CFD-based optimization of shielding gas flow in large-format selective laser melting

Abstract

In the large-format selective laser melting (SLM) process, the flow field uniformity of the shielding gas inside the build chamber significantly affects the build quality. To address this issue in large-format SLM systems, this study establishes a three-dimensional computational fluid dynamics (CFD) model incorporating the realistic geometry of the chamber and optical window, and systematically investigates the effects of different duct structures and inlet/outlet layouts on the velocity distribution across the powder bed. Simulation results indicate that the optimized inlet rectification structure can reduce the velocity non-uniformity coefficient on the powder bed by about 30% compared with the baseline case. In addition, vortical structures and low-velocity regions are largely suppressed. This improvement enhances spatter and fume removal, which is expected to reduce porosity and surface roughness—key factors for part accuracy and surface finish. These comparative results offer practical design priorities for the gas circulation systems of next-generation large-format SLM machines, particularly regarding diffuser geometry and inlet rectification.