JP2000202657A - Laser beam machining monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable detecting up to a depth without needing strictness in an installation position and becoming large size by only one set of sensor. SOLUTION: In the case that a work 10 is irradiated with laser beam 11 to machine the work 10, in a monitoring device to detect light emitting state of S part to be worked of the work piece, the light emission of the S part of the work piece which goes back to an optical system 15 on which the laser beam 11 is made incident is made to enter into a sensor 17 through a monitoring system 16 in a branched light passage separated from the laser beam 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing monitoring apparatus for monitoring a processing state of a work in process.

[0002]

2. Description of the Related Art In recent years, laser processing techniques such as laser welding and cutting have been adopted. In order to improve the reliability of the laser processing, it is necessary to inspect the processing state in-process. As for such in-process monitoring, for welding, an apparatus as shown in FIG. 9A has been proposed. That is, in FIG. 9, a plurality of sensors 3 are arranged so as to surround the irradiation position of the work 2 by the laser beam 1 so as to surround the irradiation position. In other words, we will try to monitor the beating of the beating and surface defects.

[0003]

However, in the configuration shown in FIG. 9 (a), a plurality of (for example, as shown in FIG. 9 (b)) (In the figure, four sensors are shown).
In addition, these sensors 3 need to be accurately positioned so that light can be sensed at an irradiation portion of the work 2, and high-precision positioning is required.

Further, since it is necessary to dispose the sensor 3 so as not to interfere with the laser beam 1 around the laser beam 1, the laser processing head must be increased in size.

[0005] In addition to the case where the laser processing head and the sensor 3 are integrally formed, in this case, the size of the processing head is further increased. The position of the sensor cannot be changed according to the change in the shape, and the flexibility of processing cannot be accommodated.

Although light emission in the keyhole 5 is detected by a plurality of sensors 3 as shown in FIG. 9B, the state of the keyhole 5 cannot be detected deeply.

[0007] In view of the above problems, the present invention provides one sensor in a lump, does not require much strict positioning, does not increase the size of the laser processing head, and increases processing flexibility. It is an object of the present invention to provide a laser processing monitoring device capable of responding and capable of detecting the inner deep portion and the bottom portion of the keyhole.

[0008]

The present invention that achieves the above object has the following matters specifying the invention. According to a first aspect of the present invention, in processing a workpiece by irradiating the workpiece with laser light, the monitoring apparatus detects a light emitting state of a workpiece processing part. The light emitted from the processing portion is incident on a sensor via a monitoring optical system on a branched optical path for separating the light from the laser beam.

According to a second aspect of the present invention, in the first aspect, the monitor optical system and the sensor are mounted on a processing head that irradiates a laser beam to a workpiece processing portion.

A third invention is characterized in that, in the first or second invention, the sensor has a structure in which any one of a photosensor, an optical fiber, and a CCD element is arranged in a cross shape when viewed from a plane.

A fourth invention is characterized in that, in the first or second invention, the monitor optical system is movable in the optical axis direction.

According to a fifth aspect of the present invention, in the first aspect, there is provided a computer which processes light incident on the sensor by one of the whole sensor, each sensor, and a sensor at a specific position. .

According to a sixth aspect, in the first aspect, the pulse width, which is the laser irradiation time of the pulsed laser, is monitored at the timing of pulse-on, pulse-off, or both. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an example of an embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a laser beam 11 condensed and irradiated on a work 10 is:
The light is reflected by a total reflection mirror 14 via a laser oscillator 12 and an optical fiber 13, and is condensed on a workpiece processing portion S via a laser processing optical system 15 such as a condenser lens.

In this case, when the laser oscillator 12 is, for example, a YAG laser, the total reflection mirror 14 is coated with a coating that reflects most (99%) the wavelength of the laser light (1.06 nm) and transmits other light. It is a mirror that was given.

On the other hand, in order to supplement light emission generated by the laser processing, the light passes through a laser processing optical system 15 and a mirror 14 and branches off into a laser optical system.
6 and a sensor 17 is arranged above the monitor optical system 16. In this case, the monitor optical system 16
The sensor 17 and the sensor 17 are located right above the workpiece processing portion S, and are designed so that the state of the workpiece processing portion can be observed well. In some cases, the sensor 17 is directly disposed without using the monitor optical system 16. The monitoring optical system 16 and the sensor 17 are provided on the processing head together with the laser processing optical system 15 and the total reflection mirror 14.

In such a configuration, the sensors 17 are arranged, for example, as shown in FIG.
Are arranged so that they can be seen from front to back and right and left when viewed from above. Here, a photosensor (FIG. 2P) is used as the sensor 17 for sensing the bundle of light LB generated at the workpiece processing portion S in the vertical and horizontal directions, but an optical fiber (FIG. 2F).
Or a CCD imaging device.
In FIG. 2, the sensors 17 are not only arranged in a vertical and horizontal cross shape, but may be arranged on the entire surface of the luminous flux, or may be arranged only in the vertical direction (front-back direction) or only in the horizontal direction (left-right direction). It may be. However, as a configuration in which the inside of the keyhole can be sufficiently detected in a simple arrangement, the cross arrangement shown in FIG. 2 is effective.

FIG. 3 shows a path of light emitted by the irradiation of the laser beam 11 with the work processing portion S being melted. That is, the laser processing optical system 1 includes not only the vicinity of the keyhole entrance but also the light emission from inside the keyhole.
5 shows how light passing through the monitor optical system 16 reaches the sensor 17. As can be seen from FIG. 3, the light emission state in the keyhole can be determined and identified by specifying the position of each sensor 17a. That is, the light emission state in the vertical and horizontal directions (front and rear, right and left) can be seen inside the keyhole.

Further, by providing the focusing function and the zoom function by moving the monitor optical system 16 in the vertical direction, the state around the keyhole and the inside of the keyhole can be obtained.

Returning to FIG. 2, if the signal obtained from the sensor 17 is, for example, an optical fiber,
Is converted into an electric signal via a / E (optical-electrical) converter 18,
The computer 19 performs light processing to detect a processing state.

In order to obtain light emission from the workpiece processing portion S by the sensor 17, it is necessary to focus the monitoring optical system 16 by a straight line. In other words, when it is desired to obtain the intensity of the light emission intensity of the entire processing object, for example, the focus is shifted (blurred) from the work processing object surface, the intensity is detected by all the sensors 17, and the light emission at a desired depth of the keyhole is performed. When it is desired to obtain the intensity or the luminous intensity of the surface, the monitor optical system 16 focuses on the position to obtain the luminous intensity at a desired position.

Moreover, since the elements 17a of the sensor 17 are arranged in a cross shape, for detecting the internal state of the keyhole, the element 17a in the sensor 17 is specified to further specify the internal position. be able to. For example, when it is desired to know the light emission state at the left and right positions inside as shown in FIG. 3, the element 17a at the right end or the like in FIG. In this manner, by adjusting the monitoring optical system 16 and selecting the element 17a in the sensor 17, the light emission intensity can be detected in accordance with the depth of the processing target, and the light emission intensity at the left, right, front and rear portions at the depth can be detected. Can also be obtained.

For example, in the case of welding, light emission occurs when a target metal is melted and flows by a laser beam to generate a new molten portion. In contrast to a steady waveform,
For example, when porosity (voids) is generated, the steady waveform is disturbed, and partial unevenness is observed in the amplitude, and the frequency of light emission changes. In this way, the light emission intensity whose depth and position are specified very strictly by the focusing of the monitoring optical system 16 and the selection of the element of the sensor 17 can be obtained, and the state of that location can be obtained. Of course, if the entire element of the sensor 17 is observed by performing only focusing, the light emission intensity at the entire depth can be obtained. In addition, as described above, when the focus is defocused from the surface of the object and the entire element is detected. Can obtain the luminous intensity from the entire welded portion at that time.

In the laser processing, the processing portion emits light as a whole, but the light emission at a specific depth or position is the whole light emission, for example, a plume coming out of the surface (light emission intensity by all the sensors defocused). By taking the difference between the light emission intensities of the sensors at specific depths and positions, it is possible to perform processing excluding light emitted by the plume.

In the case of processing using laser light, processing is performed using either continuous laser light or pulsed laser light. In the case where pulsed laser light is used, the pulse on-time (laser irradiation) is used. ) And the pulse off time, or both, and performs detection and processing by the sensor. In this way, the whole or desired position at the processing portion is determined by the focusing including the zoom function by the monitoring optical system for performing the focusing, and by specifying the entire position by the sensors 17 arranged in a cross shape or the position by selecting the element 17a. The light emission intensity at the depth or at the desired depth and the desired location can be freely obtained.

FIG. 4 shows the state of the light emission intensity detected by associating the position of the welding tip with the arrangement of the sensors 17 (here, four) during welding, and shows the surface state of the bead. It is a thing. FIG. 4A shows the corresponding position of the sensor 17 with respect to the bead and the laser beam, and the detectable positions of the sensor 17 with respect to the welding part are 5A, 9A, 13A, and 17A. FIG. 4B shows that the sensor positions correspond to 5S, 9S, 13S, and 17S with respect to the positions 5A, 9A, 13A, and 17A. Become. 4C and 4D show the sensors 5S, 9S, 1
FIG. 4E is a graph showing the relative intensity of light emission by 3S and 17S, and FIGS. 4E and 4F show the state of the bead surface at that time. That is, in the case of a defective bead shown in FIG. 4C, the light emission of the sensors 5S and 17S is strong, and in the case of a good bead, the light intensity of the sensor 13S is large. In other words, the results indicate that the sensor 17S or 5S has a strong light emission intensity due to the so-called skewing of the molten metal in a defective bead, and the sensor 13S has a strong result in a good bead. This change in light intensity indicates a so-called rough surface state in the defective bead shown in FIG. 4E, and a clear bead is seen in the good bead shown in FIG.

FIG. 5 shows a state of the work accompanying the cutting processing by the laser beam and a state of the light emission received by the sensor. That is, FIG. 5A shows the surface state of the work by laser cutting, and FIG. 5B shows the back state of the work. FIG. 5 (c) shows the internal cutting state of the work. FIG. 5D shows a state in which the cutting is performed and the light emission state is detected and processed by the entire sensor 17. FIG. 5D shows the boundary between the good cutting state and the poor cutting state with a waveform. In the good cutting state, the waveform is substantially constant and the light intensity is low. When it is not good, it can be seen that the waveform is irregular and irregular, and that the light intensity is high as a whole. In FIG. 5D, λ indicates the wavelength of light.

FIG. 6 shows an analysis of a good cutting state by the laser beam based on the light intensity of the sensor.
FIGS. 6A, 6B, and 6C show FIGS. 5A, 5B, and 5C.
The front, back, and internal states are shown as in (c). FIG. 6 (d)
Shows the roughness of the cut surface as a waveform. The waveform of the light intensity by all the sensors on the cut surface by the sensor 17 shown in FIG. FIG. 6 is a time-expanded view of this emission waveform.
By looking at (f), it can be seen that it is consistent with the roughness near the surface.

With respect to a good cutting state in this waveform,
The surface roughness waveform is constant and the state is common to the waveform at the left end in FIG. 5D, but also appears in the light emission state of the surface by the sensor 17 shown in FIG. 6E, and further shown in FIG. The light emission state inside is less disturbed and approximates to the waveform of FIG. 6D, and furthermore, the light emission at the bottom as shown in the lower part of FIG. Has been found to resemble a smoothed waveform.

FIG. 7 shows the light emission state as viewed from the entire sensor. Although the light emission intensity is high when the sensor is not cut, FIG.
In this case, there is no light emission due to transmission of light by cutting. However, since the waveform of the light emission state changes depending on the sensitivity level of the sensor 17, it is possible to change the level of the quality judgment of the cutting by appropriately selecting the sensitivity.

[0031]

According to the present invention as described above, the following effects can be obtained. In processing the work by irradiating the work with laser light, in a monitoring device that detects the light emission state of the work processing part, the light emission of the work processing part returning to the optical system where the laser light is incident,
By entering the sensor via the optical system for monitoring on the branched optical path separated from the laser light, the sensors can be arranged collectively, and the positioning accuracy of the sensor is not required conventionally, Also, light inside the keyhole can be detected.

The monitoring optical system and the sensor are mounted on a processing head that irradiates a laser beam to a workpiece processing portion, so that the size of the laser processing head does not become extremely large, and the processing is flexible by integration. Can also respond to sex.

Further, the sensor has a structure in which any one of a photo sensor, an optical fiber, and a CCD element is arranged in a cross shape when viewed from a plane, so that information from all front, rear, left and right portions of the object to be processed can be obtained. .

The monitor optical system is movable in the direction of the optical axis, so that it is possible to focus on a desired depth of the object to be processed and to obtain a light intensity at a strict depth. Can be.

Further, by providing a computer for processing the light incident on the sensor by any one of the whole sensor, each sensor, and a sensor at a specific position, it is possible to monitor not only the whole sensor but also a part thereof. Become.

In the case of a pulsed laser, it is expected that clearer processing results will be obtained if monitoring is performed at pulse intervals.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a sensor and a processing circuit.

FIG. 3 is an explanatory diagram showing a light emitting path.

FIG. 4 is an explanatory diagram showing a sensor arrangement, a sensor light receiving portion, and a light emitting intensity of a bead surface state during welding processing.

FIG. 5 is a diagram showing a cutting state and light emission intensity during cutting.

FIG. 6 is a diagram showing a cutting state and emission intensity at the time of a good cutting.

FIG. 7 is an uncut waveform diagram of all sensors.

FIG. 8 is a waveform diagram when all sensors are disconnected.

FIG. 9 is an explanatory view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Work 11 Laser beam 16 Monitoring optical system 17 Sensor 17a Element 18 O / E (optical / electric) converter 19 Computer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Risuke Nayama 2-1-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Mitsubishi Heavy Industries, Ltd. Takasago Research Institute (72) Inventor Hozumi Nakura 2-1-1, Araimachi, Takarai City, Hyogo Prefecture No. 1 Inside the Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory (72) Inventor Yoshio Hashimoto 2-1-1, Araicho, Araimachi, Takasago City, Hyogo Prefecture Inside the Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory (72) Inventor Koji Okimura Wa, Hyogo-ku, Kobe City, Hyogo Prefecture 1-1-1 Tazakicho Mitsubishi Heavy Industries, Ltd. Kobe Shipyard F-term (reference) 4E068 CA17 CB02 CC01 CD11 CD15

Claims (6)

[Claims] 1. A monitoring device for irradiating a laser beam to a workpiece to process the workpiece, wherein the monitoring apparatus detects a light emitting state of a workpiece processing portion. A laser processing monitoring apparatus characterized in that light emitted from a part is incident on a sensor via a monitoring optical system on a branched optical path for separating the laser light from the laser light. 2. The laser processing monitoring apparatus according to claim 1, wherein the monitoring optical system and the sensor are mounted on a processing head that irradiates a laser beam to a workpiece processing portion. 3. The laser processing monitoring apparatus according to claim 1, wherein the sensor has a structure in which one of a photosensor, an optical fiber, and a CCD element is arranged in a cross shape when viewed from a plane. 4. A laser processing monitoring apparatus according to claim 1, wherein the monitoring optical system is movable in an optical axis direction. 5. The laser processing monitoring apparatus according to claim 1, further comprising a computer for processing light incident on the sensor by any one of the whole sensor, each sensor, and a sensor at a specific position. 6. The laser processing monitoring apparatus according to claim 1, wherein a pulse width, which is a laser irradiation time of the pulse oscillation laser, is monitored at a timing of pulse-on, pulse-off, or both.