Design and Implementation of an Experimental and Numerical Framework for Powder Recoating Research in Selective Laser Melting
Massachusetts Institute of Technology Cambridge United States
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Selective Laser Melting SLM of powders remains one of the most captivating methods to additively manufacture fully dense, 3-dimensional metal parts. The process occurs largely in two steps. First a metal powder is spread in a thin layer on a powder bed. Second the powder is radiated by a laser. Most SLM research has focused on the second step, despite the powder bed being the foundation of the lasing process. Research has shown that the powder bed properties, such as packing density and uniformity are key to creating robust SLM parts.This thesis aims to explore the powder recoating process and establish a framework for research. The thesis focuses on experimental and computational methods to study powder recoating. An instrumented recoater was built with the capability to measure forces and vary important recoating parameters, such as recoating velocity, blade height and blade geometry. The instrumented recoater was then manufactured, assembled, tested and incorporated into an academic SLM testbed. On the computational side, a Discrete Element Method DEM code was calibrated to account for the cohesive forces present in SLM powder. Simulations using the code were able to demonstrate the significance of cohesive forces in the powder recoating process and demonstrate the influence of recoating parameters on powder bed properties. The experimental and computational work presented in this thesis lay the foundation for future powder bed research.
- Manufacturing and Industrial Engineering and Control of Production Systems