Analyzing Remelting Conditions based on In-Situ Melt Pool Data Fusion for Overhang Building in Powder Bed Fusion Process

Coaxial melt pool monitoring (MPM) images provide in-depth insights into the building process of laser powder bed fusion additive manufacturing. An in-situ MPM image captures the independent melting condition at specific positions within each build layer. However, identifying material defects such as horizontal lack-of-fusion using individual, discontinuous MPM images poses multiple challenges. This paper builds upon the authors’ previous work on data registration and data fusion to analyze material remelting conditions based on co-axial MPM images. MPM data are fused to formulate layerwise remelting ‘maps’ to evaluate printing quality. A 3D part with various overhang features was built to verify the method. A regular layer with solid support from the previous layers has around 30 % remelting ratio for the given laser scan conditions. In contrast, overhang regions remelted at about 10 % with the same process setting, whichis too low to provide sufficient material fusion, resulting in lack-of-fusion between melting tracks. The negative impact in remelting would not immediately disappear in subsequent layers following the overhang regions. Results shows three additional layers are required to fully recover the remelting condition back to normal. The remelting results from MPM are also visible within layerwise optical images of the same surface.