JPH0362514B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a laser processing control device, and more specifically, the present invention relates to a laser processing control device, and more specifically, it is possible to control the laser output even if reflected light from a workpiece enters the laser oscillator. The present invention relates to a laser processing control device that can stably perform processing such as welding and cutting without being affected by the effects.

[Prior art]

FIG. 1 is a configuration diagram showing a conventional laser processing control device, and FIG. 2 is a waveform diagram showing the relationship between reflected light and laser output.

In FIG. 1, 1 is a laser oscillator, 2 is a laser beam transmission path, 3 is a bend mirror, 4 is a lens that is a condensing device, 5 is a workpiece, 6 is a power source, and 7 is provided in the transmission path 2. 8 is a laser sensor, 9 is a laser output setting device, 10 is a source calculator, 11
is a magnifier.

In the above configuration, the laser beam output from the laser oscillator 1 passes through the bend mirror 3 and processes the workpiece 5 with the lens 4. At this time, a part of the laser output light is taken out by the splitter 7, converted into an electric signal by the laser sensor 8, and the difference signal between this and the laser output setting device 9, that is, an error signal, is sent to the amplifier 11.
The signal is amplified and input to the power supply 6, and the power supply 6 controls the discharge power of the laser oscillator 1 based on this signal. By controlling the discharge power, the laser output can be varied, and in the same way, the return output to the laser sensor 8 is controlled so as to be the same as the value set by the laser output setting device 9.

At this time, if the cutting conditions for the workpiece 5 do not match, or the workpiece 5 or the machining head or lens 4
If it is not cut due to an abnormality such as vibration, or if it hits some protrusion, the reflected light returns to the transmission path 2 and enters the laser oscillator 1. When entering the laser oscillator 1, reflected light is added to the laser output excited by the power supply 6 due to a phenomenon peculiar to lasers, causing oscillation. For example 1kw
If 100W of reflected light is returned at the output of , it will be amplified in the oscillator and output as about 1.3kW.

This occurs even if the power supply 6 does not change at all.
Then, a part of this output enters the laser sensor 8, and it is detected that the output has increased. Therefore, since a large feedback is returned to the laser output setting device 9, the power supply 6 is changed by the amplifier 11.
Try to lower the output of that side. In other words, the discharge power decreases.

In FIG. 2, when the reflected light returns with a steep waveform as shown at A, the laser output rises as a steep waveform as shown at B. At this time, the feedback loop tries to lower the discharge power, so the laser output decreases. However, when the reflected light suddenly disappears, the discharge power becomes insufficient, so the laser output decreases as shown by C. . Since the workpiece 5 is processed while moving, the reflected light repeatedly appears, although with no regularity, as shown in FIG.

For example, in cutting processing, the laser output increases in the direction of cutting the workpiece, but if a cutting failure occurs for some reason, the laser output then decreases, making it difficult to cut the workpiece. If it doesn't cut, the light will continue to travel in the direction of processing, so the light will shine on areas that have not been cut, making it even harder to cut.
Since the cutting process involves continuous combustion, the problem arises that if the combustion is interrupted, the laser process will be cut into pieces.

Further, for laser light with a wavelength of 10.6 μm, a bolometer using a thermocouple is used as the laser sensor 8, but since the response of the sensor is slow, the response of the feedback loop cannot be made quick. Therefore, there is also the problem that it is not possible to quickly recover from the decline.

[Summary of the invention]

This invention was made in view of these problems, and even when the reflected light from the workpiece enters the laser oscillator during laser output control, the laser output control is not affected, and the welding is performed. It is an object of the present invention to provide a laser processing control device that can stably perform processing such as cutting.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention, and FIG. 4 is a waveform diagram showing the characteristics of one embodiment of the present invention.

In FIG. 3, the same parts as in FIG. 2 are given the same reference numerals. 20 is a second laser sensor, 21
is a divider that calculates the ratio between the reflected light and the laser output to keep the operating point constant even if the laser output changes. 22 is a comparator, and 23 is a hold level setter, which presets a hold level to keep the command issued to the power source 6 constant when strong reflected light is returned. 24 is a sample and hold circuit.

Next, the operation will be explained.

The reflected light from the workpiece 5 is detected by the second laser sensor 20 from the workpiece 5 side of the splitter 7, and the ratio with the output of the laser oscillator 1, that is, C=
a/b is calculated by a divider 21, and this output C is added to a comparator 22 as an input d, and when the comparator 22 detects a value equal to or higher than the hold level set value e, it is sent to the sample hold circuit 24 as a hold signal f. Add to. This hold signal f causes the sample and hold circuit 24 to keep the command issued to the power source 6 constant, thereby holding the output of the power source 6 constant. Furthermore, when the reflected light disappears, the sample and hold circuit 24 is put into the sample state, and normal laser output feedback control is performed.

By doing this, the laser output control circuit is not affected by the reflected light, and the laser output increases due to the reflected light as shown in Figure 4, but the laser output decreases as shown in Figure 2C. It is possible to eliminate the above-mentioned problems of the conventional device. It also reduces the range of fluctuations and enables stable machining.

〔Effect of the invention〕

As can be seen from the above description, according to the present invention, a part of the output light of the laser oscillator and a part of the reflected light from the workpiece are respectively extracted from the laser light transmission path, the ratio of the two is calculated, and the Since the output of the power supply is held constant by the sample and hold circuit when a value equal to or higher than the predetermined hold level setting value is detected, the following effects can be obtained.

(1) The sample and hold circuit can be operated automatically.

(2) By calculating the ratio of reflected light and laser output, the operating point remains constant even if the output of the laser oscillator changes.

(3) Fluctuations and decreases in laser output can be reduced.

(4) Stable processing is possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional laser processing control device, Fig. 2 is a waveform diagram showing the relationship between reflected light and laser output, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is a block diagram showing the relationship between reflected light and laser output. FIG. 3 is a waveform chart showing characteristics of an embodiment of the present invention. In the figure, 1 is a laser oscillator, 2 is a transmission line, 3 is a bend mirror, 4 is a lens, 5 is a workpiece, 6 is a power supply, 7 is a splitter, 8 is a laser sensor, 9 is a laser output setting device, and 10 is a a subtracter, 11 is an amplifier,
20 is a second laser sensor, 21 is a divider, 22 is a comparator, 23 is a hold level setter, 2
4 is a sample and hold circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a control device for a laser processing machine having a laser output feedback control system, a portion of the output light of the laser oscillator and a portion of the reflected light from the workpiece are respectively transmitted from the laser light transmission path between the laser oscillator and the workpiece. A laser processing control device is characterized in that when a comparator detects a value equal to or higher than a predetermined hold level setting value by extracting the sample and calculating the ratio between the two, the output of the power supply is held constant by a sample and hold circuit.