Laser cutting method and laser cutting device

A laser cutting device capable of cutting a workpiece by covering a laser beam radiated from a laser nozzle with a cutting gas and moving the laser nozzle with respect to the workpiece, the laser cutting device comprising:

• the laser nozzle configured to radiate the laser beam with respect to the workpiece and inject the cutting gas around the laser beam;
• a laser oscillator configured to generate the laser beam;
• a gas supply unit configured to adjust a concentration of oxygen contained in the cutting gas and supply the cutting gas in which the oxygen concentration is adjusted;
• a nozzle holding unit configured to hold the laser nozzle;
• a moving means configured to move the nozzle holding unit and the workpiece in relation to each other;
• and
• a control unit,
• wherein, while the control unit is configured to set a material, a plate thickness, and a cutting trajectory of the workpiece, based on a material and a plate thickness of the workpiece, the control unit is configured to set a steady oxygen concentration contained in the cutting gas when steady cutting is performed with respect to the workpiece, a steady relative moving speed of the workpiece and the laser nozzle when the steady cutting is performed with respect to the workpiece, and laser beam steady control conditions when the steady cutting is performed with respect to the workpiece based on laser beam control conditions including a frequency, a duty, and a peak or average output of the laser beam;
• when the laser nozzle arrives at a first setting position located in front of an end point of a cutting trajectory or a corner section,
• the control unit decreases a relative moving speed of the workpiece and the laser nozzle to a first setting speed less than the steady relative moving speed;
• and
• when the laser nozzle arrives at a second setting position which is closer to the end point or the corner section than the first setting position,
• heat input to the workpiece is decreased by varying at least one of the oxygen concentration of the cutting gas and the control condition of the laser beam, and the relative moving speed of the workpiece and the laser nozzle is decreased to a second setting speed, which is less than the first setting speed, corresponding to the heat input to the workpiece.