Thermal and stress characteristics in diode laser chip-free cutting of glass

Both mechanical and CO2 laser micro-fracture cutting of glass sheets result in chip formation on the upper part of the cut sections. In this study, glass sheets are stressed thermally across the depth of the sheets simultaneously, using an 808-940 nm diode laser radiation. Instead of causing melting or local microcrack formation on the surface as seen in CO2 laser cutting of glass, a single crack is generated at a temperature well below the softening point of the glass and guided by the laser beam, resulting in chip-free laser cutting. One of the problems of applying this technique is that the cut sometimes deviate from the laser track at the leading and the trailing edges of the glass sheet. This paper presents an investigation of the effect of glass thickness and cutting speed on cut path deviation by examining the stress fields during diode laser cutting. Finite element modelling technique has been used to simulate transient effects of a moving beam and predicted thermal and stress distributions in diode laser cutting of soda-lime glass. Some of the results are validated with experimental data.