Laser cutting device including machining condition tables and laser cutting method thereof

A laser cutting method of laser cutting a workpiece by emitting a laser beam output from a laser oscillator onto the workpiece, the laser oscillator being controlled by a control unit, via a transmission fiber and a laser machining head fitted to a front end of a laser machining robot controlled by the control unit, the laser cutting method comprising:

• a basic condition input step of receiving input of basic conditions applied at execution of the laser cutting, the basic conditions including a material of the workpiece and a plate thickness of the workpiece;
• a machining condition table selecting step of checking the basic conditions input at the basic condition input step against a machining condition table group stored in a memory included in the control unit, the machining condition table group including a plurality of machining condition tables including various parameters on the laser cutting, to select a first machining condition table of the plurality of machining condition tables, the first machining condition table corresponding to the laser cutting of a desired form;
• a machining condition setting step of setting machining conditions for the laser cutting, based on the first machining condition table;
• a cutting speed judging step of judging whether a cutting speed of cutting the workpiece is within a usable range set based on a speed range determined in advance for the laser machining robot or judging whether an extent of an overlap between an effective range and the usable range of the cutting speed is equal to or larger than a given range, the effective range being demarcated by the cutting speed and a laser power output that are set so that a cut surface of the workpiece meets given finishing conditions;
• a first cutting step of controlling operations of the laser machining robot and the laser oscillator to cut the workpiece based on a result of a judgment made at the cutting speed judging step;
• a machining condition table reselecting step of changing at least either of a laser oscillation frequency or a laser power output duty when the extent of the overlap between the effective range and the usable range of the cutting speed is smaller than the given range, and selecting a second machining condition table of the plurality of machining condition tables;
• and
• a second cutting step of controlling operations of the laser machining robot and the laser oscillator to cut the workpiece based on the second machining condition table.

A laser cutting device for cutting a workpiece by emitting a laser beam output from a laser oscillator onto the workpiece via a transmission fiber and a laser machining head fitted to a front end of a laser machining robot, the laser cutting device comprising:

• a control unit,
• wherein:
• the laser machining robot has a predetermined speed range in which the laser machining robot is allowed to move with a given tracking accuracy, and a usable range of a cutting speed of cutting the workpiece is set based on the predetermined speed range;
• the control unit includes a memory storing a plurality of machining condition tables including data on cutting conditions;
• each of the plurality of machining condition tables includes, as parameters associated with a material of the workpiece and a plate thickness of the workpiece, at least a laser oscillation frequency, a laser power output, a laser power output duty, the usable range of the cutting speed, an effective range demarcated by the cutting speed and the laser power output that are set so that a cut surface of the workpiece meets given finishing conditions, and an approximation of a lower boundary of the effective range, the approximation being that the laser power output is approximated by a quadratic equation of the cutting speed;
• and
• the control unit is configured to select one of the plurality of machining condition tables stored in the memory so that the cutting speed and the laser power output meet given conditions, and control operations of the laser machining robot and the laser oscillator so that the workpiece is cut based on the one of the plurality of machining condition tables.

A laser cutting method of laser cutting a workpiece by emitting a laser beam output from a laser oscillator onto the workpiece, the laser oscillator being controlled by a control unit, via a transmission fiber and a laser machining head fitted to a front end of a laser machining robot controlled by the control unit, the laser cutting method comprising:

• a basic condition input step of receiving input of basic conditions applied at execution of the laser cutting, the basic conditions including a material of the workpiece and a plate thickness of the workpiece;
• a machining condition table selecting step of checking the basic conditions input at the basic condition input step against a machining condition table group stored in a memory included in the control unit, the machining condition table group including a plurality of machining condition tables including various parameters on the laser cutting, to select one of the plurality of machining condition tables which corresponds to the laser cutting of a desired form;
• a machining condition setting step of setting machining conditions for the laser cutting, based on the one of the plurality of machining condition tables;
• a cutting speed judging step of judging whether a cutting speed of cutting the workpiece meets given conditions under the machining conditions set at the machining condition setting step;
• a cutting step of controlling operations of the laser machining robot and the laser oscillator to cut the workpiece based on a result of a judgment made at the cutting speed judging step;
• and
• wherein each of the plurality of machining condition tables includes an effective range demarcated by the cutting speed and a laser power output that are set so that a cut surface of the workpiece meets given finishing conditions, and an approximation of a lower boundary of the effective range, the approximation being that the laser power output is approximated by a quadratic equation of the cutting speed.