A flexible multi-focus laser separation technology for thick glass

Thick glass is a widely used functional structure material, but the existing cutting methods are low quality, complex and time-consuming. In this paper, a flexible multi-focus laser separation technology (FMFLS) was developed to separate thick glass without pre-processing and follow-up polishing for the first time. The FMFLS adopted holed focusing lenses to generate multiple independent laser foci along glass thickness direction, which are beneficial to achieve optimal temperature and thermal stress distributions during separation. The positions and power densities of laser foci are flexible, which could be adjusted by changing the distances between focusing lenses to separate glass with different thickness and properties. By using FMFLS, a penetration crack could be formed and controlled easily by thermal stress to achieve safe and high-quality separation of glass. The FMFLS system was designed by optical analyzing and verified via experimental research. A numerical simulation analysis was also established to reveal the separating mechanism of FMFLS. A series of FMFLS experiments were carried out to separate the soda-lime and low-iron glass with thickness from 10 to 20 mm, which is 2–4 times thicker than that of traditional laser separating technologies. The results show that FMFLS can achieve a high-quality separation (roughness = 1.6 nm, scan length = 200 μm) of thick glass without any contamination, subsurface damage or edge breakage.