Effect of laser-plume interaction on part quality in multi-scanner Laser Powder Bed Fusion

Using multiple laser scanner units in Laser Powder Bed Fusion (LPBF) allows a significant increase in productivity compared to single scanner systems. However, the part quality can be affected by the interaction between simultaneous melting processes. This study focuses on part defects caused by the interference between an incident laser beam and the plume ejected from an adjacent melt pool generated by another laser beam. Experiments were conducted on a gantry-based LPBF prototype machine with a movable processing head containing five laser scanner units. The machine includes a camera-based observation system to capture the volumetric propagation of the plume. Within the experiments, multiple laser scanner units were used for simultaneous processing, each generating separate test specimens. A correlation between the occurrence of voids and the plume propagation pattern of an adjacent melt pool is found. The investigations cover two operating modes of the gantry-based LPBF machine. In the jump-and-shoot mode, the processing head is positioned in fixed locations over the powder bed and not moved during exposure. The findings were then transferred to processing with a synchronized movement of the gantry system during exposure (on-the-fly mode). On the basis of this work, suitable multi-scanner processing strategies can be derived to prevent laser-plume interaction between adjacent melt pools.