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.
Highlights
The use of lasers for rapid prototyping of tools for injection molds, coin dies, stamps, and product identification through engraving has been an established process for some time [1,2,3]
Lack of tool wear, ability to process a wide range of materials, high machining accuracy, and precision are some undeniable advantages in comparison to other engraving processes [4,5]
Class I is representative of closed-up grooves which result from a combination of high EDL (0.28 J/mm) and high Po (99%)
Summary
The use of lasers for rapid prototyping of tools for injection molds, coin dies, stamps, and product identification through engraving has been an established process for some time [1,2,3]. Lack of tool wear, ability to process a wide range of materials, high machining accuracy, and precision are some undeniable advantages in comparison to other engraving processes [4,5] Both ultrashort pulsed (femtosecond and picosecond) and short-pulsed (nanosecond and microsecond) lasers can be used for engraving metals. The use of the single-line machining experiments for investigating parametric influence during laser interactions is well established [11,18], the “scaling up” of findings from single lines to the more industrially relevant area engraving has not been reported This scale-up introduces a further key parameter set, namely, the laser beam scanning strategy, including interlacing, which has been reported as an effective process route for the machining of borosilicate glass [19], and more complex scanning patterns, such as halftone printing angles, that have been shown to provide a good surface polishing effect [20]. The paper concludes by demonstrating that with optimized process parameters, high throughput at high-quality engraving is achievable
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