Effect of Gas Flow Rate and Powder Size on Selective Laser Melting Process in a Renishaw AM 250 Build Chamber

Additive Manufacturing is a revolutionary new technique of manufacturing objects using a bottom-up approach and is expected to play a significant role in digitizing the manufacturing sector and enabling industry 4.0. Among the various metal additive manufacturing techniques, powder bed Selective Laser Melting (SLM) is gaining attention in various domains from aerospace to medical sectors due to its high accuracy and feature resolution. However, the quality and repeatability of the parts manufactured by the additive manufacturing facilities is still not consistent and depends on several parameters some of which are inert gas flow rate and powder size distribution. In the proposed study, a detailed flow analysis will be performed in the build chamber of a Renishaw AM 250 machine using commercial CFD code ANSYS Fluent [1]. A parametric study will be conducted by varying the flow rates and inlet/outlet designs for each powder size distribution. The simulations will assist in identifying the gas flow conditions that can improve uniformity of flow distribution within the build chamber and its possible dependence on the powder size. Different levels of model complexity/details will be incorporated in conducting numerical simulations to identify the effective gas flow rates. The effective gas flow rates will initially be identified for a single-phase inert gas flow situation while neglecting the spattering of particles. Simulations will be conducted for multiple designs of inlet and outlet with the goal of achieving uniform distribution. Next, the spattering particles will be incorporated into the simulation through the use of discrete phase model (multi-phase flow model) and the effect of particles size on the inert gas flow distribution will be determined. The results from this study are expected to provide effective designs of gas flow inlet and outlet in addition to providing effective gas flow rates for different particles size distributions. The proposed study will provide a good starting point to develop a better understanding of the gas flow distribution in the SLM build chamber, which is one of the key parameters in improving the robustness and repeatability of the final product in additive manufacturing.