JPS6133776A - Position shift correcting method in automatic arc welding - Google Patents

Abstract

PURPOSE:To perform the welding of a work surely and quickly by detecting the width of position shift with performing an arc scanning for detecting position shift and by making a teaching welding line coincided with actual welding line. CONSTITUTION:An arc scanning for detecting position shift scanning an arc along the detecting line SE crossing with a teaching weld line AB is performed prior to the arc welding of works 18a, 18b. In this case of width (d) of position shift against the actual welding line A'B' of the teaching weld line AB is detected based on the generating arc current or voltage. The correction coinciding the teaching weld line AB with the actual weld line A'B' is performed based on the detected width (d) of misregistration thereof.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for correcting misalignment in automatic arc welding, particularly for correcting misalignment between a preset taught tangent line and an actual welding line. Concerning an improved method.

[Background Art] Conventionally, automatic arc welding methods have been well known in which, for example, a teaching playback method is adopted and a predetermined welding line is taught to a computer or the like in advance. Since it is possible to automatically weld workpieces by moving the torch after the welding process has finished, it is widely used for repeated welding in, for example, automobile welding processes and other mass production lines.

By the way, in order to perform arc welding well along such a teaching welding line, it is necessary to accurately position the workpiece so that the actual welding line of the workpiece to be welded matches the predetermined teaching welding line. That is required.

However, in reality, it is unavoidable that the workpiece installation position shifts from the teaching welding line due to dimensional errors in the workpiece itself, thermal distortion during arc welding, errors in the jig used to position the workpiece, etc. If the workpiece position shifts in this way, the weld 1a position itself for the workpiece will shift, resulting in poor welding, or in the worst case, a welding defect where the workpiece itself will not be welded at all. There's a problem.

In particular, such displacement of the workpiece relative to the welding line often occurs parallel to the welding line with a certain width of displacement, and effective countermeasures have been desired.

Conventionally, the riving method is well known as a method for correcting the positional deviation of the teaching welding line with respect to the actual workpiece installation position, and this riving method involves moving the welding wire alternately at a predetermined amplitude in a direction perpendicular to the welding line. Arc welding of the workpiece is performed by vibrating riving and stitching along the welding line. According to this method, the positional shift of the workpiece is detected from the phase shift of the welding voltage and welding current during riving, and the preset teaching welding line is automatically corrected based on the detected data to weld the workpiece. can.

However, according to this riving method, it is not possible to weld the workpieces in a straight line along the teaching welding line, so the workpieces cannot be welded in a short time and at high speed. Since the amount of heat generated per distance is extremely large, there is a drawback that when the thickness of the workpiece is extremely thin, the generated heat will cause the workpiece to melt all the way to its back surface.

Furthermore, according to this riving method, if the amplitude of the riving exceeds the width of the workpiece to be welded, such as the plate pressure, this will cause a phase shift in the arc voltage and arc current. However, there is a drawback that the positional shift of the workpiece cannot be detected accurately.

In addition to this, a method using laser light, a television camera, etc. has also been adopted as a method for detecting and correcting the positional shift of the workpiece relative to the teaching welding line. It is possible to detect the positional deviation of the workpiece relative to the teaching welding line by scanning a laser beam or by pattern recognition of an image obtained by a television camera.

Therefore, according to this method, the positional deviation of the workpiece with respect to the teaching welding line can be corrected in advance before the start of arc welding, and the workpiece can be welded linearly along the corrected teaching welding line. This makes it possible to significantly reduce the time required.

However, on the other hand, with this method, it is necessary to install a special positional deviation detection and correction device such as a laser beam transmitter/receiver or a television camera in addition to the original arc welding equipment.
The disadvantage is that the number of parts in the arc welding device increases, making the entire device expensive.

Furthermore, in such a method, it is necessary to install the positional deviation detection and correction device in the vicinity of the welding torch where the welding wire is installed. They have the disadvantage that they are susceptible to measurement errors due to exposure to light, high heat, metal-containing fumes, etc., and the lifespan of these detection and correction devices is extremely short.

In addition to this, there is also a well-known method that uses a welding wire to mechanically detect the positional shift of the workpiece and perform a corrective action. The workpiece is scanned in a direction perpendicular to the welding wire, and the positional shift of the workpiece is detected by contact between the welding wire and the workpiece.

Therefore, according to this method, it is possible to correct the teaching welding line prior to arc welding in the same way as the method using the laser beam and the television camera, and in addition, in the detection, the teaching welding line can be corrected using the laser beam transmitter/receiver or the television camera. Since special equipment such as the above is not required, the entire equipment can be made inexpensive.

However, according to this conventional method, the welding wire used for arc welding is extremely thin, so the welding wire is scanned slowly to prevent mechanical deformation of the welding wire when it comes into contact with the workpiece. Therefore, there was a drawback that correction operations for the teaching welding line could not be performed quickly.

Furthermore, according to this method, it is necessary to always accurately set the distance between the tip of the welding wire and its scanning surface, and if the workpiece to be detected for position or displacement is extremely thin, the welding wire There was a drawback that the position of the workpiece could not be detected by scanning the surface of the workpiece once without the tip coming into contact with the workpiece.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to accurately detect the positional deviation of the arc and perform welding without using any special equipment. An object of the present invention is to provide a method for correcting positional deviation in automatic arc welding, which makes it possible to quickly and reliably weld workpieces by correcting lines.

[Structure of the Invention] In order to achieve the above object, the method of the present invention is a consumable electrode type automatic arc welding method in which a welding wire is moved along a preset teaching welding line to perform arc welding on a workpiece. Prior to this, positional deviation detection arc scanning is performed to scan an arc along a detection line that intersects the teaching welding line, and the deviation width of the teaching welding line with respect to the actual welding line is calculated based on the change in the arc that occurs at this time. The present invention is characterized in that the teaching welding line is detected and corrected based on the detected deviation width to match the teaching welding line with the actual welding line, and arc welding of the workpiece is started.

Note that as the change in the arc that occurs when performing the shift detection arc scan, a change in arc current may be used, or a change in arc voltage may be used.

[Example] Next, preferred embodiments of the present invention will be described based on the drawings.

FIG. 2 shows an automatic arc welding device used in this embodiment.
is attached to the arm 16 of the welding robot 14 and moves three-dimensionally to perform arc welding on the workpiece 18.

This arc welding involves positioning the workpiece along a predetermined welding line using a jig (not shown),
Thereafter, a predetermined welding voltage is applied between the workpiece 18 and the welding wire 10 using the welding power source 22, and the welding wire 1o is moved together with the torch 12 along a predetermined welding line.

When arc welding is performed in this manner, the tip of the welding wire 10 is gradually consumed (therefore, it is necessary to sequentially replenish the welding wire 1o with a length corresponding to the consumption m.For this reason, in the apparatus of the embodiment, , the welding wire 20 is predetermined m.
The welding wire 10 is wound around a drum 24, and the welding wire 10 wound in this way is moved by a wire feed motor 26 to a wire 81.
It will be supplied sequentially and continuously.

Furthermore, in the apparatus of this embodiment, the shielding gas sealed in the gas shielding cylinder 28 is blown out toward the tip of the welding wire 1o through the torch 12, so that the workpiece 12 can be welded well. It is said that

Furthermore, in the apparatus of this embodiment, the welding wire of the workpiece 18 is taught in advance in the memory in the robot control panel 30 prior to the arc welding. And robot control panel 3
0, each time the workpiece 18 is installed by the jig 20, the welding process 1-14 is controlled and the workpiece 18 is welded along the teaching welding line.

Therefore, according to this gap, it becomes possible to accurately weld the work 18, for example, automobile parts, etc., which are sequentially conveyed, along the teaching welding line.

FIG. 1 shows a case where one basic workpiece 18a and the other workpiece 18b are positioned along a predetermined teaching welding line AB using a jig 20 or the like. By performing arc welding along the teaching welding line AB using the automatic arc welding apparatus shown in FIG. 1, one workpiece 18a is reliably arc-welded to the other workpiece 18b.

By the way, as shown by the chain line in the figure, the basic work 1
8a0, when the other workpiece 18b is positioned parallel to the teaching welding line AB and uniformly shifted by Ik+d, the preset teaching welding line AB is shifted from the actual welding line A'B'. Therefore, there is a problem that it becomes impossible to weld both the works 18a and 18'b.

A characteristic feature of the present invention is that, prior to arc welding the works 18a and 18b, a position detection arc scan is performed in which the arc is scanned along the detection line SF intersecting the teaching welding line AB. Based on the arc current or voltage change, the deviation width d of the teaching welding line AB from the actual welding line A'B' is detected, and based on the detected deviation width d, the teaching welding line AB is adjusted to the actual welding line A, ', B. The purpose is to make corrections to match '.

In the embodiment, this arc scanning for detecting positional deviation is
The welding is carried out along the detection line SE, which is orthogonal to the teaching welding line AB at the starting point A.

At this time, the scanning direction may be from S to E.
You may also go from there to S.

In Examples 1. This arc scanning for detecting positional deviation is
This is done from S to E, and at this time, works 1 and 8
The misalignment in b is the teaching welding lie.

If the occurrence is expected to occur only on the 8th point side with respect to workpiece 18b, it is sufficient to scan the positional deviation detection arc from point S to point Δ2. , position, deviation is teaching, g welding, S of line A, B
What is expected to occur on both the point 4 side and the 1 point 4 side is the position from 8 points 4 to 1 point 7. Just set it like this.

Here, the scanning distance of the arc scan for positional deviation detection can be arbitrarily set according to the type of workpiece 18b and the deviation width d that is expected to occur. The extension distances from the center to point S and point E are each set to about 3 to 5 mm.

FIG. 3 shows the arc scanning for positional deviation detection of the present invention performed in this manner, and FIG. 4 shows the arc current waveform at this time.

First, arc scanning is performed for positional deviation detection from S to E. At this time, if the workpiece 18b is accurately positioned with respect to the teaching welding line ΔB, the scanning line is 8-+A- )C-+E', but if the workpiece 18b is positioned with a predetermined deviation width d from the teaching welding line AB, the scanning line changes from S→A'→C'-→E .

At this time, the change in arc current is constant in the section <S-+A', as shown in FIG. 4, increases sharply in the section A'-)C', and becomes constant again in the section C'→E.

This is because when arc scanning is performed in the A'→C' section, the tip of the welding wire 10 is consumed along A'C' and the length of the welding wire 10 is shortened, and as a result, the arc current circuit is This is caused by a decrease in resistance value.

In other words, when arc scanning the S → △' section, the feed amount of welding wire V710 balances with the consumption ♀ and its length becomes almost constant, but when arc scanning covers the A'C' section, , the wear and tear of the welding wire 10 greatly exceeds the feed rate and its length decreases rapidly, and when arc welding the section C' → E, the feed rate and consumption R of the welding wire 10 are balanced. It becomes a constant value as the length decreases.

Therefore, the resistance value in the arc current circuit is S→A
It is constant in the section 'A'→C', decreases rapidly in the section A'→C', and becomes constant again in the section C'→F.

As a result, when arc scanning for positional deviation detection is performed from point 8 to point E, the arc current [j.

As shown in Fig. 4, the arc current increases rapidly in the section <A'C', so if the point at which this arc current starts to increase is detected,
It is possible to detect the setting quality of the work 18b with respect to the work 18a, that is, the /B/ to the actual welding line of the works 18a, 18b.

Then, the works 18a, 1a detected in this way
By comparing the actual welding line A'[3' of b with the pre-stored teaching welding line AB, the deviation width d of both is determined, and based on the deviation width d, the teaching welding line AB is changed to the actual welding line. Correct to match A'B'.

According to the present invention, even when the workpiece 18b is positioned with a predetermined deviation width d from the preset teaching welding line AB, the deviation width d can be accurately detected and the teaching welding line AB can be adjusted. The workpiece 18b is corrected to match the actual welding line A'B' based on the detected deviation width d and arc welding is started.
It becomes possible to prevent the occurrence of welding defects due to misalignment of the workpieces 18a and 18b, and to perform reliable arc welding of the workpieces 18a and 18b.

At this time, according to the present invention, the teaching welding line AB
Since the deviation width d of the workpiece 18b relative to the workpiece 18b can be detected based on changes in the arc current without using any special detection device, it is possible to detect the shift width d of the workpiece 18b based on the change in the arc current. Errors in detecting the deviation width d do not occur due to heat generated during arc welding, and the structure of the entire device can be made simple and inexpensive.

Further, according to the present invention, as shown in FIG.
When performing arc scanning for positional deviation detection up to a point, the tip of the welding wire 10 is sequentially melted by arc generation, and the surface of each workpiece 18a, 18b, especially the end face AC of the workpiece 18b.
Or there is no collision with Δ/C/. Therefore, according to the present invention, it is possible to perform positional deviation detection arc scanning from point 8 to point E at high speed, and to quickly correct the teaching welding line. In addition, as a result of this, the amount of heat generated per unit distance is reduced, so thin plate workpieces of 2 mm or less
It is also possible to accurately detect the rotational deviation of the workpiece 18b and correct the teaching welding line without damaging the workpiece 18b.

Further, according to the present invention, since the correction of the teaching welding line AB is completed prior to the actual arc welding of the workpieces 18a and 18b, the subsequent actual arc welding can be performed along the teaching welding line. Therefore, the time required for arc welding can be significantly reduced compared to the conventional riving method.

In addition, in the present invention, since the distance of the detection line SE of arc scanning for positional deviation detection can be set arbitrarily, large deviations of 2 to 3 mm or more, which were difficult to detect with the conventional riving method, can be detected. It is also possible to reliably detect the width, making it possible to demonstrate high detection ability.

In addition, in the present invention, it is sufficient that the arc current used when performing arc scanning for positional deviation detection has a value that can obtain the current change shown in FIG. It is set to about.

J2 prong cover 1 In the above embodiment, when performing arc scanning for detecting positional deviation, the current change is detected in an analog manner to detect the deviation width d of the workpiece 18h. The invention is not limited to this, but it is also possible to digitally detect the deviation width d of the workpiece 18b by sampling such an arc current.

FIG. 5 shows a method for detecting the displacement width d of the workpiece 18b by performing such arc current sampling processing. According to the method of the embodiment, the displacement detection line S
As shown in FIG. 5(a), pulse welding for detecting positional deviation is performed along line E.

Then, in synchronization with each pulse of this pulse welding, each pulsed arc current is sampled, and each non-pulling current In (n is an integer) is integrated over a one-pulse period as shown in Fig. 5(b) to obtain a pulsed arc current. The corresponding current value fJndt is determined.

The current value J T+ dt, f 1 obtained in this way
2dt, . . . show current changes similar to those shown in FIG. 4, and therefore, by detecting changes in the current values obtained in this manner, the deviation width d of the workpiece 18b can be detected.

That is, when arc scanning is performed in the SA' section or C' E section of the detection line SE, the value of the sampling current is expressed by the following formula (1), but if the A'C' section of the detection line SE is When the arc is scanned, the welding current changes suddenly and shows the current change as shown in the following equation.

f(1-1)dt>Q...(2)n-1 Therefore, in this example, the sampling currents 1+, I2,... detected in this way are expressed in the second equation above. If a current change is shown, this is transferred to the workpiece 18b.
The teaching welding line AB is corrected by determining the deviation width d and correcting the teaching welding line AB.

In the first and second embodiments, the teaching welding line AB and the actual welding line A are determined based on the change in arc current that occurs when performing arc scanning for detecting positional deviation.
Although the explanation has been given taking as an example the case where the deviation width from 'B' is detected, the present invention is not limited to this, and the deviation width is calculated based on the change in arc voltage that occurs during position deviation detection arc scanning, It is also possible to correct AB.

Embodiment of an apparatus using the method of the present invention FIG. 6 shows a preferred embodiment of an automatic arc welding apparatus to which the positional deviation correction method according to the present invention is applied, and FIG. A timing chart showing the operation is shown.

The apparatus of the embodiment includes a welding line output circuit 32 in which a teaching welding line is set in advance, and from this welding line output circuit 32, a position signal of the teaching welding line AB shown in FIG. Direction is supplied.

This position control system 34 receives the supplied signal from a subtracter 36,
It includes an actuator 40 inputted via an amplifier 38, and the actuator 40 controls the position of the welding torch 12 based on the input signal.

Here, the output of the actuator 40 is fed back to the subtracter 36 via the feedback circuit 42, and therefore the actuator 40 is configured such that the output signal of the subtracter 36 is O, that is, the welding line output circuit 32. The position of the welding torch 12 is controlled so that the device signal controlled by the actuator 40 matches the position of the welding torch 12 controlled by the actuator 40.

Therefore, in the apparatus of the embodiment, welding 1 to 12 are
Movement is controlled along the signal output from the welding line output circuit 32, that is, the teaching welding line AB.

Although a plurality of such position control systems 34 for the welding torch 12 are normally provided in a welding robot, in order to simplify the explanation, only one of them is illustrated and explained in the embodiment. There is.

Further, at the same time as starting the movement control of the torch 12 along the teaching welding line AB, the welding power source 22
A predetermined welding voltage is applied between the welding wire 10 and the workpiece 18 to avoid generating an arc between the welding wire 10 and the teaching welding line.

Therefore, the works 18a and 18b are reliably arc welded along the teaching welding line AB shown in FIG.

By the way, as mentioned above, simply performing arc welding along the teaching welding line AB will not allow the workpiece 18b to be positioned with a predetermined deviation width d from the teaching welding line AS. There is a problem that arc welding cannot be performed reliably.

The characteristic feature of this embodiment is that the deviation width d of the workpiece 18b positioned on the workpiece 18a with respect to the teaching welding line AB is detected in advance, and the teaching welding line AB is adjusted based on the deviation width d during the actual welding of the workpieces 18a and 18b. The reason is that a positional deviation correction circuit 4/l is provided for correcting the line A'B' to coincide with the line A'B'.

In the embodiment, this positional deviation correction circuit 44 includes a detection line output circuit 46 in which the detection line SF of the positional deviation detection arc scan described above is set in advance, and a positional deviation detection arc along this detection line SF. a position detection circuit 48 that detects the installation position of the workpiece 18b based on scanning; a deviation width detection circuit 50 that calculates the deviation width d between the detected installation position of the workpiece 18b and the teaching welding line AB;
including.

Then, an addition unit 52 is provided at the input stage of the position control system 34 to add the position information of the welding line AB outputted from the welding line output circuit 32 and the deviation width d outputted from the deviation width detection circuit 50. The teaching welding line AS output from the line output circuit 32 is corrected to match the actual welding line A'B' of the workpieces 18a and 18b, and arc welding is performed based on this corrected welding line A'8'. This makes it possible.

In addition, in the device of the embodiment, the welding line output circuit 3
2 and the output of the detection line output circuit 46 to the adder 52 selectively, and a switch 56 that turns on/off the signal supplied from the shift width detection circuit 50 to the adder 52. correction command section 5, which will be described later.
A predetermined switching operation is performed based on the signal from 8.

Next, a detailed configuration of the deviation correction circuit 44 of the embodiment will be explained.

(1) Start of arc scanning for detecting positional deviation First, when the correction command unit 58 outputs a positional deviation detection command signal,
The switch 56 is turned off, and the selection switch 54 is switched to the detection line output circuit 46 side.

As a result, a signal representing the detection line SE of the arc scan for positional deviation detection is supplied from the detection line output circuit 46 to the position control system 34, and the torch 12 starts moving along the detection line SE. Further, at the same time that the positional deviation detection command signal 1 is output, the welding electric current 22 is also driven, and pulse welding of the workpiece 18 is started.

In this manner, according to the apparatus of the embodiment, arc scanning for positional deviation detection along the predetermined detection line SE is started simultaneously with the output of the positional deviation detection command.

(2) Calculation of deviation width When arc scanning for positional deviation detection is started in this way, the position of the workpiece 18b placed on the workpiece 18a is determined based on the change in the arc current I (d) flowing at this time. can be detected.

Therefore, in the apparatus of the embodiment, the value of the welding pulse current 1 (d) is detected by the current detection circuit 60, and the detection signal is supplied to the position detection circuit 48.

The position detection circuit 48 is driven by a welding pulse periodic signal C output from the welding power source 22 in synchronization with the welding pulse current 1(d), and receives a current signal No. 5 I(d) supplied from the current detection circuit 60. A gate circuit 62 performs limp ringing, and this limp current I n(f) is supplied to an integrating circuit 64.

The integration circuit 64 integrates the 1 non-preg current I n(f) inputted in this way over the time interval of the welding pulse cycle, and inputs the integrated value I n((1) as it is to the subtractor 68. The signal is delayed by one welding pulse through a delay memory 66 and input to a subtracter 68.

Therefore, every time the welding pulse period signal C is output, the subtracter 68 subtracts the current sampling current 1n(0) and the previous sampling current In-+(IJ), and calculates the difference current I (h). is input to the discrimination circuit 70.

The determination circuit 70 sets a predetermined threshold level in advance, determines the point in time when the input difference current 1 (h) exceeds this threshold level as the installation position of the workpiece 18b, and issues a determination signal. i is supplied to the gate circuit 72. When the determination signal i is output, the circuits 1 to 72 number the output signal of the full feedback circuit 42, that is, the installation position of the workpiece 18b, by 1, and supply the sampling signal k to the deviation width detection circuit 50. .

The deviation width detection circuit 50 is connected to the gate circuit 7 as described above.
The teaching welding line position signal 1 output from the welding line output circuit 32 and the position signal 1 of the workpiece 18b supplied from the welding line output circuit 32 are input to the deviation width calculation circuit 74.

This deviation width calculation circuit 72 calculates the difference of I for each signal inputted in this manner, and calculates the difference of I for each signal inputted in this way, and calculates the difference between the positioned workpiece 18b.
The deviation width d with respect to the teaching welding line AB is calculated, and the calculation result is stored in the memory 76.

In this manner, the apparatus of the embodiment performs arc scanning for detecting positional deviation, and by this arc scanning, the workpiece 18
The deviation width d between the actual welding line A'B' and the teaching welding line ΔB is detected, and the detection result is stored in the memory 76.
I have a deep memory within me.

In the embodiment, a switch 78 is provided between the shift width calculating circuit 7/1 and the memory 76, which is turned on only when arc scanning for position shift detection is being performed.

(3) Start of arc welding When a series of positional deviation detection operations are completed in this way, the device deviation detection command composed of the correction command section 58 is turned off, and then the work 18a along the teaching welding line, Arc welding of 18b is started.

That is, when the device deviation detection command composed of the correction command unit 58 is turned off, the switch 54 selects the output of the welding line output circuit 32 and supplies it to the adder 52 in synchronization with this, and the switch 78 is off, switch 56
is turned on, and the deviation width d stored in the memory 76 is input to the adder 52.

Therefore, in the adder 52, the welding line output circuit 32
The position signal of the teaching welding line AB output from the meter 76 is added to the deviation width d output from the meter 76, and the teaching welding line AB is corrected to match the actual welding line Δ/B/ of the workpiece 18b. position control system 3
4 will be supplied.

Therefore, according to the apparatus of the embodiment, it is possible to weld workpieces = 28-18a and 18b along the corrected teaching welding line A'B', and weld workpiece 18b.
Workpieces 18a and 18b regardless of the presence or absence of positional deviation.
This makes it possible to perform arc welding reliably.

[Effects of the Invention] As explained above, according to the present invention, the deviation width between the actual welding line and the teaching welding line of the positioned workpiece can be accurately detected without using any special equipment, The teaching welding line can be corrected to match the actual welding line, and as a result, automatic arc welding of workpieces can be performed quickly and reliably.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a preferred embodiment of the positional deviation correction method in automatic arc welding according to the present invention, FIG. 2 is an explanatory diagram of the arc welding device used in this embodiment, and FIG. Figure 1 is an explanatory diagram of the operation of positional deviation detection arc scanning along the detection line shown in Figure 3. Figure 4 is a current characteristic diagram showing the arc current at each part of the detection line shown in Figure 3. Figure 5 is a pulse Figure 6 is a block diagram showing a preferred embodiment of a positional deviation correction circuit to which the method of the present invention is applied; Figure 7 is the circuit shown in Figure 6. FIG. 3 is a timing chart diagram showing the operation of FIG. AB... Teaching welding line A'B'
... Actual welding line SE ... Detection line 10 ... Welding wire

Claims (4)

[Claims] (1) In a consumable electrode automatic arc welding method in which a welding wire is moved along a preset teaching welding line to perform arc welding on a workpiece, prior to welding the workpiece, a detection line that intersects the teaching welding line is An arc scan for detecting positional deviation is performed to scan an arc along the arc, and the deviation width of the teaching welding line with respect to the actual welding line is detected based on the change in the arc generated at this time. A method for correcting positional deviation in automatic arc welding, which comprises: correcting the line to match the actual welding line, and then starting arc welding of the workpiece. (2) A method for correcting positional deviation in automatic arc welding according to claim (1), wherein arc scanning for positional deviation detection is performed along a detection line orthogonal to a teaching welding line. (3) In the method according to any one of claims (1) and (2), actual welding at each detection point of the teaching welding line is performed based on changes in arc current that occur when performing arc scanning for detecting deviation. A method for correcting positional deviation in automatic arc welding, which is characterized by detecting a deviation width with respect to a line. (4) In the method according to any one of claims (1) and (2), the actual welding at each detection point of the teaching welding line is performed based on the arc voltage change that occurs when performing arc scanning for detecting deviation. A method for correcting positional deviation in automatic arc welding, which is characterized by detecting a deviation width with respect to a line.