Abstract: Mounds of spatter are generated in laser powder-bed fusion (L-PBF) additive manufacturing, which reduces build quality and laser lifetime. Due to the lack of supplemental airflow above the chamber, the conventional build chamber with a single gas inlet exhibits a pronounced tendency for gas to flow upward near the outlet. This phenomenon results in the formation of a large vortex within the build chamber. The vortex leads to the chaotic motion trajectory of the spatter in the build chamber. The design defects of the existing build chamber based on dual gas inlets are shown in this paper. We established a coupled computational fluid dynamics-discrete phase model (CFD-DPM) model to optimize the build chamber by adjusting the position and structure of the second gas inlet. The homogeneity of the flow is increased with a distance of 379 mm between the two inlets and a wider-reaching second inlet. The Coanda effect is also crucial in the spatter-removal process. The Coanda effect is reduced by modifying the right sidewall of the build chamber and increasing the pressure difference between the inlet and outlet. Finally, we found that the spatter-removal rate rose from 8.9% to 76.1% between the conventional build chamber with a single gas inlet and the optimized build chamber with two gas inlets.

Key words: Laser powder-bed fusion (L-PBF); Computational fluid dynamics (CFD); Flow field simulation; Structural optimization; Coanda effect

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