| Abstract Scope |
Thermal lensing of laser powder bed fusion machines can induce inconsistent energy input during the melting process, ultimately compromising part quality. This study presents a series of experiments designed to directly measure high energy laser spots using a high-speed camera. The experiment utilized realistic scanning conditions 10 by 10 mm patch on a SS316 substrate. This region was scanned repeatedly to heat specific sections of lenses and mirrors, thereby simulating multilayer fabrication conditions. The investigation evaluated various optical assemblies, including F theta lenses and diverse protective window configurations. Furthermore, the impact of different scanning strategies, specifically varying hatch distances and laser idling times, was assessed. The results indicate an observed 5% to 10% change in laser spot size under standard air-cooling conditions. Additionally, the thermal lensing effect was found to be highly sensitive to the thickness, coating, and relative position of the protective glass within the optical path. |