JPS6342434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser processing machine, and more particularly to a laser processing machine having a control mechanism for keeping laser output constant.

A conventional device of this type is shown in FIG. This conventional device shows a 3-axis orthogonal glow discharge excitation type carbon dioxide laser processing machine. In the figure, reference numerals 1 and 2 denote a total reflection mirror and a partial reflection mirror, respectively, which are arranged to face each other with a discharge part 5 in between, forming a resonator, and the laser beam 6 is extracted from the partial reflection mirror 2. . Reference numerals 3 and 4 constitute a pair of electrodes, an anode and a cathode, which are disposed to face each other.The cathode 4 is constituted by a plurality of electrodes, and a discharge portion 5 is formed between the electrodes 3 and 4. The total reflection mirror 1, the partial reflection mirror 2, the anode 3, and the cathode 4 constitute a laser oscillator. 9
1 is a chopper arranged on the optical axis of the laser beam 6, and 10 is a sensor arranged opposite to the chopper 9. The chopper 9 and the sensor 10 constitute a laser beam detector. Reference numeral 11 denotes a power damper, which has the function of absorbing the laser beam 6. 12 and 13 are shutters, respectively.
Reference numeral 12 indicates an open position, that is, a state in which the shutter is located at a position that allows the laser light 6 to pass through, and 13 indicates a closed position, that is, a state in which the shutter is disposed on the laser optical axis to block the laser light 6. Shutter 1
A power damper 11 is disposed opposite to 3.
A bend mirror 14 is arranged to bend the laser beam 6 in a predetermined direction. 15 is a condensing lens for laser light, 16 is a workpiece, and 17 is a jig for supporting the workpiece 16. 18 is anode 3
This is a constant current DC power supply that supplies voltage to the cathode 4. 19 is an amplifier for amplifying the detection signal of the laser beam detected by the sensor 10; 20 is a setting device for setting the output value of the laser beam; the setting value of the setting device 20 and the output of the amplifier 19 are compared. The setting device 20 and the amplifier 19 constitute a comparator. 21 is an error amplifier, which amplifies the signal from the comparator. 22 is a current control circuit, and an error amplifier 21
It operates in response to a signal from the power source 18, and outputs a signal to the power source 18 to control the output current from the power source 18.

Next, the operation will be explained. First, when a high voltage is applied from the power supply 18 between the anode 3 and the cathode 4, a discharge part 5 is formed, and a laser beam 6 is generated between the total reflection mirror 1 and the partial reflection mirror 2, which are opposed to each other.
It is emitted to the outside via. A portion of the laser beam 6 emitted from the laser oscillator to the outside is reflected by a chopper 9 having rotating blades, and is incident on the sensor 10 as a detection laser beam 7. The output of the sensor 10 is amplified by an amplifier 19 and compared with the voltage of a setting device 20, and the error is detected by an error amplifier 2.
Amplify with 1. The amplified voltage becomes an output command value, which determines the output current of the constant current DC power supply 18 via the current control circuit 22. In this way, an output feedback control system was constructed to maintain a constant laser output.

Next, the process of processing the workpiece 16 will be explained. As described above, the laser beam 6 that has passed through the chopper 9 is completely reflected by the shutter 13 which is in the closed position during non-processing, and is absorbed and cooled by the power damper 11. On the other hand, during processing, the shutter 12 in the open position passes the laser beam, the laser beam 6 is bent by the bend mirror 14 in a direction approximately perpendicular to the surface of the workpiece 16, and then condensed by the condenser lens 15, 16 and processing is performed. At this time, the workpiece 16 is provided with a jig 17 that can withstand the laser beam 6 or completely reflects the laser beam 6.
It is supported by

A conventional laser processing machine is configured as described above, and when reflected light is generated from the workpiece 16 or the jig 17 during welding or the like using the laser processing machine, the light is reflected by the dotted line 8 in Fig. 1. Reflected light 8 is generated as shown in FIG. This reflected light 8 follows a path opposite to that of the laser beam 6, is reflected by the total reflection mirror 1 and the partial reflection mirror 2, and is mixed into the laser beams 6 and 7 via the chopper 9. For this reason, stable control of laser output was not possible. This state will be explained using FIG. 2. In FIG. 2, the horizontal axis shows time and the vertical axis shows laser output. At time _t1 , the shutter 12 is in the open position,
At time _t2 , the shutter 13 is in the closed position. As shown in Figure 2, the detection output A is stable during non-processing, but during processing, the detection output B changes irregularly due to the addition of reflected light components, and even when the reflected light is excluded. The effective output C decreased and varied irregularly, making it difficult to perform good machining. Therefore, the first
The output control of the conventional device shown in the figure is not suitable for practical use. For this reason, a method of keeping the current of the power supply 18 constant and making the laser light output almost constant has been considered, but this method has the inconvenience of setting the output every time processing and the temperature of the gas in the discharge part when starting the oscillator. When the change is large, there are drawbacks such as difficulty in maintaining a constant output.

This invention was made to eliminate the above-mentioned drawbacks, and by keeping the output command value constant using an external signal regardless of the output feedback value, it is possible to eliminate reflected light during processing. The aim is also to provide a laser processing machine that can maintain stable output.

Hereinafter, one embodiment of the present invention is shown in FIG. 3 and will be explained in comparison with the conventional FIG. 1.

In the embodiment shown in FIG. 3, the same reference numerals as in the conventional device shown in FIG. 1 indicate the same or corresponding parts. In FIG. 3, 23 is a sample and hold circuit, and 24 is a shutter control device. The sample and hold circuit 23 is connected between the error amplifier 21 and the current control circuit 22, and is configured to receive shutter open and shutter close commands from the shutter control device 24 as sample or hold signals. Note that the shutters 12 and 13 and the shutter control device 24 constitute a discriminator.

Next, the operation of the embodiment apparatus shown in FIG. 3 will be explained. First, during non-processing, the shutter 13 is closed and a sampling signal is given from the shutter control device 24 to the sample hold circuit 23, and the circuit 23 transfers the output of the error amplifier 21 to the current control circuit 2.
2 will be transmitted as is. Therefore, the operation is similar to that of the conventional device shown in FIG. Next, during processing, the shutter 12 is open, a hold signal is given from the control device 24 to the sample and hold circuit 23, and the circuit 23 maintains the output immediately before the hold state and transmits it to the current control circuit 22. . At this time, even if the output of the error amplifier 21 fluctuates due to the influence of the reflected light 8 that has entered the sensor 10, the circuit 2
Since the output of laser beam 3 does not vary, the laser output excluding reflected light 8 remains almost constant. This will be explained using FIG. 4 in comparison with FIG. 2 of the conventional device.
In Fig. 4, the detection output A during non-processing is exactly the same as Fig. 2, but during processing, the reflected light 8 is ignored, and the effective output C during processing maintains almost the same value as during non-processing. Ru. At this time, the detection output B during processing fluctuates irregularly. This effective output C changes if the machining time is very long, but in practice it can be considered to be approximately constant since the machining time is sufficiently short.

Note that in the above embodiment, as a hold signal,
I am using the shutter open and shutter close commands, but
A similar effect can be obtained by using another external signal indicating whether or not processing is in progress. Further, even if there is disturbance in the detection output due to factors other than reflected light, control can be performed regardless of this disturbance, and the same effect can be obtained. Furthermore, it can be used even if the laser light detection method is different.

In addition, although the above embodiment describes the case where the present invention is applied to a 3-axis orthogonal glow discharge excitation type carbon dioxide laser processing machine, it can also be used in laser processing machines of other systems and configurations to maintain output stability. You can achieve the same effect by doing so.

As described above, according to the device of the present invention, the output command value can be held constant regardless of the output feedback value, so the output can be stabilized without being affected by reflected light, etc., and the laser processing This has the effect of improving the machining performance of the machine.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a conventional 3-axis orthogonal glow discharge excitation type carbon dioxide laser processing machine, Fig. 2 is a diagram for explaining the drawbacks of the operation of the conventional device shown in Fig. FIG. 3 is a diagram for explaining an embodiment of the apparatus of the present invention, and FIG. 4 is a diagram for explaining the operation of the embodiment of FIG. In the drawings, the same or corresponding parts are denoted by the same reference numerals. 1... Totally reflecting mirror, 2... Partially reflecting mirror, 3... Anode, 4... Cathode, 5... Discharge part, 6... Laser light, 7
...Detection laser beam, 8...Reflected light, 9...Chipper, 10...Sensor, 11...Power damper, 1
2... Shutter (open position), 13... Shutter (closed position), 14... Bend mirror, 15... Condensing lens, 16... Work, 17... Jig, 18... Constant current DC power supply, 19... Sensor output amplifier, 20 ...Output setting device, 21...Error amplifier, 22...Current control circuit, 23...Sample and hold circuit, 24...Shutter control device.

Claims (1)

[Claims] 1. A laser oscillator that forms a discharge section between an anode and a cathode and outputs laser light from the discharge section;
A power source that supplies voltage to the anode and cathode, a detector that detects a portion of the laser beam output from the laser oscillator, and a signal that compares the detection value detected by the detector with the laser beam setting value. a comparator that outputs an output, a discriminator that determines whether the workpiece is being processed by the output laser light from the laser oscillator, and a sample hold circuit that holds the signal from the comparator in accordance with the signal from the discriminator. . A laser processing machine comprising: a current control circuit that outputs a signal for controlling the current from the power source based on the signal from the sample and hold circuit. 2 The discriminator includes a shutter that is placed on the optical axis of the output laser from the laser oscillator and blocks the laser beam from reaching the workpiece, and a shutter control device that controls the opening and closing of the shutter and outputs a signal to the sample hold circuit. A laser processing machine according to claim 1, characterized in that the laser processing machine is constructed by: 3. The laser processing machine according to claim 1, characterized in that a chopper is used as a means for detecting a portion of the laser beam.