Effect of interlayer rescanning on surface roughness and overhang sinking distance of AlSi10Mg alloy via selective laser melting

Laser rescanning technology is usually used to improve the forming quality of 3D printed parts. In order to investigate the relationship between rescanning strategy and forming quality, this paper proposed an interlayer rescanning strategy, which scans once at each odd-number layer and rescans at each even-number layer. In this work, 3D printed parts with inner structures were manufactured via selective laser melting. White light interference profilometry, scanning electron microscope, and three coordinates were used to analyze the surface quality, overhang sinking distance, and therefore the performance of samples with rescanning. White light interference profilometry-based roughness characterization revealed that the minimum surface roughness measured was 8.338 µm with rescanning and 9.676 µm with interlayer rescanning. The range of overhang sinking distance varied to a minimum of 0.146 mm with rescanning and 0.318 mm with interlayer rescanning. Based on the force analysis of the molten pool of overhang layers, the overhang sinking was mainly due to the increasing gravity of the molten pool and the insufficient supporting force provided by lower layers.