Laser powder bed fusion of stainless steel 316L using a combination of high-power diode laser and galvanometer scanner

In recent years, Laser Powder Bed Fusion (LPBF) has become an industrially established manufacturing technique due to the possibility to manufacture complex part geometries without additional tools. State-of-the-art LPBF machines feature a combination of (multiple) fiber lasers and galvanometer scanners due to their high dynamic and excellent focusability, leading to significant investment costs. Highly efficient high-power diode lasers (HP-DL) could present an alternative for L-PBF machines. However, the lower beam quality (BPP > 8 mm · mrad) and spectral width (920 - 1050 nm) of commercial HP-DL results in chromatic aberrations and reduced focusability, thus making modifications to LPBF machines necessary. Current approaches to address these challenges rely on a combination of fixed focusing optics with a gantry-based positioning system resulting in less dynamic laser positioning and thus reduced system productivity and part quality. In this study an optical system, featuring a standard galvanometer scanner and a color corrected f-theta lens, is developed and integrated into a LPBF lab machine. The resulting machine configuration is combined with a fiber coupled HP-DL and used for the manufacturing of test specimen out of stainless steel AISI 316L. The manufactured parts using this approach are analyzed in terms of surface roughness, detail resolution and part density as well as build-up rate and compared with state-of-the-art LPBF-machines.