF manufactured polycarbonate (PC) and Polymethyl methacrylate (PMMA) coupons, both suitable for building construction applications thanks to their good mechanical strength, thermal insulation capability and resistance to ultraviolet (UV) rays, were preliminarily investigated. The aim was to assess the durability of such materials in order to possibly exploit their potential in substitution to conventional ones, in light of their recyclability, so as to eventually promote circularity.

Keywords: additive manufacturing , fused filament fabrication , PC , PMMA

Metal material extrusion is a family of metal additive manufacturing that includes atomic diffusion additive manufacturing (ADAM) and bound metal deposition (BMD). In the literature, there are just a few cost models for ADAM and no one for BMD. The paper presents an analytic cost model for BMD. It considers the entire process: pre-processing, printing and post-processing. The total manufacturing cost is split into material, machine, labour, energy and consumables items. The cost model validation on a 3D-printed part determined an accuracy of 98%.

Keywords: additive manufacturing , cost estimation , design costing , design to cost , metal material extrusion

Bioinspired strategies for scaffold design and optimization were improved by the introduction of Additive Manufacturing (AM), thus allowing for replicating and reproducing complex shapes and structures in a reliable manner, adopting different kinds of polymeric and nanocomposite materials properly combined according to the features of the natural host tissues. Benefiting from recent findings in AM, a Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique was employed for obtaining graphene-like material (GL) uniform coatings on 3D scaffolds for tissue repair strategies, towards the development of a new concept 3D scaffold with controlled morphological/architectural and surface features and mechanical and biological properties. The effect of the material-design combination through an integrated technological approach (i.e., MAPLE deposition of GL on 3D AM PCL scaffolds) was assessed through scanning electron microscopy, atomic force microscopy, contact angle measurements, mechanical measurements and biological analyses (cell viability assay and alkaline phosphatase activity) in conjunction with confocal laser scanning microscopy. The differentiation of hMSCs towards the osteoblast phenotype was also investigated analysing the gene expression profile. The obtained findings provided a further insight into the development of improved strategies for the functionalization or combination of GL with other materials and 3D structures in a hybrid fashion for ensuring a tighter adhesion onto the substrates, improving cell fate over time, without negatively altering the mechanical properties and behaviour of the neat constructs. In particular, the results provided interesting information, making 3D AM GL-coated scaffolds potential candidates for bone tissue engineering.

Additive Manufacturing provides unprecedented opportunities for designing and producing intricate, architected materials with exceptional properties while maintaining reduced weight. One of the most straightforward ways to create such structures is to mimic the lattice geometries of crystals. New approaches are now exploring how to influence the behaviour of these structures by mimicking not only the crystal arrangement but also peculiar mechanisms occurring at the crystallographic scale. In such a context, this study first presents a hexagonal close-packed (HCP) lattice derived from the homonymous crystal structures of Ti or Zr metals. Subsequently, the twinning phenomenon responsible for the plastic deformation of these metals is reproduced geometrically into this structure to improve its energy absorption capability. Compressive tests conducted on 3D-printed samples confirm such a hypothesis: the specific energy absorption of twinned structures is significantly higher than that of the equivalent HCP ones, with an increase of up to 24.3%. Introducing twinned regions stabilises the plastic deformation despite a limited reduction of the peak stress. Therefore, replicating the twinning metallurgical mechanism within an HCP-inspired metamaterial proves successful, further validating the approach of mimicking and transferring atomic phenomena at a different scale to tailor the properties of architected materials.

Keywords: Additive manufacturing , Architected materials , Crystal twinning , Hexagonal close-packed , Metamaterials

Purpose: This study aims to deepen the knowledge concerning the metal fused filament fabrication technology through an analysis of the printing parameters of a commercial 316L stainless steel filament and their influence on the porosity and mechanical properties of the printed parts. It also investigates the feasibility of manufacturing complex geometries, including strut-and-node and triply periodic minimal surface lattices. Design/methodology/approach: A three-step experimental campaign was carried out. Firstly, the printing parameters were evaluated by analysing the green parts: porosity and density measurements were used to define the best printing profile. Then, the microstructure and porosity of the sintered parts were investigated using light optical and scanning electron microscopy, while their mechanical properties were obtained through tensile tests. Finally, manufacturability limits were explored with reference samples and cellular structures having different topologies. Findings: The choice of printing parameters drastically influences the porosity of green parts. A printing profile which enables reaching a relative density above 99% has been identified. However, voids characterise the sintered components in parallel planes at the interfaces between layers, which inevitably affect their mechanical properties. Lattice structures and complex geometries can be effectively printed, debinded, and sintered if properly dimensioned to fulfil printing constraints. Originality/value: This study provides an extensive analysis of the printing parameters for the 316L filament used and an in-depth investigation of the potential of the metal fused filament fabrication technology in printing lightweight structures.

Keywords: 316L stainless steel , Design for additive manufacturing , Lattice structures , Metal fused filament fabrication , Printing parameters , Triply periodic minimal surface

Despite its significant advantages in terms of design freedom and the wide range of processable materials, the Binder Jetting technology has not yet received substantial attention in the healthcare field, especially concerning the fabrication of metal components. Hence, the paper investigates how this technology could be exploited to innovate the medical instrument field. Based on selected case studies, some preliminary design indications are derived on how to properly consider the various phases (i.e., printing, depowdering, and sintering) and related challenges of the Binder Jetting process.

Keywords: additive manufacturing , binder jetting , biomedical design , design for additive manufacturing

Ultrasonic guided waves (UGWs) based structural health monitoring (SHM) systems are widely used in several engineering fields for real-time damage detection, since they are particularly sensitive to material local changes, induced, i.e., by a damage. This paper aims to investigate on the use of SHM systems in additively manufactured laminate. Specifically, a flat panel made of XSTRAND GF30-PA6 material, fabricated by Ultimaker S5 fused filament fabrication (FFF) based 3D printer, is used as a case study. Signals recorded by a piezoelectrics (PZTs) array are analyzed to highlight the dispersive behavior of symmetric, S0, mode along different measurement paths in the excitation frequency range of 100–300 kHz.

Keywords: additive manufacturing , composite , fused filament fabrication , guided waves , structural health monitoring

Additive Manufacturing has transformed modern manufacturing with its well-known advantages. However, shrinkage remains a critical challenge, causing dimensional inaccuracies that should be properly compensated to assure geometric fidelity. This study aims to assess the reliability of a Reverse Engineering (RE) technique for dimensional compensation. A gauge-based measurement approach has been used to validate the RE method. Results confirm that the RE method is promising, while highlighting the intrinsic errors of the RE technique, and suggesting ways to evaluate and prevent them.

Keywords: additive manufacturing , design for additive manufacturing , reverse engineering , scale factor , shrinkage compensation

This research addresses the need for a protective device during binocular indirect ophthalmoscopy (BIO) exams, where traditional face shields cannot be used due to the presence of the instrument and the need for continuous manual interaction. The study aimed to design a device that is easy to fabricate using a 3D printer, usable with different models of ophthalmoscopes, and easy to apply and use. Three possible designs were produced, and the most promising one was further developed into a prototypal level. The article describes the design phase, testing of the prototype, and possible applications of design for additive principles to improve manufacturability. The study is part of the SafEye project, financed by the Tuscany Region with the Covid-19 Tuscany Research Grant, which fostered actions towards the prevention of the spread of the pandemic at all levels. The resulting device is a general-purpose personal protective equipment (PPE) for BIO that can be easily 3D printed and used worldwide, even in underdeveloped countries.

Keywords: 3D printing , 3D printing in medicine , Additive manufacturing , binocular indirect ophthalmoscopy , personal protective equipment

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

Additive manufacturing technologies spread widely in multiple scientific sectors thanks to their flexibility and property customisation. However, many aspects must be studied further since multiple factors such as their microstructure and internal defects can drastically change the overall mechanical behaviour of the final products. In this work, the stress-strain behaviour of a Selective Laser Melting AlSi10Mg alloy is retrieved through a homogenisation approach with FEM analyses using the Representative Volume Element approach. To this purpose, an in-house code has been developed to model a random spatial pore distribution inside the RVE according to literature references and to impose the periodicity boundary conditions. Results are presented at different overall porosities.

Additive manufacturing (AM) technologies are gaining widespread adoption across multiple engineering sectors due to their ability to create customised components with tailored mechanical properties and reduced material waste. This work presents different innovative Finite Element Method (FEM) models to characterise the behaviour of AM structures. A numerical model is presented to characterise AM porosity defects using the Representative Volume Element (RVE) concept; additionally, different unit cell approaches to study the behaviour of lattice structures are presented. The procedures and methodologies presented offer a range of tools, each with different trade-offs between accuracy and computational cost

Keywords: Additive Manufacturing , FEM , Lattice

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

Phantoms play a crucial role in planning and simulating surgical procedures, evaluating new medical devices, and training purposes. Current simulators, such as human cadavers, animal models, and virtual reality systems, are quite expensive and not easily accessible. This research aims to design and develop an affordable 3D replica of a child's head for paediatric neurosurgery. The process began with a Magnetic Resonance Imaging (MRI) scan of a child's head. Afterward, a phantom was fabricated using nylon 3D printing and incorporating agar to replicate the skull and soft tissue. Moreover, Vaseline balls simulating tumors and a silicone skin were added to the phantom, enabling realistic MRI scans for surgical navigation. The functionality of a novel paediatric neurosurgery robot was then evaluated using the phantom as a realistic representation of a child's head. The cost-effectiveness of this approach makes it an ideal and reproducible method for surgical simulation and training objectives.

Keywords: 3D printing , Agar , MRI-visible phantom head , Neurosurgery

This paper will focus on two possible optimizations for a novel wrist exoskeleton. Exoskeletons are structures designed to support human joints using mechanical components and are used in various fields such as rehabilitation, military, and industrial sectors. The study focuses on a new exoskeleton for the wrist with the intention of optimizing its weight and mechanical strength. Two optimization methods are employed. the first one aims to achieve traditional optimization using Computer-Aided Design (CAD) and Finite Element Method (FEM) analysis. In the second the use of Generative Design (GD) optimization, which combine topological optimization and Artificial Intelligence (AI), wants to create new organic components almost impossible to obtain without using this tool. The results indicate that GD optimization significantly reduces maximum displacement while maintaining stress levels within material limits, often improving the weight of the part. Moreover, GD optimization streamlines the design process, offering quicker iterations than traditional methods. This study highlights the efficacy of GD in achieving superior exoskeleton designs with improved mechanical properties and reduced weight, presenting it as a valuable tool for designers seeking optimal solutions in less time.

Keywords: Exoskeleton , FEM analysis , Generative Design

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