JPH10263860A - Laser transmission system diagnostic equipment - Google Patents

Abstract

(57) [Summary] [Problem] Laser welding is performed by directly monitoring the behavior of a laser spot to diagnose an abnormality in a laser transmission system, and immediately informing an operator or an operating device of the abnormality to avoid welding failure in advance. Improve efficiency. SOLUTION: In a laser welding apparatus for performing welding using a high-power laser, a laser transmission system diagnostic apparatus installed for diagnosis of a transmission system, the same transmission path as a laser used for welding is provided. A low-power laser still transmitted through the welding point, a translucent light scattering plate arranged at a position corresponding to the welding point in the laser welding apparatus, and the light scattering plate through a lens having a focal position on the surface of the light scattering plate. The two-dimensional imaging device for imaging the upper part, and the characteristics of the image obtained from the imaging device determine whether the transmission system of the high-power laser is normal or not.
A laser transmission system diagnostic device comprising an image processing device for determining abnormalities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for detecting an abnormality in a laser transmission system of a laser welding apparatus at an early stage.
The present invention relates to a technique for improving the reliability of laser welding.

[0002]

2. Description of the Related Art High power carbon dioxide laser or YA
Techniques for welding a workpiece using a G laser are known. Also, when performing welding, it is known that welding can be performed stably by welding while oscillating (weaving) the beam in a direction perpendicular to the welding direction, thereby increasing the molten volume in the welded portion. is there. An apparatus for performing such welding is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-31816.
As disclosed in Japanese Patent Laid-Open No. 1 (Kokai) No. 1, a technique has been disclosed in which a laser spot is scanned in a direction perpendicular to a welding direction (a direction in which a welding line extends) by swinging a last lens by a galvanometer. However, a device for grasping the state of the transmission system and detecting an abnormality at an early stage has not been proposed yet.

[0003]

Generally, in a laser welding apparatus, there is a laser transmission line using a mirror or a lens from a laser oscillator to a torch portion for performing welding. It is a space that is shielded from the outside for reasons such as preventing transmission and ensuring safety, increasing the transmission loss due to dust entering the transmission path, and preventing dirt from attaching to mirrors and lenses. Its internal state, especially the state of the lens and mirror, cannot be monitored. In the case where a weaving mechanism as disclosed in Japanese Patent Application Laid-Open No. Hei 5-318161 is provided, when a galvanometer or a driving motor fails, a primary abnormality diagnosis is performed by directly monitoring the output of the galvanometer. Is possible, but it is not possible to detect abnormalities such as breakage of the connecting portion between the oscillating mirror and the galvanometer by such a method.

[0004] That is, an object of the present invention is to always monitor the behavior of the final laser spot to constantly diagnose an abnormality in the laser transmission system, and to immediately notify the operator or the operating device of the abnormality, thereby preliminarily detecting a welding failure. To improve the efficiency of laser welding.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a laser transmission system diagnostic apparatus for diagnosing a laser transmission system of a laser welding apparatus for performing welding by using a high-power laser, the laser being used for welding. And a low-power laser emitted through the same transmission path, and a translucent light scattering plate arranged at a position corresponding to a welding point in the laser welding apparatus,
A two-dimensional imaging device for imaging the light scattering plate through a lens having a focal position on the light scattering plate surface, and image processing for determining whether the transmission system is normal or abnormal based on characteristics of an image obtained from the imaging device The above problem is solved by a laser transmission system diagnostic device including a device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The diagnostic apparatus is an apparatus in which the two-dimensional imaging apparatus continues exposure for a predetermined time and outputs a high-light result of the exposure duration as one frame image. When the apparatus is an apparatus that performs welding while performing weaving, the two-dimensional imaging apparatus is an apparatus that continues exposure for one or more cycles of weaving and outputs an image of the exposure continuation period as one frame screen. The image processing apparatus uses the one-frame image as an image processing unit, and performs binarization processing on a luminance level on the screen of the one frame to cut out a trajectory through which the laser has passed for one frame exposure time, and cut out the trajectory. Detect the length of the trajectory in the vertical and horizontal directions or the length of one of them, or determine the center position in the vertical and horizontal directions of the extracted trajectory as necessary. Out, a laser transmission system diagnosis means performing a diagnosis of abnormality on the basis that the result is within the allowable error with respect to the command value.

Further, of the diagnostic device, the semi-transparent light scattering plate and a two-dimensional imaging device for imaging the light scattering plate through a lens having a focal position on an open surface of the light scattering plate are welded. Place it off-line next to where you want to go,
The diagnosis is performed by moving the torch onto the light scattering plate during the waiting time during which welding is not performed, and irradiating the low power laser onto the light scattering plate during or after the movement is stopped.

According to the present invention, any abnormality in the transmission system is reflected in the position, spot diameter, etc. of the laser spot, and the abnormality in the weaving device is reflected in the amplitude of the laser spot. On the other hand, since a laser spot that is finally formed at the same position as the welding position through all the transmission systems is imaged and measured directly, all these abnormalities can be diagnosed.

That is, the state and behavior of the final laser spot are directly monitored to constantly diagnose an abnormality in the laser transmission system, and immediately notify the operator or operating device of the abnormality to avoid welding failure in advance. And the efficiency of laser welding can be improved.

[0010]

FIG. 1 shows an entire configuration of an embodiment of the present invention.
1 is a high output carbon dioxide laser oscillator, 2 is
It is a low output He-Ne laser oscillator of about 20 mW. Reference numeral 3 denotes a shutter for shielding light, and reference numeral 4 denotes a plane mirror. At the time of welding, the shutter 3 is opened, the plane mirror 4 opens the light on the carbon dioxide laser side, and outputs the carbon dioxide laser on the optical path 5. When non-welding is performed, the shutter 3 is closed, the plane mirror 4 opens the He-Ne laser side (this state is called closed), and outputs the He-Ne laser through the optical path 6 (the figure shows this state). Each laser beam passes through the plane mirror 7 and is condensed by the concave mirror 8, and then finally condensed by the plane mirror 9 at the position of the focal point 10. Here, the plane mirror 9 scans the laser spot in a direction perpendicular to the paper surface (a direction orthogonal to the welding line; weaving direction) by swinging about the rotation axis 12 by the driving device 11. The part indicated by 13 is called a welding torch.

These laser transmitters are installed on a gantry 14, and the gantry 14 is installed on a base frame 15 and is movable in the direction of arrow 16 (the direction in which the welding line extends). Reference numeral 17 denotes a material to be welded, and reference numeral 18 denotes a rotating roll. When the rotating roll 18 rotates, the material 1 to be welded is rotated.
Reference numeral 7 moves in a direction perpendicular to the paper surface and is conveyed to the next step. The focal point 10 of the laser is adjusted to the surface position (surface level; surface height) of the material 17 to be welded, and the gantry 14 moves in the direction of the arrow 16 (welding direction) while irradiating the carbon dioxide laser. Thereby, welding of the material to be welded is performed. At the time of non-welding, the gantry 14 is in the off-line position, that is, the laser directing point corresponding to the focal point 10 is indicated by a dashed line L.
Move more to the right. 19 is a ground glass, 20 is a neutral density filter, and 21 is a CCD camera. Instead of the ground glass 19, a resin plate made of cloudy plastic or the like can be used.

The CCD camera 21 has a rectangular visual field, and has a welding direction (a direction (16) in which the welding line extends) and a weaving direction (a direction perpendicular to the paper surface) on two sides thereof. The upper surface of the ground glass 19 is in focus, and the upper surface of the ground glass 19 is in focus 10.
Is the same height as In other words, the low-power He-Ne laser is focused on the upper surface of the ground glass 19.
Reference numeral 23 denotes an image processing device which processes an image from the CCD camera 21 to determine whether a laser transmission path is abnormal. An alarm device 24 generates an alarm when the image processing device 23 determines that an abnormality has occurred.

FIG. 2 shows the weaving operation of the focal point 10 (3
0) and the timing (31) for updating the screen of the CCD camera 21 of the imaging device. The horizontal axis indicates time, and the vertical axis indicates the displacement of the laser spot (10) from the welding line. A curve 30 shows the weaving operation. In this embodiment, weaving is performed so as to draw a SIN (sine wave) curve, but a short form may be used. C on straight line 31
The timing of capturing an image of one frame of the CD camera 21 is shown in FIG. Exposure is performed during HIGH period,
The CCD camera 21 outputs a current proportional to the integral value of the amount of light received during this period. The LOW part is the frame update timing. As can be seen from this figure, in this embodiment, one frame is updated by Δt longer than one weaving cycle.

FIG. 3A shows an image of one frame. In the drawing, the welding direction (X direction; direction 1 in which the welding line extends)
6) and the weaving direction (Y direction). This image shows the H on the ground glass 19 while moving the welding torch 13 in the welding direction at a constant speed while performing the weaving operation.
The reflected light (scanning light image) of the e-Ne laser is taken, and the trajectory of the laser is SIN as shown by a curve 40.
Measured as a waveform.

FIG. 3 (a) shows an image of one frame shown in FIG.
c, Yc) detection ”50. Image processing device 2
3, a video signal (brightness level) of the CCD camera 21 is binarized using a constant brightness level as a threshold, and bit data "1" is assigned to a pixel having a brightness level equal to or higher than the threshold, and the bit data is set to less than the threshold The bit data "0" is given to the pixel having the luminance level (step 51). As a result, binary pixel data is obtained in which information of a pixel (trajectory pixel) on the laser scanning locus is "1" and information of other pixels is "0".

Subsequently, X-direction projection is performed. That is, the number of track pixels present at the same Y position is counted, and
The data is written into the memory corresponding to the position (step 52y). As a result, the distribution of the count values shown in FIG. 3B (the vertical axis is the count value, and the horizontal axis is the Y position) is obtained. The distribution of this count value is
Binarization is performed using the threshold value TH, bit data "1" is given to the Y position of the count value equal to or greater than the threshold value TH, and the threshold value T
Bit data "0" is given to the Y position less than H (step 53y). Thereby, the binary level distribution shown in FIG. 3D (the vertical axis represents the binary level, and the horizontal axis represents the Y position)
Is obtained. Next, the Y positions Y1 and Y2 of the rising and falling points of the binary level distribution are extracted (step 54).
y), and calculate their intermediate point Yc (step 55)
y).

As described above, projection in the Y direction is performed. That is, the number of track pixels existing at the same X position is counted, and the counted value is written to the memory corresponding to the X position (step 52).
x). Thereby, the distribution of the count values shown in FIG. 3C (the vertical axis is the count value, and the horizontal axis is the X position) is obtained. The distribution of the count value is binarized using the threshold value TH, bit data “1” is given to the X position of the count value equal to or greater than the threshold value TH, and the bit data is assigned to the X position less than the threshold value TH. Data "0" (step 53x). Thereby, (e) of FIG.
(The vertical axis represents binary levels, and the horizontal axis represents X
Is obtained. Next, the X positions X1 and X2 of the rising and falling points of the binary level distribution are extracted (step 54x), and the intermediate point Xc is calculated (step 55x).

The amplitude of the weaving is X2-X1 (= W)
, The traveling speed of the welding torch 13 is (Y2-Y1) /
The calculation can be performed with the update time of one frame (= V). Where W
Is A> W or B for allowable minimum value A and allowable maximum value B
If <W, the image processing apparatus 23 determines that the laser transmission path is abnormal. Similarly, an allowable range is set for V, and the abnormality of the operation of the welding torch 13 is also determined. Also, whether the beam position is correct or not is checked by the center point (Xc, Yc). That is, when the center point (Xc, Yc) is within the set small area, it is determined to be normal.

The image processing device 23 has no weaving,
The same image processing, calculation, and abnormality determination as described above are performed under the welding torch fixing condition, and the correctness or wrongness of the size of the laser spot itself is determined by W and V, and the correctness or wrongness of the position is determined by the center point (Xc, Yc). Check. In this case, however, the threshold value, the reference value, and the area size are those determined in the mode of fixing the welding torch without weaving.

FIG. 5 shows the contents of the welding control incorporating the above-described laser transmission path abnormality check (laser transmission system diagnosis). In this embodiment, the laser transmission system diagnosis is always performed before the welding is performed. However, the laser transmission system diagnosis may be performed intermittently, for example, once after the completion of a plurality of weldings. .

Next, the welding control shown in FIG. 5 will be described. In the initial state, the torch 13 is located at a certain place (standby position;
Position), for example, at the off-line mobile end. Except during welding, the shutter 3 and the plane mirror 4 are closed so that a low-output He-Ne laser is irradiated.
That is, the shutter 3 is located at a position where the welding laser is shut off, the plane mirror 4 is located between the welding laser light source 1 and the plane mirror 7, and reflects the He-Ne laser to the plane mirror 7.

When the welding operation start is given from the operator or the host computer, the welding torch 13 is driven onto the glass 19, that is, onto the laser transmission system diagnostic device (step 61). He-Ne while moving
Immediately before the laser starts passing over the ground glass 19, laser transmission system diagnostic measurement is started (step 62).
When the He-Ne laser starts passing over the ground glass 19, "detection of the center point (Xc, Yc)" (step 50) shown in FIG. 4 is performed (step 63), and the measurement is ended when the laser passes over the ground glass 19. (Steps 64 and 6)
5). If the result of the diagnosis by the image processing device 23 is OK, it moves to the welding standby position (the position L in FIG. 1) (steps 66 and 67), and the ready is notified to the operation panel or the host computer, and the welding start is started. Wait for a command. When the welding start command arrives, the drive to the welding start position is started (step 68), and when the welding directing line (target position) of the welding torch 13 reaches the welding start position, the shutter 3 is closed. The flat mirror 4 is opened (the shutter 3 and the flat mirror 4 are driven to the retracted positions) to start welding (step 69). When welding is completed, the shutter 3 and the flat mirror 4 are closed, and the welding torch 13 is again moved to the initial position (FIG. 1). L) (step 71). When the next welding is to be performed, it is performed again from the start (step 61). If the diagnostic result is not OK, an alarm is issued and the welding is stopped. That is, while the shutter 3 and the plane mirror 4 are closed, the welding
Hold the switch 13 on the laser transmission system diagnostic device.

[0023]

According to the present invention, the state and behavior of the final laser spot are directly monitored by the imaging device (21), so that the laser transmission system is constantly diagnosed for abnormality, and the abnormality is immediately detected by the operator or the operator. By notifying the operating device, welding failure can be avoided in advance and the efficiency of laser welding can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention.

FIG. 2 is a time chart showing the relationship between the weaving operation of the laser sent and received by the He-Ne laser oscillator 2 shown in FIG. 1 and the timing of updating the screen of the imaging device 21, and 30 denotes the focus of the laser due to the weaving operation. The trajectory to be drawn is shown, and 31 indicates the timing of updating the screen.

3A is a plan view showing a captured image of the image pickup device 21 shown in FIG. 1, and FIG. 3B is a diagram showing an image signal of the image shown in FIG. It is a graph which counts the number of high luminance level pixels at the same Y position and shows it in correspondence with the Y position, and (c) is a graph which counts the number of high luminance level pixels in the same X position and shows it in correspondence with the X position, (D) is a graph showing a Y-direction distribution area of high-brightness level pixels obtained by binarizing the pixel number distribution shown in (b) with a threshold value TH,
(E) is a graph showing an X-direction distribution area of high-brightness level pixels obtained by binarizing the pixel number distribution shown in (c) with a threshold value TH.

FIG. 4 is a diagram showing a “center point (X) of the image processing apparatus 23 shown in FIG. 1;
c, Yc) detection ”50.

FIG. 5 is a flowchart showing details of welding control of the welding apparatus shown in FIG. 1;

[Explanation of symbols]

1: Carbon dioxide laser oscillator 2: He-Ne
Laser oscillator 3: Shutter 4: Planar mirror 5: Optical path of carbon dioxide laser 6: He-Ne
Optical path of laser 7: Planar mirror 8: Concave mirror 9: Planar mirror 10: Focus 11: Drive unit 12: Rotating axis of plane mirror 13: Welding torch 14: Mount 15: Base frame 16: Moving direction of mount 17: Workpiece 18: Rotation Roll 19: ground glass 20: neutral density filter 21: CCD camera 22: lens 23: image processing device 24: alarm device 30: curve indicating the state of weaving operation 31: straight line indicating the timing of capturing an image of one frame of the imaging device 40: Laser trajectory

Claims (5)

[Claims] 1. A laser transmission system diagnostic device for diagnosing a laser transmission system of a laser welding device that performs welding using a high-power laser, and radiates through the same transmission path as a laser provided for welding. Low-power laser and
A translucent light scattering plate disposed at a position corresponding to a welding point in a laser welding device, a two-dimensional imaging device for imaging the light scattering plate through a lens having a focal position on the surface of the light scattering plate, and the imaging device A laser transmission system diagnostic device comprising: an image processing device for determining whether the transmission system is normal or abnormal based on the characteristics of an image obtained from the image data. 2. The apparatus according to claim 1, wherein the two-dimensional imaging apparatus continues exposure for a predetermined time, and outputs an exposure result of the exposure duration as one frame image.
2. The laser transmission system diagnostic apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus using a frame image as an image processing unit. 3. A laser welding apparatus for performing welding while performing weaving, wherein the two-dimensional imaging apparatus includes:
Exposure is continued for more than one cycle of weaving,
2. The laser transmission according to claim 1, wherein the apparatus outputs the image of the exposure duration as one frame screen, and the image processing apparatus is an image processing apparatus that uses the one frame image as a unit of image processing. System diagnostic device. 4. An image processing apparatus performs a binarization process on a luminance level on the one-frame screen to cut out a trajectory through which the laser has passed for one frame exposure time, and the vertical and horizontal trajectories of the cut-out trajectory are extracted. Detect the length of each direction or one of them, or detect the center of the trajectory cut out as needed in the vertical and horizontal directions. 4. The laser transmission system diagnostic apparatus according to claim 2, further comprising a function of determining whether the distance is within the range. 5. A translucent light-scattering plate and a two-dimensional imaging device for imaging the light-scattering plate through a lens having a focal position on the surface of the light-scattering plate are located beside a welding position. By placing the torch on the light-scattering plate during the waiting time during which welding is not performed while being installed at the off-line position, by irradiating the low-power laser onto the light-scattering plate during or after the movement is stopped. A method for diagnosing a laser transmission system using the laser transmission system diagnosis device according to claim 1, wherein the diagnosis is performed.