Process Optimization for 100 W Nanosecond Pulsed Fiber Laser Engraving of 316L Grade Stainless Steel

Abstract

High average power (>50 W) nanosecond pulsed fiber lasers are now routinely available owing to the demand for high throughput laser applications. However, in some applications, scale-up in average power has a detrimental effect on process quality due to laser-induced thermal accumulation in the workpiece. To understand the laser–material interactions in this power regime, and how best to optimize process performance and quality, we investigated the influence of laser parameters such as pulse duration, energy dose (i.e., total energy deposited per unit area), and pulse repetition frequency (PRF) on engraving 316L stainless steel. Two different laser beam scanning strategies, namely, sequential method (SM) and interlacing method (IM), were examined. For each set of parameters, the material removal rate (MRR) and average surface roughness (Sa) were measured using an Alicona 3D surface profilometer. A phenomenological model has been used to help identify the best combination of laser parameters for engraving. Specifically, this study has found that (i) the model serves as a quick way to streamline parameters for area engraving (ii) increasing the pulse duration and energy dose at certain PRF results in a high MRR, albeit with an associated increase in Sa, and (iii) the IM offers 84% reduction in surface roughness at a higher MRR compared to SM. Ultimately, high quality at high throughput engraving is demonstrated using optimized process parameters.

Keywords

• nanosecond laser pulses
• pulsed fiber lasers
• engraving
• high average power
• surface roughness
• material removal rate