JPS6222714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser processing apparatus that can accurately measure and control the distance from a workpiece to a beam head, regardless of the type of workpiece or its processing pattern.

A laser processing device performs drilling, cutting, welding, etc. on a workpiece by converging a laser beam generated by a laser oscillator using a condensing lens in the beam head and irradiating the workpiece in a pot shape. It is becoming an indispensable device for precision machining. It is well known that the processing pattern of a workpiece by a laser processing device is determined by the irradiation position of the laser beam on the workpiece and the spot diameter of the laser beam on the workpiece. , changes depending on the distance between the beam head and the workpiece, so controlling the distance of the beam head with respect to the workpiece is important.

Conventionally, the distance of the beam head to the workpiece has been measured visually by an operator or by a distance sensor such as a touch sensor or a magnetic sensor. For this reason, with the visual method, accuracy cannot be expected due to individual differences among workers, and in the case of a touch sensor, not only is there a risk of damaging the workpiece surface, but the touch sensor constantly scans the workpiece. This requires a mechanism to do this, which has the drawback of complicating the configuration accordingly.

In addition, magnetic sensors have the advantage of being able to detect distance without contact, but if the material of the workpiece is changed, the conversion part that converts the detected magnetism into distance must also be changed depending on the material. When the workpiece is a non-magnetic material such as plastic, rubber, or ceramic, the magnetic sensor has disadvantages such as being completely useless.

In addition, in conventional laser processing equipment, there is a positional shift (offset) between the processing point and the detection point by the horizontal distance between the beam head and the distance sensor. During machining, the distance sensor may become detached from the workpiece. In that case, the distance control of the beam head is performed based on a random distance signal from the distance sensor, which in the worst case can lead to an undesirable situation such as a collision between the beam head and the workpiece, which may lead to a problem in the machining process. This method requires a worker to monitor collision prevention during work, which has the disadvantage of hindering automation and labor saving.

The present invention eliminates the above drawbacks, and a servo circuit controls the beam head to a constant distance from the workpiece based on the distance between the beam head and the workpiece measured using a distance sensor. It is an object of the present invention to provide a laser processing device in which an output lock circuit locks the output of the distance sensor as a safety measure when the distance sensor comes off from the workpiece to prevent collision between the beam head and the workpiece. purpose.

To achieve this objective, the present invention focuses a laser beam generated by a laser oscillator on a beam head, irradiates the workpiece facing the beam head at a predetermined distance, and irradiates the laser beam onto the workpiece while changing the irradiation position. In a laser processing device that performs laser processing, a distance sensor is provided in the beam head,
This distance sensor has a conical nozzle that injects gas at a predetermined pressure sent from the outside, and has an ejection hole that ejects the gas along the conical surface and a pressure detection hole that is formed through the axis. The pressure between the nozzle or beam head and the workpiece is determined by the interaction between the negative pressure caused by the jet ejected from the nozzle and the positive pressure caused by the jet reflected by the workpiece (reflected pressure). It is configured to detect distance, and further,
a pressure sensor receiving the output of the distance sensor; a servo circuit that maintains the distance between the beam head and the workpiece at a predetermined constant value according to the output of the distance sensor; and between the servo circuit and the pressure sensor. and when the output of the distance sensor suddenly changes beyond the allowable range for laser processing,
The gist is that an output lock circuit is provided to lock the output of the pressure sensor.

According to the present invention, since the distance between the workpiece and the beam head is detected by the distance sensor provided in the beam head, it is difficult for machining powder etc. generated as a result of machining the workpiece to enter the distance sensor. Even if the sensor malfunctions, the distance sensor will be removed from the workpiece.
When the output of the distance sensor suddenly changes beyond the allowable range, the output of the pressure sensor that receives the output of the distance sensor is locked by an output lock circuit installed between the pressure sensor and the servo circuit. Therefore, there is no need to provide a limiter circuit or the like for abnormal input in the servo circuit, and the output lock level of the distance sensor can be easily changed.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing an embodiment of the laser processing apparatus of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a main part of the distance sensor portion shown in FIG.

In FIG. 1, a laser processing device 1 guides a laser beam generated by a laser oscillator 2 to a beam head 3 through a predetermined optical path, and irradiates a workpiece 5 on a work table 4 from the beam head 3. It is configured to perform processing such as cutting, drilling, or welding using a laser beam. Either the work table 4 or the beam head 3, which serves as a base for attaching the workpiece 5, is supported so as to be able to move freely on two orthogonal axes, and is equipped with a position detector (not shown), etc. By controlling the axis position using a numerical control method, the amount of axis movement read by the
positioning is performed.

A beam bender 6 is attached to the top of the beam head 3 to reflect downward the laser beam emitted from the laser oscillator 2 in the horizontal direction.
The beam is focused by a condensing lens 8a in a holder 8 connected to a beam bender 6 via a beam bender 6, and then passes through a tapered nozzle 9 and is irradiated onto the workpiece 5 in a spot shape.

Incidentally, the holder 8 is supported and fixed to a bracket 11 by a motor-driven screw feed mechanism 10. This screw feed mechanism 10 has a nut 13 fixed unrotatably to the top of a hollow bottomed cylindrical column 12 fixed to the end of a holder 8, and a feed screw 14 screwed onto the nut 13 attached to a bearing 15. The upper end of the feed screw 14 is connected to the rotating shaft 17a of the motor 17 via a joint 16.

This motor 17 rotates in forward and reverse directions according to commands from the control device 18, and the rotation speed-changed by a gear mechanism (not shown) having an appropriate gear ratio is extracted as rotation of the rotating shaft 17a. . The control device 18 controls the distance of the beam head 3 with respect to the workpiece 5 by rotating the motor 17 in forward and reverse directions according to an output from a distance sensor 19, which will be described later.

In the case of this embodiment, two distance sensors 19 are installed symmetrically at the tip of the beam head 3 with the tip between them, and the distance sensors 19 are used to detect distance between the workpiece 5 and the beam head 3 by using pressure (reflected pressure). Measure distance. Each distance sensor 19 includes a gas supply device 20 that adjusts gas such as air to a predetermined pressure and sends it out, and a nozzle 21 that injects the gas at a predetermined pressure supplied from the gas supply device 20 toward the workpiece 5. It consists of As shown in FIG. 2, the nozzle 21 has an ejection hole 2 that ejects gas along its conical surface.
1a, and a pressure detection hole 21b provided in the center of the jet hole 21a, and the negative pressure based on the entrainment of the jet jet ejected from the jet hole 21a, and the workpiece 5.
Due to the interaction with the positive pressure caused by the jet stream reflected by the nozzle 21 or the beam head 3, a pressure (reflected pressure) corresponding to the distance between the nozzle 21 or the beam head 3 and the workpiece 5 is detected in the pressure detection hole 21b. Normally, it is not considered that the pressure of the gas supplied from the gas supply device 20 fluctuates, so the pressure (reflected pressure) detected by the pressure detection hole 21b is very accurately detected by the workpiece 5.
This corresponds to the distance between the workpiece 5 and the beam head 3, thereby making it possible to measure the distance from the workpiece 5 to the beam head 3 without contacting the workpiece 5.

In addition, this distance sensor 19 can measure any material of the workpiece 5 with the same accuracy regardless of the material of the workpiece 5, so it is highly versatile, and the gas used is For example, since it can be used in common with the gas used to purge sparks scattered during laser processing, it is also possible to reduce equipment costs.

Here, the nozzle 21 of each distance sensor 19 is connected to a pressure sensor 23 in the control device 18 via a flexible tube pipe 22, respectively. The pressure sensor 23 uses, for example, a semiconductor strain element, and converts the detection output of each distance sensor 19 supplied via the tube pipe 22 into an electrical signal, which is then used for the control operation of the control device 18. , the detection outputs sent from the two nozzles 21 are configured such that the one with the larger output is selectively converted into an electrical signal within the pressure sensor 23.

By the way, inside the control device 18, there is a pressure sensor 2.
3, a servo circuit 24 and an output lock circuit 25
is provided. The servo circuit 24 is connected to the pressure sensor 2
Distance sensor 19 converted into an electrical signal by
When the distance from the workpiece 5 to the beam head 3 deviates from a preset set distance, a servo output is supplied to the motor 17 according to the magnitude and polarity of the deviation.
The output lock circuit 25 is connected between the pressure sensor 23 and the servo circuit 24, and the output of the distance sensor 19, which is converted into an electric signal by the pressure sensor 23, both falls within a certain tolerance range for laser processing. If there is a sudden change beyond the range, i.e. two distance sensors 1
9 is not above the workpiece 5, and when it is detected that the beam head 3 is near the periphery of the workpiece 5, the distance sensor 19, which is converted into an electrical signal by the pressure sensor 19, It locks the output to a predetermined value.

When processing the workpiece 5, the workpiece 5 is first placed and fixed at a predetermined position on the work table 4, and then the laser oscillator 2, the control device 18, etc. are operated. As a result, the motor 17 rotates forward in response to a command from the control device 18, and as the feed screw 14 rotates, the nut 13, column 12, holder 8, etc. are integrally displaced downward. At the same time, gas supply to the distance sensor 19 is started, and the motor 17 rotates normally until the distance detected by the distance sensor 19 reaches a predetermined set distance.

When the beam head 3 reaches the predetermined processing position,
The motor 17 stops normal rotation in response to a command from the control device 18, and only then the workpiece 5 is irradiated with a laser beam from the laser oscillator 2, and laser processing is started.

Beam head 3 and workpiece 5 during laser processing
The distance between them is constantly monitored by two distance sensors 19, and distance control involving forward and reverse rotation of the motor 17 is performed. For example, when the distance from the workpiece 5 to the beam head 3 increases, the pressure of the nozzle 21 in the distance sensor 19 (reflected pressure) decreases, so in order to prevent this decrease, the servo in the control device 18 The circuit 24 supplies a normal rotation command to the motor 17. Conversely, if the distance from the workpiece 5 to the beam head 3 decreases, the pressure of the nozzle 21 in the distance sensor 19 (reflected pressure) increases, so control is required to prevent this increase. A servo circuit 24 within device 18 provides a reverse rotation command to motor 17.

In this way, the beam head 3 relative to the workpiece 5
Since the distance is always kept constant, the spot diameter of the laser beam does not fluctuate, making it possible to perform highly accurate processing.

Furthermore, in this embodiment, two nozzles 21 of the distance sensor 19 are provided with the tip of the beam head 3 sandwiched between them. Even if the nozzle 21 comes off from directly above the workpiece 5, the nozzle 21 of the other distance sensor 19
As long as the distance sensor 1 is in the space above the workpiece 5, distance detection is possible.
The versatility is greater than when only one 9 is provided. Note that the nozzles 21 of these two distance sensors 19 are configured so that the attachment positions to the tip of the beam head 3 can be changed at will. For example, the optimum arrangement can be made according to the processing pattern of the workpiece 5.

Furthermore, even in the unlikely event that both nozzles 21 come off the workpiece 5 during laser processing, the output of the pressure sensor 23 will change suddenly. Lock circuit 2
5 locks the output of the pressure sensor 23 at a predetermined value, so that the beam head 3 is locked at the distance up to that point, thereby reliably avoiding the phenomenon of the beam head 3 plunging. Therefore, even if a situation occurs where it is virtually impossible for the distance sensor 19 to detect the distance between the workpiece 5 and the beam head 3, the worst case scenario, such as a collision between the workpiece 5 and the beam head 3, can be avoided. Moreover, it can be reliably prevented.

Note that, upon completion of laser processing, the laser oscillator 2 stops operating, and the control device 18 controls the motor 1.
7, the beam head 3 rises and returns to the position at the start of processing.

In the case of this embodiment, the case where two distance sensors 19 are used is taken as an example, but by increasing the number of distance sensors 19 used, it becomes possible to perform distance control with higher accuracy and safety. Furthermore, even when the number of distance sensors 19 is reduced to one, since the output lock circuit 25 is connected to the pressure sensor 23, there is a complete safety measure when the distance sensor 19 comes off the workpiece 5. .

Further, in the above embodiment, a diaphragm type pneumatic converter or the like may be used instead of the pressure sensor 23.

As explained above, according to the laser processing apparatus 1 having the above structure, the distance sensor 19 provided in the beam head 3 allows the distance between the workpiece 5 and the beam head 3 to be adjusted.
In order to detect the distance between Similar to when the object 5 is detached, when the output of the distance sensor 19 suddenly changes beyond the allowable range, the output of the pressure sensor 23 that receives the output of the distance sensor 19 is transferred between the pressure sensor 23 and the servo circuit 24. Since it is configured to be locked by the output lock circuit 25 provided between the two, there is no need to provide a limiter circuit for abnormal input in the servo circuit 24, and the output lock level of the distance sensor 19 can be easily changed. be able to.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the laser processing apparatus of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a main part of the distance sensor portion shown in FIG. 1... Laser processing device, 2... Laser oscillator,
3... Beam head, 5... Workpiece, 18...
Control device, 19... Distance sensor, 23... Pressure sensor, 24... Servo circuit, 25... Output lock circuit.

Claims (1)

[Claims] 1. In a laser processing apparatus that converges a laser beam generated by a laser oscillator by a beam head, irradiates it onto a workpiece facing a predetermined distance from the beam head, and performs laser processing on the workpiece while changing the irradiation position. A distance sensor is provided in the beam head, and the distance sensor includes a conical nozzle that injects gas at a predetermined pressure sent from the outside, and a jet hole that jets the gas along a conical surface;
A pressure detection hole is provided on the shaft, and the pressure determined by the interaction between the negative pressure from the jet ejected from the nozzle and the positive pressure from the jet reflected from the workpiece (reflected pressure) is detected. , configured to detect the distance between the nozzle or beam head and the workpiece, further comprising a pressure sensor that receives the output of the distance sensor, and a pressure sensor that detects the distance between the beam head and the workpiece according to the output of the distance sensor. A servo circuit is provided between the servo circuit and the pressure sensor to maintain the distance sensor at a predetermined constant value, and when the output of the distance sensor suddenly changes beyond the allowable range for laser processing, the pressure sensor A laser processing device equipped with an output lock circuit that locks the output.