Two-side percussion microdrilling method for improved hole accuracy employing a reflective mirror lens

Laser percussion drilling of microholes has established itself as a prominent micromachining technique rivaling both conventional and nonconventional microdrilling processes. Despite its broader use, the laser percussion drilling process has some limitations, particularly the achievable microholes’ accuracy. The research reports a novel method to address this shortcoming by improving the holes’ dimensional and geometrical accuracy. Specifically, the proposed two-side method for laser percussion drilling of microholes utilizes a penetrating laser beam that is refocused at the hole exit by a reflective concave mirror lens. So, additional ablation occurs at the hole exit to improve the hole accuracy, i.e., a significant increase in minimum (neck) diameter, taper angle, and volumetric ratio (the ratio between the ablated and nominal hole volumes), i.e., 44%, 74%, and 57%, respectively, was achieved in the conducted experimental trials. Notably, these improvements are achieved without affecting the processing efficiency with the proposed laser drilling setup being relatively simple to implement.