Laser machining apparatus and laser machining method

A laser machining apparatus, comprising:

• a machining head with a nozzle being attached to a tip end of the machining head, the nozzle having an opening formed therein, a laser beam for cutting a sheet metal being emitted through the opening;
• a moving mechanism configured to relatively move the machining head with respect to a surface of the sheet metal;
• and
• a beam vibrating mechanism configured to vibrate the laser beam in a parallel direction with a cutting advancing direction of the sheet metal when the sheet metal is cut by the machining head being relatively moved by the moving mechanism,
• wherein a calculation value Va is expressed by the following expression,
• Va=(Qx+rtop+√{square root over (2)}×rbottom)
• where an amplitude amount of the laser beam by the beam vibrating mechanism is Qx, a radius of a first circular region having an area occupying 86% beam energy at a center side of total beam energy in a sectional area of the laser beam on a top surface of the sheet metal is rtop, and a radius of a second circular region having an area occupying 86% beam energy at a center side of total beam energy in a sectional area of the laser beam in a bottom surface of the sheet metal is rbottom, and
• when a standard deviation of the calculation value Va at a time of cutting sheet metals of a plurality of plate thicknesses is Vasd,
• a nozzle having a diameter of an opening between a minimum value obtained by 2Va−Vasd, and a maximum value obtained by 2.5 Va+Vasd is used as the nozzle.