Abstract
Six rocks were subjected to CO2 laser beam in preliminary experiment. A rock sample subjected to CO2 laser was cut on a plane perpendicular to cutting surface, and kerf was carefully examined. A sandstone, a tuff and a andesite were found to be mostly melted and partly vaporized. A granite and a dolomite failed with many fractures around kerf filled with molten rock.
Further study was conducted for a granite and a sandstone where laser power, traverse speed and beam width on rock surface were taken as parameters. With increase of power of laser and decrease of traverse speed, depth of kerf and specific kerfing energy increased. When laser was exposed on rock, at the bottom of the kerf was the molten rock, and excessive energy of laser was consumed to vaporize a part of molten rock. So high intensity of laser energy caused the increase of specific kerfing energy.
Excavated volume of sandstone increased linearly with power of laser, and specific energy was approximately maintained to be constant. The excavated volume of granite also increased linearly with power of laser when power of laser was relatively low. However, with high power of laser such as 10 kW, the fractured zone spreaded over 31-10cm around the molten rock, so the excavated volume rapidly increased with power of laser, and the specific energy decreased sharply.
Several trials were made to remove molten rock and to increase the efficiency. With the help of air jet, molten rock was removed and the kerf depth increased by approximately 20%. When the kerf, however, reached a certain depth, molten rock was no more removed, so the cutting efficiency decreased.
