METHOD AND APPARATUS FOR MONITORING A NON-MELTING WELDING ELECTRODE OF AN AUTOMATIC ARC WELDING APPARATUS

Abstract

In a method and apparatus for monitoring a non-melting welding electrode of an automated arc welding apparatus, using at least one camera, welding electrode images are captured and processed, and the state of the welding electrode is concluded therefrom. The images are captured during a welding process carried out with the arc welding apparatus, the images are reprocessed, and the arc of the welding process is extracted. The shape of the electrode end is determined from the reprocessed images and compared with a predefined shape of the electrode end. The images are reprocessed by capturing at least two images with different exposure times, cutting out and/or weighting partial areas from the at least two images with different exposure times, and combining them to form a composite image. If the determined shape of the electrode end deviates from the predefined shape of the electrode end, a signal is output.

Claims

1. A method for monitoring a non-melting welding electrode (2), in particular a tungsten electrode, of an automated arc welding apparatus (1), in particular a TIG welding apparatus, wherein with the aid of at least one camera (3), images (B.sub.i) of the welding electrode (2) are captured and the images (B.sub.i) are processed and the state of the welding electrode (2) is concluded therefrom, and the images (B.sub.i) of the welding electrode (2) are captured during a welding process carried out with the arc welding apparatus (1), the images (B.sub.i) are reprocessed and the arc (L) of the welding process is extracted, and the shape (F.sub.d) of the end (4) of the welding electrode (2) is determined from the reprocessed images (B.sub.i′) and compared with a predefined shape (F.sub.v) of the end (4) of the welding electrode (2), wherein the images (B.sub.i) are reprocessed by capturing at least two images with different exposure times, cutting out and/or weighting partial areas from the at least two images with different exposure times, and combining them to form a composite image and, in the event of a deviation (ΔF) of the determined shape (F.sub.d) of the end (4) of the welding electrode (2) from the predefined shape (F.sub.v) of the end (4) of the welding electrode (2), a signal is output.

2. The monitoring method according to claim 1, wherein the position of the end (4) of the welding electrode (2) is determined from the reprocessed images (B.sub.i′) and compared with a predefined position (P.sub.v) of the end (4) of the welding electrode (2), and a signal is output in case of deviation (ΔP) of the determined position (P.sub.d) of the end (4) of the welding electrode (2) from the predefined position (P.sub.v) of the end (4) of the welding electrode (2).

3. The monitoring method according to claim 1, wherein the shape (F) of the end (4) of the welding electrode (2) is determined by the angle (α.sub.E) of a tip of the welding electrode (2) and/or the length (l.sub.E) of the welding electrode (2) projecting from the end of a gas nozzle (5) and/or the diameter (D.sub.E) of a cylindrical part of the welding electrode (2).

4. The monitoring method according to claim 1, wherein a warning signal, in particular an acoustic or optical warning signal, a control signal for the automated arc welding apparatus (1) and/or a switch-off signal for the automated arc welding apparatus (1) is output as the signal (S, S′).

5. The monitoring method according to claim 1, wherein the signal (S, S′) is changed as a function of the deviation (ΔF) of the determined shape (F.sub.d) of the end (4) of the welding electrode (2) from the predefined shape (F.sub.v) of the end (4) of the welding electrode (2) and/or as a function of the deviation (ΔP) of the determined position (P.sub.d) of the end (4) of the welding electrode (2) from the predefined position (P.sub.v) of the end (4) of the welding electrode (2).

6. The monitoring process according to claim 1, wherein the images (B.sub.i) of the end (4) of the welding electrode (2) are captured during the polarity change of an AC welding process.

7. The monitoring method according to claim 1, wherein the images (B.sub.i) of the end (4) of the welding electrode (2) are captured during process phases of the welding process with lower welding current (I).

8. The monitoring method according to claim 1, wherein the predefined shape (F.sub.v) and, if necessary, the predefined position (P.sub.v) of the end (4) of the welding electrode (2) are determined and stored by capturing images of the end (4) of a new welding electrode (2) before the welding process is carried out.

9. The monitoring method according to claim 1, wherein the at least one camera (3) is calibrated before capturing the images (B.sub.i) of the welding electrode (2).

10. An apparatus (10) for monitoring a non-melting welding electrode (2), in particular a tungsten electrode, of an automated arc welding apparatus (1), in particular a TIG welding device, having at least one camera (3) for capturing images (B.sub.i) of the welding electrode (2) and an image processing device (11) for processing the images (B.sub.i) and for obtaining a conclusion therefrom as to the state of the welding electrode (2), wherein the at least one camera (3) is configured for capturing the images (B.sub.i) of the welding electrode (2) during a welding process carried out with the arc welding apparatus (1), the image processing device (11) being configured for reprocessing the images (B.sub.i) and extracting the arc (L) of the welding process and for determining the shape (F.sub.d) of the end (4) of the welding electrode (2) from the reprocessed images (B.sub.i′) and for comparison with a predefined shape (F.sub.v) of the end (4) of the welding electrode (2), wherein the image processing device (11) is configured for cutting and/or weighting sub-areas from at least two images captured with different exposure time and for combining the sub-areas to form a composite image, and the image processing device (11) is connected to a signal device (12) configured for outputting a signal (S) in the event of deviation (ΔF) of the determined shape (F.sub.d) of the end (4) of the welding electrode (2) from the end (4) of the welding electrode (2) formed by the predefined shape (Fv) of the end (4) of the welding electrode (2).

11. The monitoring apparatus (10) according to claim 10, wherein the image processing device (11) is designed for determining the position (P.sub.d) of the end (4) of the welding electrode (2) from the reprocessed images (B.sub.i′) and for comparison with a predefined position (P.sub.v) of the end (4) of the welding electrode (2), and the image processing device (11) is connected to a signal device (12) which is designed for outputting a signal (S′) in case of deviation (ΔF) of the determined position (P.sub.d) of the end (4) of the welding electrode (2) from the predefined position (P.sub.v) of the end (4) of the welding electrode (2).

12. The monitoring apparatus (10) according to claim 10, wherein the signal device (12) is formed by a warning signal device (13), in particular a loudspeaker (14) for outputting an acoustic warning signal as a signal (S, S′) or by a display (15) for outputting an optical warning signal as a signal (S, S′) and/or by a control device (16) connected to the automated arc welding apparatus (1) for outputting a control signal as a signal (S, S′).

13. The monitoring apparatus (10) according to claim 10, wherein a calibration device (17) is provided for calibrating the at least one camera (3) before capturing the images (B.sub.i) of the welding electrode (2).

14. The monitoring apparatus (10) according to claim 10, wherein at least one light source (6) is provided.

Description

[0031] The present invention is explained in more detail with reference to the appended drawings. In the figures:

[0032] FIG. 1 shows a schematic block diagram of an automated arc welding apparatus having a non-melting welding electrode;

[0033] FIG. 2 shows a block diagram of an apparatus according to the invention for monitoring the non-melting welding electrode of an automated arc welding apparatus;

[0034] FIG. 3 shows a view of the end of a non-melting welding electrode; and

[0035] FIGS. 4A-4C schematically show the camera images to be compared in the monitoring of the non-melting welding electrode.

[0036] FIG. 1 shows a schematic block diagram of an automated arc welding apparatus 1 with a non-melting welding electrode 2, in particular a TIG (tungsten inert gas) welding device with a tungsten electrode. A current source SQ is connected both to the non-melting welding electrode 2 arranged on the welding torch SB and to the workpiece W of electrically conductive material. For carrying out an automated welding process, the welding torch SB is connected to a manipulator MP, such as a robot, linear running gear, bogie or the like, via which the welding torch SB is moved along a predetermined welding path over the workpiece W. The current source SQ generates a welding current I between the non-melting electrode and the workpiece W, as a result of which an arc L is ignited between the end of the non-melting welding electrode and the surface of the workpiece W. The time sequences are controlled and the respective values of the welding current I and of the welding voltage U are regulated via a control device (not shown) which is usually located in the current source SQ. In order to connect two workpieces W to one another or to apply a layer to the surface of the workpiece W, a melting material is usually fed into the arc L in wire form and melted in the arc L (not shown).

[0037] While in manual welding processes the state of the welding electrode can be continuously assessed by the welder and it can be estimated when grinding of the electrode tip or replacement of the welding electrode is necessary, in automated welding processes this must be done via camera images. Due to the bright arc, however, evaluation of the camera images during the welding process has hitherto been impossible or inadequately possible.

[0038] FIG. 2 shows a block diagram of an apparatus 10 according to the invention for monitoring the non-melting welding electrode 2 of an automated arc welding apparatus 1. During the welding process, images B.sub.i of the non-melting welding electrode 2 or of the end 4 of the welding electrode 2 are captured with at least one camera 3. A light source 6 for illuminating the welding region can be arranged on the at least one camera 3 or in the vicinity. In an image processing device 11, the images B.sub.i captured with the camera 3 are processed in order to achieve a quality of the images B.sub.i which, despite the arc L, allow an analysis and a conclusion to be drawn therefrom as to the state of the welding electrode 2. The at least one camera 3 is designed to capture the images B.sub.i of the welding electrode 2 during the welding process carried out with the arc welding apparatus 1. The capture of the images B.sub.i can be carried out in process phases of the welding process during which the arc does not burn or burns only weakly, for example during short-circuit phases or base current phases of a welding process. The image processing device 11 is used for the corresponding reprocessing of the images B.sub.i and extraction of the arc L of the welding process. Furthermore, the shape F.sub.d and, if necessary, the position P.sub.d of the end 4 of the welding electrode 2 are determined in the image processing device 11 from the reprocessed images B.sub.i′. Thereafter, the determined shape F.sub.d and possibly position P.sub.d of the end 4 of the welding electrode 2 is compared with a predefined shape F.sub.v and possibly predefined position P.sub.v of the end 4 of the welding electrode 2 and the corresponding deviation ΔF of the shape and possibly deviation ΔP of the position is calculated. The image processing device 11 is connected to a signal device 12 which serves to output a signal S as soon as the deviation ΔF of the shape or deviation ΔP of the position of the end 4 of the welding electrode 2 exceeds a certain amount. The processing takes place continuously during the welding process. Since the state of the welding electrode 2 does not change abruptly, a time delay in the reprocessing of the images B.sub.i is not a problem or an evaluation in real time is not necessary.

[0039] The signal device 12 can be formed by a warning signal device 13, in particular a loudspeaker 14, for outputting an acoustic warning signal as a signal S in the event of a deviation ΔF of the shape of the end 4 of the welding electrode 2 or as a signal S′ in the event of a deviation ΔP of the position of the end 4 of the welding electrode 2. Alternatively or in addition to the warning signal device 13, a display 15 may also be connected to the signal device 12 for outputting an optical warning signal as a signal S or S′. Furthermore, a control device 16 can be connected to the signal device 12, via which a control signal can be emitted as a signal S, S′ to the automated arc welding apparatus 1 if wear of the welding electrode 2 has been detected.

[0040] The signal device 12 thus continuously observes the welding process, so that wear of the welding electrode 2 is also monitored. Accordingly, it is possible to report on the state of the welding electrode 2 by means of warning stages (for example via a traffic light system). This takes place, for example, after each welding process or after predefined times when a welding process (such as, for example, build-up welding) lasts for a long period of time. The signal device 12 thus informs about the current state of the welding electrode 2 and, for example, issues recommendations as to when the welding electrode 2 is to be changed or machined.

[0041] Calibration of the camera 3 before capturing the images B.sub.i of the welding electrode 2 can be carried out via a calibration device 17, for example via corresponding calibration patterns.

[0042] FIG. 3 shows a view of the end 4 of a non-melting welding electrode 2. In order to determine the shape F of the end 4 of the welding electrode 2, the angle α.sub.E of a tip of the welding electrode 2 and/or the length l.sub.E of the welding electrode 2 projecting from the end of a gas nozzle 5 and/or the diameter D.sub.E of a cylindrical part of the welding electrode 2 can be determined from the images B.sub.i.

[0043] FIG. 4A schematically shows a reference image of the end 4 of a welding electrode 2, in particular the image of a new welding electrode 2. FIG. 4B shows a current image of the end 4 of the welding electrode 2, with a welding splatter SP adhering to the tip of the welding electrode. By means of the image processing device 11, a difference of the current image of the welding electrode 2 according to FIG. 4B and the reference image according to FIG. 4A is now generated (see FIG. 4C). The difference image according to FIG. 4C can now be used to determine the deviation ΔF of the determined shape F.sub.d of the end of the welding electrode (FIG. 4B) from the predefined shape F.sub.v of the end of the welding electrode (FIG. 4A), and a signal S can be output when a specific deviation is exceeded. This signal S can be changed as a function of the deviation ΔF of the shape.

[0044] FIG. 4C also shows that the diameter D.sub.E of the welding electrode 2 can change. Particularly in the case of welding processes with a long duration, a layer which increases the diameter D.sub.E can form on the welding electrode 2 owing to the adhesion of welding spatter, which is distributed over the surface. Likewise, the difference image according to FIG. 4C can be used to determine the deviation ΔP of the determined position P.sub.d of the end 4 of the welding electrode 2 (FIG. 4B) from the predefined position P.sub.v of the end of the welding electrode, and a signal S′ can be output or generated. Also this signal S can be changed as a function of the deviation ΔP of the position.

[0045] The present invention allows a quick and reliable determination of the state of the welding electrode during the welding process of an automated arc welding apparatus and thus ensures a constant optimum welding quality.