High-throughput multibeam laser microdrilling using millisecond pulses

There is an increasing demand for high-speed microdrilling of 316L stainless steel in medical, aerospace, automotive, electronics and filtration industries, particularly for components requiring a large number of microholes. However, existing methods often face limitations in throughput, consistency, or quality when processing such high-density arrays. This study presents an innovative approach utilizing multiple beamlets produced by a Diffractive Optical Element (DOE) to enhance drilling efficiency and throughput rate of ‘stop-and-drill’ laser drilling. A single-mode millisecond laser system is combined with a specially designed DOE to generate an array of beamlets that simultaneously process multiple sites by percussion drilling on 316L stainless-steel sheets. The experimental setup involved 0.5mm thick 316L stainless steel sheets, subjected to high-speed laser microdrilling using a 2 kW 1070nm single-mode millisecond fibre laser. The DOE, engineered to create a 5x1 pattern of beamlets, was employed to drill an interlaced array of micro-holes. This investigation looked at the effects of varying pulse energy, number of pulses, frequency, pulse duration, gas composition and processing strategies on the size, quality, and consistency of the drilled holes. Additionally, the effects of these parameters on the repeatability of the hole formation are investigated. Optical microscopy and SEM were utilized to analyze the size and quality of the resulting holes. The melt-ejection and hole formation dynamics were investigated through high-speed of the drilling process. Results demonstrate that the DOE-assisted long-pulse multi-beamlet approach significantly increases the throughput rate compared to traditional single position percussion drilling and achieves a similar magnitude to ‘on-the-fly’ laser drilling methods, while maintaining suitable hole quality.