AN ISLAND TYPE NOVEL SCAN PATTERN WITH NON-LINEAR ISLAND INTERSECTIONS FOR LASER POWDER BED FUSION ADDITIVE MANUFACTURING PROCESSES

Thermal gradient and solidification time dictate the prominent mechanical properties and printing qualities of metal parts produced through the Laser Powder Bed Fusion (LPBF) additive manufacturing (AM) techniques. Printing defects such as warpage, delamination, and cracking originate from the thermal history of the printed parts. The relatively smaller heat source (laser) following a given scan pattern results in rapid solidification and uneven distribution of thermal energy, which in turn develops residual stresses in the printed parts. Through island-type scanning, the rapid solidification phenomenon is inhibited as it allocates the thermal energy within the islands thereby raising the surface temperature. In this paper, a novel island-type scan pattern with non-linear island boundary is proposed to distribute the Heat Affected Zones (HAZs) along the lateral direction of the island span. The proposed pattern is island-type and zigzag that reflects the regular hexagonal shape arranged periodically along each island span, creating nonlinear intersections between two adjacent islands. The effect of the proposed scan pattern on residual stress development is then investigated through a numerical approach and compared with that of the existing Zigzag and Island Zigzag scan patterns. The simulation results exhibit comparable characteristics of the proposed scan pattern with a 6.67% reduction in residual stress achieved as compared to the other two scan patterns.