Laser machining method adjusting focus shift depending on type and level of contamination of external optical system before laser machining

A laser machining method executed by a laser machining device configured to perform laser machining on a workpiece after measuring an amount of focus movement due to contamination of an optical system to compensate a focus position, the laser machining method comprising, before laser machining:

• (a) issuing a command to emit a laser beam with a high power to the extent used for laser machining toward a laser beam elimination part capable of eliminating the laser beam in order to warm up an external optical system configured to guide a laser beam from a laser oscillator to concentrate the laser beam on a surface of a workpiece;
• (b) after the external optical system is warmed up, issuing a command to adjust a focus position on a surface of a plate disposed in a position different from a position of the laser beam elimination part and having a small-diameter hole and a command to align an optical axis of the laser beam with a center of the small-diameter hole;
• (c) in a state where the external optical system is warmed up, issuing a command to emit a laser beam with a low power to the extent that the plate is not melted or deformed;
• (d) in a state where the external optical system is warmed up, measuring an amount of energy of the laser beam passing through the small-diameter hole as a first measurement value;
• (g) issuing a command to move the focus position to an upward position and a downward position from the surface of the plate;
• (h) issuing a command to emit a laser beam with the low power in a state where the focus position is adjusted to each of the upward position and the downward position;
• (i) measuring an amount of energy of the laser beam passing through the small-diameter hole as a third measurement value in a state where the focus position is adjusted to each of the upward position and the downward position;
• (j) generating a graph including the first measurement value measured in a state where the focus position is adjusted on the surface of the plate, and the third measurement value measured in a state where the focus position is adjusted to each of the upward position and the downward position from the surface of the plate, the graph being based on a type and level of contamination of the external optical system;
• (k) calculating a focus position from the graph and calculating an amount of focus movement on a basis of a difference between the calculated focus position and the focus position commanded to adjust on the surface of the plate;
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• (f) compensating a focus position in laser machining on a basis of the calculated amount of focus movement.

A laser machining method executed by a laser machining device configured to perform laser machining to a workpiece after measuring an amount of focus movement due to contamination of an optical system to compensate a focus position, the laser machining method comprising, before laser machining:

• (a) issuing a command to emit a laser beam with a high power to the extent used for laser machining toward a laser beam elimination part capable of eliminating the laser beam in order to warm up an external optical system configured to guide a laser beam from a laser oscillator to concentrate the laser beam on a surface of a workpiece;
• (b) after the external optical system is warmed up, issuing a command to adjust a focus position on a surface of a plate disposed in a position different from a position of the laser beam elimination part, having a small-diameter hole, and capable of absorbing a laser beam, and a command to align an optical axis of the laser beam with a center of the small-diameter hole;
• (c) in a state where the external optical system is warmed up, issuing a command to emit a laser beam with a low power to the extent that the plate is not melted or deformed;
• (d) in a state where the external optical system is warmed up, measuring an amount of energy of the laser beam passing through the small-diameter hole as a first measurement value;
• (s) in a state where the external optical system is warmed up, measuring an amount of energy of the laser beam absorbed by the plate as a second measurement value;
• (t) determining whether the external optical system is contaminated by comparing the first measurement value being the amount of energy of the laser beam passing through the small-diameter hole with a first reference value predetermined depending on a type of contamination of the external optical system;
• (u) determining contamination of only a window in the external optical system by comparing the second measurement value being the amount of energy of the laser beam absorbed by the plate with a second reference value predetermined depending on the type of contamination of the external optical system;
• (v) determining contamination of only a lens in the external optical system by comparing the first measurement value being the amount of energy of the laser beam passing through the small-diameter hole with a third reference value predetermined depending on the type of contamination of the external optical system and less than the first reference value;
• (w) in a case where only the lens in the external optical system is contaminated, calculating an amount of focus movement on a basis of the second measurement value being the amount of energy of the laser beam absorbed by the plate, a fourth reference value predetermined depending on a contamination level of the external optical system, and an amount of focus movement predetermined depending on the fourth reference value;
• and
• (f) compensating a focus position in laser machining on a basis of the calculated amount of focus movement.