JPH07245437A - Method and apparatus for determining life of output mirror of gas laser oscillator, and laser processing machine - Google Patents

Abstract

PURPOSE:To judge the life of the output mirror of a gas laser oscillator surely. CONSTITUTION:The power density distribution of the laser beam from a CO2 laser oscillator is measured, and the diameter D of the power density is detected by comparing this power density distribution with a minimum threshold value CS contributing laser beam machining. And the judgment of the life of the output mirror of the CO2 laser oscillator is performed by detecting a rapid changing point Da of this diameter D which appears with the increase of its working time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a judging method for judging the life of an output mirror of a gas laser oscillator, a concrete judging device therefor, and a laser processing machine equipped with the judging device.

[0002]

2. Description of the Related Art Gas laser oscillators, such as CO2 laser oscillators, are widely used as a high energy density heat source for cutting, welding or heat treating materials.
The power density distribution of the laser light is generally determined by individual CO2 laser oscillators based on an ideal distribution called a Gaussian distribution, in various forms (low-order mode, multimode, etc.). . In this case, when the CO2 laser oscillator is used for a long time, it is often impossible to maintain the initial laser oscillation performance due to the deterioration of the parts used over time. This causes fluctuations and the required processing performance such as cutting, welding or heat treatment cannot be obtained.

By the way, among the optical parts used for the resonator of the CO 2 laser oscillator, the deterioration due to the long-time use of the output mirror composed of the half mirror arranged on the side for outputting the laser light is as described above. It is considered to be the main cause of the reduction in the processing capability of the CO2 laser oscillator. That is, in general,
When the output mirror is used for a long time, the coating layer on the surface of the output mirror is deteriorated and it is easy to absorb the laser beam, which increases the temperature of the output mirror during use and makes its temperature distribution non-uniform, It is said that the refractive index of the laser light of the output mirror is greatly affected and the performance of the oscillated laser light is significantly changed. Therefore, it is necessary to maintain the oscillation performance of the CO2 laser oscillator by determining the degree of deterioration of the output mirror, that is, the life of the output mirror and knowing the proper replacement time of the output mirror.

However, conventionally, the degree of deterioration of the output mirror has not been determined. Normally, the usage time of the output mirror is integrated and the total usage time is set to a set time (for example, 2000 hours to 4000 hours). ), The output mirror is replaced with a new one, and the output mirror is currently replaced based on empirical judgment regardless of the degree of deterioration. .

[0005]

When the replacement is performed based on the usage time of the output mirror as in the prior art, there are the following problems.

For example, when the CO 2 laser oscillator is used in a dusty environment or a high humidity environment,
Dust adheres to the output mirror, or dew condensation occurs, which easily promotes the deterioration of the output mirror.
Also, even if the CO2 laser oscillator is in a stable environment,
Lubricating oil components, abrasion powder generated from rotating parts of the laser processing machine, or foreign substances generated by discharge of the discharge electrode adhere to the output mirror, causing deterioration of the output mirror. Therefore, the conventional method of exchanging the output mirror after the set time cannot maintain the oscillation performance of the CO2 laser oscillator and cannot supply the required processing performance.

In this case, conversely, it is conceivable to set the use limit time to a short time and replace the output mirror to maintain the processing performance of the CO 2 laser oscillator.
In this case, the output mirror may have to be replaced even though the deterioration of the output mirror has not progressed, resulting in an increase in cost.

On the other hand, recently, a method of determining the life of an output mirror by measuring the power density distribution of laser light output from a CO 2 laser oscillator has been attempted. That is, assuming that the power density distribution of the laser light is a Gaussian distribution, the diameter of the power density that is the square of 1 / e of the peak value of the power density distribution is the diameter of the laser light, and whether the laser light is good or bad depends on the size of the diameter. , The life of the output mirror is determined. However, this method is suitable when the power density distribution of the laser light is a Gaussian distribution, but when the laser light causes diffraction, interference, etc., the power density distribution does not become a Gaussian distribution. I can't make a proper decision.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a determination method and an apparatus therefor capable of reliably determining the life of an output mirror of a gas laser oscillator. It is an object of the present invention to provide a laser processing machine that can maintain the performance of laser processing.

[0010]

A method of determining the life of an output mirror of a gas laser oscillator according to the present invention measures a power density distribution of laser light output from the output mirror of the gas laser oscillator, and measures the measured power density distribution with the measured power density distribution. The diameter of the power density is detected from the minimum threshold value that contributes to laser processing,
It is characterized in that the life of the output mirror is judged by the point of abrupt change that appears with the use time of the diameter (claim 1).

An apparatus for determining the life of an output mirror of a gas laser oscillator according to the present invention comprises a measuring means for measuring the power density distribution of laser light output from the output mirror of the gas laser oscillator, and a power density distribution measured by this measuring means. The detection means for detecting the diameter of the power density by comparing with the minimum threshold value that contributes to the laser processing, and the diameters detected by this detection means are sequentially stored and have a sudden change point that appears with the use time of the diameter. The present invention is characterized in that it comprises a determination means for determining the life of the output mirror (claim 2).

A laser beam machine according to the present invention is equipped with a life determining device for an output mirror of a gas laser oscillator according to claim 2 (claim 3).

[0013]

According to the method and apparatus for determining the life of the output mirror of the gas laser oscillator according to the first and second aspects, the power density distribution of the laser light and the minimum threshold value contributing to the laser processing are used to determine the power density of the laser light. Since the diameter is detected and the sudden change point that appears with the use time of this diameter is determined as the life of the output mirror, the life of the output mirror can be accurately determined without excess or deficiency of deterioration.

According to the laser processing machine of the third aspect, the life determining device of the output mirror of the gas laser oscillator according to the second aspect is mounted, so that it is possible to appropriately determine the replacement time of the output mirror. Therefore, the processing performance can be maintained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, in FIG. 3, a CO 2 laser oscillator 1 which is a gas laser oscillator outputs a laser beam LS from an output mirror 2 which is a half mirror. The laser beam LS is diffracted by bender mirrors 3, 4 and 5. Laser cutting machine 6 which is a laser processing machine
Is supplied to the processing head 7. A lens 8 is housed in the processing head 7, and the lens 8 condenses the laser light LS from the bender mirror 5 and irradiates the workpiece 10 on the processing table 9. . The laser light path from the laser light LS from the CO2 laser oscillator 1 to the processing head 7 is the laser light L
A protective tube made of a flame-retardant material is used to prevent S from being accidentally irradiated to the outside, but the protective tube between the bender mirrors 4 and 5 is a bellows that can expand and contract so as to follow the movement of the processing head 7. It is composed of a tubular tube 11.

On the other hand, in the laser cutting machine 6, the processing table 9
Is reciprocated in the X-axis direction by an X-axis drive mechanism 13 including an X-axis drive motor 12, and is reciprocated in the Y-axis direction by a Y-axis drive mechanism 15 including a Y-axis drive motor 14. There is. A control circuit 16 composed of a microcomputer and its peripheral circuits controls the CO2 laser oscillator 1, the X-axis drive mechanism 13 and the Y-axis drive mechanism 15. That is, as is well known, the control circuit 16 uses C
By exchanging the information signal with the O2 laser oscillator 1,
The operation of the CO2 laser oscillator 1 is started, stopped, and the power of the laser light is increased / decreased, and is controlled between the X-axis drive motor 12 of the X-axis drive mechanism 13 and the Y-axis drive motor 14 of the Y-axis drive mechanism 15. The position of the processing table 9 in the X-axis and Y-axis directions is controlled by transmitting and receiving the information signal.

A beam profile detector 17 as a measuring means is arranged between the CO 2 laser oscillator 1 and the bender mirror 3. That is, as shown in FIG. 4, in the optical path of the laser light LS from the output mirror 2 of the CO 2 laser oscillator 1 to the bender mirror 3, a detection mirror 18 composed of a half mirror is arranged. Is configured to reflect a part of the laser light LS as a detection laser light LSa to a predetermined portion. Further, the detection laser light LSa detected by the detection mirror 18
The laser light reaches the heat sink 20 after being condensed into a predetermined beam diameter by the condenser lens 19.

A rotating disc 22 is fixed to a shaft 21a of a synchro motor 21 which is a driving source of the beam profile detector 17, and a detecting wire 23 extending in the radial direction is attached to the rotating disc 22. ing. Then, the detection wire 23 traverses the detection laser beam LSa condensed by the condenser lens 19, and a part of the detection wire 23 is sequentially reflected as a reflected laser beam LSb by the light receiver 24 to receive the reflected laser beam LSb. . In this case, the synchro motor 21
Signals are exchanged between the light receiver 24 and the control circuit 16. The control circuit 16 is
As will be described later, when it is determined that the output mirror 2 has reached the end of its life, the oscillating operation of the CO2 laser oscillator 1 is stopped and the alarm device 2 such as a buzzer or a lamp serving as an alarm means.
5 is made to perform a notification operation.

Next, the operation of this embodiment will be described with reference to FIGS. 1 and 2. When the beam profile detector 17 is operated by the control circuit 16, the reflected laser light LSb from the detection wire 23 is received by the photodetector 24, whereby the power density distribution as shown in FIG. 1A is measured. This is given to the control circuit 16.

In this case, as shown in FIG.
As the deterioration of the output mirror 2 progresses, the power density distribution of the laser light changes. That is, when a new output mirror 2 is used, the first power density distribution A of the Gaussian distribution is obtained, but with the passage of oscillation time, the output mirror 2
Of the second power density distribution B, the third power density distribution B
The power density distribution C is gradually transformed from the Gaussian distribution, and it becomes impossible to uniquely represent the distribution with a constant power density.

When performing laser cutting with the laser cutting machine 6, there is a power density that contributes to laser cutting, which is laser processing. Arata et al. (Yoshiaki ARA
TA, Hiroshi MARUO, Isamu MI
YAMOTO and Sadao TAKEUCH
I, "Dynamic Behavior in La
ser Gas Cutting of Mild S
"Teel", Transactions of JWR
I, Vol. 8, No. 2 (1979)), as shown in FIG. 2, in the case of soft iron (SS41), the power density ES for starting the oxidation reaction of iron and the power density EF for stopping the oxidation reaction depend on the cutting speed. . For example, when the cutting speed is 100 cm / min, the power density at the start of the oxidation reaction is about 50 KW / cm @ 2 and the power density at the end of the oxidation reaction is about 20 KW / cm @ 2. If the lower power density of these contributes to the cutting, the power density contributing to the cutting can be said to be the power density for stopping the oxidation reaction, and its minimum value is the minimum threshold CS for laser cutting, which is controlled It is stored in advance in the storage means (ROM) of the circuit 16.

The control circuit 16 calculates the diameter D of the power density from the information of the power density distribution given from the light receiver 24 and the minimum threshold value CS every time the beam profile detector 17 is operated. The data is sequentially stored in a storage means (RAM) having a backup power source, and changes in the diameter D are observed. The relationship between the degree of deterioration depending on the usage time (oscillation time) of the output mirror 2 and the diameter D of the power density is shown in FIG.
It becomes like (b). That is, when the total oscillation time is short, the diameter D does not change significantly, but when the total oscillation time becomes long, the diameter D changes rapidly. Therefore, the control circuit 16
Determines the life of the output mirror 2 by determining the total oscillation time at the change point Da where the diameter D changes rapidly, stops the oscillation operation of the CO2 laser oscillator 1, and causes the alarm 25 to perform the alarm operation. , Informs the operator that it is time to replace the output mirror 2.

The measurement of the power density distribution of the laser light by the beam profile detector 17 may be performed during the oscillating operation of the CO2 laser oscillator 1, or immediately before the start of machining, or CO2. The laser oscillator 1 may be periodically performed every oscillation operation for a fixed time,
Alternatively, it may be performed constantly or periodically after the CO2 laser oscillator 1 oscillates for a predetermined time.

As described above, according to the present embodiment, the beam profile detector 17 measures the power density distribution of the laser light, and the control circuit 16 minimizes the measured power density distribution and laser cutting. Threshold CS
The diameter D of the power density is detected by comparison with the above, and a sudden change point Da that appears with the use time of the diameter D is determined as the life of the output mirror 2. Therefore,
It is possible to prevent the output mirror 2 from being used excessively for a long time and causing a disconnection defect, as compared with the conventional method in which the life is simply determined by the lapse of a set time. The life of the output mirror 2 can be surely determined without excess or deficiency of the deterioration, such that the mirror 2 is not determined to be defective. Moreover, as described above, even in the case of the power density distribution in which the diffraction and interference of the laser light are mixed, the life of the output mirror 2 is determined based on the sudden change point Da of the diameter D. Can be determined.

The present invention is not limited to the above embodiment, but the following modifications or expansions can be made. As the measuring means for measuring the power density distribution of the laser light, other than the beam profile detector 17 using the detection wire 23 may be used. The laser processing machine is not limited to the laser cutter 6, and may be one that performs welding and heat treatment. Even in this case, the minimum threshold value that contributes to laser processing may be set. The control circuit 16 may have a hardware configuration in addition to the software configuration. As the gas laser oscillator, in addition to the CO2 laser oscillator 1, one using another laser gas may be provided.

[0026]

Since the present invention is as described above, it has the following excellent effects. According to the method for determining the life of the output mirror of the gas laser oscillator and the apparatus therefor according to claim 1 and 2, the diameter of the laser density is detected by comparing the power density distribution of the laser light with the minimum threshold value that contributes to the laser processing. Then, the life of the output mirror is determined based on the sudden change point that appears with the use time of this diameter, so that the life of the output mirror can be reliably and appropriately determined without excess or deficiency of deterioration.

According to the laser processing machine of the third aspect, since the life determining device for the output mirror of the gas laser oscillator of the second aspect is mounted, stable maintenance of the laser processing can be achieved.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, (a) is a diagram showing the relationship between the degree of deterioration of the output mirror and the change in the power density distribution, and (b) is the degree of deterioration of the output mirror and the diameter of the power density. Diagram showing the relationship between

FIG. 2 is a diagram showing the basis of the minimum threshold value.

FIG. 3 is a block diagram of a laser cutting machine.

FIG. 4 is a block diagram of a beam profile detector.

[Explanation of symbols]

In the drawing, 1 is a CO2 laser oscillator (gas laser oscillator), 2 is an output mirror, 6 is a laser cutting machine (laser processing machine), 7 is a processing head, 16 is a control circuit (detection means, determination means), and 17 is a beam profile. A detector (measuring means) is shown.

Claims (3)

[Claims] 1. A power density distribution of laser light output from an output mirror of a gas laser oscillator is measured, and a diameter of the power density is detected from the measured power density distribution and a minimum threshold value that contributes to laser processing. A method for determining the life of an output mirror of a gas laser oscillator, characterized in that the life of the output mirror is determined based on a sudden change point that appears with the use time of the diameter. 2. A measuring means for measuring a power density distribution of laser light output from an output mirror of a gas laser oscillator and a power density distribution measured by this measuring means and a minimum threshold value contributing to laser processing are compared. A detecting means for detecting the diameter of the power density, and a judging means for sequentially storing the diameters detected by the detecting means and determining the life of the output mirror at a sudden change point that appears with the use time of the diameter. A life determining device for an output mirror of a gas laser oscillator provided. 3. A laser beam machine equipped with the life determining device for the output mirror of the gas laser oscillator according to claim 2.