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Abstract: Knowledge of defect formation mechanisms in the manufacturing process helps improve product quality. In this study, defect formation due to re-melting of each layer in selective laser melting of Ti-6Al-4V demonstrated the physical behavior in the manufacture of metallic parts. The re-melting strategy was based on scanning with low energy density (ED) and increased ED with various combinations of laser processing parameters. The increased EDs and their parameters, namely laser power, scanning speed, and hatch distance, were selected based on the previous research experience by the authors. The concept of selecting a low ED followed by a high ED was to reduce the spattering of the powder material during the process. The low ED caused partial sintering of the powder, while the high ED caused the melting of the material, resulting in different metallurgical properties of the manufactured parts. Densities, pore properties, porosity in the initial layers, surface morphologies, and microstructures in the defective areas of the samples were studied to determine the effects of re-melting. Advantages and disadvantages were found with respect to the range of applications of the products
Keywords: re-melting, pore properties, defect, surface morphology, Ti-6Al-4V, selective laser melting
Published in DKUM: 14.03.2025; Views: 0; Downloads: 2
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Abstract: This article has presented a technical concept for producing precisely desired Additive Manufactured (AM) metallic products using Artificial Intelligence (AI). Due to the stochastic nature of the metallic AM process, which causes a greater variance in product properties compared to traditional manufacturing processes, significant inaccuracies in metallurgical properties, as well as geometry, occur. The physics behind these phenomena are related to the melting process, bonding, cooling rate, shrinkage, support condition, part orientation. However, by controlling these phenomena, a wide range of product features can be achieved using the fabricating parameters. A variety of fabricating parameters are involved in the metal AM process, but an appropriate combination of these parameters for a given material is required to obtain an accurate and desired product. Zero defect product can be achieved by controlling these parameters by implementing Knowledge-Based System (KBS). A suitable combination of manufacturing parameters can be determined using mathematical tools with AI, considering the manufacturing time and cost. The knowledge required to integrate AM manufacturing characteristics and constraints into the design and fabricating process is beyond the capabilities of any single engineer. Concurrent Engineering enables the integration of design and manufacturing to enable trades based not only on product performance, but also on other criteria that are not easily evaluated, such as production capability and support. A decision support system or KBS that can guide manufacturing issues during the preliminary design process would be an invaluable tool for system designers. The main objective of this paper is to clearly describe the metal AM manufacturing process problem and show how to develop a KBS for manufacturing process determination.
Keywords: metallurgical properties, geometry, additive manufacturing, artificial intelligence, knowledge-based system
Published in DKUM: 25.09.2024; Views: 0; Downloads: 9
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Abstract: The selective laser melting (SLM) process for manufacturing metals continues to be challenging in terms of achieving the maximum metallurgical properties that the process can provide. There are a variety of manufacturing parameters in the process that have individual characteristics, and when combined with other variables, the characteristics can be varied. However, in this study, the two most important manufacturing parameters, namely build direction and laser power, were considered to investigate their effects on density and tensile properties. Previously, the best scanning speed, hatch spacing, and layer thickness were determined, which directly affect the volumetric energy density in the SLM process. In this study, three different orientations and three different laser powers were selected, namely the X, Y, and Z directions and 55 W, 75 W, and 95 W laser power, respectively. Significant differences in product density were observed for the samples fabricated in the different orientations and with the different laser powers. The specimens fabricated in the Z direction always exhibit higher strength and ductility, which are significantly different from the specimens fabricated in the X and Y directions, while the laser power was 75 W and 95 W, respectively
Keywords: cobalt-chromium alloy, orientation, density, tensile strength, ductility, selective laser melting
Published in DKUM: 25.09.2024; Views: 0; Downloads: 8
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Abstract: When manufacturing complicated products where both material and design play a role, especially thin and curved components, it is difcult to maintain accurate dimensions in Selective Laser Melting. Considering these difculties, this article presents the dimensional errors in the fabrication of Ti-6Al-4V discs and their thermomechanics during manufacturing. Various combinations of laser processing parameters were used to fabricate the 2.00 mm thick discs with a diameter of 5.70 mm. It was found that the thickness shortened and the round shape changed to an oval shape for most of the discs. The thickness decreased along the build-up direction from the bottom to the top and formed a taper that increased with increasing energy density (ED). The horizontal diameter of the discs changed slightly, while the vertical diameters changed remarkably with increasing ED. On the other hand, reducing the laser power resulted in a reduction of the roundness error, while it caused a reduction of the thickness. The hatch spacing signifcantly afected the volume of the melt pool and caused a change in the vertical diameter. The central part of the curved surface of the discs became concave and the concavity increased due to the increasing ED.
Keywords: dimension, Ti-6Al-4V, lase power, scanning speed, hatch spacing, selective laser melting
Published in DKUM: 29.03.2024; Views: 219; Downloads: 9
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Abstract: Technological parameters included in energy density (ED) are the more powerful tools in selective laser melting (SLM) technology which can be used in the time of fabrication to regulate chemical, metallurgical, and mechanical properties of a product. The volumetric Energy Density (ED) depends on the energy input employed by the laser power, scanning speed, hatch spacing, and the layer thickness. Density, microstructure, surface morphology, dimension accuracy, strength and porosity including the number of pores, place of the pore, size of a pore shape of a pore, inclusions of pores of an SLM product depends on the processing parameters. As the powder material fusion process is done by track by track and layer by layer, the architecture of the microstructure in a product is oriented as the direction of building up too. The research has emphasized on metallurgical properties, tensile properties, and producing the non-porous products from Ti-6Al-4V alloy powder and surface modification using bioactive polymer for orthopedic application. The research has followed four steps to study the metallurgical properties and finding out the combinations of technological parameters in producing non-porous products. The purpose of the first step of the study was to examine the effects of ED on the product properties and to obtain an optimum ED as well as the optimal range of scanning speed. The second step of the study has focused on the influences of laser power. The third step of the study has investigated the effect of amounts of track overlapping and hatch spacing. Almost a zero-porosity product has been able to produce by following these three steps of the ongoing research. The fourth step has studied the metallurgical properties emphasizing on re-melting of every layer. High-density products have been found in the fourth step where a small amount of very small sized pores are present as a result of keyhole effect and gaseous bubble entrapment mainly. Four buildup orientations have been selected for each ED in the first step of the study to examine the tensile properties of the products. The best buildup orientation has been seen in longitudinally vertical tensile specimens considering tensile properties. The tensile properties have also been studied in the second and third step of the study with best build up orientation of the tensile specimens. The alterations of metallurgical and tensile properties have also been investigated after heat-treatment of the specific samples. Dimensional accuracies were also invigilated on the cubic, and tensile specimens over the studies and consequently, inaccuracies have been noticed. The fifth step of the study has observed the pore properties, adhesion properties, the compressive strength of gelatin coating manufactured using unidirectional freezing and the freeze-drying process of three different gelatin concentrations on four different surfaced Ti-6Al-4V alloy substrates. The results indicate that the coating properties depend on the substrate’s surface texture as well as the concentration of gelatin. Above 80% of porosity, interconnected and well-aligned pores of 75-200 μm have been obtained which is required to stimulate bone ingrowth histologically.
Keywords: selective laser melting, unidirectional freezing, fabricating parameters, porosity, microstructure, mechanical strength
Published in DKUM: 01.04.2019; Views: 1896; Downloads: 147
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