Water assisted laser cutting of brittle materials

Abstract

<p>The synergistic effects of coupling a laser with the assistance of water on the material removal mechanism and energy efficiency were investigated in cutting of glass, silicon, alumina and concrete. A water assisted laser cutting manufacturing process was utilized to machine samples at low pressures of water-jet (<100 psi) and low powers (<500 W) of CO2 laser and results were compared to the samples that were cut with just laser alone. Temperature profiles of the heat affected zones were obtained using thermocouples and data acquisition system. Finite element analysis was applied to predict the temperature and thermal stress distributions developed during both water-assisted and dry laser cutting operations. Temperature histories of the samples recorded during cutting were compared with numerical model predictions to determine heat transfer parameters associated with wet and dry laser cutting of alumina samples. The water assistance enabled the laser beam to cut the materials by thermal stress fracturing and washing away the debris from the kerf. It was found that glass, alumina and silicon acted very similar to each other and produced good quality cuts. However, the hybrid method had a relatively smaller effect on concrete. The proposed mechanism involves induction of compressive stresses during laser heating followed by a change in stress field to tension during water-jet cooling, leading to crack initiation and growth from the top to bottom surface. Due to the water assisted laser capability of removing material by thermally shock-induced fracture rather than energy-intensive erosive wear (water-jet) or melting and subsequent evaporation (laser); it offers potential benefits such as reduced energy, increased cutting speed, improved accuracy and finish, and controlled depth and shape.</p>