JPH04327392A - Monitoring method for laser cutting - Google Patents

Abstract

PURPOSE:To surely judge a cutting condition by parallel observing the radiation light of another wavelength from the wavelength of the radiation light from a cutting part. CONSTITUTION:An optical fiber 3 for transmitting a YAG laser and plural pieces of small-diameter optical fibers 4 for monitoring for transmitting the radiation light are connected to a laser cutting tool 2. A material 1 to be cut is irradiated with the YAG laser directionally changed by a reflection mirror 7 via an exit hole 8 on the side face of a tool body 5. The complete cut off of the material 1 to be cut is judged if the radiation light of the same wavelength lambda1, of the exit light 9 and the specific wavelength lambda2. radiated when the material to be cut melts are monitored.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring laser cutting, which is applicable when the cutting situation cannot be directly observed visually.

0002

[Prior Art] Laser cutting is applied, for example, when collecting test specimens from mechanical structural members of heat exchanger tubes, but when the cutting situation can be directly observed visually, a mask or the like is used. Then, the quality of the cutting is determined, such as whether the material to be cut is completely cut and separated.

0003

[Problems to be Solved by the Invention] However, although it is conceivable to perform laser cutting by remote control in areas that cannot be directly visually observed, in this case there is a problem in that it is not possible to monitor the quality of the cutting.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a method for monitoring laser cutting that can determine the quality of cutting in remote-controlled laser cutting in which the cutting situation cannot be directly observed visually.

[0005]

[Means for Solving the Problems] A method for monitoring laser cutting according to the present invention that achieves the above-mentioned object is a method for monitoring laser cutting using a laser beam, in which emitted light from a cutting section having the same wavelength as the laser beam is emitted. and the emitted light from the cutting section with a different wavelength are observed in parallel, and it is determined that the cutting is complete by detecting that the light intensity of both emitted lights has decreased at the same time. shall be.

[0006]

[Operation] In the case of laser cutting, there is emitted light from the material to be cut, but this includes reflected light with the same wavelength as the wavelength of the irradiated laser, and reflected light emitted by the material to be cut when it melts. There is mainly melting radiation with wavelengths specific to the material, and changes in these components over time are closely related to cutting conditions. When a material to be cut is irradiated with a laser, reflected light is emitted, but as the material to be cut is heated, the reflected light decreases and the melting radiation increases. It is considered that when the material to be cut at the irradiation point is completely cut, both the reflected light and the melting radiation light decrease. Therefore, by monitoring both the reflected light and the melting radiation, it can be determined that the beam has been cut and separated when both have decreased at the same time.

[0007]

EXAMPLES The present invention will be explained below based on examples.

FIG. 1 is an explanatory diagram showing laser cutting for carrying out the method of the present invention. As shown in the figure, a laser cutting tip tool 2 is inserted into a tubular material to be cut 1, and this laser cutting tool 2 includes an optical fiber 3 that transmits a YAG laser and a thin fiber that transmits synchrotron radiation. A plurality of monitoring optical fibers 4 having different diameters are connected to each other. Here, the optical fiber 3 is connected to a YAG laser oscillator (not shown), and the monitoring optical fiber 4 is connected to a radiation light detector (not shown). The laser cutting tool 2 also includes YAG, which is transmitted through the optical fiber 3 into the tool body 5
It includes a condensing optical system 6 that condenses the laser beam, and a reflecting mirror 7 that reflects and changes the direction of the laser beam condensed by the condensing optical system 6. Then, the YAG laser whose direction is changed by the reflection mirror 7 is emitted through an emission hole 8 formed on the side surface of the tool body 5.
The material to be cut 1 is irradiated with the emitted light 9 through the emitted light 9 .

[0009] When cutting the workpiece 1 by laser using such a laser cutting tip tool 2, while emitting the emitted light 9, the monitoring optical fiber 4 receives the emitted light from the emitting part. is received by the monitoring optical fiber 4 and reflected light having the same wavelength λ1 as the emitted light 9,
By monitoring the melting radiation with a unique wavelength λ2 emitted by the material 1 to be cut when it melts, using a radiation detector (not shown), it can be determined that the material 1 to be cut has been completely cut and separated.

This method will be explained in detail based on FIG. As shown in FIG. 2, when the material to be cut 1 is irradiated with the emitted light 9, at the same time, reflected light with a wavelength λ1 begins to be emitted. As the irradiation continues, as time passes, the material to be cut 1
is heated, and a through hole is formed (region A in FIG. 2). In this region, there is little change in the reflected light, but the intensity of the melting radiation at wavelength λ2 gradually increases. but,
The material to be cut at the irradiation point is completely cut and the material to be cut at the irradiation point 1
When the wavelength λ1 disappears, the intensity of both the reflected light with the wavelength λ1 and the melting radiation light with the wavelength λ2 decreases (region B in Fig. 2).
. Therefore, cutting can be achieved by shifting the irradiation point while maintaining this state. If the workpiece 1 is cut during this cutting process,
If it is completely cut and there is a part that is not separated,
The intensity of both the reflected light with the wavelength λ1 and the melted radiation light with the wavelength λ2 increases again (region C in FIG. 2), so in this case, the output light 9 is irradiated again and the reflected light with the wavelength λ1 and the wavelength It is necessary to create a state in which the melting radiation of λ2 decreases (region D in FIG. 2).

In this way, the reflected light of wavelength λ1 and the reflected light of wavelength λ2
By monitoring the melting radiation light in parallel, the material to be cut 1 is completely cut during laser cutting,
It is possible to determine whether they are separated.

The material to be cut 1 is a tube made of N1-Cr-Fe alloy with a plate thickness of 1.3 mm and an outer diameter of 22 mm, and a YAG laser with a wavelength of 1.06 μm and an output of about 250 W is used as the emitted light 9, and the cutting speed is adjusted. Laser cutting was performed at approximately 0.7 m/min. At this time, when the reflected light with a wavelength λ1 = 1.06 μm and the melting radiation light with a wavelength λ2 = 0.94 μm were monitored, the situation in area A in FIG. 2 could be maintained, and as a result, the workpiece 1 was completely cut. Separated.

[0013]

As explained above, according to the method of the present invention, since the emitted light of two wavelengths from the material to be cut is monitored, the cutting process can be easily monitored even in remote-controlled laser cutting where the cutting situation cannot be directly observed visually. This has the effect that it can be determined whether the material to be cut has been completely cut and separated.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a laser cutting tip tool used in an example.

FIG. 2 is an explanatory diagram showing a monitoring situation according to the present invention.

[Explanation of symbols]

1 Material to be cut 2 Laser cutting tip tool 3 Optical fiber 4 Optical fiber for monitoring 5 Tool body 6 Condensing optical system 7 Reflection mirror 8 Output hole 9 Emitted light

Claims (1)

[Claims] [Claim 1] A method for monitoring laser cutting using a laser beam, in which light emitted from a cutting section having the same wavelength as the laser beam and emitted light from a cutting section having a different wavelength are emitted in parallel. A monitoring method for laser cutting, characterized in that the laser cutting is determined to have been completed by observing and detecting a simultaneous decrease in the light intensity of both synchrotron radiation beams.