Design and validation of a hybrid laser/water-jet machining system for brittle materials

A unique laser/water-jet (LWJ) cutting head has been designed, built, and interfaced with a CO2 laser for cutting and scribing of hard and brittle ceramic materials. Alumina samples were used to validate the effectiveness of the LWJ cutting head in thermal fracture mode. The results were compared with vaporization mode (focused beam) as well as thermal fracture mode (defocused beam) of air-assisted laser cutting. The thermal fracture mode in both LWJ and air-assisted laser cutting required three to five times less energy input for material separation than the vaporization mode. However, the quality of the cut surfaces of the LWJ was superior to both vaporization and thermal fracture modes of air-assisted laser cutting in terms of kerf, recast zone, density of microcracks, undercutting, and spatter. The synergistic effects of laser and water-jet facilitated precise material separation and better cut quality through: thermal shock-induced fracture mode of material separation rather than energy-intensive erosive wear (water-jet alone) or melting and subsequent evaporation (laser alone); and expulsion of cracked material with kinetic energy associated with the water-jet, leaving a clean cut surface. (C) 2008 Laser Institute of America.