Laser welding monitoring device and method

Abstract

To reduce influence of light emission by a plume or an induced plasma generated during laser welding, and improve monitoring accuracy of the laser welding.SOLUTION: A laser welding monitoring device includes: an optical sensor 11 for measuring light-emission intensity of light generated in a workpiece melting part by laser welding on workpiece 1 as a welding object; a filter 12 which is installed in the optical sensor, and sets the light incident on the optical sensor to be light in a light-emission wavelength band required for monitoring in a welding state; a CPU 13 for calculating a threshold related to the light-emission intensity for discriminating whether the welding state by the laser welding is in a penetrated state or in a non-penetrated state, on the basis of a condition including a laser welding condition; and a determination part 16 for comparing the light-emission intensity measured by the optical sensor with the threshold, and determining whether the welding state in the laser welding is in the penetrated state or the non-penetrated state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a laser welding monitoring device and a laser welding monitoring method for monitoring a welding state of laser welding. [Background technology]

[0002] Laser welding is a welding technique that can obtain deep penetration in one pass by irradiating metal materials with a high density of laser light transmitted from a laser oscillator and focusing it with a lens. Using this characteristic, metal materials with a thickness of about several mm to 10 mm can be welded in one pass, and a technology is known in which the emission intensity of visible light, infrared light, reflected light, etc. generated from the molten part is measured with an optical sensor to monitor the welding condition and welding quality. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3275988 [Patent Document 2] Patent Publication No. 2021-90992 [Patent Document 3] JP 2000-146852 A [Patent Document 4] JP 2000-117467 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in Patent Document 1, a threshold value for reflected light intensity is set in advance, and if the measured value of the reflected light intensity is higher than the threshold value, it is determined that the laser has not penetrated the metal material, and if the measured value of the reflected light intensity is lower than the threshold value, it is determined that the laser has penetrated the metal material. Patent Document 2 is a monitoring technology that detects a decreasing change in luminance value when the light intensity changes from non-penetration welding to full penetration welding and determines that the laser has penetrated.

[0005] Patent Document 3 describes a technology that focuses light at multiple depths in the keyhole, extracts the light amount, and monitors the occurrence of bubbles (porosity) inside the weld metal from the light amount. Furthermore, Patent Document 4 describes a technology that monitors the positions of the keyhole and the molten bath from image data obtained by a CCD camera and controls parameters.

[0006] However, in keyhole welding, which can achieve deep penetration, high-intensity light emission occurs discontinuously due to plumes and induced plasma depending on the conditions. This light emission becomes stronger as the laser output is increased to increase the energy density, and becomes unnecessary information for monitoring the welding condition. Therefore, depending on the configuration of the monitoring device, the light emission from the plumes and induced plasma may adversely affect the monitoring accuracy of laser welding.

[0007] The embodiments of the present invention have been made in consideration of the above-mentioned circumstances, and aim to provide a laser welding monitoring device and a laser welding monitoring method that can reduce the influence of light emission due to a plume or induced plasma generated during laser welding and improve the accuracy of monitoring laser welding. [Means for solving the problem]

[0008] A laser welding monitoring device in an embodiment of the present invention is characterized in that it is configured to include a measuring device that measures the emission intensity of light generated in a molten portion of an object to be welded by laser welding the object, a filter that is installed in the measuring device and selects the light to be incident on the measuring device to be light of an emission wavelength band required for monitoring the welding state, a calculation unit that calculates a threshold value for the emission intensity for determining whether the welding state by the laser welding is through or non-through, based on conditions including laser welding conditions, and a judgment unit that compares the emission intensity measured by the measuring device with the threshold value to judge whether the welding state in the laser welding is through or non-through.

[0009] A laser welding monitoring method in an embodiment of the present invention includes preparing a measuring device that measures an emission intensity of light generated in a molten portion of an object to be welded by laser welding the object, and a filter that is installed in the measuring device and selects light to be incident on the measuring device so that the light is in an emission wavelength band necessary for monitoring the welding state, and includes a step in which a calculation unit calculates a threshold value related to the emission intensity for determining whether the welding state by the laser welding is through or non-through, based on conditions including laser welding conditions, a step in which the measurement unit measures, by the filter, the emission intensity of light in the emission wavelength band necessary for monitoring the welding state, from the light generated in the molten portion of the object by the laser welding, and a step in which a judgment unit compares the emission intensity measured by the measuring device with the threshold value to judge whether the welding state in the laser welding is through or non-through. Effect of the Invention

[0010] According to an embodiment of the present invention, the influence of light emission due to a plume or induced plasma generated during laser welding can be reduced, thereby improving the accuracy of monitoring laser welding. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a configuration diagram showing a laser welding monitoring device according to a first embodiment. [Diagram 2] Graphs showing the emission intensity in the molten zone during laser welding measured by the optical sensor in Figure 1, where (A) is a graph for a non-penetration welding state, (B) is a graph for a full-penetration welding state, and (C) is a graph in which the non-penetration welding state and the full-penetration welding state are superimposed. [Diagram 3] 4 is a flowchart showing a laser welding monitoring method executed by the laser welding monitoring device of FIG. 1. [Figure 4] FIG. 11 is a configuration diagram showing a laser welding monitoring device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [A] First embodiment (FIGS. 1 to 3) Fig. 1 is a configuration diagram showing a laser welding monitoring device according to the first embodiment. The laser welding monitoring device 10 shown in Fig. 1 judges whether a welding state is penetration or non-penetration based on the emission intensity of light generated in a molten part of a workpiece 1 when the workpiece 1, which is an object to be welded and is made of a metallic material, is laser-welded by a laser welding device 20. The laser welding monitoring device 10 is configured to include an optical sensor 11 as a measuring device, a filter 12, a CPU (Central Processing Unit) 13 as a calculation unit, a memory unit 14, a device configuration input unit 15, a judgment unit 16, and a notification / display unit 17.

[0013] Here, the laser welding device 20 for welding the workpiece 1 includes a laser oscillator 21 that oscillates a laser beam L, an optical fiber 22 that transmits the laser beam L oscillated by the laser oscillator 21, and a welding head 23 that condenses the laser beam L transmitted by the optical fiber 22 by a lens 24 and irradiates the welding position of the workpiece 1. Furthermore, the laser output, irradiation start, irradiation end, and irradiation interruption of the laser beam L irradiated by the laser welding device 20 are controlled by a laser control device 25. In addition, the welding head 23 is scanned on the welding line by an articulated robot or an NC processing machine during irradiation of the laser beam L. Laser welding by the laser welding device 20 makes it possible to perform penetration welding of metal materials having a thickness of several mm to about 10 mm in one pass.

[0014] The optical sensor 11 of the laser welding monitoring device 10 measures the emission intensity of light (visible light, infrared light, reflected light, etc.) generated in the molten part of the workpiece 1 by the laser welding of the laser welding device 20. The optical sensor 11 of the first embodiment is a coaxial type optical sensor that measures the emission intensity of the light generated in the molten part of the workpiece 1 by using a reflection mirror 26 installed in the welding head 23 or the like to make the light incident coaxially with the passage axis of the laser light L irradiated from the welding head 23 to the workpiece 1 using the reflection mirror 26 installed in the welding head 23 or the like. This optical sensor 11 is composed of a PD (Photo Diode). The optical sensor 11 is installed in, for example, the welding head 23, and outputs the measured emission intensity information to the CPU 13.

[0015] The filter 12 is installed on the light incident side of the optical sensor 11, and sets the light incident on the optical sensor 11 to be light in an emission wavelength band necessary for monitoring the welding state, and transmits this light to allow the optical sensor 11 to measure it. In other words, the filter 12 attenuates light (first unnecessary light) in the same emission wavelength band as the laser light L irradiated to the work 1. The filter 12 also attenuates light (second unnecessary light) in an emission wavelength band in the plume or induced plasma generated during laser welding. The filter 12 is composed of one or more filters that attenuate the first unnecessary light, or is composed of one or more filters 12 that attenuate the second unnecessary light, or is composed of a combination of the filter 12 that attenuates the first unnecessary light and the filter 12 that attenuates the second unnecessary light.

[0016] Furthermore, the emission intensity measured by the optical sensor 11 tends to vary depending on the material of the workpiece 1 irradiated with the laser light L. For this reason, by increasing or decreasing the number of filters 12 according to the type of material of the workpiece 1, the amount of light incident on the optical sensor 11 is changed, and the emission intensity measured by the optical sensor 11 is adjusted.

[0017] Information on the emission intensity measured by the optical sensor 11 is input to the CPU 13, which then stores it in the memory unit 14. Furthermore, the device configuration input unit 15 inputs the type of optical sensor, such as whether the optical sensor 11 is a coaxial type optical sensor or a direct-view type optical sensor (described in detail in the second embodiment), the number of filters 12, the emission wavelength band attenuated by the filters 12, and other device configuration information. The device configuration input by the device configuration input unit 15 is stored in the memory unit 14, for example.

[0018] The CPU 13 stores the information on the emission intensity measured by the optical sensor 11 in the memory unit 14 as described above, and calculates a threshold value for the emission intensity for determining whether the welded state by laser welding is through or non-through based on the following conditions. The above conditions include the laser welding conditions such as the output of the laser light L input from the laser control device 25, the type of the optical sensor 11 input to the device configuration input unit 15, the number of filters 12, the emission wavelength band attenuated by the filters 12, etc. The above threshold value varies depending on the difference in these conditions. An example of this threshold value is shown in FIG. 2(C).

[0019] The determination unit 16 compares the information on the emission intensity measured by the optical sensor 11 and stored in the memory unit 14 with a threshold calculated by the CPU 13 to determine whether the welding state of the laser welding is through or non-through. That is, as shown in Fig. 2(C), when the emission intensity is higher than the threshold, the determination unit 16 determines that the welding state of the laser welding is non-through, and when the emission intensity is lower than the threshold, the determination unit 16 determines that the welding state of the laser welding is through. Here, the waveform of emission intensity shown in Fig. 2 is a plot of the emission intensity of light generated in the molten part from the start of irradiation of the laser light L to just before the end when the laser welding device 20 irradiates the laser light L under the condition of a laser output of 7 kW.

[0020] Furthermore, after the laser welding by the laser welding device 20 is completed, the determination unit 16 causes the notification / display unit 17 to chronologically display images of whether the welding state in the laser welding is through or non-through. Generally, in laser welding by the laser welding device 20, it is desirable that the welding state is consistently through or non-through, and the welding state should not be changed during welding. Therefore, when the welding state during laser welding by the laser welding device 20 transitions from non-through to through, or from through to non-through, the determination unit 16 causes the notification / display unit 17 to notify the fact by at least one of a notification sound and image display.

[0021] Next, a laser welding monitoring method using the laser welding monitoring device 10 configured as described above will be described with reference to FIG. The optical sensor 11 of the laser welding monitoring device 10 starts measuring the emission intensity (S1), and then the laser welding device 20 starts laser welding to the workpiece 1 (S2). The order of steps S1 and S2 may be reversed. Here, the measurement of the emission intensity by the optical sensor 11 is performed by a filter 12 installed on the input side of the optical sensor 11, which measures the emission intensity of light in an emission wavelength band required for monitoring the welding state of the laser welding. Thereafter, the CPU 13 of the laser welding monitoring device 10 takes in information on the emission intensity of the molten part by the laser welding measured by the optical sensor 11, and stores it in the memory unit 14 (S3).

[0022] When the laser welding monitoring device 10 executes monitoring after laser welding (S4), the CPU 13 causes the memory unit 14 to continue storing information on the emission intensity measured by the optical sensor 11 until the laser welding by the laser welding device 20 is completed (S5). After the laser welding is completed, the determination unit 16 compares the information on the emission intensity stored in the memory unit 14 with a threshold value calculated in advance by the CPU 13 to determine whether the welding state is through or non-through (S6), and causes the notification / display unit 17 to display images of the determination results (through or non-through welding state) in chronological order (S7). This makes it possible to check the welding quality after the laser welding is completed.

[0023] When laser welding monitoring device 10 performs monitoring during laser welding (S4), determination unit 16 compares the emission intensity information measured by optical sensor 11 and stored in memory unit 14 with a threshold value at predetermined time intervals while laser welding is continuing, and determines whether the welding state is through or non-through (S8). In this step S8, when the welding state transitions from through to non-through, or from non-through to through, determination unit 16 notifies notification / display unit 17 of that effect by at least one of a notification sound and image display (S9).

[0024] After laser welding by the laser welding device 20 is completed (S10), the determination unit 16 causes the notification / display unit 17 to display images of the welded state (through / non-through) in chronological order (S11). This makes it possible to check and correct the welded state during welding by the laser welding device 20.

[0025] As configured as above, the first embodiment provides the following effect (1). (1) Filter 12 installed on the incident side of optical sensor 11 sets the light incident on optical sensor 11 to be light in an emission wavelength band necessary for monitoring the welding state. Therefore, optical sensor 11 can suppress measurement of unnecessary light in an emission wavelength band due to a plume or induced plasma generated during laser welding. As a result, when monitoring laser welding, the influence of light emission due to a plume or induced plasma generated during laser welding can be reduced, and the monitoring accuracy of laser welding can be improved.

[0026] [B] Second embodiment (Fig. 4) 4 is a configuration diagram showing a laser welding monitoring device according to a second embodiment. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description thereof will be simplified or omitted.

[0027] The laser welding monitoring device 30 of the second embodiment differs from the first embodiment in that the optical sensor 31 serving as a measuring device is not a coaxial type optical sensor, but a direct-view type optical sensor that is installed away from the laser light L irradiated to the workpiece 1 and at a position where the molten part of the workpiece 1 can be directly observed, and measures the emission intensity of light generated in the molten part.

[0028] For example, the optical sensor 31 is installed diagonally upward and forward in the scanning direction of the welding head 23, and is disposed so that the incident side faces the molten part of the workpiece 1. The optical sensor 31 is configured to move in synchronization with the scanning of the welding head 23, so that the emission intensity of light from the molten part can be constantly measured.

[0029] Furthermore, in the direct-view type optical sensor 31, the measurable emission intensity tends to be lower than that of the coaxial type optical sensor 11. Therefore, the optical sensor 31 is adjusted to increase the amount of light incident on the optical sensor 31 by, for example, reducing the number of filters 12 installed on the incident side, thereby improving the measurement accuracy of the optical sensor 31.

[0030] As configured as above, the second embodiment also provides the same effect as the effect (1) of the first embodiment.

[0031] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, and combinations can be made without departing from the spirit of the invention. Furthermore, these substitutions, changes, and combinations are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0032] 1...workpiece (object), 10...laser welding monitoring device, 11...optical sensor (measuring instrument), 12...filter, 13...CPU (calculating unit), 16...judgment unit, 17...notification / display unit, 20...laser welding device, 30...laser welding monitoring device, 31...optical sensor (measuring instrument), L...laser light

Claims

1. a measuring device for measuring the emission intensity of light generated in a molten portion of an object to be welded by laser welding the object; a filter that is installed in the measuring device and selects light to be incident on the measuring device to be light in an emission wavelength band required for monitoring the welding condition; a calculation unit that calculates a threshold value related to the emission intensity for determining whether the welded state by the laser welding is through or non-through based on conditions including laser welding conditions; a judgment unit that compares the light emission intensity measured by the measuring device with the threshold value and judges whether the welding state in the laser welding is through or non-through.

2. 2. The laser welding monitoring device according to claim 1, wherein the filter is configured to attenuate light having the same emission wavelength band as the laser light irradiated onto the target object.

3. The laser welding monitoring device according to claim 1 , wherein the filter is configured to attenuate light in an emission wavelength band in a plume or induced plasma generated during laser welding.

4. 4. The laser welding monitoring device according to claim 1, wherein the filter is configured by combining the filter according to claim 2 and the filter according to claim 3.

5. 2. The laser welding monitoring device according to claim 1, wherein the measuring device is configured to make the light generated in the molten portion of the object incident coaxially with the passage axis of the laser light irradiated to the object, and measure the emission intensity of the light.

6. 2. The laser welding monitoring device according to claim 1, wherein the measuring device is installed at a position away from the laser light irradiated to the object and capable of directly observing the molten portion of the object, and is configured to measure the emission intensity of light generated in the molten portion.

7. The laser welding monitoring device according to claim 1 , wherein the determining unit is configured to display in chronological order whether the welding state in the laser welding is through or non-through.

8. The laser welding monitoring device according to claim 1, characterized in that the judgment unit is configured to notify, when the welding state during laser welding transitions from non-penetrating to penetrating, or from penetrating to non-penetrating, of this transition by at least one of a notification sound and a display.

9. a measuring device for measuring the emission intensity of light generated in a molten portion of an object to be welded by laser welding the object; a filter that is installed in the measuring device and selects light to be incident on the measuring device to be light in an emission wavelength band required for monitoring the welding condition; a calculation unit calculating a threshold value related to the emission intensity for determining whether the welding state by the laser welding is through or non-through based on conditions including a laser welding condition; The measuring unit measures, by the filter, an emission intensity of light in an emission wavelength band required for monitoring a welding state, among light generated in the molten portion of the object by the laser welding; A laser welding monitoring method comprising: a step of a judgment unit comparing the light emission intensity measured by the measuring device with the threshold value to judge whether the welding state in the laser welding is through or non-through.

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