A statistical approach for the characterization of Additive Manufacturing (AM) processes is presented in this paper. Design of Experiments (DOE) and ANalysis of VAriance (ANOVA), both based on Nested Effects Modeling (NEM) technique, are adopted to assess the effect of different laser exposure strategies on physical and mechanical properties of AlSi10Mg parts produced by Direct Metal Laser Sintering (DMLS). Due to the wide industrial interest in AM technologies in many different fields, it is extremely important to ensure high parts performances and productivity. For this aim, the present paper focuses on the evaluation of tensile properties of specimens built with different laser exposure strategies. Two optimal laser parameters settings, in terms of both process quality (part performances) and productivity (part build rate), are identified.
Additive manufacturing refers to a wide class of manufacturing processes based on the progressive building of functional parts through the addition of material layer upon layer. These technologies were first confined to prototyping, but the subsequent development of additive manufacturing processes for further materials, such as metals, has encouraged their worldwide industrial spread, from the biomedical field to the automotive and the aerospace industries. Additively manufactured parts are required to meet high and stable performance, at least comparable to that of conventional wrought materials, so as to comply with strict and well-defined international standards. This paper presents an investigation into the mechanical properties of AlSi10Mg parts produced by laser powder bed fusion technique, using different spatial orientations within the build volume. The effects of the part position and orientation on the static (tensile) properties of the produced parts were assessed by means of the two-way analysis of variance technique. The build angle was found to be the most effective parameter, while the variability ascribable to the effect of part position resulted mainly as physiological. The fatigue resistance showed a globally decreasing trend with increasing build angle.
Ti-6Al-4V alloy is characterised by having excellent mechanical properties and corrosion resistance combined with low specific weight and biocompatibility. This material is ideal for many high-performance engineering applications. It is increasingly used in additive manufacturing (AM) thanks to the possibility of producing very complex lightweight structures, often not achievable with conventional manufacturing techniques, as well as to easily customise products according to specific customer requirements. In powder bed fusion (PBF) processes, only a small percentage of the powder is actually melted and solidified to achieve the final part while most is left after the build. Since the surface morphology and chemistry, the shape and size distribution of the un-melted particles are inevitably modified during the process, and this may affect the resulting properties of the final products, many companies tend to use virgin powders for AM builds to keep compliance with manufacturing requirements and minimise risk. From both an economic and environmental point of view, it results crucial to develop recycling methods to reuse the metal powder as many times as possible while maintaining compliance with manufacturing standards. In this work, the effect of Ti-6Al-4V powder reuse on the evolution of powder characteristics and mechanical properties of final products additively manufactured is investigated through a systematic approach based on design of experiments.
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