Welding wire deviation amount detection device and method for detecting welding wire deviation amount

Abstract

[Problem] To detect a deviation amount associated with positional deviation of a welding wire. [Solution] This welding wire deviation amount detection device comprises: a detection plate 30 in which a first detection groove 31 extending in an X direction (first direction) is formed, the first detection groove having a shape in which a groove width 31a decreases toward the X direction; an operation control unit; and a detection unit. The operation control unit controls the operation of a welding robot on the basis of teaching data and traces the welding wire toward the X direction inside the first detection groove. The detection unit detects the amount of deviation of the welding wire in a Y direction (second direction) orthogonal to the X direction on the basis of the position of the welding wire along the X direction and the groove width of the first detection groove at the position of the welding wire when the welding wire comes into contact with the inner-side surface 31d of the first detection groove.

Description

Welding wire displacement detection device and welding wire displacement detection method

[0001] The present invention relates to a welding wire displacement detection device and a welding wire displacement detection method.

[0002] Welding robots that perform arc welding have a welding wire extending from the tip of the torch. If the welding wire is misaligned, it will not be able to weld along the target line, resulting in a so-called derailment. This derailment during welding can lead to welding defects, such as poor penetration of the deposited metal into the base material.

[0003] A technique for checking the positional misalignment of a welding wire is known (see Patent Document 1). In the arc welding method disclosed in Patent Document 1, the welding wire is moved along a passage path provided on a checking jig while the torch is moved to a welding position. The positional misalignment of the tip of the welding wire is checked based on whether the welding wire can pass through the passage path. When the welding wire is not in contact with the wall surface of the passage path, it is determined that no positional misalignment has occurred. When the welding wire is in contact with the wall surface of the passage path, it is determined that a positional misalignment has occurred.

[0004] Patent Publication No. 2018-126753

[0005] The passage path in Patent Document 1 has a constant width in a direction perpendicular to the direction of movement of the welding wire. The technology in Patent Document 1 merely determines whether a positional misalignment has occurred based on whether the welding wire abuts the wall surface of the passage path. It does not aim to detect the amount of welding wire positional misalignment itself. A specific example will be described. Take, for example, a case where the width of the passage path is, for example, 3 mm and the diameter of the welding wire is, for example, 1.2 mm. Even if the welding wire is misaligned less than 0.9 mm from the groove center in the groove width direction, it is determined that no positional misalignment has occurred because the welding wire does not abut the wall surface of the passage path. When the welding wire is misaligned less than 0.9 mm, the amount of misalignment itself is not detected. Only when the welding wire is misaligned 0.9 mm from the groove center in the groove width direction does it abut the wall surface of the passage path and it is determined that a positional misalignment has occurred. The amount of misalignment at this time is a single 0.9 mm determined by the width dimension of the passage path and the diameter of the welding wire.

[0006] As described above, since the objective is not to detect the amount of misalignment of the welding wire itself, it is not possible to manage the tendency of the amount of misalignment of the welding wire to increase over time. As a result, consumables around the torch (e.g., contact tips) must be replaced empirically at a timing calculated from the weld length and the number of welds completed, and it is not possible to optimize the replacement cycle.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a welding wire displacement detection device and a welding wire displacement detection method that are capable of detecting the displacement amount itself associated with the positional displacement of the welding wire.

[0008] One aspect of the present invention is a device for detecting a displacement of a welding wire extending from a tip of a torch of a welding robot. The device for detecting a displacement of a welding wire includes: a detection plate having a first detection groove formed therein extending in a first direction and having a shape in which the groove width narrows in the first direction; an operation control unit that controls an operation of the welding robot based on teaching data and causes the welding wire to trace inside the first detection groove in the first direction; and a detection unit that, when the welding wire contacts an inner surface of the first detection groove, detects a displacement of the welding wire in a second direction perpendicular to the first direction based on a position of the welding wire extending in the first direction and the groove width of the first detection groove at the position of the welding wire.

[0009] Another aspect of the present invention is a method for detecting a displacement of a welding wire extending from a tip of a torch of a welding robot. The method controls the operation of the welding robot based on teaching data, and causes the welding wire to trace in a first direction inside a first detection groove formed in a detection plate and extending in the first direction, the first detection groove having a groove width that narrows in the first direction. When the welding wire contacts an inner surface of the first detection groove, the method detects a displacement of the welding wire in a second direction perpendicular to the first direction based on a position of the welding wire extending in the first direction and the groove width of the first detection groove at the position of the welding wire.

[0010] According to the present invention, it is possible to provide a welding wire displacement detection device and a welding wire displacement detection method that can detect the displacement amount itself associated with positional displacement of the welding wire.

[0011] 1 is a schematic configuration diagram showing a welding apparatus to which a welding wire displacement detection device is applied; FIG. 2 is a front view showing a detection plate of the welding wire displacement detection device; FIG. 3 is a block diagram showing a control system of the welding wire displacement detection device; FIG. 4 is a schematic view illustrating wear of a contact tip, which is a cause of welding wire displacement; FIG. 5 is a schematic view illustrating deformation and loosening of a torch, which are causes of welding wire displacement; FIG. 6 is a schematic view illustrating positional displacement of a welding jig, which is a cause of welding wire displacement; FIG. 7 is a schematic view showing a state in which a welding wire is traced inside a first detection groove; FIG. 8 is a cross-sectional view showing a state in which a welding wire is traced inside a first detection groove; FIG. 9 is a schematic view illustrating the amount of displacement in the X direction, the amount of displacement in the Y direction, and a combined amount of displacement in the X and Y directions; FIG. 10 is a schematic view used to explain the structures of first data and second data; FIG. 11 is a schematic view showing a state in which the amount of displacement is detected using the first data and the second data; FIG. 12 is a schematic view showing a mode in which a determination of whether welding wire displacement is good or bad is made based on the combined amount of displacement; FIG. 13 is a front view showing an operation and display unit. 10A is a diagram showing an example of a time series graph displayed on a display; FIG. 10B is a diagram showing an example of data displayed on a time series graph; FIG. 10C is a diagram showing an example of a display of a pass / fail judgment of a welding wire displacement; FIG. 10D is a diagram showing another example of a judgment to be displayed; FIG. 10E is a diagram showing another example of a judgment to be displayed; FIG. 10F is a flowchart showing the procedure of a welding operation to which a method for detecting a welding wire displacement is applied; FIG. 10G is a flowchart showing the procedure of a welding operation following FIG. 10A; FIG. 10H is a front view showing a modified detection groove (stepped straight type); FIG. 10H is a front view showing a modified detection groove (convex tapered type); FIG. 10I is a front view showing a modified detection groove (convex tapered type); FIG. 10I is a front view showing a modified detection groove (convex tapered type); FIG. 10I is a front view showing a modified detection groove (one-sided tapered type); FIG. 10I is a front view showing a modified detection groove (one-sided tapered combined type).

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments shown here are merely examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other embodiments, examples, and operational techniques that can be conceived by those skilled in the art without departing from the spirit of the present invention are included within the scope and spirit of the present invention, as well as within the scope of the claims and their equivalents.

[0013] In addition, for the convenience of illustration and ease of understanding, the drawings attached to this specification may be represented schematically with the scale, aspect ratio, shape, etc. appropriately changed from the actual product, but these are merely examples and do not limit the interpretation of the present invention.

[0014] In this specification, ordinal numbers such as "first" and "second" may be used. However, unless otherwise specified, these ordinal numbers are used to identify components for the convenience of explanation and do not specify the number or order.

[0015] 1 shows a welding apparatus 10 incorporating a welding wire displacement detection device. The welding apparatus 10 generally includes a welding robot 11, a robot controller 12 for controlling the welding robot 11, a welding jig 14 on which a workpiece 13 to be welded is set, and a displacement detection device 20 (hereinafter simply referred to as the "detection device 20") for a welding wire 21 (hereinafter simply referred to as the "wire 21"). The welding robot 11 and the welding jig 14 are mounted on a base 15. The welding robot 11 includes multiple robot arms 16 and a torch 17 attached to the robot arm 16. The wire 21 is automatically supplied from a supply device (not shown). The wire 21 extends from a contact tip 18 provided at the tip of the torch 17. The robot controller 12 controls the posture of the welding robot 11, the supply of the wire 21, the supply of the welding current, and the like.

[0016] First, factors that cause misalignment of the wire 21 will be described. Figures 4A, 4B, and 4C each show factors that cause misalignment of the wire 21. As shown in Figure 4A, before the contact tip 18 is worn (upper state), the wire 21 is positioned at the center of the tip hole 18a or rubs against the tip of the tip hole 18a due to the wire 21's tendency to bend. Repeated welding operations cause the wire 21 to rub against the tip hole 18a, gradually wearing the tip hole 18a. As wear of the contact tip 18 progresses (lower state), the diameter of the tip hole 18 increases. The increase in the hole diameter is indicated by arrow 18b. This causes misalignment of the wire 21. As shown in Figure 4B, repeated welding operations increase the deformation of the torch 17, indicated by arrow 17a, and the loosening of the torch 17, indicated by arrow 17b, increases. This causes misalignment of the wire 21. 4C , when welding jig 14 is replaced on base 15, a positional deviation occurs in welding jig 14 as indicated by the dashed line, which causes a deviation in wire 21. In order to detect the amount of deviation itself that accompanies such a positional deviation of wire 21, detection device 20 is configured as follows.

[0017] FIG. 2 shows the detection plate 30 of the detection device 20, and the block diagram of FIG.

[0018] Detector 20 detects the amount of misalignment of wire 21 extending from the tip of torch 17 of welding robot 11. As shown in Figures 2 and 3, detector 20 has detection plate 30 and controller 40 that performs control for detecting the amount of misalignment. Controller 40 is connected to robot controller 12 and exchanges signals with robot controller 12. Controller 40 has an operation control unit 41, a detection unit 42, a storage unit 43, and an operation display unit 44.

[0019] 1, the detection plate 30 is fixed to the welding jig 14. The detection plate 30 is made of a conductor.

[0020] As shown in Fig. 2, the detection plate 30 is formed with a first detection groove 31 extending in a first direction and a second detection groove 32 extending in a second direction perpendicular to the first direction. The first detection groove 31 has a groove width 31a that narrows toward the first direction. The second detection groove 32 has a groove width 32a that narrows toward the second direction. In the following description, the first direction and the second direction are referred to as the X direction and the Y direction, respectively. The X axis and the Y axis in Fig. 2 indicate the X direction and the Y direction, respectively.

[0021] The first detection groove 31 has a start end 31b (right end in FIG. 2 ) where the groove width 31a is the widest and a finish end 31c (left end in FIG. 2 ) where the groove width 31a is the narrowest. The second detection groove 32 has a start end 32b (lower end in FIG. 2 ) where the groove width 32a is the widest and a finish end 32c (upper end in FIG. 2 ) where the groove width 32a is the narrowest.

[0022] 5A and 5B show the wire 21 being traced inside the first detection groove 31. As shown in FIG. 5A , when detecting the amount of misalignment of the wire 21 in the Y direction, the wire 21 is traced inside the first detection groove 31 from the starting end 31 b of the first detection groove 31 to the ending end 31 c of the first detection groove 31. When detecting the amount of misalignment of the wire 21 in the X direction, the wire 21 is traced inside the second detection groove 32 from the starting end 32 b of the second detection groove 32 to the ending end 32 c of the second detection groove 32. As shown in FIG. 5B , the wire 21 extends a predetermined length L (e.g., 15 mm) from the contact tip 18 and can contact the inner surface 31 d of the first detection groove 31. The wire 21 can also contact the inner surface 32 d of the second detection groove 32.

[0023] In this embodiment, the first detection groove 31 has a shape in which the groove width 31a decreases linearly in the X direction. Similarly, the second detection groove 32 has a shape in which the groove width 32a decreases linearly in the Y direction. For convenience of explanation, the first detection groove 31 and the second detection groove 32 are referred to as a "basic tapered type." The basic tapered first detection groove 31 and the second detection groove 32 can continuously and uninterruptedly detect the point where the wire 21 contacts the inner surfaces 31d and 32d. The groove width 31a of the first detection groove 31 is known in the X direction. The groove width 32a of the second detection groove 32 is known in the Y direction. Therefore, the amount of misalignment of the wire 21 can be detected and recorded in detail based on the "distance from the starting ends 31b and 32b." This makes it easy to manage the tendency of the wire 21 to misalign, for example, the tendency for the amount of misalignment to increase with the number of welding operations. As will be described later, the first and second detection grooves 31 and 32 of the basic tapered type can be divided into multiple sections, and the amount of misalignment of the wire 21 can be detected based on the "contact section." In the first and second detection grooves 31 and 32 of the basic tapered type, the wire 21 continues to contact the inner surfaces 31d and 32d from the point where the wire 21 makes contact with the inner surfaces 31d and 32d. This prevents the contact signal from being missed. In the basic tapered type, if the amount of misalignment is large, the wire 21 continues to contact the inner surfaces 31d and 32d. Therefore, to suppress wear over long-term use, it is preferable to apply a conductive coating or the like to the inner surfaces 31d and 32d to reduce sliding resistance. The basic tapered type has a simple shape. Therefore, it can be processed relatively inexpensively.

[0024] The detection plate 30 has a connecting groove 33 that connects the end of the first detection groove 31 to the end of the second detection groove 32. In the illustrated example, the connecting groove 33 connects the terminal end 31c of the first detection groove 31 to the starting end 32b of the second detection groove 32. The connecting groove 33 allows the wire 21 to be continuously traced from the inside of the first detection groove 31 to the inside of the second detection groove 32. Therefore, after detecting the amount of misalignment of the wire 21 in the Y direction, it is possible to continuously detect the amount of misalignment in the X direction.

[0025] The connecting groove 33 can be formed at a position that connects the terminal end 32c of the second detection groove 32 with the starting end 31b of the first detection groove 31. In this case, the connecting groove 33 allows the wire 21 to be continuously traced from the inside of the second detection groove 32 to the inside of the first detection groove 31. Therefore, after detecting the amount of misalignment of the wire 21 in the X direction, it is possible to continuously detect the amount of misalignment in the Y direction.

[0026] When detecting the amount of misalignment of wire 21 in the Y direction, operation control unit 41 controls the operation of welding robot 11 based on the teaching data. Wire 21 is traced in the X direction inside first detection groove 31. The teaching data at this time pre-sets a start position, an intermediate position, and an end position in order so that the tip of wire 21 is positioned at the center of first detection groove 31. When welding robot 11 is operated automatically, the tip of wire 21 passes through the center of first detection groove 31.

[0027] Similarly, when detecting the amount of misalignment of wire 21 in the X direction, operation control unit 41 controls the operation of welding robot 11 based on the teaching data. Wire 21 is traced in the Y direction inside second detection groove 32. The teaching data at this time pre-sets a start position, an intermediate position, and an end position in order so that the tip of wire 21 is positioned at the center of second detection groove 32. When welding robot 11 is operated automatically, the tip of wire 21 passes through the center of second detection groove 32.

[0028] When the wire 21 contacts the inner surface 31d of the first detection groove 31, the detection unit 42 detects the amount of deviation of the wire 21 in the Y direction, which is perpendicular to the X direction, based on the position of the wire 21 facing in the X direction and the groove width 31a of the first detection groove 31 at the position of the wire 21.

[0029] When the wire 21 comes into contact with the inner surface 31d of the first detection groove 31 during tracing, electricity is passed through the path indicated by the dashed line in FIG. 1 . The welding robot 11 outputs an ON signal indicating contact. The detector 42 identifies that the wire 21 has come into contact with the inner surface 31d of the first detection groove 31 based on the ON signal. The position of the wire 21 can be determined from the operating position of the welding robot 11, which is controlled by the operation controller 41. The groove width 31a of the first detection groove 31 is known at its position in the X direction. Therefore, the detector 42 can detect the amount of deviation of the wire 21 in the Y direction based on the ON signal, the operating position of the welding robot 11, and the known groove width 31a of the first detection groove 31.

[0030] Similarly, when the wire 21 contacts the inner surface 32d of the second detection groove 32, the detection unit 42 detects the amount of deviation of the wire 21 in the X direction based on the position of the wire 21 facing in the Y direction and the groove width 32a of the second detection groove 32 at the position of the wire 21.

[0031] When the wire 21 comes into contact with the inner surface 32d of the second detection groove 32 while being traced, the welding robot 11 outputs an ON signal indicating the contact. The position of the wire 21 can be known from the operating position of the welding robot 11, which is controlled by the operation control unit 41. The groove width 32a of the second detection groove 32 is known in the Y direction. Therefore, the detection unit 42 can detect the amount of misalignment of the wire 21 in the X direction based on the ON signal, the operating position of the welding robot 11, and the known groove width 32a of the second detection groove 32.

[0032] The operation control unit 41 causes the wire 21 to continuously trace both the first detection groove 31 and the second detection groove 32 via the connecting groove 33. Therefore, the amount of misalignment of the wire 21 in the Y direction and the amount of misalignment in the X direction can be detected continuously and quickly.

[0033] The detector 42 detects a combined amount of misalignment in the Y and X directions based on the amount of misalignment of the wire 21 in the Y and X directions. If the amount of misalignment of the wire 21 in the Y direction is y and the amount of misalignment in the X direction is x, the combined amount of misalignment r is expressed as follows: r=(x ２ +y ２ ) １／２... (Equation 1)

[0034] 5C is a schematic diagram illustrating the combined misalignment amount. In FIG. 5C, wa indicates the groove width 31a of the first detection groove 31, xa and ya indicate the misalignment amounts of the wire 21 in the X and Y directions, yb indicates the allowable dimension of misalignment of the wire 21 in the Y direction, and yc indicates the gap dimension between the misaligned wire 21 and the inner surface 31d. For example, if wa=3.0 mm, the diameter of the wire 21=1.2 mm, xa=0.7 mm, and ya=0.7 mm, then yb=0.9 mm and yc=0.2. The combined misalignment amount ra is calculated from Equation 1 as r=(0.7 ２ +0.7 ２ ) １／２ = 0.99. Because the wire 21 is not in contact with the inner surface 31d, the result is an "OK" judgment, but in reality, a misalignment of 0.99 mm occurs, which exceeds the allowable dimension yb = 0.9 mm. Therefore, it is preferable to judge the pass / fail of the misalignment of the wire 21 based on the combined amount of misalignment in the X and Y directions rather than judging the amount of misalignment in the X direction and the amount of misalignment in the Y direction separately.

[0035] Next, a control will be described in which the basic tapered first detection groove 31 and second detection groove 32 are divided into a plurality of sections, and the amount of misalignment of the wire 21 is detected based on the "contact section."

[0036] 3, the storage unit 43 of the detection device 20 further includes a first storage unit 43a and a second storage unit 43b. The first storage unit 43a stores first data in which the amount of misalignment of the wire 21 in the Y direction is set for each of a plurality of sections obtained by dividing the first detection groove 31 in the X direction. The second storage unit 43b stores second data in which the amount of misalignment of the wire 21 in the X direction is set for each of a plurality of sections obtained by dividing the second detection groove 32 in the Y direction.

[0037] FIG. 6 is a schematic diagram used to explain the structures of the first data and the second data. The structure of the first data will be described. In this embodiment, the second data also has the same data structure. The first data includes a section number indicating a section of the first detection groove 31 and the Y-direction displacement amount of the wire 21 in that section. The diameter of the wire 21 is, for example, 1.2 mm, the groove width 31a at the starting end 31b (the right end in FIG. 6 ) of the first detection groove 31 is, for example, 2.9 mm, and the groove width 31a at the ending end 31c (the left end in FIG. 6 ) is, for example, 1.3 mm. The length of the first detection groove 31 is, for example, 40.0 mm, and the length of each section is, for example, 5.0 mm. The first detection groove 31 is divided into eight sections, and each section has a tapered shape in which the groove width 31a changes by 0.1 mm on one side. The section numbers of the first detection groove 31 are assigned sequentially from the starting end 31b to the ending end 31c, from "1" to "8." The amount of deviation in the Y direction for section "1" is set to 0.8 mm. Values ​​are set that decrease in increments of 0.1 mm for sections "2" and onward. The amount of deviation in the Y direction for the final section "8" is set to 0.1 mm.

[0038] When the wire 21 comes into contact with the inner surface 31d of the first detection groove 31, the detection unit 42 detects the amount of deviation of the wire 21 in the Y direction based on the section in which the wire 21 comes into contact and the first data stored in the first memory unit 43a.

[0039] When the wire 21 moves within the first detection groove 31, it is necessary to recognize which section of the first detection groove 31 the wire 21 is passing through and how many millimeters the wire 21 is displaced from the reference. The welding robot 11 has a function of communicating with the controller 40. When the wire 21 is passing through the range of section number "1" in the first detection groove 31, the welding robot 11 outputs "signal 1." When "signal 1" is input to the controller 40, the counter of the detection unit 42 counts "1." Thereafter, when the wire 21 is passing through the range of section number "2" in the first detection groove 31, the welding robot 11 outputs "signal 2." When "signal 2" is input to the controller 40, the counter of the detection unit 42 counts "2." Thereafter, when the wire 21 is passing through the range of section number "3" in the first detection groove 31, the welding robot 11 outputs "signal 1." When "signal 1" is input to the controller 40, the counter of the detection unit 42 counts "3." In this way, the welding robot 11 alternately outputs "signal 1" and "signal 2" each time the travel section of the wire 21 switches. The counter of the detection unit 42 increments by one each time "signal 1" and "signal 2" are alternately input to the control device. By performing this process for section numbers "1" to "8" of the first detection groove 31, the counter records which section in the first detection groove 31 the wire 21 is passing through. Figure 6 also shows the values ​​recorded in the counter.

[0040] When the wire 21 comes into contact with the inner surface 31d of the first detection groove 31 while tracing the wire 21, the welding robot 11 outputs an ON signal indicating the contact. The current value of the counter can be used to determine which section of the first detection groove 31 the wire 21 is passing through. The first data contains the amount of deviation of the wire 21 in the Y direction for each section of the first detection groove 31. Therefore, the detection unit 42 can detect the amount of deviation of the wire 21 in the Y direction that corresponds to the section where the wire 21 first came into contact, based on the ON signal, the current value of the counter, and the amount of deviation set in the first data.

[0041] Similarly, when the wire 21 comes into contact with the inner surface 32d of the second detection groove 32, the detection unit 42 detects the amount of displacement of the wire 21 in the X direction based on the section in which the wire 21 comes into contact and the second data stored in the second memory unit 43b.

[0042] As described above, the counter records which section of the second detection groove 32 the wire 21 passes through. When the wire 21 comes into contact with the inner surface 32d of the second detection groove 32 while tracing the wire 21, the welding robot 11 outputs an ON signal indicating the contact. The section of the second detection groove 32 that the wire 21 is passing through can be known from the current value of the counter. The second data is set with the amount of deviation of the wire 21 in the X direction for each section of the second detection groove 32. Therefore, the detection unit 42 can detect the amount of deviation of the wire 21 in the X direction that corresponds to the section where the wire 21 first came into contact, based on the ON signal, the current value of the counter, and the amount of deviation set in the second data.

[0043] FIG. 7 is a schematic diagram showing how the amount of deviation is detected using the first data and the second data. As shown in FIG. 7 , for example, if the wire 21 comes into contact with the inner surface 31 d of the first detection groove 31 while passing through section number "7" within the first detection groove 31, the detection unit 42 detects, based on the first data, that the amount of deviation y of the wire 21 in the Y direction from the reference, corresponding to the counter value "7," is 0.2. Also, if the wire 21 comes into contact with the inner surface 32 d of the second detection groove 32 while passing through section number "5" within the second detection groove 32, the detection unit 42 detects, based on the second data, that the amount of deviation x of the wire 21 in the X direction from the reference, corresponding to the counter value "5," is 0.4. Then, the detection unit 42 calculates the composite amount of deviation r from Equation 1 as r = (0.4 ２ +0.2 ２ ) １／２ = 0.45. In this way, the detection unit 42 can recognize the combined amount of misalignment in the Y and X directions.

[0044] FIG. 8 is a schematic diagram illustrating a manner in which the misalignment of the wire 21 is determined based on the composite misalignment amount. FIG. 8 illustrates a state in which the wire 21 is misaligned in the Y and X directions from a reference O. The reference O is the center of the first detection groove 31 and the center of the second detection groove 32. The diameter of the wire 21 used is selected according to the welding location, welding speed, and the like. In this embodiment, the misalignment index is a value obtained by adding the radius of the wire 21 to the composite misalignment amount in the Y and X directions. The misalignment is determined based on the misalignment index. The threshold value of the misalignment index is indicated by the symbol 50. When the misalignment amount of the wire 21 in the Y direction is y1 and the misalignment amount in the X direction is x1, the composite misalignment amount r1 is calculated using Equation 1. In this case, the misalignment index (composite misalignment amount r1 + radius of the wire 21) is within the allowable range inside the threshold value 50, so the misalignment of the wire 21 is determined to be "OK." On the other hand, when the misalignment amount of the wire 21 in the Y direction is y2 and the misalignment amount in the X direction is x2, the composite misalignment amount r2 can be calculated using Equation 1. In this case, the misalignment index (composite misalignment amount r2 + radius of the wire 21) is outside the allowable range outside the threshold value 50, so the misalignment of the wire 21 is determined to be "NG." Because the composite misalignment amount and therefore the misalignment index itself can be detected, the impact on welding quality caused by the misalignment of the wire 21 can be reduced. Furthermore, the threshold value 50 for the misalignment index can be set to a different value for each product and each diameter of the wire 21 used.

[0045] Figure 9A is a front view showing the operation display unit 44, Figure 9B is a diagram showing an example of a time series graph 44b displayed on the display 44a, Figure 9C is a diagram showing an example of data displayed on the time series graph 44b, Figure 9D is a diagram showing an example of a display of a pass / fail judgment of the misalignment of the wire 21, and Figures 9E and 9F are diagrams showing other examples of the judgments displayed.

[0046] 9A, the operation display unit 44 has a display 44a and operation buttons. The operation display unit 44 is configured as a tablet. The operation display unit 44 has an internal memory and a slot for an external storage medium such as a memory card.

[0047] As shown in FIG. 9B , the display 44a can display a time series graph 44b. The vertical axis of the time series graph 44b represents the Y-direction deviation y of the wire 21, the X-direction deviation x, and the combined deviation r. The horizontal axis represents the number of operations initiated by the welding robot 11. In this embodiment, the Y-direction deviation and the X-direction deviation of the wire 21 are detected before welding is performed on the workpiece 13 to be welded. Therefore, the number of operations of the welding robot 11 is the same as the number of times the deviation of the wire 21 is detected. The time series graph 44b indicates the Y-direction deviation y with a black triangle, the X-direction deviation x with a black square, and the combined deviation r with a black circle. The illustrated time series graph 44b indicates a combined deviation r of 0.5 mm as a warning line 44c and a combined deviation r of 0.6 mm as an abnormal line 44d. The warning line 44c is indicated, for example, in yellow. The abnormal line 44d is shown in red, for example. The time series graph 44b visualizes the deviation amount and deviation trend. Therefore, the worker can easily understand the tendency of the combined deviation amount r increasing with the number of activations of the welding robot 11.

[0048] 9C, data 44e displayed on the time series graph 44b includes a production counter, an X-direction deviation x, a Y-direction deviation y, and a composite deviation r. The data is stored in the internal memory. The data can also be stored in an external storage medium for external viewing and traceability.

[0049] As shown in FIG. 9D, the display 44f of the judgment of the quality of the misalignment of the wire 21 includes a judgment on the number of operations of the welding robot 11, the misalignment amount x in the X direction, the misalignment amount y in the Y direction, the composite misalignment amount r, and the misalignment index (composite misalignment amount r + radius of the wire 21).

[0050] There are three types of judgments that can be displayed: "OK" (see FIG. 9D), "Caution" (see FIG. 9E), and "NG" (see FIG. 9F). "OK" indicates that the deviation index is within the allowable range, "Caution" indicates that the deviation index is approaching the limit of the allowable range, and "NG" indicates that the deviation index is outside the allowable range. When it is "OK", for example, a green lamp is lit. When it is "Caution", for example, a yellow lamp is lit. When it is "NG", for example, a red lamp is lit.

[0051] If the judgment is "OK" or "Caution", the deviation index does not exceed the threshold value 50, so the welding robot 11 proceeds to the next operation for welding work. If the judgment is "NG", the deviation index exceeds the threshold value 50, so the operation of the welding device 10 is stopped and an abnormality alert is issued.

[0052] Next, the welding procedure will be described.

[0053] 10A and 10B are flowcharts showing the procedure of a welding operation to which the method for detecting the amount of displacement of the wire 21 is applied. Control is performed by the CPU of the robot controller 12 and the CPU of the controller 40 of the detection device 20.

[0054] The amount of misalignment of the wire 21 in the Y and X directions is detected every time before welding is performed on the workpiece 13. The welding robot 11 advances toward the detection plate 30 to detect the amount of misalignment of the wire 21 (S101).

[0055] First, the amount of misalignment of the wire 21 in the Y direction is detected. The wire 21 is traced in the X direction inside the first detection groove 31. Sampling of the amount of misalignment begins at the starting end 31b of the first detection groove 31 (S102) and ends at the ending end 31c (S103). When the wire 21 contacts the inner surface 31d of the first detection groove 31, the amount of misalignment of the wire 21 in the Y direction is detected based on the position of the wire 21 in the X direction and the groove width 31a of the first detection groove 31 at the position of the wire 21. The detected amount of misalignment in the Y direction is sampled.

[0056] Regardless of whether the wire 21 has come into contact with the inner surface 31d of the first detection groove 31, the wire 21 is traced from the starting end 31b to the ending end 31c of the first detection groove 31. By tracing the wire 21 to the ending end 31c of the first detection groove 31, it is not necessary to change the posture of the welding robot 11 midway. This makes it easier to control the welding robot 11 when detecting the amount of misalignment of the wire 21 in the Y direction.

[0057] Next, the amount of misalignment of the wire 21 in the X direction is detected. The wire 21 is traced in the Y direction inside the second detection groove 32. Sampling of the amount of misalignment begins at the starting end 32b of the second detection groove 32 (S104) and ends at the ending end 32c (S105). When the wire 21 contacts the inner surface 32d of the second detection groove 32, the amount of misalignment of the wire 21 in the X direction is detected based on the position of the wire 21 in the Y direction and the groove width 32a of the second detection groove 32 at the position of the wire 21. The detected amount of misalignment in the X direction is sampled.

[0058] Regardless of whether the wire 21 has come into contact with the inner surface 32d of the second detection groove 32, the wire 21 is traced from the starting end 32b to the ending end 32c of the second detection groove 32. By tracing the wire 21 to the ending end 32c of the second detection groove 32, it is not necessary to change the posture of the welding robot 11 midway. This makes it easier to control the welding robot 11 when detecting the amount of misalignment of the wire 21 in the X direction.

[0059] When the sampling of the amount of deviation is completed, the welding robot 11 leaves the detection plate 30 (S106) and moves to a standby position for the welding operation.

[0060] A deviation index is calculated (S107). The deviation index is a value obtained by adding the radius of the wire 21 to the combined deviation amounts in the Y and X directions. The combined deviation amount is calculated based on the sampled deviation amounts in the Y and X directions of the wire 21. A pass / fail determination is made on the deviation of the wire 21 based on the deviation index (S108), and the determination result is output to the operation display unit 44 (S109).

[0061] If the deviation index is equal to or less than the threshold value 50 (S110: YES), the welding robot 11 starts welding (S111). When the welding is completed (S112), the welding robot 11 moves to a standby position for detecting the deviation amount of the wire 21.

[0062] On the other hand, if the deviation index exceeds the threshold value of 50 (S110: NO), an abnormality is reported and the equipment is stopped (S113). Appropriate repair measures are taken for the abnormal deviation of the wire 21 (S114). The repair measures include, for example, replacing the worn contact tip 18.

[0063] When the repair measures are completed (S115: YES), the abnormality alarm and the equipment shutdown are cancelled (116).

[0064] As described above, the detection device 20 of this embodiment has the detection plate 30 in which the first detection groove 31 and the second detection groove 32 are formed. The first detection groove 31 has a groove width 31a that narrows in the X direction, and the second detection groove 32 has a groove width 32a that narrows in the Y direction. The operation control unit 41 controls the operation of the welding robot 11 based on teaching data to cause the wire 21 to trace inside the first detection groove 31 in the X direction, and further cause the wire 21 to trace inside the second detection groove 32 in the Y direction. When the wire 21 contacts the inner surface 31d of the first detection groove 31, the detection unit 42 detects the amount of misalignment of the wire 21 in the Y direction based on the position of the wire 21 in the X direction and the groove width 31a of the first detection groove 31 at the position of the wire 21. The detection unit 42 further detects the amount of displacement of the wire 21 in the X direction when the wire 21 contacts the inner surface 32d of the second detection groove 32 based on the position of the wire 21 facing in the Y direction and the groove width 32a of the second detection groove 32 at the position of the wire 21.

[0065] With this configuration, the groove widths 31 a, 32 a of the first detection groove 31 and the second detection groove 32 are narrowed, so that the amount of misalignment of the wire 21 in the Y direction and the amount of misalignment of the wire 21 in the X direction can be accurately detected based on the position where the wire 21 contacts the groove and the groove widths 31 a, 32 a known at that position. Therefore, it is possible to provide a detection device 20 that can detect the amount of misalignment itself that accompanies the positional misalignment of the wire 21.

[0066] Since the amount of misalignment of the wire 21, which is a cause of derailment during welding, can be accurately detected, the occurrence of welding defects can be reduced. Furthermore, the detected amount of misalignment of the wire 21 can be used to understand changes over time and manage the tendency of misalignment of the wire 21. For example, if consumable parts such as the contact tip 18 are replaced early to be on the safe side, this results in excessive replacement, which is disadvantageous in terms of cost. In this embodiment, since the tendency of misalignment of the wire 21 can be managed, consumable parts can be replaced at the optimal replacement time, thereby reducing costs.

[0067] The first storage unit 43a stores first data that sets the amount of misalignment of the wire 21 in the Y direction for each of a plurality of sections obtained by dividing the first detection groove 31 in the X direction. The second storage unit 43b stores second data that sets the amount of misalignment of the wire 21 in the X direction for each of a plurality of sections obtained by dividing the second detection groove 32 in the Y direction. When the wire 21 contacts the inner surface 31d of the first detection groove 31, the detection unit 42 detects the amount of misalignment of the wire 21 in the Y direction based on the section where the wire 21 contacted and the first data stored in the first storage unit 43a. When the wire 21 contacts the inner surface 32d of the second detection groove 32, the detection unit 42 further detects the amount of misalignment of the wire 21 in the X direction based on the section where the wire 21 contacted and the second data stored in the second storage unit 43b. In this way, the amount of misalignment of the wire 21 in the Y direction and the amount of misalignment of the wire 21 in the X direction can be detected based on the section where the wire 21 contacted. Therefore, the amount of deviation caused by the positional deviation of the wire 21 can be detected.

[0068] The detector 42 detects the combined misalignment in the Y and X directions based on the misalignment of the wire 21 in the Y and X directions. This configuration makes it possible to detect when the combined misalignment is outside the allowable range, even if the misalignment in the Y or X direction is within the allowable range when it is alone. Being able to detect the combined misalignment itself further prevents welding defects caused by misalignment of the wire 21.

[0069] The detection plate 30 has a connecting groove 33 that connects the terminal end 31c of the first detection groove 31 with the starting end 32b of the second detection groove 32. The operation control unit 41 causes the wire 21 to continuously trace both the first detection groove 31 and the second detection groove 32 via the connecting groove 33. This configuration simplifies the operation of the welding robot 11 and enables the amount of misalignment in the Y direction and the amount of misalignment in the X direction to be detected more quickly.

[0070] The detection plate 30 is fixed to the welding jig 14. With this configuration, it is possible to detect a displacement of the wire 21 caused by a positional displacement of the welding jig 14.

[0071] The first detection groove 31 has a shape in which the groove width 31a decreases linearly in the X direction, and the second detection groove 32 has a shape in which the groove width 32a decreases linearly in the Y direction. With this configuration, the wire 21 continues to contact the inner circumferential surface of the first detection groove 31 or the inner surface 32d of the second detection groove 32 from the point where the wire 21 makes contact. Therefore, no contact signal is missed, and the amount of misalignment of the wire 21 can be detected more accurately.

[0072] The method for detecting the misalignment of the wire 21 according to this embodiment uses a detection plate 30 having a first detection groove 31 and a second detection groove 32 formed therein. The first detection groove 31 has a groove width 31a that narrows in the X direction, and the second detection groove 32 has a groove width 32a that narrows in the Y direction. The operation of the welding robot 11 is controlled based on teaching data to cause the wire 21 to trace inside the first detection groove 31 in the X direction, and further cause the wire 21 to trace inside the second detection groove 32 in the Y direction. When the wire 21 contacts an inner surface 31d of the first detection groove 31, the amount of misalignment of the wire 21 in the Y direction, which is perpendicular to the X direction, is detected based on the position of the wire 21 in the X direction and the groove width 31a of the first detection groove 31 at the position of the wire 21. Furthermore, when the wire 21 contacts the inner surface 32d of the second detection groove 32, the amount of deviation of the wire 21 in the X direction is detected based on the position of the wire 21 facing in the Y direction and the groove width 32a of the second detection groove 32 at the position of the wire 21.

[0073] With this configuration, the groove widths 31 a, 32 a of the first detection groove 31 and the second detection groove 32 are narrowed, so that the amount of misalignment of the wire 21 in the Y direction and the amount of misalignment of the wire 21 in the X direction can be accurately detected based on the position where the wire 21 contacts and the groove widths 31 a, 32 a known at that position. Therefore, a method for detecting the amount of misalignment of the wire 21 can be provided that can detect the amount of misalignment itself associated with the positional misalignment of the wire 21.

[0074] Since the amount of misalignment of the wire 21, which is a cause of derailment during welding, can be accurately detected, the occurrence of defective welding can be reduced. Furthermore, the detected amount of misalignment of the wire 21 can be used to understand changes over time and manage the tendency of misalignment of the wire 21. Therefore, consumable parts such as the contact tip 18 can be replaced at the optimal replacement time, thereby reducing costs.

[0075] The wire 21 is traced from the starting end 31b to the ending end 31c of the first detection groove 31 regardless of whether the wire 21 has contacted the inner surface 31d of the first detection groove 31. Furthermore, the wire 21 is traced from the starting end 32b to the ending end 32c of the second detection groove 32 regardless of whether the wire 21 has contacted the inner surface 32d of the second detection groove 32. With this configuration, the operation of the welding robot 11 can be simplified, and the amount of misalignment in the Y direction and the amount of misalignment in the X direction can be detected more quickly.

[0076] Before welding the workpiece 13, the amount of misalignment of the wire 21 in the Y direction is detected, and further the amount of misalignment of the wire 21 in the X direction is detected. With this configuration, it is possible to prevent poor welding before it occurs.

[0077] 11A, 11B, 11C, 11D, 11E, and 11F are front views showing modifications of the detection grooves. In these figures, portions other than the detection grooves are hatched to clarify the shapes of the detection grooves.

[0078] The first detection groove 31 is not limited to a shape in which the groove width 31 a decreases linearly in the X direction. Similarly, the second detection groove 32 is not limited to a shape in which the groove width 32 a decreases linearly in the Y direction. As long as the detection groove has a shape in which the groove width 31 a, 32 a narrows in the direction in which the detection groove extends (the X direction or the Y direction), the shape can be modified as appropriate, as described below.

[0079] As shown in FIG. 11A , the detection groove 61 may have a shape in which the groove width 61 a decreases in a stepped manner at regular intervals in the direction in which the detection groove 61 extends (the X direction or the Y direction). For ease of explanation, this type of detection groove 61 is referred to as a "stepped straight type." Like the basic tapered detection groove of the embodiment, the stepped straight type detection groove 61 allows the wire 21 to continue contacting the inner surface 61 d from the point where the wire 21 makes contact. This prevents a missed contact signal. The width of each section is straight. Therefore, unlike the basic tapered type, it is not possible to detect the amount of misalignment of the wire 21 based on the "distance from the starting end 31 b, 32 b." In the stepped straight type, the amount of misalignment of the wire 21 is detected based on the "contact section." Like the basic tapered type, the stepped straight type allows the wire 21 to continue contacting the inner surface 61 d when the amount of misalignment is large. Therefore, to prevent wear over long-term use, it is preferable to apply a conductive coating or the like to the inner surface 61 d to reduce sliding resistance.

[0080] As shown in FIG. 11B , the detection groove 62 has protrusions 62e at regular intervals in the direction in which the detection groove 62 extends (X direction or Y direction). The protrusions 62e protrude from the inner surface 62d of the detection groove 62. For ease of explanation, this type of detection groove 62 is referred to as a "tapered protrusion type." The tapered protrusion type detection groove 62 also has a shape in which the groove width 62a decreases stepwise at regular intervals in the direction in which the detection groove 62 extends (X direction or Y direction). The tapered protrusion type detection groove 62 detects contact of the wire 21 with the inner surface 62d at the protrusions 62e. Therefore, unlike the basic tapered type, the amount of misalignment of the wire 21 cannot be detected based on the "distance from the starting ends 31b, 32b." The tapered protrusion type detects the amount of misalignment of the wire 21 based on the "section of contact." The tapered protrusion type reduces wear over long-term use because the wire 21 is in contact for a short period of time. Of course, the protrusion 62e may be coated with a conductive material or the like to reduce sliding resistance.

[0081] The shape of the convex portion 62e is not limited to a semicircular arc shape, but can be modified to an appropriate shape such as a rectangular shape (FIG. 11C) or a triangular shape (FIG. 1D).

[0082] As shown in FIG. 11E , the detection groove 63 has a shape in which the groove width 63a decreases linearly in the direction in which the detection groove 63 extends (the X direction or the Y direction). However, only one side of the inner surface 63d is tapered. For ease of explanation, this type of detection groove 63 is referred to as a "single-sided tapered type." Like the basic tapered type detection groove, the one-sided tapered detection groove 63 allows the wire 21 to continue contacting the inner surface 63d from the point where the wire 21 makes contact with the inner surface 63d. Therefore, no contact signal is missed. Like the basic tapered type, the amount of misalignment of the wire 21 can be detected based on the "distance from the starting ends 31b, 32b." Like the basic tapered type, the one-sided tapered type allows the wire 21 to continue contacting the inner surface 63d when the amount of misalignment is large. Therefore, to suppress wear over long-term use, it is preferable to apply a conductive coating or the like to the inner surface 63d to reduce sliding resistance. The one-sided tapered type can be suitably used when the displacement direction of the wire 21 is specified to be one direction (upward in the drawing).

[0083] 11F, the detection groove 64 has a shape in which two one-sided tapered grooves are arranged inverted with the left-right direction in the figure as a boundary and offset in the longitudinal direction. For ease of explanation, this type of detection groove 64 is referred to as a "combined one-sided tapered groove." Compared to the one-sided tapered groove, the combined one-sided tapered groove detection groove 64 can detect the amount of misalignment of the wire 21 even if the direction of misalignment of the wire 21 is not specified.

[0084] As described above, the first detection groove 31 may have a shape in which the groove width 31a decreases stepwise at regular intervals in the X direction. The second detection groove 32 may have a shape in which the groove width 31a decreases stepwise at regular intervals in the Y direction. Even with this stepped configuration, the wire 21 continues to contact the inner circumferential surface of the first detection groove 31 or the inner surface 32d of the second detection groove 32 from the point where the wire 21 makes contact with the inner circumferential surface of the first detection groove 31 or the inner surface 32d of the second detection groove 32. Therefore, no contact signal is missed, and the amount of misalignment of the wire 21 can be detected more accurately.

[0085] (Other Modifications) The present invention is not limited to the above-described embodiment and can be modified as appropriate. In the embodiment, both the Y-direction misalignment amount and the X-direction misalignment amount of the wire 21 are detected, but it goes without saying that only one of the misalignment amounts may be detected. In the present embodiment, the misalignment index is a value obtained by adding the composite misalignment amount r to the radius of the wire 21. However, the misalignment index may be only the composite misalignment amount r, or may be a value obtained by adding a value other than the radius of the wire 21 to the composite misalignment amount r.

[0086] REFERENCE SIGNS LIST 10 Welding device 11 Welding robot 12 Robot controller 14 Welding jig 17 Torch 18 Contact tip 20 Welding wire displacement detection device 21 Welding wire 30 Detection plate 31 First detection groove 31a Groove width 31b Starting end 31c Ending end 31d Inner surface 32 Second detection groove 32a Groove width 32b Starting end 32c Ending end 32d Inner surface 33 Connecting groove 40 Controller 41 Operation control unit 42 Detection unit 43 Memory unit 43a First memory unit 43b Second memory unit 44 Operation display unit 50 Threshold value 61, 62, 63, 64 Detection groove

Claims

1. An apparatus for detecting the displacement amount of a welding wire extending from the tip of a torch of a welding robot, comprising: a detection plate in which a first detection groove extending in a first direction is formed, the first detection groove having a shape in which the groove width becomes narrower in the first direction; an operation control unit that controls the operation of the welding robot based on teaching data and traces the welding wire in the first direction inside the first detection groove; and a detection unit that detects the displacement amount of the welding wire in a second direction orthogonal to the first direction based on the position of the welding wire in the first direction and the groove width of the first detection groove at the position of the welding wire when the welding wire contacts the inner surface of the first detection groove. An apparatus for detecting the displacement amount of a welding wire.

2. The apparatus for detecting the displacement amount of a welding wire according to claim 1, further comprising a first storage unit in which first data setting the displacement amount of the welding wire in the second direction is stored for each section obtained by dividing the first detection groove into a plurality of sections in the first direction, wherein the detection unit detects the displacement amount of the welding wire in the second direction based on the section with which the welding wire contacts and the first data stored in the first storage unit when the welding wire contacts the inner surface of the first detection groove.

3. The apparatus for detecting the displacement amount of a welding wire according to claim 1, wherein a second detection groove extending in the second direction is further formed in the detection plate, the second detection groove having a shape in which the groove width becomes narrower in the second direction, the operation control unit controls the operation of the welding robot based on teaching data and traces the welding wire in the second direction inside the second detection groove, and the detection unit detects the displacement amount of the welding wire in the first direction based on the position of the welding wire in the second direction and the groove width of the second detection groove at the position of the welding wire when the welding wire contacts the inner surface of the second detection groove.

4. The welding wire displacement amount detection device according to claim 3, further comprising a second storage unit storing second data in which the displacement amount of the welding wire in the first direction is set for each section obtained by dividing the second detection groove into a plurality of sections in the second direction. When the welding wire contacts the inner surface of the second detection groove, the detection unit detects the displacement amount of the welding wire in the first direction based on the section where the welding wire contacts and the second data stored in the second storage unit.

5. The welding wire displacement amount detection device according to claim 3 or claim 4, wherein the detection unit detects a composite displacement amount in the second direction and the first direction based on the displacement amount of the welding wire in the second direction and the displacement amount in the first direction.

6. The detection plate has a connecting groove that connects the end portion where the groove width of the first detection groove is the narrowest and the start portion where the groove width of the second detection groove is the widest, or connects the end portion where the groove width of the second detection groove is the narrowest and the start portion where the groove width of the first detection groove is the widest. The operation control unit continuously traces the welding wire through the connecting groove to both the first detection groove and the second detection groove. The welding wire displacement amount detection device according to claim 3 or claim 4.

7. The welding wire displacement amount detection device according to claim 1 or claim 3, wherein the detection plate is fixed to a welding jig for setting a workpiece to be welded.

8. The welding wire displacement amount detection device according to claim 1, wherein the first detection groove has a shape in which the groove width decreases linearly in the first direction, or a shape in which the groove width decreases stepwise at regular intervals in the first direction.

9. The welding wire displacement amount detection device according to claim 3, wherein the second detection groove has a shape in which the groove width decreases linearly in the second direction, or a shape in which the groove width decreases stepwise at regular intervals in the second direction.

10. A method for detecting the deviation amount of a welding wire extending from the tip of a torch of a welding robot, comprising controlling the operation of the welding robot based on teaching data, and tracing the welding wire in a first direction along a first detection groove formed in a detection plate and extending in the first direction, wherein the groove width of the first detection groove becomes narrower in the first direction, and detecting the deviation amount of the welding wire in a second direction perpendicular to the first direction based on the position of the welding wire in the first direction and the groove width of the first detection groove at the position of the welding wire when the welding wire contacts the inner surface of the first detection groove.

11. The method for detecting the deviation amount of a welding wire according to claim 10, wherein the welding wire is traced from a starting end portion having the widest groove width to an ending end portion having the narrowest groove width of the first detection groove regardless of whether the welding wire contacts the inner surface of the first detection groove.

12. The method for detecting the deviation amount of a welding wire according to claim 10 or claim 11, wherein the deviation amount of the welding wire in the second direction is detected before performing a welding operation on a workpiece to be welded.

13. A method for detecting the deviation amount of a welding wire according to claim 10, comprising controlling the operation of the welding robot based on teaching data, and tracing the welding wire in a second direction along a second detection groove formed in the detection plate and extending in the second direction, wherein the groove width of the second detection groove becomes narrower in the second direction, and detecting the deviation amount of the welding wire in the first direction based on the position of the welding wire in the second direction and the groove width of the second detection groove at the position of the welding wire when the welding wire contacts the inner surface of the second detection groove.

14. The method for detecting the deviation amount of a welding wire according to claim 13, wherein the welding wire is traced from a starting end portion having the widest groove width to an ending end portion having the narrowest groove width of the second detection groove regardless of whether the welding wire contacts the inner surface of the second detection groove.

15. The method for detecting the deviation amount of a welding wire according to claim 13 or claim 14, wherein the deviation amount of the welding wire in the first direction is detected before performing a welding operation on a workpiece to be welded.

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