Numerical control device

A method of a numerical control device controlling a machining head of a laser processing device, the method comprising:

• storing an output voltage corresponding to a gap size which is a distance from a workpiece surface;
• generating in advance a correlation table of a correlation between the output voltage and the gap size, the correlation table including first voltage values in association with first gap sizes and second voltage values in association with second gap sizes, the first gap sizes calculated based on a first measurement interval between gap sizes for linearly approximating the first gap sizes based on the first voltage values, and the second gap sizes calculated based on a second measurement interval between the gap sizes for linearly approximating the second gap sizes based on the second voltage values, wherein the first measurement interval is different from the second measurement interval;
• calculating a displacement amount equal to a first gap size among the first gap sizes which is a distance from a reference position set in a vicinity of the workpiece surface, based on an output voltage newly measured corresponding to a first voltage value among the first voltage values associated with the first gap size;
• controlling the gap size so that the displacement amount calculated based on the output voltage associated with the first gap sizes becomes equal to a reference displacement amount;
• switching, in response to the displacement amount calculated switching from among the first gap sizes to the second gap sizes, from controlling the gap size based on the output voltage associated with the first gap sizes to controlling the gap size so that the displacement amount calculated based on the output voltage associated with the second gap sizes becomes equal to the reference displacement amount;
• and
• controlling a drive shaft of a machining head according to the distance from a reference point, based on the gap size controlled, to machine the workpiece surface.

A method of a numerical control device controlling a machining head of a laser processing device, the method comprising:

• acquiring a voltage output by a gap sensor attached to a tip of a machining head configured to perform laser machining on a workpiece;
• determining a gap size of a gap between the tip of the machining head and reference position relative to a surface of the workpiece based on the voltage and a first linear approximation of a non-linear correlation between first voltage values and first gap sizes between the tip of the machining head and the reference position sampled at a first sampling interval;
• controlling a drive shaft of the machining head to control the gap size of the gap to be equal to a reference amount based on the voltage and a second linear approximation of the non-linear correlation between second voltage values and second gap sizes between the tip of the machining head and the reference position sampled at a second sampling interval that is different from the first sampling interval;
• and
• controlling the machining head of the laser processing device to perform laser machining of the workpiece while maintaining the gap size of the gap to be constant based on the voltage output by the gap sensor and the second linear approximation.