JPH0292457A - Root gap detecting method for automatic welding equipment - Google Patents

Abstract

PURPOSE:To automatically, easily and surely detect a root gap by using positional information of points on the surfaces and the groove face of joint members to be welded and detected by a welding torch to operate intersections between a straight line of the gap position and groove straight lines. CONSTITUTION:At the time of performing automatic welding on a groove of the first and second joint members 9a and 9b to be welded, a consumable electrode of the welding torch is used to impress the sensing voltage and detect the work position. The positions of two points P1 and P2 on the surface 9c of the first member 9a are first detected. Further, two points P1' and P2' on the rear are calculated from the plate thickness (t) thereof and the straight line L1 of the gap position in parallel with the changing direction of the root gap is operated from the above points P1' and P2'. The positions of points P3 and P5 on the groove faces 9d and 9f are then detected and the groove lines L2 and L3 along the respective groove faces 9d and 9f are operated from groove angles thetaR and thetaL of the respective members 9a and 9b. The intersections Q1 and Q2 between the straight line L1 of the gap position and the groove straight lines L2 and L3 mentioned above are operated and then, the distance between both intersections Q1 and Q2 mentioned above is operated and detected as the root gap between the above-mentioned joints to be welded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies a sensing voltage to a consumable electrode type welding torch in an automatic welding device that reproduces predetermined work contents, and uses this welding torch as a sensor. The present invention relates to a groove gap detection method for automatic welding equipment that detects the groove gap of a welded joint.

[Prior Art] In general, the groove of a welded joint to be welded has a groove of 4 mm depending on the plate thickness of the welding member in order to prevent insufficient penetration during welding.
A groove gap of about 10 mm may be set in advance. This gap inevitably fluctuates by about ±2 to 4 mm due to assembly errors of the objects to be welded. Further, even if a groove gap is not set, a gap is generated due to the above-mentioned assembly error and changes.

Automatic welding equipment that stores and reproduces such welded joints during welding work! (hereinafter referred to as a welding robot), for example, when performing weaving welding, the welding robot is used regardless of gap fluctuations.

Perform welding under the taught weaving conditions.

For this reason, after the welding robot completes welding, a worker performs correction welding in a subsequent process.

Even in this correction welding, if the gap fluctuation is too large, the worker will have to carry out rework welding, so welding robots that are used for welding structures with thick plates that are particularly prone to assembly errors are required to detect gaps. It was desired to have a function to modify the weaving conditions.

[Problems to be Solved by the Invention] Therefore, by using the memory and calculation device of the welding robot, the weaving conditions are taught for each welded joint before welding work, and the weaving conditions are taught for each welded joint in the welding line direction. A technique has also been proposed in which the welding torch is moved to both ends of the groove edge at a position where there is gap variation, and the width at both ends of the groove edge, that is, the gap variation, is detected and the weaving width is changed using the position data taught. (Unexamined Japanese Patent Publication No. 1986-
172678).

In this technology, the welding torch is positioned in advance at the groove edge position where there is gap variation in the welding line direction of the welded joint,
In that the gap variation is calculated and determined from the position data, the gap variation can be detected without providing any other detection device.

However, even though gap fluctuations tend to occur at approximately the same position in the welding line direction, the amount of fluctuation is not constant, and it is difficult to position the groove edges with gap fluctuations every time weld. Moreover, it is extremely inefficient and its accuracy is unstable due to the teaching.

The present invention has been made to solve the above-mentioned problems, and uses a welding torch to which a sensing voltage is applied at the start of welding, without adding any other equipment to the welding torch.
It is an object of the present invention to provide a groove gap detection method for an automatic welding device that can automatically and reliably detect the groove gap and perform welding work efficiently and accurately.

[Means for Solving the Problems] In order to achieve the above object, the method for detecting a groove gap in an automatic welding device of the present invention includes: (1) setting the amount of protrusion of the consumable electrode from the welding torch to a predetermined length; Alternatively, attach a dummy tip of a predetermined length to the tip of the welding torch, apply a sensing voltage to the welding torch, and
a point, at least one point on the groove surface of the first member, and a second point.
After detecting with a welding torch at least one point on the groove surface of the member or on the surface of the member forming the groove and storing the position information.

■ Calculates a gap position straight line parallel to the direction of variation of the gap that occurs in the groove of the welded joint based on the position information of the detection point on the surface of the first member and the predetermined plate thickness dimension of the first member that has been input and stored in advance. , based on the position information of the detection point on the groove surface of the first member and the groove angle of the first member, or based on the position information of a plurality of detection points on the groove surface of the first member. Based on the position information of the detection point on the groove surface of the second member or the surface of the member and the groove angle of the second member, or on the groove surface of the second member or the member A groove straight line of the second member is calculated based on position information of a plurality of detection points on the surface.

(2) After calculating the intersection between the gap position straight line and the groove straight line of the first member, and the intersection between the gap position straight line and the groove straight line of the second member.

(1) The distance between the two obtained intersection points is calculated and detected as the gap of the welded joint.

[Function] In the groove gap detection method for an automatic welding device of the present invention described above, the groove gap of a welded joint is detected by using a memory/calculation device in the automatic welding device and a welding torch to which a sensing voltage is applied. Therefore, there is no need to provide a special device for gap detection other than the welding torch near the welding torch at the tip of the automatic welding device. By teaching the detection operation at each point on the member, it is possible to automatically calculate and detect the gap even if the amount of gap variation differs for each welded joint, so it is possible to automatically calculate and detect the gap even if the amount of gap fluctuation differs for each welded joint. There is no need to position the welding torch and perform gap detection operations.

[Embodiments of the Invention] Hereinafter, a method for detecting a groove gap in an automatic welding apparatus as an embodiment of the present invention will be described with reference to the drawings.

First, the configuration of an arc welding robot, which is one type of automatic welding apparatus applied to the method of the present invention, will be explained with reference to FIG. As shown in FIG. 3, a consumable electrode type welding torch 2 is attached to a wrist portion 1a of an articulated arc welding robot 1, and its position and posture are controlled. This control is performed by the robot control panel 3 or the teaching box 4 attached to the robot control panel 3. In addition, the welding torch 2 has a wire (consumable electrode)
is fed, and this wire always protrudes from the welding torch 2 by an appropriate amount.

In order to use the welding torch 2 as a sensor, the welding power source 6 includes a sensing power source (not shown) so that a welding voltage and a sensing voltage can be selectively applied between the welding torch 2 and the workpiece 7. It is provided.

Note that the workpiece 7 is fixed and supported at a suitable position and in a suitable posture by a positioner 8. Further, the welding work of the workpiece 7 by the arc welding robot 1 is performed in accordance with a program stored in the storage device of the robot control panel 3 after the contents of the welding work are taught in advance.

Below, the basic procedure and operation when performing the groove gap detection method in the workpiece 7 according to the present invention using the above-mentioned arc welding robot 1 will be explained in the first part.
This will be explained based on the figure and FIGS. 2(a) to 2(e). Note that FIG. 1 is a flowchart for explaining the basic operation, and FIGS. 2(a) to 2(e) are diagrams showing the shape of a welded joint to which the method of the present invention can be applied. Here, Fig. 2(a)
- (e) are respectively a side-shaped groove butt, a V-shaped groove butt,
X-type groove butt, X-type groove butt, and mold groove butt are shown, and the same reference numerals are used in each case.

9a and 9b are the first and second members constituting the welded joint, respectively; 9c is the surface of the first member 9a that is parallel to the direction of gap variation occurring in the groove of the welded joint.

9d is the groove surface of the first member, 9e is the member surface of the second member,
9f is the groove surface of the second member.

As shown in FIG. 1, in detecting the groove gap, first, the amount of wire protrusion from the welding torch 2 is set to a predetermined length, and then a sensing voltage is applied to the welding torch 2 (step Sl). . In addition, instead of adjusting the protruding length of the wire, a dummy chip of a predetermined length is attached only when detecting a gap.

This may be automatically removed during welding after detecting the gap.

Then, according to the teaching operation performed in advance (described in detail later in FIGS. 4 and 5), each point Pi to P shown in FIGS. 2(a) to (e) is detected by the welding torch 2, and its position is Remember information.

That is, first, the two members 9a and 9 forming the welded joint are
b, for the first member 9a having a member surface 9c parallel to the fluctuating direction of the groove gap, the member surface 9c
Above two points p1. p, is detected by the welding torch 2 and its position information is stored (step S2).
Among the welded joints shown in a) to (e), Fig. 2 (a) and (
In the joint shown in e), only one member 9a can be the first member (because it has a member surface parallel to the fluctuating direction of the groove gap), and in the joint shown in FIGS. 2(b) to 2(d), It is bilaterally symmetrical, and either of the members 9a and 9b may be the first member.

In addition, here, two points P□, P2 on the member surface 9c of the first member 9a are detected, but these two points detection is for calculating the straight line p1'p,'' (Ll), which will be described later. Therefore, two or more points may be detected.

Next, one point P or two points p, p4 on the groove surface 9d of the first member 9a is detected by the welding torch 2, and the position information is stored (step S3).

Here, the point on the groove surface 9d of the first member 9a is detected in order to calculate the groove straight line L2, which will be described later.If the groove angle θk is known, only one point P is detected. However, since the first member 9a is thick and the length of its groove surface is long, if it is possible to detect multiple points on the groove surface 9d, two points P3. P.

(two or more points may be used) and calculate the groove straight line L2 without using the groove angle OR. If there is not much, the two points P□, P in step S2
Even with the detection of step S2, the direction of deviation of the entire welded joint cannot be detected yet, so there is a high possibility that the point P on the groove surface 9d will be falsely detected. It is desirable to apply the known techniques described in Japanese Patent Publication No. 58-39029 and Japanese Patent Application No. 63-30832.

Then, the member surface 9e or groove surface 9f of the second member 9b
Welding torch 2 at 1 point P or 2 points P, Ps on the top
Detect and store the position information (step S4)
, here, the member surface 9e or groove surface 9 of the second member 9b
The purpose of detecting the point on f is to calculate the groove straight line L1, which will be described later.In the joints shown in FIGS. 2(b) to 2(d), the groove angle θ is known, and as shown in FIG. In the joints shown in a) and (e), if it is assumed that the members 9a and 9b are assembled at right angles to each other, it is only necessary to detect one point P5.
In addition, in the joints shown in FIGS. 2(b) to (d), if the groove angle θL is unknown or the groove processing is not constant, 2
Detect the point ps, p.

Note that the order in which the points P1 to P are detected is not limited to the order described above. It may be.

Now, after obtaining the positional information of the detection point pL-p as described above, first, the positional information of the two points p, , p on the member surface 9c of the first member 9a and the previously input and memorized The first
Based on the dimension t regarding the plate thickness of the member 9a, two points p t
's p, t are determined, and a gap position straight line (a straight line parallel to the direction of variation of the gap occurring in the groove) L passing through these two points P, ', P,'' is calculated (step S5).
Here, in the joints shown in FIGS. 2(a) to (c), the dimension t
corresponds to the thickness of the first member 9a, and the gap position straight line L1
is a straight line along the back surface of the member surface 9c of the first member 9a.

In addition, in the joints shown in FIGS. 2(d) and (e), one dimension t is the known design dimension of the first member 9a, and based on Q, tz
-(fl/2), and the gear position straight line L is a straight line that passes through the position where the distance between members 9a and Qb is the minimum, which is inside the member by a dimension t from the member surface 9c of the first member 9a. Become.

Also, one point P on the groove surface 9d of the first member 9a.

or when the position information of two points PJ and P4 on the groove surface 9d of the first member 9a is obtained based on the position information of and the groove angle θR of the first member 9a that is input and stored in advance. Based on the position information of these two points p, p4,
Calculate the groove straight line L3 along the groove surface 9d (step S
6).

Similarly, the groove surface 9f or the member surface 9 of the second member 9b
2 on the groove surface 9f of the second member 9b or the member surface 9e based on the positional information of one point P on e and the groove angle θL of the second member 9b that has been input and stored in advance. If the position information of points Ps and P6 is obtained, these two
A groove straight line L□ along the groove surface 9f or the member surface 9e is calculated based on the positional information of points p, , pG (step S7).

Then, the intersection point Q□ of the gap position straight line L1 calculated in step S5 and the groove straight line L2 calculated in step S6 is calculated, and the gap position straight line L1 and the groove straight line calculated in step S7 are calculated. An intersection point Q2 between and is calculated (step S8).

These intersection points Q, , Q are located at both end points of the gap, and the groove gap is detected by calculating the distance σ g between these intersection points Q, , Q (step S9).
).

Next, a specific example in which the groove gap detection method of the present invention is applied to a welded joint with groove butts shown in FIG. 2(a) will be described in detail with reference to FIGS. 4 to 8. Note that the groove angle θR of the first member 9a is known, and is 1 on the groove surface 9d.
It is assumed that only points are detected.

First, each point P1 to P5 necessary for groove gap detection
Detection operations using sensing will be taught. In other words, the fourth
As shown in the figure, the protruding length of the wire 2a from the welding torch 2 is set to a predetermined length, and the two points PL and P2 on the member surface 9c of the first member 9a having the groove surface 9d are One point P3 on the front surface 9d and two points P4 on the member surface 9e of the second member 9b assembled substantially perpendicularly to the first member 9a. We will teach you the operation for detecting P5 by sensing. Note that each point P1 to P5 is set and taught so as to be as close as possible to a predetermined cross section perpendicular to the weld line (parallel to the gap variation direction).

Then, during teaching, each point P i (i = 1
5), the neighboring points Psi (i=1 to 5) as shown in FIG. 4 are taught for each point Pi. That is, as shown in FIG. 5, for each point Pi (i=1 to 5), the tip of the welding torch 2 is positioned at the point Psi (i=1 to 5), and the position information is memorized. (Step A2
), which side 9 is the sensing start command code and teaching point?
c, 9 d, 9 e is input in a code to a predetermined address (step A3), then the tip of the welding torch 2 is positioned at point Pi (i=1τ5) and the position information is memorized (step A4), where 1 point Pi (i=1
The purpose of incorporating the position information in ~5) is to set the moving direction vector of the welding torch 2 from the point Psi during the regeneration operation, so if this moving direction vector is set, the point It is not necessary to store the position information of Pi itself. Such a teaching operation is performed for each point P1 to P5 (steps AI, A5.A
6) A teaching program is created.

After the teaching operation described above, the created teaching program is reproduced. The flowchart at this time is shown in FIG. 6. In order to detect point P1 during regeneration, first, the welding torch 2 is
Step Bl, B2) to position the welding torch 2), apply a sensing voltage to the welding torch 2 (step B3), then move the welding torch 2 toward the point P1 (step B
4) When the wire 2a comes into contact with the member surface 9c of the first member 9a and becomes energized (step B5), the positional information of the tip of the welding torch 2 is sent to the specified address as the positional information of the point P1 at the time of reproduction. Storing/memorizing (step B6)
Similarly, the positional information of points P2 to P5 during reproduction is detected and stored (steps B7 and B8).

Although not shown in FIG. 6, when the welding torch 2 is moved toward the point Pi, even if the welding torch 2 passes the point Pi at the time of teaching and reaches a certain distance, the energization state remains. If this is not the case, a sensing error will be generated.

After storing the positional information of each point P1 to P5 as described above, the groove gap W is determined by the following calculation procedure.

First, when performing calculations, the coordinate system at the groove cross section is
Settings are made as shown in FIG. 7(a) or FIG. 7(b).

The groove cross section includes points Pi, P2. A plane defined by the three points P3, the direction of the vector P2P1 is the positive direction of the X axis, the direction of the cross product PT7'yXP2P1 is the positive direction of the two axes, and the cross product (
rYrix P 2 P L )x p'T'i”Tt
ty Positive direction of the y-axis! -7-Define the Z coordinate system and point P
L, P2. Each coordinate value of P3 is (Xx*yz+O)
t (XzyyayO)y CX5e'/s*o), and point P4. Although P5 cannot generally be located strictly on the groove cross section, it is located very close to this groove cross section, so each point P4. Point P4” (Xn+y4+O)y P obtained by projecting P5 onto the groove cross section
5" (Xs+ysyO). In order to obtain each coordinate value mentioned above, each point P1 to P1 stored by the detection operation is used.
It is necessary to coordinate transform the position information of P5 (coordinate values in the coordinate system of the robot 1 itself) into coordinate values in the xy-2 coordinate system described above.

In the x-y-z coordinate system described above, when point P2 is closer to the groove side than point P1, it becomes as shown in FIG. 7(a) (this is called the A coordinate system), and one point P1 becomes point P2. If it is closer to the groove side, the result will be as shown in FIG. 7(b) (this is referred to as the B coordinate system).

The case of calculating the groove gap W in the A coordinate system will be explained with reference to FIG. 7(a) and FIG. 8.

The equation of the groove straight line (straight line along the member surface 9e) L3 passing through the points P4'' and P5'' is as follows.

5-X4. Also, from the X axis, the thickness t of the first member 9a is -y
The equation for the gap position straight line L1 in the force direction is as follows. Also, the groove angle OR with respect to the X axis through point P3
The groove straight line (straight line along the groove surface 9d) L2 that forms the following.

y−y3=(X−x,)·tanθR−(3).

In FIG. 8, point Q1 is the intersection of straight lines L1 and L2, and point Q2 is the intersection of straight lines L1 and L3.

The groove gap W is the distance between the five points Ql and 02.

Here, since the y-coordinates of points Ql and Q2 are both the same -t, it is only necessary to consider the x-coordinate value.

Therefore, the X coordinate value XQi of one point Q1 is (2), (3
), and the X coordinate value XQz of one point Q2 is ys-y4 from equations (1) and (2). Using these equations (4) and (5), the groove gap W is , is calculated by the following equation (6).

w=lXez Xol...(6
) On the other hand, the case of calculating the groove gap W in the B coordinate system will be explained with reference to FIG. 7(b). In FIG. 7(b), the equation of the straight line L1 is expressed in the same way as equation (2). Further, the equation of the straight line L3 is the same as equation (1). On the other hand, the equation of straight line L2 is y-ya=(x x3)・
(-janOB) ・-・(7) Therefore, point Q
The X coordinate value xQ of 1 is from equations (2) and (7).

On the other hand, the X coordinate value XQ2 of point Q2 is expressed by equation (5), and groove gap W is calculated by substituting equations (8) and (5) into equation (6). Ru.

In this way, due to the positional relationship between points P1 and P2, the straight line L
The equations for 2 are different. At this time, Fig. 7 (a), (b)
As is clearer, for example, if x3 is a negative value, it can be determined that the A coordinate system is used, and if X is a positive value, it can be determined that the B coordinate system is used. (
7) Formulas can be summarized.

y-ys = (X-X3)' [-sign (x
a))' (tanθR) −(9) Therefore,
By using the above equation (9), the groove gap W can be calculated by the same calculation procedure regardless of the positional relationship between the points P1 and P2. Also.

Similarly, using the X coordinate values of points P4'' and P5°, (9)
sign (xa) in the expression, sign (x,)
or sign (xs).

In the above description, two points P4. on the member surface 9e of the second member 9b. P5 is detected and the slope of the straight line L3 along the member surface 9e is determined. However, if the members 9a and 9b are arranged perpendicularly to each other, the detection is performed when calculating the groove gap W. The point to be made is P4. P
Either one of 5 can be omitted to make 4.

Therefore, when teaching, it is only necessary to create a program that detects the four points P1 to P4. At this time, the X coordinate value XQ of point Q2
a is x4, and the groove gap W is calculated by substituting this value and the X coordinate value XQz of point Q1 obtained from equations (2) and (9) into equation (6).

Next, a specific example in which the groove gap detection method of the present invention is applied to a welded joint with a V-shaped groove butt shown in FIG. 2(b) will be briefly described in drawings 9 and 1o. In addition, member 9a
, 9b, the groove angle θR9θL is known, and the groove surface 9d
, 9f, only one point is detected each.

First, each point PL-P4 necessary for groove gap detection
The detection operation by sensing will be taught in the same way as in FIG. Here, as shown in FIG. 9, two points P1 and P2 on the member surface 9c of the first member 9a, and one point on the groove surface 9d.
An operation for detecting the point P3 and one point P4 on the groove surface 9f of the second member 9b by sensing is taught, and a teaching program is created.

After the above-mentioned teaching operation, the created teaching program is played back in the same manner as shown in FIG. Based on the position information, the gap W of the V-shaped opening is calculated using the following formula.

At this time, the gap position line L1 and the groove line L2 are exactly the same as equations (2) and (9), respectively, while the groove line L3 along the groove surface 9f of the second member 9b is.

y − y4=(X x,)・sign(x,)・ta
nθL...(10), therefore, straight line L1
The X coordinate value XQ□ of the intersection Q1 between and L2 is expressed by the following equation.

Also, the X coordinate value XQa of the intersection Q2 between straight lines L1 and L3 is as follows from equations (2) and (10), and (4) and (12
) is substituted into equation (6) to calculate the gap W of the V-type aperture.

Note that the gap W can be similarly calculated for the joints shown in FIGS. 2(c) to 2(e).

As described above, according to the groove gap detection method of the present embodiment, a predetermined position on members 9a, 9b forming a welded joint is detected using the storage/computation device in the arc welding robot 1 and the welding torch 2 to which a sensing voltage is applied. By detecting the point and following the calculation procedure described above based on the position information,
The groove gap W of the welded joint is calculated and detected. Therefore, there is no need to provide a special device for detecting the gap other than the welding torch 2 near the welding torch 2 near the wrist portion 1a of the robot 1. In addition, by simply teaching the detection operation at each point on the members 9a and 9b once in advance according to the shape of the welded joint to be welded, the gap fluctuation amount will be different for each welded joint of the same type. The gap W can be automatically detected even when the welding torch 2 is positioned at the groove edge of each joint, and there is no need to perform a gap detection operation for each joint.

Thereby, the groove gap W can be automatically and reliably detected without adding any other device to the welding torch 2, and the welding work can be performed extremely efficiently and accurately.

Furthermore, gaps in welded joints such as those shown in FIGS. 2(a) and 2(e) could not be detected by the conventional means of positioning the welding torch 2 at the groove edge and performing the gap detection operation. 1. According to the method of the present invention, gaps can be easily detected even in this type of welded joint.

[Effects of the Invention] As detailed above, according to the groove gap detection method for an automatic welding device of the present invention, welding joints can be welded using the memory/calculation device in the automatic welding device and the welding torch to which a sensing voltage is applied. Since the structure is configured so that a predetermined point on the members constituting the welding torch can be detected and the groove gap of the weld joint can be calculated and detected based on the position information, other devices for detecting the gap in addition to the welding torch can be installed near the welding torch. In addition, gaps can be automatically calculated and detected for welded joints of the same type by simply teaching the detection operation at each point on the first and second members once according to the shape of the welded joint. This has the effect of allowing welding work to be performed extremely efficiently and accurately.

[Brief explanation of drawings]

Fig. 1 is a flowchart for explaining the basic procedure of a groove gap detection method for an automatic welding device as an embodiment of the present invention, and Fig. 2 (a) to (, 15) respectively show the method of the present invention. Fig. 3 is a perspective view showing an arc welding robot to which the method of the present invention is applied, and Figs. It shows a specific example when applied to
The figure is a perspective view of the joint for explaining the teaching operation, FIG. 5 is a flowchart for explaining the teaching operation, and FIG.
The figure is a flowchart to explain the playback operation, Figures 7(a) and (b) are diagrams to explain the coordinate systems used during gap calculation, and Figure 8 specifically explains the calculation procedure. Figures 9 and 10 show a specific example in which the method of the present invention is applied to a welded joint with a butt type groove. FIG. 9 is a perspective view of the joint for explaining the teaching operation, and FIG. 10 is a diagram for specifically explaining the calculation procedure. In the figure, 1... - arc welding robot (automatic welding device), la - wrist, 2 - welding torch, 2a - wire (
consumable electrode), 3-robot control panel, 4-teaching box, 6-welding power source, 7...-work, 8-positioner, 9a-first member, 9b-second member, 9cm member surface of first member, 9d - groove surface of the first member, 9e - member surface of the second member, 9f - groove surface of the second member. Patent applicant: Kobe Steel, Ltd.

Claims (1)

[Claims] Using an automatic welding device having a function of detecting the position of a workpiece by applying a sensing voltage to a welding torch that supports a consumable electrode and detecting the energized state,
When starting to weld the groove of a welded joint made of parts, first, the amount of protrusion of the consumable electrode from the welding torch is set to a predetermined length, or a dummy of a predetermined length is placed at the tip of the welding torch. After attaching the tip, a sensing voltage is applied to the welding torch to apply a sensing voltage to at least two points on the surface of the first member, at least one point on the groove surface of the first member, and to the groove surface of the second member. At least one on the leading edge or on the surface of the member forming the groove
After detecting the points with the welding torch and storing their position information, based on the position information of the detection points on the surface of the first member and the predetermined plate thickness dimension of the first member input and stored in advance, A gap position straight line parallel to the direction of variation of the gap occurring in the groove of the welded joint is calculated, and the position information of the detection point on the groove surface of the first member and the groove angle of the first member input and stored in advance are calculated. or based on positional information of a plurality of detection points on the groove surface of the first member.
Calculate the groove straight line along the groove surface of the member, and based on the position information of the detection point on the groove surface of the second member or the member surface and the groove angle of the second member input and stored in advance. or calculate a groove straight line along the groove surface of the second member or the member surface based on position information of a plurality of detection points on the groove surface or the member surface of the second member, and then calculate the groove straight line along the groove surface of the second member or the member surface; After calculating the intersection between the position straight line and the groove straight line of the first member, and the intersection between the gap position straight line and the groove straight line of the second member, calculate the distance between the two intersection points as described above. A groove gap detection method for an automatic welding device, characterized by calculating and detecting a gap in a welded joint.