Comparative assessment of picosecond laser induced plasma micromachining using still and flowing water

Laser induced plasma micromachining (LIPMM) process is an effective approach to create micro-features with high aspect ratio and reduced heat affected zone. However, the throughput of this process is limited by the low scanning speed and low frequency used in the conventional underwater condition due to the disturbance of water layer, generation of bubbles and ablation debris. In this study, a new alternate process using flowing water was developed to provide a stable and thin water layer on the top workpiece surface. Thereafter, the influences of laser parameters like scanning speed, frequency and pulse energy on the machining characteristics between LIPMM using still and flowing water were experimentally investigated and comparatively evaluated. It was found that the influences of scanning speed, frequency and pulse energy on the machining characteristics between two processes were similar. However, LIPMM using flowing water created micro-channels with smaller heat affected zone, smoother surface, higher aspect ratio and higher MRR in comparison with that of using still water.