| 摘要 |
PURPOSE:To provide a high quality laser beam cutting method for a thick plate by which reduction of cutting accuracy is prevented by evading generation of self-burning phenomenon and cutting is efficiently and economically carried out. CONSTITUTION:When the thick plate is cut by a laser beam, a surface condition of the plate at a position in immediately front of the cutting position is monitored and cutting is carried out alternatively switching cutting gas in accordance with change of the surface condition as when a hot red heated zone 11 is expanding, the cutting gas is switched from an oxygen gas 15 to an inert gas 14 and when the red heated zone 11 is shrinking, the cutting gas is switched from the inert gas 14 to the oxygen gas 15. |
