Effective Spiral Laser Path for Minimizing Local Heating and Anisotropic Microstructures in Powder Bed Fusion Additive Manufacturing.

Heat accumulation due to repetitive simple laser processing paths during building up a three-dimensional structure is a well-known issue that needs to be settled to reduce the excessively high residual stress and thermal deformation in a powder bed fusion (PBF) additive manufacturing process. Because of the dependency of laser path on the thermal dispersion, it is essential to analyze the heat accumulation phenomenon during laser processing. A computational fluid dynamics (CFD) analysis based on the volume of fraction method is used to optimize the laser path for minimizing the local heating up in the PBF process. In this work, a novel spiral laser path with optimal rotation angle is proposed and compared with the commonly used scanning paths. As the results, the accumulated temperature of the optimal spiral path shows a 200.9 K less compared with that of the general repetitive path. The thermal deformation of a cantilever structure made by the optimal spiral path is experimentally evaluated. From the experimental test, we verify that the spiral laser path reduces thermal deformation by 52.3% compared with the one made by the general one-directional laser path. This work based on numerical simulations and experiments utilizes the proposed spiral laser path to obtain higher precision, less residual stress, and more uniform microstructure of an additive-manufactured structure.