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Traditional sintering processes are carried out to achieve complete material densification. In an electron beam powder bed fusion (EB-PBF) process, the same sintering mechanisms occur but only with the aim to form small connections between the particles (necks). A proper neck formation is central for the EB-PBF process because, among other effects, ensures the thermal stability of the process and helps to avoid smoke phenomena. This work presents a numerical study of neck formation under the EB-PBF processing conditions. A new type of modelling is introduced for the temperature sintering load and included in a phase-field model, which simulates the neck growth during the EB-PBF process of Ti6Al4V powders. The model was validated with an ad-hoc experiment, which provided a deviation with respect to the estimated neck diameter of about 9%. The deviation was investigated by reasonably varying the processing conditions. The results showed that the thermal history, the process time scale (including also the cooling phase), and the geometrical characteristics of the particles significantly affected the sintering rate and neck radius.

Lattice structures are 3D open topologically ordered geometries that repeat an elementary cell in a predefined 3D space. Struts connected in specific nodes define the cell. Lattice structures are typical geometries that represent the design freedom unlocked by additive manufacturing (AM) and are unachievable with traditional processes. By tuning the morphometric parameters of the cell, its mechanical response can be significantly altered. Because of that, an accurate understanding of the process capabilities is crucial for achieving the nominally designed properties. Considering an electron beam powder bed fusion process, in this work, the same nominal lattice structure is produced under different processing conditions to determine the relationship between the process parameters, the actual cell morphometric parameters, and its mechanical response. Strut dimension, relative density and cross-section are measured using advanced X-ray computed tomography scanning analyses. Uniaxial compressive tests describe the mechanical performance. Inferential and descriptive statistical analyses are applied to investigate the effect of process parameters on the actual strut dimension and infer regression models. The results show that even slight variations of the process parameters significantly affect the morphometric structure parameters that result deviated from the nominal ones. The work demonstrates a strong correlation between all morphometric structure parameters and corresponding mechanical properties. The obtained regression model can predict the strut dimension from the process parameters, which can be then used to estimate the actual relative density and strut size. With this control and without any complex design procedure, a fine-tuning of process parameters allows a precise 3D spatial and localised control of structure properties to produce functionalised structures directly.

3D printing has been widely adopted not only by individuals or people printing in the community, such as the Markers’ movement but also by industries from different sectors. Unlike traditional manufacturing technologies, layer-wise manufacturing enables live monitoring of the process and part quality layer after layer through proper sensors installed in the working volume of the 3d printing system. Therefore, from the sustainability perspective, unnecessary waste of material and energy can be avoided by aborting the fabrication when a serious defect is detected in one or more layers. In this paper, a low-cost camera and computer vision algorithms are used for the implementation of an in-situ monitoring system for open 3D printing. After printing each layer, the step of image capture is introduced by modification of the open ISO G-code file. The image of the single part layer is then compared to the information extracted from the G-code for automatic detection of manufacturing defects. The area of missing or exceeding material is computed and shown to the user, which can decide to cancel the job in case of important flaws to avoid any unnecessary waste in terms of material, time and costs.

Stereolithography is known as one of the best Additive Manufacturing technologies in terms of geometrical and dimensional precision for polymeric materials. In recent years, a lot of studies have shown that the creation of ceramic resins, through a particular combination of monomeric components and ceramic powders, allows to obtain complex shape geometries thanks to the photopolymerization process. This review highlights the characteristics and properties of ceramic resins, peculiarities of the ceramic stereolithography processes, up to the relationship between the composition of the ceramic resin and the complexity of the post-processing phases. The comparison of different studies allows outlining the most common steps for the production of ceramic resins, as well as the physical and chemical compatibility of the different compounds that must be studied for the good feasibility of the process.

Electron Beam Melting (EBM) is an Additive Manufacturing technique to produce functional components. Because of the high temperature during the EBM process, the surface texture of the as-built parts is extremely complex and unique. This distinctiveness of the surface depends on many factors and needs to be well understood to predict final surface properties accurately. Chief among these factors is the surface design. A proper surface design makes it possible to tailor a surface with specific properties such as biomimetics. However, predictive models are difficult to determine especially for downskin surfaces. To properly tailor a surface, a full factorial Design Of Experiment (DOE) was designed, and 2D and 3D roughness profiles were collected on an ad-hoc artefact using a profilometer and a confocal profilometer. This reference part comprises several surfaces to investigate the effect on surface roughness of different sloping angles, including upskin and downskin surfaces and cavities. The data are analysed using descriptive and inferential statistical tools, also by distinguishing the role of roughness and waviness in the overall surface texture. A deep investigation of the causes of surface roughness made it possible to obtain analytical predictive models. These models are robust and consistent with respect to the experimental observations. Finally, the accurate design of the artefact allows highlighting the relationship between the roughness and the surface slope.

Ti-48Al-2Cr-2Nb (Ti-48-2-2) is an intermetallic alloy belonging to a family of gamma-TiAl intermetallic alloys that are attracting significant attention. Electron Beam Melting (EBM) process is today the only manufacturing process that allows effective production of parts made by these kinds of alloys. Proper process control avoids high temperatures in the surrounding areas that may generate significant residual stresses that could cause micro-cracks. In this paper, an investigation on the residual stress state on Ti-48-2-2 parts is carried out using the hole drilling method. In particular, the influence of EBM process parameters is evaluated in order to understand the effects of the residual stresses on part integrity.

Additive manufacturing processes are considered advanced manufacturing methods. It would be possible to produce complex shape components from a computer-aided design model in a layer-by-layer manner. As one of the complex geometries, lattice structures could attract lots of attention for both medical and industrial applications. In these structures, besides cell size and cell type, the microstructure of lattice structures can play a key role in these structures’ mechanical performance. On the other hand, heat treatment has a significant influence on the mechanical properties of the material. Therefore, in this work, the effect of the heat treatments on the microstructure and mechanical behaviour of Ti-6Al-4V lattice structures manufactured by electron beam melting was analysed. The main mechanical properties were compared with the Ashby and Gibson model. It is very interesting to notice that a more homogeneous failure mode was found for the heat-treated samples. The structures’ relative density was the main factor influencing the mechanical performance of the heat-treated samples. It is also found that the heat treatments were able to preserve the stiffness and the compressive strength of the lattice structures. Besides, an increment of both the elongation at failure and the absorbed energy was obtained after the heat treatments. Microstructure analysis of the heat-treated samples confirms the increment of ductility of the heat-treated samples with respect to the as-built one.

As the selective laser sintering (SLS), multi jet fusion (MJF) is a powder bed fusion additive manufacturing (AM) process that emerged in the last few years. The possibility to nest parts into the build volume and the absence of support structures make both technologies attractive for the large series production of polymeric components. However, to exploit these process features, it is essential to understand the part orientation's effect on the final material performance. A comparison between polyamide 12 (PA12) parts printed by SLS and MJF was carried out in this work. A design of experiment (DoE) approach is adopted to characterise the tensile strength of specimen printed in different orientations and rotations with respect to the machine reference system. Tomography has been used to characterise the porosities present in the printed sample. The results show that it is not sufficient to define only the orientation of the principal axes of the part because the material proprieties may also vary according to the part rotation with respect to the build direction. MJF technology offers greater breaking strength, while SLS prevails over other calculated features. According to the specimen orientation and printing technology, the levels of porosities and the pores have different morphology and distribution in the specimen. A tight correlation was pointed out between the pores and their descriptors and the samples' mechanical behaviour.

Cellularized scaffold is emerging as the preferred solution for tissue regeneration and restoration of damaged functionalities. However, the high cost of preclinical studies creates a gap between investigation and the device market for the biomedical industry. In this work, bone-tailored scaffolds based on the Ti6Al4V alloy manufactured by electron beam melting (EBM) technology with reused powder were investigated, aiming to overcome issues connected to the high cost of preclinical studies. Two different elementary unit cell scaffold geometries, namely diamond (DO) and rhombic dodecahedron (RD), were adopted, while surface functionalization was performed by coating scaffolds with single layers of polycaprolactone (PCL) or with mixture of polycaprolactone and 20 wt.% hydroxyapatite (PCL/HA). The mechanical and biological performances of the produced scaffolds were investigated, and the results were compared to software simulation and experimental evidence available in literature. Good mechanical properties and a favorable environment for cell growth were obtained for all combinations of scaffold geometry and surface functionalization. In conclusion, powder recycling provides a viable practice for the biomedical industry to strongly reduce preclinical costs without altering biomechanical performance.

The conventional approach to design and manufacturing often has geometries with an efficient material distribution. For the high-precision machines, that approach involves the design of heavy components that guarantees the stiffness requirements. However, the higher the weight of the part, the higher inertia it has. As a result, when the feed axes are accelerated, the inertial forces deform the machine components and the precision of the machine is reduced. This study investigated the designing for additive manufacturing (DfAM) and designing for assembly (DfA) to increase the material efficiency of components for high-precision applications. A new methodology which considered the design and manufacturing issues and machining as well is given. A comprehensive model for cost evaluation of the part is presented. The case study refers to the rails and the bracket that support and move the flying probe of a testing machine for micro-electromechanical systems (MEMS). The weight of the rails has been decreased by 32% and the components to be assembled have been reduced from 16 to 7. The optimized bracket is more than 50% stiffer than the original one, 10% lighter, and economically competitive.

Electron beam melting (EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications. Especially, lattice structures made by Ti–6Al–4V have represented a hot topic for the industrial sectors because of having a great potential to combine lower weights and higher performances that can also be tailored by subsequent heat treatments. However, the little knowledge about the mechanical behaviour of the lattice structures is limiting their applications. The present work aims to provide a comprehensive review of the studies on the mechanical behaviour of the lattice structures made of Ti–6Al–4V. The main steps to produce an EBM part were considered as guidelines to review the literature on the lattice performance: (1) design, (2) process and (3) post-heat treatment. Thereafter, the correlation between the geometrical features of the lattice structure and their mechanical behaviour is discussed. In addition, the correlation among the mechanical performance of the lattice structures and the process precision, surface roughness and working temperature are also reviewed. An investigation on the studies about the properties of heat-treated lattice structure is also conducted.

Each manufacturing process produces geometric features with some dimensional errors from the ideal nominal geometry. The knowledge of the dimensional tolerances associated with the specific fabrication process is fundamental for choosing the proper sequence of finishing operations to meet the design requirements. While the ranges of dimensional tolerances for traditional manufacturing processes are well mapped in the literature, a little information is available for additive manufacturing (AM) techniques. In this paper, a benchmarking analysis is carried out between two different AM processes for metals and the dimensional accuracy of each AM machine is defined using the ISO IT grades of a reference artifact.

Additive manufacturing (AM) processes allow producing the complex components in a layerwise fashion. The complexity includes the design of lighter and stronger components by using lattice structures that can be quickly realized through AM technologies. However, the mechanical behaviour of lattice structures is not completely known, especially in the post-treated state. Thus, this work aims to explore the effect of post-treatment on the compressive strength of specimens with lattice structures. The samples are produced using Ti-6Al-4V powder processed by Electron Beam Melting (EBM). The outcomes of this work confirm the correlation between the heat treatment and final mechanical properties.

Atomic Diffusion Additive Manufacturing (ADAM) is a recent layer-wise process patented by Markforged for metals based on material extrusion. ADAM can be classified as an indirect additive manufacturing process in which a filament of metal powder encased in a plastic binder is used. After the fabrication of a green part, the plastic binder is removed by the post-treatments of washing and sintering (frittage). The aim of this work is to provide a preliminary characterisation of the ADAM process using Markforged Metal X, the unique system currently available on the market. Particularly, the density of printed 17-4 PH material is investigated, varying the layer thickness and the sample size. The dimensional accuracy of the ADAM process is evaluated using the ISO IT grades of a reference artefact. Due to the deposition strategy, the final density of the material results in being strongly dependent on the layer thickness and the size of the sample. The density of the material is low if compared to the material processed by powder bed AM processes. The superficial roughness is strongly dependent upon the layer thickness, but higher than that of other metal additive manufacturing processes because of the use of raw material in the filament form. The accuracy of the process achieves the IT13 grade that is comparable to that of traditional processes for the production of semi-finished metal parts.

3D printing is one of the most interactive recent manufacturing technologies at both design and manufacturing levels. To date, the interest and involvement that people have shown towards the possibility to model and produce parts by themselves have boosted the proliferation of 3D printers. Nevertheless, an uncorrected design or a design that does not fit the machine capabilities could lead to parts with poor aesthetic features that reduce the user-perceived quality and the expectation of the easy user-usability of the technology. The purpose of this paper is to validate the robustness of the aesthetic quality index (AQI) that is used for the evaluation of the user-perceived quality of 3D printed parts. A specific reference part that was designed for 3D printing defects to have a high probability of occurrence is considered to be representative and greatly significant for the aesthetic quality of 3D printed parts. In this work a replica of the reference part is printed with three different 3D printers and evaluated by nine users. An additional replica is also produced for consistency assessment, and the quality evaluation test was repeated twice in 1 month. The AQI indicator results to be consistent and robust over the users and time. The measure of the AQI and the reference part seem user-friendly tools and may provide a useful design-aid for an immediate understanding of the feasibility of a specific design feature in a framework of user interactivity.

An additive manufacturing process should produce repeatable results as far as the properties of the material and the geometric dimensions that have to be adopted by a company as a production method are concerned. This represents a challenge for such high-volume sectors as the automotive industry, where quality and reliability are extremely important. One way of addressing this challenge is to qualify the process. A common framework has here been identified starting from the analysis of the factors that influence the stability of the result in the main phases of metal powder bed fusion (PBF) processes. A qualification procedure (QP), which offers possible solutions to help reduce risk factors, has been proposed. This procedure is independent of the industrial sectors, of which type of materials and metal PBF processes, and of the manufacturer of the used PBF system.

Additive manufacturing technologies are currently envisaged to boost the development of a next generation of microwave devices intended for satellite telecommunications. Due to their excellent electromagnetic and mechanical properties, metal waveguide components are key building blocks of several radio frequency (RF) systems used in these applications. This article reports the perspectives deriving from the use of laser powder bed fusion (L-PBF) technology to the production of high-performance microwave waveguide devices. A robust design of filters has been implemented in several prototypes manufactured in AlSi10Mg alloy. The corresponding measured performance confirm the applicability of the L-PBF process to the intended applications

Part 11: 3D Printing and Additive Manufacturing; International audience; The comprehensive approach to the development of a product should analysis all of the phases, from the design to the manufacturing for the selection of a good combination of materials, designs and manufacturing processes. Due to the complexity of addressing an all-inclusive problem, the decision is usually entrusted to the manufacturing engineers for which products that have producible features easily and simple geometries are desirable, even if sacrificing the component performances. However, today, Additive Manufacturing (AM) processes offer a wide degree of design freedom that allows overcoming the traditional manufacturing limitations.The aim of this paper is to provide a thorough review of the process selection (PS) approaches by taking into account manufacturing technologies in conjunction with the material and design performance. The paper attempts to provide as result a basic and generic methodology, which provides guidelines for the effective introduction of the AM processes in the process selection problem.