Tracking and controlling the morphology evolution of 3D powder-bed fusion in situ using inline coherent imaging

Abstract

Inconsistent part quality is a challenge to the widespread adoption of powder-bed fusion additive manufacturing. Previous efforts to monitor the PBF process in situ have been mostly limited to single tracks. The lack of quantitative, in situ monitoring results from full 3D PBF builds remains a barrier to closed-loop control. We track morphology in situ using coherent imaging, providing an immediate check on surface roughness, recoater blade damage, and powder packing density. Defects are corrected through manual closed-loop control; protrusions and depressions identified by in situ imaging are compensated through laser ablation and refilling, respectively, during a 3D build. Maximum surface roughness is reduced by 54% and the number of layers with increased surface roughness relative to the steady-state value is reduced by 60%. Manual closed-loop control, successfully achieved using coherent imaging of PBF layer morphology, is an important step towards full feedback control capabilities.