Predicting recoater interference in laser powder bed fusion process by considering both global thermal deformation and local edge deformation using the modified inherent strain method

Abstract

Preventing recoater interference and crash is essential in the laser powder bed fusion (L-PBF) process for printing parts with overhangs, as these issues compromise product quality by increasing surface roughness, reducing dimensional accuracy, and introducing defects into the parts. This work proposes an integrated simulation and experimental framework to predict initial recoater interference for a given part designed for L-PBF fabrication. In this framework, the criterion for recoater interference is defined to occur at an overhang edge when its deformation in the build direction exceeds the thickness of a newly spread powder layer after recoating. The build-directional deformation at an overhang edge is postulated to be the sum of two contributions: global thermal deformation and local edge deformation. The global thermal deformation, generated by the relaxation of thermal stresses induced by rapid laser melting and solidification over the entire part, is predicted using the modified inherent strain (MIS) method. A key novelty of this work lies in employing location-dependent inherent strains (ISs) in the MIS method for overhangs, which shows a 65 % improvement in the prediction accuracy of the global thermal deformation compared to using constant ISs. The local edge deformation, associated with the melt pool dynamics and induced near the edge, is estimated by reconciling the MIS simulated and experimentally measured deformation on several overhang wedges. The validity of the proposed framework for predicting recoater interference is confirmed by experiments on different part geometries with overhangs.