CUTTING METHOD BY LASER

PURPOSE:To cut a plate without any defect at a constant cutting width by increasing the depth of a groove while maintaining the balance between the rate of formation of the melt to be removed by cutting and the pressure of a cutting gas and overlapping and cutting the groove part after penetration of beams. CONSTITUTION:Laser power is kept low at the beginning of the start of cutting. Upon starting of cutting, the laser power is sloped up until the beam penetrates. The dross produced in an inclined and tapered cutting groove 9 is flowed in the direction shown by an arrow 10 and is scattered from the back of the groove 9, whereby the production of a large hole is prevented. When the thickness of the plate to be cut increases, the dross increases and hampers the cutting; therefore, an auxiliary nozzle 12 is provided beforehand in the position of the cutting start point, and an auxiliary gas 13 is blown therethrough to blow off surface dross balls 14, whereby the effect of cutting is improved.