Simulation and fabrication of pyrex glass drilling using CO2 laser

The traditional glass drilling using mechanical processing and laser processing in air would produce many kinds of defects such as bugle, debris, crack and scorch. In this paper, we have applied the method of liquid-assisted laser processing (LALP) to reduce the temperature gradient, heat-affect zone region for achieving crack-free glass drilling. At the parameters of laser power 6 W, scanning speed 11.4 mm/s and 5 scanning passes by LALP, the crack-free hole with reduced heat-affect zone can be achieved compared to the traditional laser drilling in air. The alpha-step measured profile showed less bugle around the rim of LALP microstructure whose height was about 0.5-1.5 μm in 0.5-1.0 mm water depth while that in air was 6.9-10.5 μm. The relationship between cutting depth, scanning passes and water depths was studied. The ANSYS software was also used to analyze the temperature distribution and thermal stress field in air and water ambient during glass drilling. The higher temperature gradient in air induced higher stress for crack formation while the smaller temperature gradient in water had the less heat-affect zone range and eliminated the crack during processing.