JP2010279994A - Method for detecting abnormality of laser beam welding system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and accurately detect the abnormality of a laser beam welding system when forming a weld zone. <P>SOLUTION: A method for detecting the abnormality of a laser beam welding system includes an abnormality detecting step for detecting an abnormality of the component during welding in the laser beam welding system in which welding conditions are beforehand optimized before forming the weld zone on a workpiece. In the abnormality detecting step, first, when forming the reference weld zone as a normal weld zone by irradiating a reference workpiece with a laser beam in a step before welding, a reference light intensity data relating to the light intensity of the reference weld zone is obtained (S11), a moving average is calculated by applying a moving average processing to the reference light intensity data (S12) and the average of the moving average is calculated as the reference value (S13). Next, in a step during welding, the light intensity data relating to the light intensity of the weld zone when forming the weld zone is obtained and the abnormality of the component during welding is detected on the basis of the result of setting a sample line to the reference value in the light intensity data and the analysis. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an abnormality detection method for a laser welding system, and more particularly to an abnormality detection method for detecting an abnormality relating to an element that operates when forming a welded part in a laser welding system.

  As a conventional method for detecting an abnormality in a laser welding system, when forming a welded part by irradiating a workpiece with a laser beam, the light intensity information of the welded part is obtained, and the welding abnormality is based on the obtained light intensity information. Is known (for example, see Patent Document 1).

JP 2007-253220 A

  Incidentally, in general, in a laser welding system, an abnormality is particularly likely to occur when forming a welded portion (that is, during welding). Therefore, the abnormality detection method for the laser welding system as described above is particularly required to be able to accurately detect abnormality during welding. Furthermore, it is desired that the abnormality detection method of the laser welding system in recent years can easily detect the abnormality of the laser welding system.

  Then, this invention makes it a subject to provide the abnormality detection method of the laser welding system which can detect the abnormality of the laser welding system at the time of forming a welding part easily and accurately.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, when the welding conditions of the laser welding system are optimized, the abnormality detected during welding is usually an abnormality related to an element that operates during welding. The knowledge that it is limited to (for example, abnormal gas injection angle, abnormal gas flow rate, abnormal gas component, etc.) was obtained. And when abnormality could be limited in this way, it discovered that abnormality and normal of a laser welding system were distinguishable comparatively easily based on the light intensity data of a welding part. Therefore, the present inventors have made further studies and obtained the knowledge that if the sample line is appropriately set in the light intensity data, it is possible to easily and accurately detect the abnormality of the laser welding system when forming the welded portion. The invention has been completed.

  That is, the abnormality detection method of the laser welding system according to the present invention is performed when forming a welded part in a laser welding system in which welding conditions are optimized in advance before forming a welded part on a workpiece by laser beam irradiation. An abnormality detection step for detecting an abnormality relating to an operating element is provided, and the abnormality detection step is a first step for obtaining a reference value for detecting an abnormality before forming a welded portion, and when forming a welded portion. A second step of acquiring light intensity data relating to the light intensity of the welded portion, and detecting an abnormality based on a result obtained by analyzing the light intensity data by setting a sample line as a reference value. Then, when the reference workpiece is irradiated with a laser beam to form a reference weld as a normal weld, reference light intensity data relating to the light intensity of the reference weld is obtained, and the reference light intensity data is obtained. Moved to Calculating a moving average value by performing averaging processing, and calculates the average value of the moving average value as a reference value.

  In this laser welding system abnormality detection method, an abnormality of the laser welding system in which the welding conditions are optimized in advance is detected. Therefore, the abnormality detected during welding is an abnormality relating to an element that operates when forming a welded portion. (Hereinafter, also referred to as “element abnormality during welding”). Therefore, the moving average value of the reference light intensity data, which is normal data, is further averaged to obtain a reference value, and the sample line is set to the reference value in the light intensity data and analyzed, so that the normal light intensity data and It is possible to easily and accurately distinguish the light intensity data at the time of element abnormality during welding. Therefore, based on the analysis result, it is possible to easily and accurately detect the abnormality of the laser welding system when forming the welded portion.

  In the second step, it is preferable to detect an abnormality when the number of intersections between the light intensity data and the sample line is smaller than a preset threshold value. In this case, the light intensity data at the normal time and the light intensity data at the time of abnormality in the element being welded can be suitably distinguished. Therefore, it is possible to preferably exhibit the above-described effect of easily and accurately detecting an abnormality of the laser welding system when forming the welded portion.

  At this time, the threshold value is preferably 80% of the number of intersections between the reference light intensity data and the sample line. Thereby, the light intensity data at the normal time and the light intensity data at the abnormal state of the welding element can be distinguished in consideration of the variation (error) of the light intensity data.

  In the second step, it is preferable to detect an abnormality when the number of light intensity data exceeding the sample line is smaller than a preset lower threshold or larger than a preset upper threshold. Even in this case, the light intensity data at the normal time and the light intensity data at the time of abnormality in the element being welded can be suitably distinguished, and thus the above-described effects can be preferably exhibited.

  At this time, the lower limit threshold is a value of 80% of the number of data of the reference light intensity data exceeding the sample line, and the upper limit threshold is a value of 120% of the number of the data of the reference light intensity data exceeding the sample line. It is preferable that Thereby, the light intensity data at the normal time and the light intensity data at the time of abnormality of the element being welded can be distinguished in consideration of the variation of the light intensity data.

  In addition, the element that operates when forming the welded portion may include at least one of an abnormal gas injection angle, an abnormal gas flow rate, and an abnormal gas component.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to detect the abnormality of the laser welding system at the time of forming a welding part easily and accurately.

It is the schematic which shows the structure of the laser welding system which implements the abnormality detection method which concerns on one Embodiment of this invention. It is a flowchart which shows the process process by the laser welding system of FIG. It is a flowchart which shows the process of calculating | requiring the reference value and threshold value for detecting element abnormality during welding in the pre-welding process of FIG. It is a flowchart which shows the process of detecting element abnormality during welding in the process during welding of FIG. 6 is a graph showing an example of reference light intensity data. It is a graph which shows an example of light intensity data. It is a graph which shows an example of a differential characteristic value.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  FIG. 1 is a schematic diagram showing a configuration of a laser welding system that performs an abnormality detection method according to an embodiment of the present invention. As shown in FIG. 1, the laser welding system 1 forms a linear welded portion W at a substantially central portion of workpieces (workpieces) 10A and 10B, and lap welds the workpieces 10A and 10B. As the workpieces 10A and 10B, plate-like outer plate panels and bone members that are formed of a metal such as stainless steel and are used for a railway vehicle structure are used. The laser welding system 1 includes a laser welding device 2 and an abnormality detection device 3.

  The laser welding apparatus 2 forms a welded portion W by irradiating a laser beam, and includes a feeding device 21, a workpiece fixing device 22, a laser irradiation device 23, and a gas supply device 24. Each of these devices 21 to 24 is connected to a host control device (not shown), and automatically executes each operation in accordance with operation instruction information output from this control device.

  The feeding device 21 scans the irradiation position of the laser beam on the workpieces 10A and 10B. Specifically, the feeding device 21 moves the workpieces 10 </ b> A and 10 </ b> B placed on the movable stage 25 relative to the laser beam by the laser irradiation device 23 along the planned welding region R.

  The workpiece fixing device 22 fixes the workpieces 10A and 10B to the movable stage 25. In the workpiece fixing device 22, both end portions of the workpieces 10 </ b> A and 10 </ b> B sandwiching the planned welding region R are pressed against the movable stage 25 by a long pressing plate 26 a.

The laser irradiation device 23 irradiates a laser beam toward the planned welding region R of the workpieces 10A and 10B. Specifically, the laser irradiation device 23 emits a laser beam such as a YAG laser or a CO ₂ laser for a predetermined time from the tip of the laser head 27 above the workpieces 10A and 10B. The laser irradiation device 23 includes an output switching mechanism (not shown) inside, and can be switched between continuous irradiation with the laser beam and irradiation with the laser beam in pulses. .

  The gas supply device 24 supplies assist gas (argon gas or the like) to the planned welding region R of the workpieces 10A and 10B. In the gas supply device 24 here, the supply nozzle 28 is disposed so as to be inclined by about 30 degrees with respect to the thickness direction of the workpieces 10A and 10B. The gas supply device 24 supplies assist gas to laser beam irradiation positions (hereinafter referred to as “processing points”) of the workpieces 10A and 10B with a predetermined supply amount.

  The abnormality detection device 3 is for detecting an abnormality related to an element that operates when forming the welded portion W in the laser welding system 1 (hereinafter, also referred to as “element abnormality during welding”). The abnormality detection device 3 is physically a computer system including a CPU, a memory, a communication interface, a storage unit such as a hard disk, a display unit such as a display, and the like.

  A light intensity detection sensor 4 is connected to the abnormality detection device 3 via a filter 5. The light intensity detection sensor 4 is a photosensor for acquiring light intensity data relating to the light intensity at the processing point, and is disposed in the vicinity of the irradiation position of the laser beam. The filter 5 is an optical filter that selectively passes a predetermined wavelength. As a result, the light intensity data is input from the light intensity detection sensor 4 to the abnormality detection device 3 via the filter 5.

  In addition, the abnormality detection device 3 includes an abnormality detection unit 31 and a storage unit 32 as functional components. The abnormality detection unit 31 detects an element abnormality during welding based on the input light intensity data (details will be described later). The storage unit 32 receives and stores the detection result output from the abnormality detection unit 31. In addition, the storage unit 32 stores a reference value that is a sample line value set in the light intensity data in order to detect an element abnormality during welding. The “sample line” here means a horizontal line appropriately set on the data waveform.

  Next, the processing steps of the laser welding system 1 described above will be described with reference to the flowcharts shown in FIGS.

  In the laser welding system 1, as a pre-welding process, the workpieces 10 </ b> A and 10 </ b> B are first placed on the movable stage 25, and the pressing jig 26 is lowered from above to fix the reference workpieces 10 </ b> A and 10 </ b> B to the movable stage 25. . Then, the laser welding system 1 optimizes the welding conditions and confirms the operation (S1). In the optimization of the welding conditions here, process management is performed for the feeding device 21, the workpiece fixing device 22, the laser irradiation device 23, the gas supply device 24, and the power source that supplies power to these devices 21 to 24. Detected abnormalities are normalized and optimized.

  Subsequently, as a welding process, a laser beam is irradiated from the laser head 27 and the movable stage 25 is moved to scan the workpieces 10A and 10B in the direction of arrow A (see FIG. 1). At the same time, the assist gas is supplied by the gas supply device 24 at a flow rate of 15 L / min. Thereby, the welding part W is formed along the welding planned area | region R of workpiece | work 10A, 10B (S2). Finally, as a post-welding process, the quality of the welded portion W is determined, the workpiece fixing device 22 is released, and the workpieces 10A and 10B welded to each other are carried out (S3).

  Here, in this embodiment, the abnormality detection process for detecting element abnormality during welding is provided. Here, as an element abnormality during welding, an abnormality related to the assist gas supplied by the gas supply device 24, that is, a gas injection angle abnormality (gas nozzle installation attitude abnormality) or a gas flow rate abnormality is detected. Details will be described below.

  First, in the pre-welding process, a reference value and a threshold value for detecting an element abnormality during welding are obtained. Specifically, the reference workpieces 10A and 10B are irradiated with a laser beam from the laser head 27, and the movable stage 25 is moved to scan the workpieces 10A and 10B. In addition, the assist gas is supplied by the gas supply device 24. As a result, the reference welded portion W as a normal welded portion is formed on the reference workpieces 10A and 10B.

  When forming the reference weld W, the light intensity detection sensor 4 acquires reference light intensity data relating to the light intensity at the processing point (S11). As shown in FIG. 5, the reference light intensity data D0 can be represented by a time-series waveform with the horizontal axis representing time and the vertical axis representing light intensity. Of course, the time on the horizontal axis can be expressed as a data number based on the time resolution of the light intensity detection sensor 4.

  Subsequently, the abnormality detecting unit 31 performs a moving average process on the reference light intensity data D0 at a time interval of, for example, 200 data, and calculates a moving average value MA (S12). Then, the moving average value MA is averaged, and this average value is calculated as the reference value S (S13).

  Subsequently, the sample line L is set to the reference value S of the reference light intensity data D0. A differential characteristic value (amount of change) as a time-series waveform that is the number of intersections between the light intensity data D and the sample line L in a predetermined time (between a predetermined number of data) is calculated (S14). A value of 80% of the minimum value of the differential characteristic value is calculated as a threshold value α (see FIG. 7) (S15). Finally, the reference value S and the threshold value α are stored in the storage unit 32.

  Next, in the process during welding, when forming the welded portion W, the light intensity detection sensor 4 acquires light intensity data relating to the light intensity of the welded portion W (S21). Here, the light intensity data D (see FIG. 6) is configured in the same manner as the above-described reference light intensity data, and can be represented by a time-series waveform with the horizontal axis representing time and the vertical axis representing light intensity.

  Subsequently, the abnormality detection unit 31 detects the presence / absence of an element abnormality during welding based on the result of setting and analyzing the sample line L to the reference value S of the light intensity data D. That is, a differential characteristic value as a time series waveform that is the number of intersections between the light intensity data D and the sample line L in a predetermined time (between a predetermined number of data) is calculated (S22). If this differential characteristic value is smaller than the threshold value α, an element abnormality during welding is detected, and a detection result indicating “element abnormality during welding” is stored in the storage unit 32 (S23 → S24). On the other hand, when the differential characteristic value is equal to or greater than the threshold value α, the detection result “no welding element abnormality” is stored in the storage unit 32 (S23 → S25).

  As described above, in the present embodiment, as described above, the abnormality of the laser welding system 1 in which the welding conditions are optimized in advance is detected. This is because, when the welding conditions of the laser welding system 1 are optimized, an abnormality that occurs during welding can be limited to an element abnormality during welding such as a gas injection angle abnormality or a gas flow rate abnormality. In this case, it is found that the light intensity data at the normal time and the light intensity data at the time of abnormality of the element being welded can be distinguished relatively easily.

  Therefore, in this embodiment, as described above, the moving average value MA of the reference light intensity data D0, which is normal data, is further averaged to obtain the reference value S, and the sample line is added to the reference value S in the light intensity data D. L is set and analyzed to detect the presence or absence of element abnormality during welding. That is, the sample line L is suitably set in the light intensity data D, and the light intensity data D at the normal time and the light intensity data D at the time of abnormality of the element being welded are identified. Therefore, according to the present embodiment, it is possible to easily and accurately detect the presence or absence of abnormality during welding in the laser welding system 1.

  In the present embodiment, as described above, an element abnormality during welding is detected when the differential characteristic value is smaller than a preset threshold value α. When the differential characteristic value is used in this way, the differential characteristic value at the normal time is necessarily larger than the differential characteristic value at the time of the abnormal element during welding. The light intensity data D at the time can be easily distinguished by one threshold value α. Therefore, it is possible to preferably exhibit the above-described effect of easily and accurately detecting the presence or absence of abnormality during welding in the laser welding system 1.

  FIG. 6 is a graph showing an example of light intensity data. In FIG. 6, the solid line waveform indicates the light intensity data D1 when normal, the wavy line waveform indicates the light intensity data D2 when the gas blowing angle is abnormal, and the alternate long and short dash line waveform indicates the light intensity data D3 when the gas flow rate is abnormal. Is shown. From the example shown in FIG. 6, the possibility of separating the three waveforms can be confirmed, and it can be confirmed that the light intensity data D1 at the normal time and the light intensity data D2 and D3 at the time of abnormality in the welding element can be distinguished relatively easily. .

  FIG. 7 is a graph showing an example of the differential characteristic value. In FIG. 7, the solid line waveform indicates the differential characteristic value B1 when normal, the wavy line indicates the differential characteristic value B2 when the gas injection angle is abnormal, and the one-dot chain line waveform indicates the differential characteristic value B3 when the gas flow rate is abnormal. Is shown. As shown in FIG. 7, it can be seen that the difference between the normal differential characteristic value B1 and the differential characteristic values B2 and B3 when the welding element is abnormal is significant. It can also be seen that the normal differential characteristic value B1 is the largest value. Therefore, based on the differential characteristic values B1 to B3 and the threshold value α, it can be seen that the presence or absence of element abnormality during welding can be detected easily and accurately.

  By the way, it is known that the variation of the normal light intensity data D1 is ± 20% at most from the configuration / characteristics and experience of the entire system (see FIG. 7). Accordingly, the threshold value α of the present embodiment is set as a value that is 80% of the number of intersections between the reference light intensity data D0 and the sample line L as described above. Thereby, normal light intensity data D1 and abnormal light intensity data D2 and D3 can be suitably distinguished in consideration of variations (errors) in light intensity data D, and element abnormality during welding can be more accurately detected. It becomes possible to detect.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the above embodiment, an element abnormality during welding is detected using the differential characteristic value that is the number of intersections between the light intensity data D and the sample line L. However, the number of data of the light intensity data D exceeding the sample line L ( In other words, an element abnormality during welding may be detected using an integral characteristic value (existence amount) which is the number of data of the light intensity data D existing above the sample line L.

  Specifically, first, after the reference value S is calculated and the sample line L is set to the reference value S of the reference light intensity data D0 in the pre-welding process (S13 above), a predetermined time (between a predetermined number of data) The integral characteristic value as a time-series waveform that is the number of reference light intensity data D0 exceeding the sample line L is calculated. Then, 80% of the minimum value of the integral characteristic value is calculated as the lower limit threshold, and 120% of the minimum value of the integral characteristic value is calculated as the upper limit threshold.

  Next, after obtaining the light intensity data D in the mid-welding process (S21), an integral characteristic value as a time series waveform that is the number of data of the light intensity data D exceeding the sample line in a predetermined time is calculated. . When the integral characteristic value is smaller than the lower threshold or larger than the upper threshold, an element abnormality during welding is detected.

  Even when the integral characteristic value is used as described above, the light intensity data at the normal time and the light intensity data at the time of abnormality of the element during welding are suitably distinguished, and the presence or absence of abnormality during welding in the laser welding system 1 can be easily and The above effect of detecting with high accuracy is exhibited. Furthermore, in this case, variations in the light intensity data are taken into consideration for the lower limit threshold and the upper limit threshold.

  Further, in the above embodiment, a gas injection angle abnormality or a gas flow rate abnormality is detected as an element abnormality during welding, but a gas component abnormality or the like may be detected as an element abnormality during welding. Any abnormality relating to an element that operates when forming a welded portion may be used. Further, the mode of laser welding is not limited to the lap welding as in the above-described embodiment, and may be various modes such as butt welding, or a mode using a filler material such as a flat wire. Also good.

  Moreover, said threshold value, an upper limit threshold value, and a lower limit threshold value are not limited to the value mentioned above, You may set suitably according to the aspect and environment of laser welding. Note that “80%” and “120%” include approximately 80% and approximately 120%, respectively, and include errors in measurement or calculation.

  In the present invention, the value of the light intensity data that has passed through the bandpass filter may be averaged so that the moving average is performed, and the average value may be calculated as the reference value. That is, a value obtained by filtering light intensity data with a bandpass filter having a predetermined bandwidth may be handled as the moving average value.

  DESCRIPTION OF SYMBOLS 1 ... Laser welding system, 10A, 10B ... Workpiece (workpiece), W ... Welding part.

Claims (6)

An abnormality detection step for detecting an abnormality relating to an element operating when forming the welded part in a laser welding system in which welding conditions are optimized in advance before forming the welded part on the workpiece by irradiation with a laser beam. Prepared,
The abnormality detection step includes
A first step of obtaining a reference value for detecting the abnormality before forming the weld;
The light intensity data relating to the light intensity of the welded portion is obtained when forming the welded portion, and the abnormality is detected based on the result of analysis by setting a sample line to the reference value in the light intensity data. Including two steps,
In the first step,
When the reference workpiece is irradiated with the laser beam to form a reference weld as a normal weld, reference light intensity data relating to the light intensity of the reference weld is obtained,
An abnormality detection method for a laser welding system, wherein a moving average value is calculated by performing a moving average process on the reference light intensity data, and the average value of the moving average values is calculated as a reference value.   2. The laser welding system according to claim 1, wherein in the second step, the abnormality is detected when the number of intersections between the light intensity data and the sample line is smaller than a preset threshold value. Anomaly detection method.   3. The abnormality detection method for a laser welding system according to claim 2, wherein the threshold value is a value that is 80% of the number of intersections between the reference light intensity data and the sample line.   In the second step, the abnormality is detected when the number of data of the light intensity data exceeding the sample line is smaller than a preset lower threshold or larger than a preset upper threshold. The method for detecting an abnormality of a laser welding system according to claim 1. The lower threshold is a value that is 80% of the number of the reference light intensity data exceeding the sample line,
5. The method for detecting an abnormality in a laser welding system according to claim 4, wherein the upper limit threshold value is 120% of the number of data of the reference light intensity data exceeding the sample line. The element that operates when forming the welded portion includes at least one of an abnormal gas injection angle, an abnormal gas flow rate, and an abnormal gas component, according to any one of claims 1 to 5. Abnormality detection method for laser welding system.

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