Analysis of Density, Roughness, and Accuracy of the Atomic Diffusion Additive Manufacturing (ADAM) Process for Metal Parts

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

A Finite Element approach for the prediction of the mechanical behaviour of layered composites produced by Continuous Filament Fabrication ({CFF})

Continuous Filament Fabrication (CFF) is the additive manufacturing process for producing material reinforced with long fibres. Differently from other processes, CFF allows producing components in composite materials without using tools, moulds or post-processing operations and with a strengthened area only where it is strictly required. This innovative way of producing composites makes a new design approach necessary for better exploitation of the material. This work presents a preliminary study based on 3D Finite Element (FE) method to predict the mechanical behaviour of composite materials fabricated by CFF. With this aim, a FE model is developed to determine the actual material properties in terms of longitudinal, transverse and shear modulus. Comparisons between experimental and numerical tensile results at different fibre orientations validate the model. The robustness of the proposed approach is confirmed by the comparison with the experimental characterisation of composites produced with two different fibre reinforcements, Carbon and Kevlar®

Surface Roughness Characterisation and Analysis of the Electron Beam Melting (EBM) Process

Electron Beam Melting (EBM) is a metal powder bed fusion (PBF) process in which the heat source is an electron beam. Differently from other metal PBF processes, today, EBM is used for mass production. As-built EBM parts are clearly recognisable by their surface roughness, which is, in some cases, one of the major limitations of the EBM process. The aim of this work is to investigate the effects of the orientation and the slope of the EBM surfaces on the surface roughness. Additionally, the machine repeatability is studied by measuring the roughness of surfaces built at different positions on the start plate. To these aims, a specific artefact was designed. Replicas of the artefact were produced using an Arcam A2X machine and Ti6Al4V powder. Descriptive and inferential statistical methods were applied to investigate whether the surface morphology was affected by process factors. The results show significant differences between the upward and downward surfaces. The upward surfaces appear less rough than the downward ones, for which a lower standard deviation was obtained in the results. The roughness of the upward surfaces is linearly influenced by the sloping angle, while the heat distribution on the cross-section was found to be a key factor in explaining the roughness of the downward surfaces

Additive manufacturing redesigning of metallic parts for high precision machines

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 microelectromechanical 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

Experimental analysis of residual stresses on AlSi10Mg parts produced by means of Selective Laser Melting (SLM)

Abstract During the Selective Laser Melting (SLM) process, the scanned layers are subjected to rapid thermal cycles. Steep temperature gradients generate residual stresses. Residual stresses can be detrimental to the proper functioning and the structural integrity of built parts. In this paper, the semi-destructive hole-drilling method has been used to measure the residual stresses on AISi10Mg parts after building, stress relieving and shot-peening, respectively. The outcomes have shown the presence, on the as-built components, of high tensile stresses that the usual post-processing operations are not able to minimize. The adopted method has proved to be a suitable tool to identify optimal process parameters for each step of the production cycle

Redesigning a flexural joint for metal-based additive manufacturing

Traditional rigid mechanisms exhibit problems such as assembly difficulties, friction and lubrification. Flexure-based compliant mechanisms, instead, are monolithic and gain their mobility thanks to proper design and materialdeflection. Designing and producing a compliant mechanism accurately and conveniently iscrucial. Thanks to its capabilities, additive manufacturing (AM) approach can provide optimal design and production and open the way to new, unexploited performances. This study investigates the redesign of a traditional cantilevered pivot. The redesign considers the performance improvements by exploiting the advantages of the AM based on laser powder bed fusion (L-PBF). The maximum tensileand compressive loads of the redesigned joint were identified. The structure was optimised by considering the most critical geometricalparameters in terms of mechanical performance. The geometricalfactorscomply with the design rules for L-PBF process, to maximise the dimensional and surface accuracies.The new approach to the flexural joint design presented in this paper provided higher mobility if compared with the traditional approach. Therefore, this study makes a major contribution to research on the production of precision alignment mechanisms and scientific instruments

The Use of Self-replicated Parts for Improving the Design and the Accuracy of a Low-cost 3D Printer

Abstract Low-cost entry-level 3D printers suffer from reduced optimization, that is a consequence of development cost savings. A student challenge was used to modify four Prusa i3 machines with the aim of enhancing the design and performances by means of self-replicated parts. The challenge results were assessed through benchmarking of the four modified 3D printers, whose dimensional accuracy was evaluated by means of CMM measurements of 3D printed replicas of a reference part. The ISO IT grades related to the dimensional quality of the replicas were considered in the analysis of the CMM measures for the challenge assessment

Accuracy of down-facing surfaces in complex internal channels produced by laser powder bed fusion (L-PBF)

5noAdditive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite communication systems, electronics and gas turbine airfoils. These applications can have complex shape and make traditional finishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces be as close as possible to the tolerance of the field of application. In this study, a complex component was designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Using the data from the 3D scans, internal surface roughness and deviations from the CAD model were calculated.openopenCalignano F.; Iuliano L.; Galati M.; Minetola P.; Marchiandi G.Calignano, F.; Iuliano, L.; Galati, M.; Minetola, P.; Marchiandi, G