?How can the surface roughness of side walls be improved by using the orientation method to finish LPBF copper printing
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Date
2024
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Publisher
University of Nottingham
Abstract
This research examined the effect of laser power, spot size, scan speed, hatch spacing, layer height, and contour scanning on the surface roughness of the side walls of the copper specimens fabricated by Laser Beam Powder Fusion (LBPF). The experiments were done on LBPF machines, where the optimum parameters were set to improve the surface quality, and EOS copper CuCP powder was used. The laser power of 700 W and the spot size of 80 microns were kept constant to produce a steady melt pool and to control surface defects like balling and spattering. The scan speed was set to 550 mm/s, and the hatching distance was maintained at 210 microns to regulate the energy density and uniformity of the material laid down to avoid surface roughness. A lower layer height of 40 microns with refined contour scanning also helped enhance the surface finish of the side walls. All the surface roughness measurements were taken with Alicona G5 using the side walls of the microstructures instead of the top surface. Findings indicated that the variation of LBPF parameters directly impacted the surface finish, which is essential for aerospace, medical, and electronics applications. The results are useful in identifying appropriate configurations for LBPF variables to achieve better surface textures, little or no finishing required, and increased throughputs.
Description
Directions for further research are available to enhance surface roughness in LBPF processes. Improvement of powder preparation methods, including the investigation of ways of handling copper powder other than gas atomization, may lead to the production of better-quality copper powders. Improving powder preparation technique especially in areas of the choice of gas atomization to enhance surface roughness in LBPF processes. Highly irregular and variable gas atomization exposes the powders to the creation of particle shapes and sizes, which affect the flow and distribution of powders in printing. In the case where either plasma atomization or mechanical milling is used, powders with better morphology and more optimized size distribution could be prepared. This would enhance the uniformity of the powder bed to result in better layers in deposition and a reduction of imperfections such as balling, spattering, or insufficient fusing. Therefore, these improvements would lead to skin layer side wall surface finish that is smoother and more uniform, quality of printed parts would be improved and less post processing would be needed.
Creating a new generation of thermal control systems capable of providing feedback can maintain the melt pool steadily and, thus, decrease the number of defects. Exploring the strategies in contour scanning and using machine learning for predictive modelling and contour scanning process optimizations is very promising. Contouring which is the use of laser energy to focus on the contour of the part in the finishing phase can prove beneficial in that the finer control of the melt pool is achievable and layer adhesion enhanced. By performing machine learning on historical printing data it becomes possible to determine by the use of different algorithms the best scanning technique, laser power, speed of the scan and spacing of the hatch for use on different materials and geometries. The directions can improve the effectiveness of LBPF-printed parts, leading to better surface finishes and performance in many industrial uses.
Keywords
Laser Beam Powder Fusion (LBPF), surface roughness, parameters, Alicona G5, side walls
Citation
Harvard