JP2023032065A - Laser welding apparatus and control method thereof - Google Patents

Abstract

An object of the present invention is to stabilize welding quality in laser welding. An observing means (laser Irradiation part monitoring equipment 14, bead monitoring equipment 15, welding bead imaging camera 16), light intensity detection sensor 17 for acquiring light signals from the laser irradiation part and the weld bead, and the amount of molten metal in the laser irradiation part and the weld bead Judgment auxiliary means 18 that predicts and stores in advance, prediction data of the amount of molten metal from the judgment auxiliary means, imaging data from the observation means during welding, welding input conditions, and acquired data from the light intensity detection sensor are used. and welding state determination means 19 for calculating a welding quality criterion for determining the welding state, and the welding quality criterion is set as a threshold for the light signal acquired by the light intensity detection sensor. [Selection drawing] Fig. 1

Description

An embodiment of the present invention relates to a laser welding device and a control method of the laser welding device.

Laser welding is a technique in which a laser beam of a specific wavelength is focused on the surface of a base material in an arbitrary shape by a focusing optical system or the like to melt and join the base material. Laser welding has the advantage of obtaining a high energy density, so that welding can be performed at a higher speed and with a deeper penetration than arc welding, and its application is expanding. Quality monitoring performed during the execution of this laser welding has conventionally been variously studied as an approach for control.

Japanese Unexamined Patent Application Publication No. 2010-52009 JP 2020-163413 A

Patent document 1 has a camera that observes a laser irradiation part, builds a neural network model for detecting welding abnormal elements from images captured in advance by this camera, and during subsequent welding, Abnormal elements are detected by comparing the data acquired by the light intensity detection sensor with the teacher data.

Further, in Patent Document 2, there is a measure to maintain welding quality by subjecting an image obtained by an imaging means for imaging a laser irradiation part to machine learning as a teaching image for each welding state, and performing feedback control using the degree of matching as a judgment criterion. is done.

However, since laser welding is a high-speed construction method, in the technique of Patent Document 1 or 2, when the image during welding is compared with the teaching data or the teaching image and feedback control is performed, the welding speed is 1000 mm. /min, and even if the processing time is assumed to be 0.1 seconds, the welding progresses by about 2 mm from the image acquisition timing to the feedback. This makes sequential processing and feedback control of laser welding very difficult. In addition, when successive laser welding processes are performed continuously, it is necessary to constantly change the laser output, welding speed, etc., and it is difficult to maintain a stable welding state.

The embodiments of the present invention have been made in view of the above circumstances, and an object of the present invention is to provide a laser welding apparatus capable of stabilizing welding quality in laser welding and a control method thereof.

The laser welding apparatus according to the embodiment of the present invention captures images of a welding head that irradiates a laser beam by condensing or forming an image on the surface of a workpiece, and a laser irradiation portion that is irradiated with the laser beam and its vicinity. a light intensity detection sensor that acquires optical signals from the laser irradiation section and its vicinity; and an auxiliary determination means that predicts and stores in advance the amount of molten metal in the laser irradiation section and its vicinity. , using the prediction data of the amount of molten metal from the determination auxiliary means, the imaging data from the observation means during welding, the welding input conditions, and the acquired data from the light intensity detection sensor, for determining the welding state and welding state determination means for calculating a welding quality criterion, wherein the welding quality criterion is set as a threshold for the light signal acquired by the light intensity detection sensor.

A control method for a laser welding apparatus according to an embodiment of the present invention includes a welding head that irradiates a laser beam by condensing or forming an image on the surface of a workpiece, and a laser irradiation part that is irradiated with the laser beam and its vicinity. , an observation means for observation including imaging, a light intensity detection sensor for acquiring optical signals from the laser irradiation unit and its vicinity, and a determination that predicts and stores in advance the amount of molten metal in the laser irradiation unit and its vicinity Determining the welding state using auxiliary means, prediction data of the molten metal amount from the judgment auxiliary means, imaging data from the observation means during welding, welding input conditions, and acquired data from the light intensity detection sensor. and a welding state determination means for calculating a welding quality criterion for determining the welding quality criterion, setting the welding quality criterion as a threshold value for the light signal acquired by the light intensity detection sensor, and detecting the light intensity The data obtained from the sensor is compared with the threshold value to predict a welding failure, and control is performed to change the welding input conditions in order to avoid the welding failure.

ADVANTAGE OF THE INVENTION According to embodiment of this invention, the welding quality in laser welding construction can be stabilized.

The block diagram which shows the structure of the laser welding apparatus which concerns on one Embodiment. FIG. 2 is a perspective view for explaining the function of the light intensity detection sensor in FIG. 1; FIG. 2 shows the laser irradiation part and the weld bead in the vicinity thereof, (A) is a perspective view showing the bead shape after welding, (B), (C) and (D) are schematic diagrams showing the welding situation during welding. . Sectional drawing which shows typically the form of a welding defect.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing.
FIG. 1 is a block diagram showing the configuration of a laser welding device according to one embodiment. A laser welding apparatus 10 shown in FIG. 1 irradiates a base material 1 as a work piece with a laser beam 2 to weld the base material 1. A welding head 11 as a laser irradiation system, a laser oscillator 12 and A laser oscillator control means 13, a laser irradiation portion monitoring device 14 as observation means, a bead monitoring device 15, a bead imaging camera 16 during welding, a light intensity detection sensor 17, an auxiliary determination means 18, and a welding state determination means 19. configured with

Welding head 11 is connected to laser oscillator 12 using optical fiber 20 . The laser oscillator 12 transmits the emitted laser light 2 to the welding head 11 through the optical fiber 20 . The welding head 11 converges or forms an image of the laser beam 2 by an internal optical system (not shown), and irradiates the surface of the base material 1 with the laser beam 2 with an arbitrary beam diameter. In addition, the welding head 11 is provided with a shield gas nozzle (not shown), from which an inert gas for preventing oxidation of the surface of the base material 1 is applied to the laser-irradiated portion of the base material 1 irradiated with the laser beam 2. 3.

The welding head 11 is held by a head holding device (not shown), and the base material 1 is fixed to a base material fixing stage (not shown). In order to move the welding head 11 in the welding direction P during laser welding, only the head holding device may move, or only the base material fixing stage may move, or the head holding device and the base material fixing stage may move. You can move in sync.

The laser oscillator control means 13 is connected to the laser oscillator 12 and is also connected to the laser irradiation portion monitoring device 14 and the bead monitoring device 15 via the welding state determination means 19, and controls the laser oscillator 12 that emits the laser beam 2. Control. That is, when the laser oscillator 12 fluctuates or the state of the laser irradiation portion 3 on the base material 1 fluctuates, the laser oscillator control means 13 ensures that the welding input conditions such as the laser output satisfy the desired values. The laser oscillator 12 is controlled as follows.

The laser irradiation part monitoring device 14 is installed in the welding head 11 and monitors the laser irradiation part 3 of the base material 1 irradiated with the laser beam 2 from the welding head 11 . This laser irradiation unit monitoring device 14 is configured by including a camera, a temperature measuring device, a laser output measuring device, a brightness measuring device, and the like. Also, the laser irradiation part monitoring device 14 is connected to the welding state determination means 19 and outputs the brightness, temperature, etc. of the laser irradiation part 3 monitored by the laser irradiation part monitoring device 14 to the welding state determination means 19 . This laser irradiation unit monitoring device 14 may be installed coaxially with or non-coaxially with the optical axis of the laser beam 2 emitted from the welding head 11 .

A bead monitoring device 15 is installed on the welding head 11 and monitors the weld bead 4 in the vicinity of the laser irradiation portion 3 on the base material 1 . This bead monitoring device 15 comprises a camera, a bead height gauge, a bead width gauge and a temperature gauge. The bead monitoring device 15 is also connected to the welding state determining means 19 and outputs the bead width, bead height, etc. monitored by the bead monitoring device 15 to the welding state determining means 19 .

The welding bead imaging camera 16 is installed in the welding head 11, and the laser irradiation part 3 of the base material 1 irradiated with the laser light 2 from the welding head 11 and the vicinity of this laser irradiation part 3, that is, in the laser irradiation part 3 The weld bead 4 behind the welding direction P is also imaged during welding. 3(B), (C) and (D) schematically show images during welding by the bead imaging camera 16 during welding. In addition, the bead-in-welding imaging camera 16 is connected to the welding state determination means 19 , and outputs image data imaged by the bead-in-welding imaging camera 16 to the welding state determination means 19 .

The light intensity detection sensor 17 is installed in the welding head 11, and detects and acquires light signals (for example, luminance) from the surface of the laser irradiation portion 3 of the base material 1 and the weld bead 4 in the vicinity thereof. The light intensity detection sensor 17 is connected to the welding state determination means 19 and outputs acquired data of the light signal acquired by the light intensity detection sensor 17 to the welding state determination means 19 .

As shown in FIG. 2, a plurality of, for example, six, light intensity detection sensors 17 are arranged side by side. In addition, a plurality of observation optical systems 21, for example, six observation optical systems 21, which are installed in front of the light intensity detection sensor 17 and used to change the observation range, are arranged side by side. By changing the arrangement of either the light intensity detection sensor 17 or the observation optical system 21, arbitrary positions of the laser irradiation portion 3 and the weld bead 4 on the base material 1 are detected by the light intensity detection sensor 17, and an optical signal is configured to be retrievable.

In FIG. 2, the range of the molten metal A in the laser irradiation part 3 and the weld bead 4 is divided into four parts, and the range of the solidified metal B in the weld bead 4 is divided into two parts and observed by the light intensity detection sensor 17. Although the optical signal from the bead 4 is detected, the division number and division position can be changed. Further, by adjusting the combination of the plurality of light intensity detection sensors 17 and the observation optical system 21, acquisition data (for example, luminance data) suitable for acquisition purposes can be acquired from the laser irradiation section 3 and the weld bead 4. FIG. Further, by increasing and changing the number of divisions for the laser irradiation portion 3 and the weld bead 4, the light intensity detection sensor 17 obtains detailed optical signal data (for example, luminance data) from the laser irradiation portion 3 and the weld bead 4. becomes possible.

By the way, in FIG. 3, (A) shows the weld bead 4 after welding, and (B), (C) and (D) are schematic images of the welding situation during welding taken by the welding bead imaging camera 16. clearly shown. In the weld bead 4 after welding, as shown in FIG. 3(A), burn-through 5 as a welding defect occurs in a certain range. On the other hand, in the laser irradiation portion 3 and the weld bead 4 during welding, the burn-through 5 does not occur in the early stage of welding shown in FIG. C)), and after that, it is confirmed that the molten metal A behind the welding direction P burns down and the burn down 5 propagates over a wide range (Fig. 3(D)). In addition, the symbol C in FIG. 3B indicates a metal vapor (plume).

The burn-through 5 of the molten metal A described above occurs when the weight of the molten metal A becomes greater than the surface tension of the molten metal A and the molten metal A cannot be retained. Therefore, the surface area of the molten metal A can be measured by detecting the range of the molten metal A with the light intensity detection sensor 17 shown in FIG. The weight of metal A becomes predictable. This makes the occurrence of burn-through 5 predictable.

Therefore, the determination assisting means 18 shown in FIG. 1 predicts and stores in advance the weight of the molten metal A (amount of molten metal) in the laser-irradiated portion 3 of the base material 1 and the weld bead 4 . That is, first, the determination assisting means 18 uses the welding input conditions from the laser oscillator control means 13 and the material information of the base material 1 to perform a simulation such as a heat conduction analysis to determine the laser irradiation portion 3 and the weld bead 4. The melt shape (surface melt width, back melt width, melt area, melt volume and melt depth) is calculated. Next, the determination assisting means 18 compares and matches the calculated molten shape with the surface shapes of the laser irradiation portion 3 and the weld bead 4 captured by the bead imaging camera 16 during welding, thereby matching the welding input conditions. The weight of the molten metal A (amount of molten metal) of the laser irradiation portion 3 and the weld bead 4, which depends on the plate thickness of the base material 1, is predicted and stored in advance.

The welding state determination means 19 is connected to the laser irradiation portion monitoring device 14, the bead monitoring device 15, the bead imaging camera 16 during welding, and the light intensity detection sensor 17 as described above. Therefore, data during welding from the laser irradiation monitoring device 14, the bead monitoring device 15, the bead imaging camera 16 during welding, and the light intensity detection sensor 17 are continuously input to the welding state determination means 19 during welding. saved. Here, as the data during welding, for example, the brightness and temperature of the laser irradiation part 3 from the laser irradiation part monitoring device 14, the width and height of the weld bead 4 from the bead monitoring device 15, the bead imaging camera during welding image data of the laser irradiation portion 3 and the weld bead 4 from 16, and luminance data of the laser irradiation portion 3 and the weld bead 4 from the light intensity detection sensor 17. FIG. As a result, by using the data stored in the welding state determining means 19, it is possible to manage the welding quality of any welding point without inspecting the actual welding point.

In addition, the welding state determination means 19 is connected to the determination assistance means 18 and the laser oscillator control means 13, and the molten metal A at the laser irradiation portion 3 of the base material 1 and the weld bead 4 predicted by the determination assistance means 18 Along with inputting the weight (amount of molten metal), the welding input conditions during welding are input from the laser oscillator control means 13 . Then, the welding state determination means 19 uses the weight of the molten metal A of the laser irradiation portion 3 and the weld bead 4 and the image data during welding from the bead imaging camera 16 during welding to predict the burn-through 5. The width fluctuation amount of the weld bead 4, which is the weight fluctuation amount of the molten metal A, is calculated.

The welding state determination means 19 receives the width fluctuation amount of the weld bead 4, welding input conditions during welding from the laser oscillator control means 13, and light signal acquisition data during welding from the light intensity detection sensor 17 (e.g., luminance data). ) and the result of the post-welding welding quality confirmation test, the welding quality criterion for determining the welding state is calculated and set as a threshold for the light signal (for example, luminance) acquired by the light intensity detection sensor 17. Here, the welding quality confirmation test result is a test result acquired in advance from observation of the appearance and cross section of the weld bead 4 and the like.

Furthermore, the welding state determination means 19 constantly compares the acquired data (e.g., luminance data) of the light signal from the light intensity detection sensor 17 during welding with the threshold during welding, and the acquired data becomes equal to or less than the threshold. Occasionally, the occurrence of burn through 5 as a weld defect is predicted. In order to avoid the occurrence of the burn-through 5, the welding state determination means 19 feedback-controls the laser oscillator 12 via the laser oscillator control means 13 so as to change the welding input conditions.

With the configuration as described above, the present embodiment has the following effects (1) to (3).
(1) The welding state determination means 19 sets the welding quality determination standard for determining the welding state as a threshold value for the light signal (for example, luminance) acquired by the light intensity detection sensor 17. Therefore, the welding quality determination standard can be easily determined. can be set to Further, the welding state determination means 19 simply compares the data acquired by the light intensity detection sensor 17 with a threshold value during welding, without performing complicated signal processing such as image processing. immediately predictable. As a result of this immediate prediction of the burn-through 5, the welding state determination means 19 can control the laser oscillator 12 by the laser oscillator control means 13 to quickly change the welding input conditions for adjusting the output of the laser beam 2. Therefore, it is possible to avoid the occurrence of welding defects (burn-through 5) and stabilize the welding quality in laser welding.

(2) The welding bead imaging camera 16 and the light intensity detection sensor 17 can observe the surface state of the laser irradiation part 3 and the weld bead 4 in the base material 1, but the inside and the back surface of the laser irradiation part 3 and the weld bead 4 Inability to observe the side. The welding state determination means 19 determines the laser irradiation portion 3 and the weld after the determination assisting means 18 simulates the molten shape of the laser irradiation portion 3 and the weld bead 4 when calculating the welding quality criterion for determining the welding state. Prediction data for predicting the weight of the molten metal A (amount of molten metal) of the bead 4 is used. Therefore, the welding state determining means 19 can accurately predict the welding failure (burn-through 5).

(3) By changing the arrangement of either the light intensity detection sensor 17 or the observation optical system 21, the light intensity detection sensor 17 observes an arbitrary position of the laser irradiation portion 3 and the weld bead 4 on the base material 1 and outputs an optical signal. It can be detected and acquired. Therefore, the light intensity detection sensor 17 can easily cope with the weight of the molten metal A (amount of molten metal) of the laser irradiation portion 3 and the weld bead 4, which varies depending on the welding input conditions. By using the data obtained from the light intensity detection sensor 17, the welding state determination means 19 can reliably predict welding defects (burn-through 5) regardless of changes in welding input conditions.

Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. , is included in the scope and gist of the invention, and is included in the scope of the invention described in the claims and its equivalents.

For example, in the present embodiment, the case where the weld defect is burn-through 5 has been described, but it can be applied to other weld defects. That is, the blowhole (Fig. 4 (A)), pit (Fig. 4 (B)), slag entrainment (Fig. 4 (C)), overlap (Fig. 4 (D)), fusion failure (Fig. 4 (D)) shown in Fig. 4 4(E)), poor penetration (FIG. 4(F)), and undercut (FIG. 4(G)).

DESCRIPTION OF SYMBOLS 1... Base material (workpiece), 2... Laser beam, 3... Laser irradiation part, 4... Weld bead (near laser irradiation part), 5... Burn through (welding defect), 10... Laser welding device, 11... Welding head 16 Welding bead imaging camera (observation means) 17 Light intensity detection sensor 18 Judgment auxiliary means 19 Welding state judgment means 21 Observation optical system A Molten metal

Claims (5)

A welding head that condenses or forms an image of laser light on the surface of the workpiece and irradiates it;
Observation means for observing, including imaging, the laser irradiation portion irradiated with the laser beam and its vicinity;
a light intensity detection sensor that acquires optical signals from the laser irradiation unit and its vicinity;
a determination assisting means for predicting and storing in advance the amount of molten metal in the laser irradiation portion and its vicinity;
Welding for judging the welding state using the prediction data of the molten metal amount from the judgment auxiliary means, the imaging data from the observation means during welding, the welding input conditions, and the acquired data from the light intensity detection sensor Welding condition determination means for calculating quality criteria,
A laser welding apparatus according to claim 1, wherein said welding quality criterion is set as a threshold for the light signal acquired by said light intensity detection sensor. The welding state determination means is configured to predict welding defects by comparing the data acquired from the light intensity detection sensor with a threshold value, and perform control to change welding input conditions in order to avoid the welding defects. The laser welding device according to claim 1, characterized in that: The determination assisting means simulates the molten shape at and near the laser irradiated portion using the welding input conditions, compares this molten shape with image data from the observation means, and determines the amount of molten metal depending on the welding input conditions. 3. The laser welding apparatus according to claim 1 or 2, which is configured to predict and store in advance. A plurality of the luminous intensity detection sensors and observation optical systems installed in front of the luminous intensity detection sensors for changing the observation range are respectively installed, and the arrangement of either the luminous intensity detection sensors or the observation optical systems is changed. 4. The laser welding apparatus according to any one of claims 1 to 3, wherein the laser irradiation part and any position in the vicinity thereof can be observed. A welding head that condenses or forms an image of laser light on the surface of the workpiece and irradiates it;
Observation means for observing, including imaging, the laser irradiation portion irradiated with the laser beam and its vicinity;
a light intensity detection sensor that acquires optical signals from the laser irradiation unit and its vicinity;
a determination assisting means for predicting and storing in advance the amount of molten metal in the laser irradiation portion and its vicinity;
Welding for judging the welding state using the prediction data of the molten metal amount from the judgment auxiliary means, the imaging data from the observation means during welding, the welding input conditions, and the acquired data from the light intensity detection sensor Prepare a laser welding device having welding state determination means for calculating quality criteria,
The welding quality criterion is set as a threshold value for the light signal acquired by the light intensity detection sensor, and the data acquired from the light intensity detection sensor is compared with the threshold value to predict welding defects and avoid the welding defects. A control method for a laser welding apparatus, characterized in that control is performed so as to change the welding input conditions for the purpose.

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