JPS6316889A - Laser light abnormality monitoring device - Google Patents

Abstract

PURPOSE:To discover an abnormality at early date and to improve the working yield of a product by monitoring the power of a laser light, using the temp. detecting device consisting of the plural thermocouples which are installed at the position far from the imaging focus of a condensing lens. CONSTITUTION:Plural thermocouples 4a, 4b, 4c, 4d are set up on the outer peripheral part of a laser beam mode by a laser light 1. When the shape of the laser beam mode by the laser light 1 varies the beam approaches either of the thermocouples 4a, 4b, 4c, 4d and the temp. of either rises. Since the abnormality can be discovered earlier with the device of this composition the working yield can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technique for detecting abnormalities in laser light during laser processing.

[Conventional technology]

FIG. 3 is a schematic diagram for explaining the operation mode of a conventional laser processing lens. In FIG. 1, 1 is a laser beam,
2 is a condensing lens for processing. As shown in Figure 3,
A laser beam 1 is transmitted from a laser oscillator (not shown), is condensed by a condensing lens 2, passes through an optical path shown by a solid line in FIG. 3, and is focused at a focal point position A. Here, a workpiece (not shown) is placed at a position with a focal length f near the focal point position A, and thereby the workpiece is laser-processed.

However, if /ξ× of the laser beam 1 to the condenser lens 2 is larger than a predetermined value, or there is a thermal influence from the workpiece, or if there is a problem between the condenser lens 2 and the workpiece. The surface of the condenser lens 2 becomes dirty due to the fact that snokters (particularly common during welding) during machining enter from the workpiece side through a nozzle hole (not shown) and adhere to the condenser lens 2. This has the disadvantage that the coating film on the surface of the condenser lens 2 deteriorates and the heat absorption rate increases. When the heat absorption rate of the condenser lens 2 increases in this way, for example, when the heat absorption rate of the normal 0.3% becomes around 0.5%, the condenser lens 2 is heated. A so-called thermal lens effect occurs, and the condenser lens 2 bulges as shown by the dotted line in FIG. 3, resulting in a short focal length with equal constraints. By shortening the focal length of the condensing lens 2 in this way, the laser beam 1 passes through the optical path shown by the dotted line in FIG. 3 and is focused at the focal position B. Therefore, when the workpiece is installed at the focal position A, the distance between the workpiece and the condensing lens 2,
In other words, the focal length that was initially f becomes fT,
The focal length is shifted by Δf = f - fT and becomes shorter. As a result, the condensing diameter and depth of focus of the laser beam 1 on the workpiece change, and the irradiated laser energy density becomes smaller. For this reason, depending on the processing serial number of the workpiece, the allowable limit of laser energy density becomes narrower, resulting in defects in the processing results. Note that the thermal lens effect progresses over time as the processing time for the workpiece increases. In addition, even if a change occurs in the laser beam 1 for some reason on the upstream side of the condenser lens 2, and the diameter and laser energy distribution of the incident light to the condenser lens 2 change, the change due to the condenser lens 2 [Problem to be solved by the invention] Since the conventional laser processing lenses described above exhibit the above-mentioned operation mode, Judging from the processing results, the laser processing must be performed by replacing the condenser lens 2 as appropriate. For this reason, the processing yield of the workpiece deteriorates, and no measures are taken to extend the life of the expensive condensing lens 2, so it is necessary to perform periodic cleaning at an early stage, making the operation complicated. There were problems such as.

This invention was made to solve these problems, and it is possible to detect the deterioration of the condenser lens at an early stage and use it as a means to extend the life of the condenser lens. The object of the present invention is to obtain a laser beam abnormality monitoring device that can measure improvements and automatically monitor a laser processing machine.

[Means for Solving Problem 8] The laser beam abnormality monitoring device according to the present invention has a laser beam at a position farther than the focal point imaging position of the condensing lens and at the outer periphery of the laser beam mode of the laser beam. It is equipped with a temperature detection device consisting of a plurality of thermocouples for measuring the temperature of light.

[Effect]

In the laser beam abnormality monitoring device of the present invention, the electromotive force (voltage) corresponding to the temperature from the plurality of thermocouples constituting the temperature detection device is equal to the voltage of each predetermined reference value from the reference voltage generator. If the voltage difference is greater than a predetermined allowable voltage difference, an abnormality alarm is generated or the laser oscillator is stopped.

〔Example〕

FIGS. 1(a) and 1(a) are schematic diagrams for explaining the operation mode of a laser beam abnormality monitoring device, which is an embodiment of the present invention. In the figure, 1 is a laser beam, 2 is a condensing lens for processing, 4a@4b#4Ce4d is a thermocouple, 3 is a temperature detection device consisting of each thermocouple 4a to 4d, 14
15 and 16 are a power damper and a cooling water inlet and a cooling water outlet of the power damper 14, respectively.

FIG. 2 is a schematic diagram showing the configuration of a laser beam abnormality monitoring device which is an embodiment of the present invention. In the figure, 5 is an amplifier, 6 is a reference voltage generator, 7 is a voltage comparator, 8, 9.1
0.12 is a control cable line, 11 is a control device that issues an alarm for abnormality of the laser beam 1 based on a comparison signal, 1
3 is the alarm display.

Next, the operation of the laser beam abnormality monitoring device which is an embodiment of the present invention will be described. As shown in FIG. 1fa), a plurality of thermocouples 4a, 4b, 4c are provided at the outer periphery of the laser beam mode of the laser beam I.

4d is installed. In this way, if there are about four thermocouples 4a to 4d, even if the shape of the laser beam mode is asymmetric, temperature detection can be performed by changing the setting positions of the respective thermocouples. Now, if for some reason the shape of the laser beam mode of the laser beam 1 changes from the position shown by the solid line to the position shown by the dotted line as shown in FIG. At a position at a distance icl>f, which is farther than the distance f0, the electromotive force becomes larger and approaches each thermocouple 4a to 4d, so the temperature of each thermocouple 4a to 4d becomes higher and the electromotive force increases. Here, it is physically difficult to install each of the thermocouples 4a to 4d at a distance l<<1> because there is a nozzle, etc., not shown, at this position, and it is also difficult to detect the significance of an abnormality.

As shown in FIG. 2, the electromotive force corresponding to the temperature detected by each thermocouple 4a to 4d is amplified by an amplifier 5, and its output voltage is a voltage of a predetermined reference value from a reference voltage generator 6. If the voltage difference is determined to be greater than a predetermined allowable voltage difference in the control device 11, an abnormality alarm signal is issued and the alarm indicator 13 sounds a buzzer or turns on the indicator lamp. It lights up to instruct the laser oscillator (not shown) to stop oscillation.

Now, the abnormality in the shape of the laser beam (7) caused by the laser beam 1 is due to the thermal lens effect of the condenser lens 2, and the laser beam diameter of the incident light to the condenser lens 2 is already larger than a predetermined value. Although there are some abnormalities such as large or small, all of them can be detected by the method according to the present invention. Furthermore, by providing a plurality of thermocouples 4a to 4d, it is possible to detect an abnormality with only one specific pair of thermocouples. It exerts great power.

In order to implement the laser beam abnormality monitoring device according to the present invention before and after normal machining operations, it is necessary to install it in advance on the machining table on which the Kaloe head is mounted and at a position where it will not interfere with the mounting of the workpiece. good. Therefore, it is extremely easy to move the processing head directly above the apparatus.

Further, a power damper 14 is installed below the temperature detection device 3 consisting of each thermocouple 4a to 4d, and a power damper 14 is installed below each thermocouple 4a to 4d.
It is necessary to absorb the power heat of the laser beam 1 while detecting the temperature at ~4d. The laser beam 1 irradiates the power damper 14 for a period of several seconds to several tens of seconds until the condenser lens 2 is thermally saturated. In addition, the power damper 14 has a part of the incident power shaped like a cone, and the circumference of the power damper 14 is cooled by the cooling water circulating from the cooling water population 15 to the cooling water outlet 16, resulting in a large output power (approx. It is designed to absorb.

Further, it is convenient to integrate the temperature detection device 3 consisting of each of the thermocouples 4a to 4d and the power damper 14 into an integral structure and compactly when mounting it on the processing table.

Furthermore, in the laser beam abnormality monitoring device according to the above embodiment, it is possible to detect an abnormality in the laser beam side caused by the laser beam 1 before and after the processing operation, for example, by operating the processing head before the processing operation. , this processing head is moved directly above this apparatus equipped with each thermocouple 4a to 4d, and the laser beam 1 is oscillated for a certain period of time to power the power damper 14.
detects abnormalities in the temperature around the laser beam,
After this detection, it is also possible to stop the laser oscillator and move the processing head again to the position required for the processing operation. Further, it is also possible to carry out unmanned operation and automated operation of such a series of operations.

〔Effect of the invention〕

As explained above, in a laser beam abnormality monitoring device, the present invention measures the temperature of the laser beam at a distance farther than the focal point of the condensing lens and at the outer periphery of the laser beam mode of the laser beam. Since the configuration is equipped with a temperature detection device consisting of multiple thermocouples for It has excellent effects such as improving the processing yield and making it easy to detect abnormalities in the laser energy distribution of the laser beam during unmanned and automated operation of the laser processing machine. be.

[Brief explanation of drawings]

1A and 1B are schematic diagrams for explaining the operating mode of a laser beam abnormality monitoring device which is an embodiment of the present invention, and FIG. 2 is a schematic diagram for explaining the operation mode of a laser beam abnormality monitoring device which is an embodiment of the present invention. FIG. 3 is a schematic diagram showing the configuration of a monitoring device, and FIG. 3 is a schematic diagram for explaining the operation mode of a conventional laser processing lens. In the figure, 1... laser beam, 2... condensing lens,
3... Temperature detection device, 4a to 4d... Thermocouple, 5.
...Amplifier, 6...Reference voltage generator, 7...Direct voltage comparator, 8.9, 10.12...Cable line, 11.
...Control device, 13...Alarm indicator, 14...Power damper, 15...Cooling water inlet, 16...Cooling water outlet. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (4)

[Claims] (1) In a laser processing machine that focuses laser light with a processing lens and irradiates it onto a workpiece, and performs processing such as welding on the workpiece, from the focal position of the focusing lens A laser beam abnormality monitoring device characterized in that it is equipped with a temperature detection device consisting of a plurality of thermocouples at a position far away. (2) Measure the temperature distribution of the laser beam with the plurality of thermocouples, compare the measured temperature with a predetermined temperature, and when it is detected that the temperature has changed beyond the predetermined temperature, an abnormality alarm will be issued. 2. The laser beam abnormality monitoring device according to claim 1, further comprising a control device for generating a laser oscillator or stopping a laser oscillator. (3) The laser beam abnormality monitoring device according to claim 1, wherein the temperature detection device is provided on a processing table on which a processing head incorporating the condensing lens is mounted. (4) The laser beam abnormality monitoring device according to claim 1, further comprising a power damper below the temperature detection device comprising the plurality of thermocouples.