JP2712937B2 - Gas laser oscillation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser oscillating apparatus used for processing, welding and heat treatment of various materials, which does not require replacing a condenser lens according to the thickness of a workpiece.

[0002]

2. Description of the Related Art A gas laser oscillator excites a laser gas by a discharge between metal electrodes provided in a discharge tube, generates laser light by a resonator formed by mirrors provided at both ends of the discharge tube, and generates a laser beam from an output mirror. The emitted laser light is focused using a focusing lens, and various materials are processed, welded, and heat-treated.

Hereinafter, an example of a laser processing apparatus using a conventional gas laser oscillation device will be described with reference to the drawings. FIG. 5 shows a conventional laser processing apparatus. In FIG. 5, reference numeral 1 denotes a gas laser oscillation device, which is mainly composed of the following parts. That is, 2 is two discharge tubes made of a dielectric material such as glass, 3 and 4 are paired metal electrodes provided inside the discharge tube 2, 5 is a high-voltage power supply connected to the metal electrodes 3 and 4, 6 is a laser gas inlet, 7 is a laser gas outlet, 8 is a final mirror, 9 is an output mirror, 10 is a cooling water circuit for cooling the output mirror 9, and 11 is a laser output from the output mirror 9 of the gas laser oscillator 1. A beam 12 is a total reflection mirror for guiding the laser beam 11 to a workpiece (hereinafter referred to as a work) 14, and 13 is a laser beam 1
This is a condenser lens that collects 1 light.

[0004] The operation and working principle of the laser processing apparatus having the above configuration will be described. First, a laser gas is flowed into the discharge tube by a blower (not shown), a high voltage is applied from a high-voltage power supply 5 between the paired metal electrodes 3 and 4, and a pair of metal electrodes 3 and 4 is formed in the discharge tube 2. To generate a discharge. The discharge space is excited by the discharge, and the energy of the discharge space is resonated by the optical resonator formed by the output mirror 9 and the last-stage mirror 8,
The laser beam 11 is output from the output mirror 9 after being amplified. When the laser beam 11 passes through the output mirror 9, a part of the laser light is absorbed. If the output mirror 9 excessively absorbs the laser beam, a phenomenon called a thermal lens effect, that is, a temperature difference occurs in the output mirror 9, and the output mirror 9 deforms into a convex shape to have a lens effect. For this reason, it is known that the diameter of the laser beam 11 is reduced, and the laser beam 11 is cooled by cooling water as much as possible so as not to change. The laser beam 11 is guided to the condenser lens 13 by the total reflection mirror 12, and as shown in FIG.
At a focal length of. The condensed laser light is applied to a work 14 such as a rope to perform a cutting process. This condensed laser light is represented by two indices, a spot diameter and a depth of focus. Usually, the spot diameter is about 0.2 mm, and the energy density reaches a range of 10 ⁶ to 10 ⁷ J / cm ² , that is, a depth of focus. It becomes several mm or more, and it becomes possible to melt and cut an iron plate or the like having a thickness of several mm. In general, in laser processing, it is considered that a thin plate should have a small spot diameter and a thick plate should have a large depth of focus.

[0005]

However, in laser processing, a work having a thickness of 1 mm or less is required to reduce the thickness of the work to 19 mm.
Processing up to a thick plate of mm is required. On the other hand, according to the optical theory, as shown in FIG. 4, (1) the spot diameter is determined by the diameter of the laser beam entering the condenser lens, and the depth of focus is inversely proportional to the spot diameter. That is, when the laser beam diameter is large, the spot diameter is small and the depth of focus is small.

(2) The spot diameter is proportional to the focal length of the condenser lens. Are clearly proved and well known.

[0007] Therefore, in order to machine the workpiece optimally, it is necessary to replace the condenser lens with a small focal depth when cutting a thin plate and with a large focal depth when cutting a thick plate in accordance with the work. There was a problem that had to be done.

The present invention solves such a conventional problem, and provides a gas laser oscillation device that generates a laser beam that can always be cut satisfactorily in accordance with the thickness of a work without replacing a condenser lens. The purpose is to do.

[0009]

A gas laser oscillator according to the present invention comprises at least one discharge tube made of an insulator in which a laser gas to be excited is disposed, and a resonator formed at both ends of the discharge tube. and the final-stage mirror and the output mirror, before
A cooling control unit that controls the cooling amount of the output mirror is provided.
In the cooling control unit, the thickness of the work to be laser-processed is thin
The work thickness is thicker than the cooling amount of the output mirror when
This is to reduce the amount of cooling of the output mirror at that time.

[0010]

The present invention utilizes the fact that when a temperature distribution occurs in the output mirror, a phenomenon called a thermal lens effect, in which the diameter of the laser beam is reduced, occurs. FIG. 4 shows the relationship between the spot diameter and the depth of focus. That is, in FIG. 4, 13 is a condenser lens, φA is a laser beam diameter when the thermal lens effect is not generated, φB is a laser beam diameter when the thermal lens effect is generated, and the laser beam diameter is small. In this case, the spot diameter increases and the depth of focus increases.

With the above configuration, the cooling capacity of the output mirror is changed by the laser output, and this thermal lens effect is intentionally generated and used. The cutting performance can be improved by setting the laser beam diameter to obtain a large depth of focus for the plate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the gas laser oscillation device according to the present invention will be described below. FIG. 1 shows a configuration of a main part of an embodiment of a laser processing apparatus using the gas laser oscillation device of the present invention.

In FIG. 1, the same parts as those in FIG. 5 showing the conventional example are denoted by the same reference numerals, and description thereof will be omitted, and different points will be described. In FIG. 1, reference numeral 15 denotes a laser output setting signal generator, and 16 denotes a cooling amount (cooling amount) for cooling an output mirror section.
Here, the cooling water controller is a cooling controller that controls the flow rate of the cooling water (a flow rate of the cooling water) by a signal from the laser output setting device 15, and the other configuration is the same as that of FIG.

In the laser machining apparatus having such a configuration, the output mirror 9 absorbs the heat amount P represented by P = laser output × absorption rate. The temperature distribution changes. Although not uniformly determined by the cooling method, the relationship between the amount of cooling water and the laser beam diameter at a point 4 m from the output mirror 9 and the relationship between the amount of cooling water and the temperature of the output mirror 9 were measured in FIG. An example is shown. In a test performed at an output of 3 kW, a thermal lens effect was observed by reducing the amount of cooling water of the output mirror 9. The life of the output mirror 9 can be estimated from the surface temperature. However, even if the cooling water is stopped, the temperature rise limit is about 70 ° C., and there is a margin for the use limit of the output mirror 9 to 100 ° C. confirmed.

FIG. 3 shows the measured results of the relationship between the laser output and the laser beam diameter at a point 4 m from the output mirror 9 in the gas laser oscillation device of the present invention. According to FIG. 3, when the cooling capacity is low, the laser beam diameter is large and constant when the laser output is 1.5 kW or less, and the laser beam diameter gradually decreases as the output increases. As described above, it has been found from the optical theory that the smaller the laser beam diameter, the larger the spot diameter and the larger the depth of focus. Therefore, FIG. 3 shows that the range of the laser output in which the laser output is constant differs depending on the cooling capacity. In the range where the laser output is large,
This shows that the depth of focus can be changed depending on the cooling state of the output mirror 9 even with the same laser output.

According to the above results, if the gas laser oscillation device 1 provided with the cooling water control unit 16 for changing the cooling capacity of the output mirror 9 by the output laser value setting signal is manufactured, the output mirror 9 can be controlled by the amount of the cooling water. By changing the temperature of the laser beam, the spot diameter and the depth of focus of the collected laser beam can be changed, and the cutting performance of the laser processing apparatus can be improved. (1) In the area of a thin plate using a small laser output, the heat absorption by the output mirror 9 is small and the thermal lens effect does not occur, so that the laser beam diameter is large and a small spot diameter can be obtained, and the thin plate is cut. Suitable for.

(2) In a region of a thick plate using a large laser output, heat absorption at the output mirror 9 is large, a thermal lens effect occurs, a laser beam diameter is reduced, a large depth of focus is obtained, and a cooling water amount is obtained. Is controlled in accordance with the laser output, so that the depth of focus suitable for cutting a thick plate of each thickness can be obtained.

In the gas laser oscillator described above, the output mirror 9 is of a water-cooled type. However, even if the output mirror 9 is cooled by forced air cooling, the same result as described above can be obtained. However, in this case, the cooling water control unit 16 for controlling the amount of cooling water for cooling the output mirror 9 in the above embodiment is
The cooling air control unit controls the amount of cooling air for cooling the output mirror 9.

[0019]

As is apparent from the above description, in the region where the work is a thin plate, the laser beam is small and the thermal lens effect does not occur, so that the laser beam is large and a small spot diameter suitable for cutting the thin plate can be obtained. In the area where the workpiece is a thick plate, the laser output is large and the thermal lens effect is generated, so the laser beam is small, and a large depth of focus can be obtained. By controlling the laser beam diameter, the focal depth suitable for cutting a thick plate of each thickness can be obtained. As described above, by changing the degree of cooling of the output mirror together with the laser output according to the thickness of the work, a spot diameter and a depth of focus suitable for each thickness can be obtained, and the cutting performance can be improved.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of an embodiment of a laser processing apparatus using a gas laser oscillation device of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a cooling water amount and an output mirror temperature and a relationship between a cooling water amount and a laser beam diameter.

FIG. 3 is a characteristic diagram showing a relationship between a laser output and a laser beam diameter.

FIG. 4 is a cross-sectional view of a condenser lens showing a relationship between a laser beam diameter, a spot diameter, and a focal depth.

FIG. 5 is a main part configuration diagram of a laser processing apparatus using a conventional gas laser oscillation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas laser oscillator 2 Discharge tube 3, 4 Metal electrode 5 High voltage power supply 8 Final mirror 9 Output mirror 15 Laser output signal generator 16 Cooling water controller

Claims (2)

(57) [Claims] At least one discharge tube made of an insulator in which a laser gas to be excited is disposed, a final mirror and an output mirror disposed at both ends of the discharge tube to form a resonator, and A cooling control unit that controls a cooling amount, wherein the cooling control unit controls the cooling amount of the output mirror when the thickness of the work is thicker than the cooling amount of the output mirror when the thickness of the work to be laser-processed is small. A gas laser oscillation device characterized by reducing the size of the gas laser. 2. A signal of a laser output signal generator is input to a cooling control unit, and a laser output is applied to a plate of a work to be laser-processed.
2. The gas laser oscillation device according to claim 1, wherein the thickness is increased according to the thickness .