JPH0780677A - Laser cutting method and device - Google Patents

Abstract

PURPOSE:To increase the power of a laser beam which can be cast with the laser cutting device. CONSTITUTION:This laser cutting device is provided with a nozzle 24 which condenses the laser beam from a laser oscillator 22 by a concave mirror 27 in a machining head 23, irradiates a work 35 with the condensed laser beam and supplies an assist gas to the circumference of an optical axis 37 of the laser beam near the focus of the laser beam. The nozzle 24 has a body 31 which is an annular tubular body and an endless annular slit 36 is formed on the work 35 side surface of the body 31. The assist gas is injected from the slit 36 to an irradiation direction 38 of the laser beam. Then, the machining head 23 is not required any more to have a mechanism for injecting the assist gas coaxially with the optical axis 37. As a result, the need for disposing a condenser lens functioning as a pressure partition and a transmission element in the optical route of the laser beam is eliminated and the use of the concave mirror capable of withstanding large power as a condenser means is made possible. The cutting of the thick work is thus possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser cutting method and apparatus suitable for cutting thick metal materials.

[0002]

2. Description of the Related Art A typical prior art laser cutting method is shown in Japanese Patent Laid-Open No. 1-95890, and FIG. 5 is a sectional view of a laser cutting apparatus 1 using the conventional cutting method. The laser cutting device 1 is roughly configured to include a laser oscillator 2 and a processing head 3. The processing head 3 has a cylindrical casing 4, and has an entrance 5 to an exit 6 through which the laser light from the laser oscillator 2 enters.
It is formed by narrowing it down into a nozzle shape toward the side.
A convex condensing lens 7 is provided near the entrance 5 of the casing 4, and a gas is supplied to a space 8 in the casing 4 defined by the condensing lens 7 through a pipe line 9. A high-pressure assist gas is supplied from the source 10.

The laser light incident from the entrance 5 is focused near the exit 6 by the condenser lens 7, narrowed down to a spot diameter of, for example, about 0.3 to 0.4 mm, and applied to the work 12. It At this time, high-pressure assist gas is injected from the emission port 6 toward the work 12 again. As a result, the molten dross is scattered by the assist gas, and the cut surface is kept clean.

The assist gas is used as the work 12
When iron is iron, oxygen gas is used. Therefore, the heat generated by the laser light irradiation and the heat generated by the oxidation reaction of iron are used to make the work 12 thick,
The cutting is possible.

FIG. 6 shows another prior art laser cutting device 1.
1 is a cross-sectional view of FIG. 1, similar to the laser cutting device 1 described above,
Corresponding parts are designated by the same reference numerals. The processing head 13 of the laser cutting device 11 is formed in a substantially L shape, and a condenser mirror 17 realized by a concave mirror is arranged in the vicinity of the bent portion thereof, instead of the condenser lens 7. Further, in the processing head 13, there is a transmissive element capable of transmitting a laser beam in order to play a role of a pressure partition wall capable of injecting a high pressure gas from the emission port 6 toward the work 12. As shown by at least one of the symbols 14a and 14b, it is interposed in the optical path of the laser light.

[0006]

In the above-mentioned prior art,
A space 8 needs to be formed in the processing heads 3 and 13 so that the assist gas can be ejected coaxially with the laser light on the workpiece 12 so that the space 8 is defined. In order to do so, it is necessary to interpose the condenser lens 7 or the transmission elements 14a and 14b having a function as a pressure partition wall.

Therefore, a structure for cooling the heat generated by the passage of the laser beam through the condenser lens 7 made of ZnSe and the transmission elements 14a, 14b is required, and from the viewpoint of its cooling capacity and the like. ,
The power of the laser light that can be applied to the work 12 is, for example, about 3 kW. On the other hand, the laser oscillator 2 is, for example, a CO ₂ laser, and the maximum output currently obtained is, for example, 45 kW or more. Therefore, even if an attempt is made to cut a thick workpiece using such a high-power laser oscillator, it has been impossible due to the problem of the cooling surface as described above.

An object of the present invention is to provide a laser cutting method and apparatus capable of irradiating a work with a laser beam of higher power.

[0009]

According to the present invention, a laser beam outputted from a laser oscillator is condensed by a condensing unit, and in the vicinity of its focal point, from the periphery of the optical axis of the laser beam to the irradiation direction of the laser beam. It is a laser cutting method characterized in that an assist gas is jetted toward.

Further, according to the present invention, a condensing means for condensing the laser light outputted from the laser oscillator, and a light converging means disposed near the focal point of the condensing means, around the optical axis of the laser light, are provided. And an assist gas injecting means for injecting an assist gas toward the laser cutting device.

Furthermore, the present invention is characterized in that shield gas injecting means for injecting a shield gas in a direction opposite to the irradiation direction is provided upstream of the assist gas injecting means in the irradiation direction.

[0012]

According to the present invention, when the laser beam outputted from the laser oscillator is condensed by the condensing means and the work arranged at the focal point of the condensing means is irradiated with the laser beam, the assist gas injection means is provided near the focal point. To provide. The assist gas injecting means is arranged around the optical axis of the laser light from the condensing means to the work, and injects a high-pressure assist gas such as oxygen toward the irradiation direction of the laser light, that is, toward the work. . That is, for example, the assist gas injecting means is composed of a tubular body formed in an annular shape so as to surround the optical axis, and an endless annular slit is formed in the work-side surface of the outer peripheral surface of the tubular body. .

Therefore, when injecting the assist gas toward the workpiece coaxially with the laser beam, it is necessary to form a space as the flow path of the assist gas as described in the prior art in the processing head provided with the light converging means. Disappears. As a result, a concave mirror, which generates less heat even if it is placed in the optical path of the laser light, is used as the light collecting means, and only this light collecting means is provided in the light path, thereby increasing the power of the laser oscillator. It is possible to cut thick work pieces.

Preferably, a shield gas injecting means is provided on the upstream side of the assist gas injecting means in the irradiation direction, that is, on the light collecting means side, and the shield gas injecting means is provided in a direction opposite to the irradiation direction. A shield gas such as oxygen gas should be injected.
As a result, it is possible to suppress mixing of ambient air into the assist gas, maintain the purity of the assist gas at a high value, and prevent deterioration of cutting quality due to uneven combustion of the cut surface.

[0015]

1 is a sectional view of a laser cutting device 21 according to an embodiment of the present invention. The laser cutting device 21 is roughly configured to include a laser oscillator 22, a processing head 23, and a nozzle 24. To the processing head 23,
The laser light output from the laser oscillator 22 is generated by the waveguide 2
It is input via 5. The processing head 23 has a substantially L-shaped cylinder.
It has a casing 26 formed by being bent in a letter shape, and a concave mirror 27 as a light converging means is provided near the bent portion of the casing 26. The laser light input to the processing head 23 through the waveguide 25 enters the concave mirror 27 through the entrance 28, is condensed, and is output through the exit 29. A nozzle 24 is provided near the focal point of the laser light.

FIG. 2 shows the nozzle 24 taken along the section line A-- of FIG.
It is sectional drawing seen from A. With reference to FIG. 2 and FIG. 1 described above, the nozzle 24 is composed of a main body 31 and a connecting portion 32, and the connecting portion 32 is connected to a gas supply source 34 via a conduit 33. The main body 31 is generally configured by forming an endless annular slit 36 on a surface facing the work 35 on the outer peripheral surface of an annular tubular body.

Therefore, the high-pressure assist gas supplied from the gas supply source 34 is supplied from the connecting portion 32 to the main body 31.
And is jetted from the slit 36 toward the work 35. The nozzle 24 is arranged so that the center of the annular main body 31 is aligned with the optical axis of the laser beam indicated by the reference numeral 37, and thus the focus of the laser beam focused by the concave mirror 27 on the work 35. Assist gas is jetted from around the optical axis 37 toward the direction, and the molten dross is scattered from the cut surface, so that the cutting quality is improved.

The work gas 35 is used as the assist gas.
When is iron, oxygen is used. Therefore, the work 35 is cut using the heat of the laser light irradiation and the heat of the iron oxidation reaction.

Thus, in this embodiment, the processing head 23
A nozzle 24 for injecting an assist gas is provided on the downstream side of the laser light irradiation direction indicated by reference numeral 38, and the nozzle 24 extends from the periphery of the laser light optical axis 37 toward the optical axis 37. Inject assist gas. Therefore, it is not necessary to provide the processing head 23 with a condenser lens or a transmission element having a function of a pressure partition wall that defines a space for ejecting the assist gas coaxially with the optical axis 37 of the laser light as described in the prior art. Absent. As a result, the processing head 23 need only be provided with the concave mirror 27 capable of withstanding a large power as the light converging means. Therefore, the output of the laser oscillator 22 is increased and the thickness of the work 35 that can be cut is increased. be able to.

FIG. 3 is a bottom view of a nozzle 44 according to another embodiment of the present invention. Similar to the nozzle 24, the nozzle 44 is supplied with an assist gas to the annular main body 41 via the connecting portion 42, and the assist gas is evenly distributed on the outer peripheral surface of the main body 41 on the bottom surface facing the work 35. It is configured to eject from the nozzle hole 45 formed in. This also eliminates the need to form a space for supplying the assist gas in the processing head 23.

FIG. 4 is a sectional view of a laser cutting apparatus 51 according to still another embodiment of the present invention, which is similar to the above-mentioned embodiment,
Corresponding parts are designated by the same reference numerals. In this embodiment, the nozzle 54 has a two-layer structure. Therefore, in addition to the main body 31, the irradiation direction 38 of the main body 31
Another main body 50 is provided on the upstream side of the. To the main body 50, a high-pressure shield gas realized by the same gas as the assist gas is supplied from a gas supply source 55 from a connecting portion 52 through a conduit 53. Further, the main body 50 is formed with an endless annular slit 56 for injecting the shield gas in a direction opposite to the irradiation direction 38.

Therefore, the slit 36 of the body 31 is
Assist gas is jetted in the direction of the workpiece 35 from the slit 56, and the shield gas is jetted from the slit 56 to the machining head 23 side, so that the vicinity of the central portion 57 of the nozzle 54 has a negative pressure. It is possible to prevent the air on the side of the processing head 23 from being mixed into the assist gas through the central portion 57. As a result, the assist gas can be maintained at a high purity, the cut surface can be burned uniformly, and the cutting quality can be improved.

Although the concave mirror 27 is used as the light collecting means in the above embodiment, a convex lens may be used as another embodiment of the present invention. In this case, the convex lens serves as the pressure partition wall. Since it is not necessary to provide such a function, it becomes possible to design by giving priority to the laser light transmittance and the like over the intensity.

[0024]

As described above, according to the present invention, the assist gas is jetted from the periphery of the optical axis of the laser light in the vicinity of the focal point of the laser light in the irradiation direction of the laser light. It is no longer necessary to form a space that serves as a flow path for the assist gas in the processing head that is provided with a condensing means such as a convex lens or a concave mirror that condenses the light, thereby defining the space in the optical path of the laser light. Therefore, it is not necessary to provide a lens or an element that serves as a pressure partition wall, and the power of the laser oscillator can be increased to cut a thick member.

Further, preferably, since the shield gas is injected in the direction opposite to the injection direction of the assist gas, it is possible to suppress the mixing of ambient air into the assist gas and maintain the purity of the assist gas high. It is possible to suppress irregular burning of the cut surface and improve the cutting quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a laser cutting device 21 according to an embodiment of the present invention.

FIG. 2 is a nozzle 2 used in the laser cutting device 21.
FIG. 4 is a cross-sectional view taken along section line AA of FIG.

FIG. 3 is a bottom view of a nozzle 44 according to another embodiment of the present invention.

FIG. 4 is a laser cutting device 5 according to still another embodiment of the present invention.
2 is a sectional view of FIG.

FIG. 5 is a cross-sectional view of a typical prior art laser cutting device 1.

FIG. 6 is a cross-sectional view of another prior art laser cutting device 11.

[Explanation of symbols]

 21, 51 Laser cutting device 22 Laser oscillator 23 Processing head 24, 44, 54 Nozzle 27 Concave mirror 34, 55 Gas supply source 35 Workpiece 36, 56 Slit 37 Optical axis 38 Irradiation direction

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Inuzuka 3-1, 1-1 Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries Ltd. Kobe factory (72) Hiroshi Hase, Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo 3-1-1 Kawasaki Heavy Industries Ltd. Kobe factory

Claims (3)

[Claims] 1. A laser beam outputted from a laser oscillator is condensed by a condensing means, and an assist gas is jetted from around the optical axis of the laser beam in the irradiation direction of the laser beam in the vicinity of its focal point. A laser cutting method characterized by the above. 2. A light condensing means for condensing the laser light outputted from the laser oscillator, and a light concentrating means arranged near the focal point of the light converging means around the optical axis of the laser light and directed toward the irradiation direction of the laser light. A laser cutting device comprising: an assist gas injecting means for injecting an assist gas. 3. The laser according to claim 2, further comprising a shield gas injection means for injecting a shield gas in a direction opposite to the irradiation direction, on the upstream side of the assist gas injection means in the irradiation direction. Cutting device.