Abstract

In metal laser powder bed fusion (L-PBF), repetitive melting and solidification of newly added layers lead to thermal stresses and distortions during part build-up. Particularly at critical component features such as unsupported overhangs, elevated edges pose a risk in terms of crashes with the recoating system during powder spreading. Damaged recoater lips lead to irregularities in the form of stripes in the powder bed. This local inhomogeneity affects not only the part that caused the crash, but also the adjacent parts on the build plate. In order to minimize waste caused by insufficient part quality due to damaged recoater lips, we investigate the properties of parts after recoater crashes occurred during the build job. In this work, we use a part-scale thermomechanical Finite Element (FE) model to estimate the risk of recoater crashes. The FE model predicts initial interferences and the subsequent crashes between elevating part edges and the recoating system. The simulation results are validated by images of the powder layers from the L-PBF machine’s layer control system (LCS) as well as by optical measurements of the depths of grooves on the rubber lip. We conduct experiments to evaluate the geometric deviation, surface roughness, porosity, hardness and tensile properties of damage-causing and damage-affected specimen. Based on the simulative and experimental results and taking into account component-specific quality requirements, we provide recommendations for the usability of parts after recoater crashes.