Laser piercing method and laser-beam working machine

A laser-beam working machine comprising:

• at least one laser oscillator configured to emit a first laser beam and a second laser beam;
• an optical fiber having a first end at which the first laser beam and the second laser beam are received from the at least one laser oscillator and having a second end opposite to the first end, the optical fiber comprising:
• a first transmission portion through which the first laser beam is passed;
• a second transmission portion which is provided around the first transmission portion and through which the second laser beam is passed;
• and
• a reflector provided between the first transmission portion and the second transmission portion;
• a lens provided to face the second end of the optical fiber and configured to focus the first laser beam and the second laser beam toward a workpiece after the first laser beam and the second laser beam have been transmitted through the optical fiber;
• a torch having an opening through which the beams focused by the lens and gas to be sprayed to the workpiece are passed;
• at least one actuator configured to move the torch;
• a nozzle configured to spray oil to the workpiece;
• a first pump configured to send the oil to the nozzle;
• a second pump configured to send the gas to the torch;
• a processor;
• and
• a memory storing instructions that, when executed by the processor, cause the laser-beam working machine to perform operations to control the at least one laser oscillator, the first pump, the second pump, and the transfer mechanism,
• the operations comprising:
• controlling the first pump to spray the oil to the workpiece to generate a coated portion coated with the oil;
• and
• controlling the at least one laser oscillator and the second pump to emit a bundle of laser beams including the first laser beam and the second laser beam to the coated portion and spray the gas to molten material that is the workpiece melted by the first laser beam to pierce the coated portion to form a pierced hole, and
• wherein the first laser beam has a first laser output density, and the second laser beam has a second laser output density that is smaller than the first laser output density.