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Support structures are used in especially overhang areas in laser metal additive manufacturing to prevent parts from distortion due to high thermal gradients. Since the support structures are not a part of the final component, extra time and material are needed for manufacturing. Moreover, they need to be removed after the build is completed. In ad...
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Short Abstract While additive manufacturing enables fast production of parts with high geometrical complexity, the post-processing step for obtaining high-quality surfaces of these parts is getting increasingly difficult. In addition, not all state-of-the-art polishing techniques are capable of achieving satisfactory results. Moreover, many of them...
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... The result shows that the specimen is fabricated by a bi-directional line scanning along with the 67º rot-scan strategy. The obtained R a value of the formed surface is 9.415 µm, and the R q value is 11.862 µm, respectively, which is improved compared to the past studies on the fabrication of SS 316L [41,42]. The 2D surface roughness profile was captured at five different locations named slices 1 to 5 and depicted in Fig. 2(b and c). ...
This study aims to compare the microstructural and biotribological behavior of additively manufactured and commercially available stainless steel 316L (SS 316L) implants under simulated body fluid. The surface integrity, microstructures, and micro-hardness characterizations were performed. FESEM micrographs and 3D surface profiles dictate that the specimen is manufactured using a bi-directional 67º rot-scanning strategy. Further, the microstructure, XRD, and micro-hardness outcomes dictate that the selective laser melted (SLMed) sample has an anisotropic fine-grained (18.49 µm) gamma austenite phase with an improved hardness of 280.35HV0.05, which is 146% higher compared to casted counterpart. In-vitro state biotribological results indicate that the SLMed part has a minimum coefficient of friction (COF: 0.287) value under simulated body fluid, which is 58% less than the casted part (COF: 0.494), and an improved volumetric wear loss at different loading conditions was also observed. The obtained outcomes dictate that selective laser melting is a better processing route to manufacture SS 316L permanent implants with enhanced microstructural, mechanical, and biotribological behavior.
... The regression polynomial for the weight of the biomass composite workpiece consumables m is shown in Equation (14). The model has R 2 = 0.9998, Adjusted R 2 = 0.9998, Predicted R 2 = 0.9996, and the signal-to-noise ratio of this polynomial is 272.6389 ...
When using selective laser sintering to print parts with thin-walled structures, the thermal action of the laser can cause thermal stresses that lead to plastic deformation, resulting in large warpage and dimensional deviations. To address this issue, this study proposes a bottom support method for selective laser sintering. The impact of lattice-type, concentric-type, and cross-type support structures with varying filling densities and thicknesses on the suppression of warpage and dimensional errors was investigated. The optimal process parameters for each support structure were then determined through optimization. The findings of this study demonstrated a reduction in Z-axis dimensional errors of the workpiece following the addition of supports. The reduction amounted to 33.809%, 86.160%, and 66.214%, respectively, compared to the original workpiece. Moreover, the corresponding warpage was reduced by 35.673%, 46.189%, and 46.059% for each respective case, showcasing an improvement in the printing precision. Therefore, the bottom support effectively reduces dimensional and shape errors in thin-walled parts printed by selective laser sintering. Specifically, the results obtained indicated that the concentric type of support is more effective in reducing dimensional errors and enhancing the shape accuracy of the printed workpiece. Conversely, the cross type of support demonstrated superior capabilities in minimizing the consumption of printing materials while still delivering satisfactory results. Thus, this study holds promise for contributing to the advancement of thin-walled part quality using selective laser sintering technology. This research can contribute to achieving greater accuracy in the fabrication of parts through 3D printing.
... Since lower average thickness deviation means higher performance, it can be concluded from Fig. 11 that contactless support with 1.27 mm support thickness and 0.51 mm support spacing is the optimum parameter set for the lowest average thickness deviation in the scope of the experimental set used in this study. It was also observed in the literature that dimensional accuracy for contactless supported specimens is related to not only support thickness and support spacing but also support gap [37]. On the other hand, line support with 0.76 mm support thickness and 1.02 mm support spacing is the worst parameter set for the highest average thickness deviation. ...
Additive manufacturing technologies give engineers and researchers a high level of design freedom to produce complex components or entire assemblies previously impossible or impractical to manufacture by conventional means. Although additive manufacturing has many advantages compared to conventional machining, it has some drawbacks, two of which are higher surface roughness and dimensional inaccuracy of as-built part surfaces especially in overhang features. Support structures are one of the solutions to mitigate these drawbacks at a cost of additional post-processing efforts. The aim of the present study is to investigate the effect of different support geometries on the mechanical properties of laser powder bed fusion manufactured Inconel 718 overhang parts. The tested support geometries are comprised of several pieces to ease post-processing instead of using single-piece supports filling all over the overhang surface. One of the tested support structures is contactless support with no direct contact between the part and the support itself. The others are tooth support where the contact is on the tooth faces and line support where the contact is along a line. The thickness of each support piece and the spacing between the two support pieces were used as design variables. The dimensional accuracy of printed specimens with respect to the computer-aided geometry, distortion of overhang features, microhardness through the thickness, microstructural changes of overhang surface, and surface roughness of overhang features was experimentally evaluated. The results revealed that support type, support spacing and support thickness directly affect the performance characteristics used in this study.
... The optimum gap distance was identified based on observing no partial connection between the support and component due to excessive powder fusion and not getting too far to completely eliminate thermal conduction. In a follow-up work [49], the effect of distance between contactless support parts, the thickness of each support pieces, and the spacing between two contactless support pieces on the dimensional accuracy, Fig. 4 a Tree-like support, b Bar support, and c Tree-like support with 0.4 mm stem diameter that failed during the build [7] microhardness, microstructure, and distortion of samples were studied. It was observed that by decreasing support thickness, support spacing, and support gap, dimensional deviation and surface roughness decreased. ...
The use of support structures is an essential requirement for powder-bed fusion additive manufacturing (AM) processes. Supports are responsible for fixing the component on the build plate, carrying the weight of the structure, providing heat dissipation from the component to the build plate and preventing distortion during the process. Support efficiency and performance can be evaluated through the ease of removability, strength, thermal management, cost-effectiveness, and material consumption. As the support structures are the waste material during manufacturing of metal AM components, their design has a significant impact on the productivity and cost of the manufacturing process. Due to lack of concentrated information on the effect of each mentioned support function, this paper aims to gather studies and innovations in support design and production, specifically for the powder-bed fusion methods. At first, the effect of support type and contributing geometrical parameters on the overall performance of support structures is discussed. Then, an in-detail approach is taken to categorize each key characteristics of metallic support structures and reinforce the discussion with related published papers. Finally, the role of topology optimization (TO) in designing optimum support geometry is presented. The overall conclusion is that unless there are several studies on design and manufacturing of support structures, achieving the best setup has not been guaranteed by the existing tools. The research trend is toward developing more cost-effective optimization methods based on genetic algorithms (GA) and multi-objective functions to generate automated and high-performance supports, especially for complex geometries. Furthermore, integrating AM constraints with GA and TO can be achieved through defining self-supporting index or coupling with multi-objective optimization methods, which leads to a more efficient solution.
In laser powder bed fusion additive manufacturing support, structures are crucial for constructing overhang features and maintaining dimensional accuracy. However, traditional support structures exhibit inherent drawbacks, including compromised surface quality, prolonged postprocessing times, and other challenging requirements. This study investigates innovative approaches to address these issues by analyzing two types of specimens—cuboid and lap shear. The cuboid samples explore the manipulation of process parameters to adjust energy densities, transitioning from powder to porous support structures, with porosity measurement assessment. Subsequently, a shear test specimen objectively evaluates porous support parameters alongside traditional block‐type support, analyzing their impact on removal force, distortion, and surface quality. Results reveal that optimized porous support structures surpass traditional counterparts, showcasing superior surface quality, reduced removal forces, and minimized part distortion. Specifically, the shear test demonstrates a 94.25% reduction in removal forces and a 33.67% decrease in upper part distortion. Moreover, the maximum surface roughness (Rz) improves by 22.8% with the implementation of porous supports. By introducing a methodology for comparative analyses of measurable performance indicators, this research enhances understanding of support structure dynamics in additive manufacturing, facilitating advancements in efficiency and quality within the field.
Warpage deformation inevitably occurs when laser powder bed fusion (LPBF) is applied on an overhanging structure. An effective support added to the system can mitigate warpage and improve the accuracy of formed parts. Four types of support structures are designed, and sheet tensile specimens and overhanging structures with different support structures are fabricated in this study. The tensile failure behavior and warpage suppression ability of different support structures are investigated, with the relation of the support influence to the design of support structure analyzed. The results show that the support with reinforcement can effectively restrain warpage deformation of the overhanging structure. During the process of tension, the main failure area of the support structure is located on the top of the support structure, close to the overhanging solid body. Increasing the change ratio of the support cross-sectional area is helpful to improve the constraint ability of the support. This design provides a new method for accurate forming of overhanging structures via LPBF and evaluating the restrain ability of support structures.
Owing to its excellent mechanical properties, triply periodic minimum surfaces (TPMS) lattice structures have recently gained more interest in engineering applications. The superior properties of these structures make it easier to achieve engineering design goals such as strength and weight. However, technological advancements compel the designer to enhance the traditional TPMS design qualities. Hybridization of different lattice types emerges as a strong candidate for enhancing overall design performance. Therefore, a hybrid optimization scheme based on genetic algorithms (GA) and anisotropic homogenization-based topology optimization is considered to generate a functionally graded multi-morphology for a Messerschmitt–Bölkow–Blohm (MBB) beam design in this paper. The GA is performed to identify the best lattice morphology, including Diamond (D), Gyroid (G), I-WP, and Primitive (P), and their relative densities prior to topology optimization (TO). Once the best lattice morphology of the design domain is obtained via the GA, the homogenization-based topology optimization is applied to grade the multi-morphology lattice to improve the design performance further. The final step is the reconstruction of the graded multi-morphology using a novel blending algorithm. The reconstructed MBB beams are made of cobalt-chromium (CoCr) alloy and are then manufactured using the laser sintering method, direct metal laser melting (DMLM) technique. Destructive metallographic and non-destructive metrological techniques are utilized to assure manufacturing quality. An impact hammer test is conducted on the fabricated beams to validate and compare the proposed graded multi-morphology geometry with graded and uniform single lattice morphologies. Experimental results show that the stiffness of the graded multi-morphology structure designed by the proposed hybrid optimization is 4.5 % and 13.0 % higher than the graded form of D and P-type single lattice morphologies, respectively. Also, it is observed that the graded form single lattice morphologies deliver superior performance than their uniform encounters namely D and P-type lattice structures.
