Towards supportless laser powder bed fusion: fundamental understanding of the formation of 1^st layer overhang through parameter optimisation and in-situ high-speed thermal imaging

One of the most revolutionary aspects Laser Powder Bed Fusion (LPBF) is to be able lift design constraints from conventional manufacturing. However, as a rule thumb, any surfaces lower than 45° with respect horizontal plane would still require sacrificial supports in order complete printing. Fundamentally, it unclear whether feasible print 1st layer 0° overhang nor how parameters for can optimised. This research demonstrates that large overhangs printed coverage above 90%. For first time, parameter space laser power, scan speed and hatch spacing has been simultaneously explored efficiently. The use rate change mushy zone proposed selection instead average melt pool temperature. Adaptive Parameter 28 (AP28: 250W_4000 mm/s_50 µm) best choice. Several surface morphological phenomena are discussed. core (285W_960 mm/s_110 causes severe balling its mechanism revealed. temperature by bulk. ramifications beyond also illustrated.