In-Situ Defect Detection and Correction in Laser Powder Bed Fusion

The laser powder bed fusion (LPBF) technology has gained an increasing interest in different industrial sectors for the realization of innovative structures, complex shapes and customized parts. However, the limited process stability and repeatability still represents a limitation, especially in sectors characterized by stringent quality requirements. The capability to produce first-time- right parts is critical to reduce material wastes and decrease both production costs and lead times. This has motivated an increasing amount of research developments focused on in-situ monitoring solutions aimed at detecting the onset of defects during the process, but there is still a lack of methods to correct or remove a defect once it has been identified. This paper presents a novel approach that combines an off-axial in-situ monitoring methodology with an in-line defect removal system. Layerwise imaging combined with data fusion techniques is presented to automatically signal the onset of local deviations from the nominal geometry and out- of-plane distortions in a robust way. Such deviations would lead to defects that are difficult or even impossible to correct in post- processing phases. The proposed approach to remove the defect during the additive production of the part consists of a patent- pending self-repairing system where a surface grinding wheel allows one to remove the last printed layers before going on with possibly modified LPBF process parameters. Preliminary results are presented to demonstrate the feasibility of the in-line defect removal strategy.