Position Dependency of Surface Roughness in Parts from Laser Beam Melting Systems

Laser Beam Melting is a promising Additive Manufacturing technology for the production of complex metal components. During batch production of multiple identical parts in a single build job, we observed parts with deviating surface roughness in certain areas, which all faced away from the laser. This suggests a dependency of surface roughness on the part position in the build chamber. In this work we systematically reproduce and analyze this effect. We place hollow pyramids with twelve faces and two different overhanging angles at nine positions on the substrate plate and build this setup twice, using an imaging setup for process documentation. Surface roughness is measured by contact profilometry on three lines for each pyramid face. Our experiments reproduce the effect. Based on these findings we present a hypothesis for the cause and show metallographic images to support our theory. As a consequence, the position relative to the laser should be considered in the design phase for parts with high surface quality requirements.