JPH1177307A - Automatic welding method and its equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate high-precision high-quality automatic multi-layer welding, in such cases where no lamination is possible in accordance with design conditions and where deformation is caused by welding heat, by picking up image around the tip end of a welding torch during the welding and automatically correcting welding conditions based on the detected data of a shape and position. SOLUTION: With the automatic welding operation started, a measurement starting signal is outputted from a welding torch controller 1 to an image processor 9, which fetches an image and, on the basis of these detected data, determining the deviation of the tip end position of the welding torch 3 from the center in the width direction of the groove 7a of a welding work 7. The image processor 9 also calculates a distance between the tip end of a welding pool and that of the welding torch 3, determining a difference between the distance so calculated and the optimum value stored preliminarily in the memory of the image processor 9. The controller 1, based on these data, corrects the operation of a welding head 2, modifying a position for the Y axis direction of the welding torch 3 and positioning its tip end in the center of the groove 7a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic welding apparatus and an automatic welding method suitable for performing multi-layer welding.

[0002]

2. Description of the Related Art FIG. 14 shows a configuration example of a conventional automatic welding apparatus. As shown in FIG. 14, a conventional automatic welding apparatus includes a welding torch 3 for performing welding, a welding head 2 for holding and moving the welding torch 3, and a welding power source 4 for supplying a welding current to the welding torch 3. , Welding head 2 and welding power source 4
, A welding line scanning sensor 5 for detecting a welding line, and a scanning sensor drive mechanism 6.

In this conventional automatic welding apparatus, the operation control of the welding head 2 and the output control of the welding power source 4 are performed by the control unit 1a based on a welding sequence and welding conditions set in advance. And the output is controlled to perform automatic welding.

The data for controlling the movement of the tip of the welding torch 3 at the time of automatic welding is obtained by detecting a welding position with the welding line following sensor 5 and storing it in the control device 1a in advance, or by using the welding line following sensor 5 in advance. The operation is performed in advance of the welding head 2 so as to be stored in the control device 1a. At the time of welding, the operation trajectory of the tip of the welding torch 3 is controlled by regenerating the welding head 2 based on the stored data so that welding is automatically performed so as to follow a predetermined welding line. Has become.

[0005]

As described above, in the conventional apparatus, automatic welding is performed by simply moving the welding torch so as to follow the welding line based on data detected by the welding line following sensor. It is carried out.

However, when the groove cross-sectional area is different from a predetermined value due to a change in the groove machining accuracy of the welded work or a change in the groove gap, or a change in the groove shape due to thermal deformation during welding. In the case of a change, if automatic welding is performed using the welding conditions determined based on the design shape of the welding work as it is, defects such as poor melting on the groove wall surface and insufficient or excessive weld overlay may occur. There is also. In such a case, the operator must determine the situation and adjust the welding torch position, adjust the welding conditions, or interrupt the welding and correct the conditions.

In addition, when performing multi-layer welding with an automatic welding apparatus, the number of layers of welding beads and the number of welding passes must be determined in advance as welding conditions. If welding is performed to the end with the determined number of layers and the number of passes, a desired welding result may not be obtained.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an automatic welding apparatus and a welding method capable of performing automatic multi-layer welding in accordance with a change in groove shape.

[0009]

In order to achieve the above object, the present invention relates to an automatic welding method, wherein an image around the tip of a welding torch is taken during welding, and a welding work is opened based on the taken image. Tip position, tip position of welding torch,
Detecting the shape of the welding arc and the shape of the weld pool, based on the detected shape and position data, so that the tip of the welding torch is located at the center in the width direction of the groove and the weld pool shape is an appropriate shape, It is characterized in that multi-layer welding is performed by automatically correcting predetermined welding conditions.

Further, the present invention provides an automatic welding method for performing multi-layer welding by weaving a welding torch, wherein an image around the tip of the welding torch in synchronization with the stop of the weaving operation at both ends of the weaving operation range of the welding torch. Is performed, and based on the captured image,
The present invention is characterized in that the operation of the welding torch is automatically corrected such that the amplitude of the weaving operation and the center of the weaving operation fall within a predetermined appropriate range, and multi-layer welding is performed.

The present invention also relates to an automatic welding apparatus for performing multi-layer welding, a welding head for holding and moving a welding torch, and a welding power source for supplying electric power for generating a welding arc to the welding torch. An imaging device for imaging the periphery of the tip of the welding torch, and a groove position of the welding work, a tip position of the welding torch, a shape of the welding arc light, and a shape of the molten pool based on the image captured by the imaging device. And an image processing apparatus for calculating a correction welding condition such that the tip of the welding torch is located at the center of the groove and the shape of the molten pool is an appropriate shape, based on the detected data, and the image A control device for controlling the welding head and the welding power source based on the corrected welding conditions calculated by the processing device.

Further, the present invention is directed to an automatic welding apparatus for weaving a welding torch to perform multi-layer welding, in which a welding head for holding and moving a welding torch, and for generating a welding arc in the welding torch. A welding power supply for supplying power of the welding torch, an imaging device for imaging the periphery of the welding torch tip, and an image from the imaging device captured in synchronization with the stop of the weaving operation at both ends of the weaving operation range, based on this image. The groove position of the welding work and the tip position of the welding torch are detected, and the correction welding conditions are determined based on the detected position data so that the width of the weaving operation and the center of the weaving operation are within a predetermined appropriate range. An image processing device and the welding welding condition based on the corrected welding conditions calculated by the image processing device. A controller for controlling the de-and the welding power supply, is characterized in that it comprises a.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] First, a first embodiment will be described with reference to FIGS. As shown in FIG. 1, the automatic welding apparatus includes a welding head 2 for holding and moving a welding torch 3, a welding power source 4 for supplying a current for generating a welding arc to the welding torch 3, and a welding head. 2 and a control device 1 for controlling the welding power source 4 (welding torch control device); a CCD camera 8 as an example of an imaging device for imaging the periphery of the tip of the welding torch;
An image processing apparatus 9 is provided for processing images captured by the camera and detecting various shapes and dimensions.

Next, the operation of the first embodiment having the above configuration will be described with reference to the flowchart of FIG. 5 while referring to FIGS.

As shown in FIG. 5, when the automatic welding operation is started, a measurement start signal is output from the control device 1 to the image processing device 9, and an image is taken in by the image processing device 9 (step S101). .

The image processing device 9 captures an image picked up by the CCD camera 8 and performs image processing. The groove position of the welding work 7 (step S102), the tip position of the welding torch 3 (step S103), the welding arc A (Step S104) and the shape of the molten pool P (step S1)
05) is detected.

Then, the image processing device 9 determines the width (Y) of the groove 7a of the welding work 7 based on the detected data.
A deviation amount (a required correction amount) TY of the position of the tip 3a of the welding torch 3 from the center position (axial direction) is calculated (step S106).

As shown in FIG. 2B, the shift amount TY is
The distance TPL from the tip of the welding torch 3 to the left side of the groove wall of the welding work, and the distance TP from the tip of the welding torch to the right side of the groove wall.
If R is calculated by the following equation. TY = (TPL-TPR) / 2 Also, as shown in FIG. 4, when the tip of the molten pool P is ahead of the tip of the arc light A with respect to the traveling direction of the welding torch 3, There is a possibility that the welding work 7 cannot be sufficiently melted, resulting in poor melting. Therefore, as shown in FIG. 3, the tip of the molten pool P and the tip of the welding arc A are in the traveling direction of the welding torch 3 (X-axis direction).
Must be maintained in approximately the same position with respect to

The image processor 9 calculates the distance Lbf between the tip of the weld pool P and the tip 3a of the welding torch 3 in order to perform operation control to maintain an appropriate positional relationship between the weld pool P and the welding arc A. Then, a difference (a required correction amount) between the obtained distance Lbf and the optimum value LbfR stored in the memory of the image processing apparatus 9 in advance is obtained (Step S10).
7).

The deviation amount TY calculated by the image processing device 9
The data of the difference Lbf-LbfR is transmitted to the control device 1.

The controller 1 corrects the operation of the welding head 2 based on these data to correct the position of the welding torch 3 in the Y-axis direction, and as shown in FIG. The tip 3a is positioned at the center of the groove 7a (step S108).

At the same time, the control device 1 determines the difference (L
bfR-Lbf), the welding speed (welding torch 3
(The moving speed in the X-axis direction) and / or the welding current is corrected so that the distance between the tip of the welding torch 3 and the tip of the molten pool is always constant. That is, the control device 1
By controlling the welding head 2 and / or the welding power source 4, control is performed so that the distance Lbf between the tip of the molten pool P and the tip 3a of the welding torch 3 becomes the optimum value LbfR (step). S109).

As described above, according to this embodiment, the state around the tip 3a of the welding torch 3 is constantly monitored by the CCD camera 8 and the image processing device 9. And
Based on the monitoring result, the control device 1 controls the position of the tip 3a of the welding torch 3 so that it is always located at the center of the groove 7a of the welding work 7, and the welding torch 3 tip 3a and the molten metal P The multi-layer welding is performed in a state where the distance from the tip of the metal is controlled to be always constant.

For this reason, for example, even when the groove shape changes due to thermal deformation during welding, high-quality multi-layer welding can be performed at an appropriate welding torch position.

[Second Embodiment] Next, a second embodiment will be described with reference to FIGS. The second embodiment provides a control method suitable for performing a weaving operation (oscillating operation) on a welding torch. Second
In this embodiment, the configuration of the welding device is substantially the same as that of the first embodiment, and a detailed description of the welding device itself is omitted.

In this embodiment, the welding torch 3 performs a weaving operation in the Y-axis direction (width direction of the groove) in FIG. 6, as shown in FIG. While moving in the X-axis direction (the longitudinal direction of the groove, ie, the direction of the welding line). The movement of the welding torch 3 is transmitted from the control device 1 to the welding head 2.
The movement of the welding torch 3 in the Y-axis direction is determined by the movement of the swing shaft (not shown) of the welding head 2.

When the automatic welding operation is started, the control device 1
Outputs a weaving position signal for controlling the weaving operation of the welding torch 3 (the position of the welding torch 3 in the Y-axis direction) to the welding head 2 and to the image processing device 9. As shown in FIG.
Operate repeatedly at a constant speed in the Y-axis direction, and stop the operation in the Y-axis direction at both ends for a predetermined time.

The image processing device 9 detects the weaving speed of the welding torch 3, that is, the Y-direction component of the speed of the welding torch 3 based on the weaving position signal, and when the Y-direction component of the speed becomes zero, the CCD camera. 8 to capture the image taken. That is, the image processing device 9
It is automatically detected that the welding torch 3 is at both ends in the Y-axis direction and the operation of the welding torch 3 in the Y-axis direction is stopped, and an image is captured.

FIG. 6A shows an image obtained when the welding torch 3 stops moving in the Y direction at the left end (hereinafter referred to as “at the time of stopping at the left end”). FIG. 6B shows images obtained when the image moves to the right end and stops at the right end (hereinafter referred to as “at the time of stopping at the right end”).

Based on the obtained image, the image processing device 9 starts the welding torch 3 from the left side wall of the groove when the left end is stopped.
TPL to the tip 3a of the welding torch 3 from the right side wall of the groove when the right end is stopped.
Detect each R.

The image processing device 9 calculates the displacement TY of the tip 3a of the welding torch 3 from the center of the groove based on the following equation. TY = (TPL-TPR) / 2 The image processing device 9 transfers the data of the deviation amount TY to the control device 1, and the control device 1 determines the (Y) of the locus of the tip 3a of the welding torch 3 in the weaving operation. The movement of the welding head 2 is corrected so that the center Yc (in the axial direction) (see FIG. 7) always coincides with the groove center position.

The weaving operation amplitude Yw (FIG. 7)
Is calculated by the formula Yw = YL -YR.

Here, the optimum value YGL of the distance from the left side wall of the groove to the tip 3a of the welding torch 3 when the left end is stopped.
The optimum value YGR of the distance from the right side wall of the groove to the tip 3a of the welding torch 3 when the right end is stopped is set in advance and stored in the memory of the image processing device 9, and the image processing device 9 Based on the values and the previously detected values TPL and TPR, the amplitude correction amount Ywh of the weaving operation of the welding torch 3 is calculated based on the following equation. Ywh = (TPL-YGL) + (TPR-YGR) The image processing device 9 transfers the data of the amplitude correction amount Ywh to the control device 1. Then, the control device 1 corrects the amplitude of the weaving operation and controls so that the distance between the groove wall surface and the tip of the welding torch 3 when both ends are stopped is always constant.

In this embodiment, as in the first embodiment, it is preferable to control the positional relationship between the tip of the welding torch 3 and the tip of the molten ground P in the traveling direction of the welding torch.

As described above, according to the present embodiment, the center of the weaving operation of the welding torch 3 coincides with the center position of the groove, and when the welding torch 3 stops at the left and right ends, Control is performed so that the distance from the groove wall surface is constant and an optimal value.When performing multi-layer welding, if the groove shape changes due to variations in the amount of fusion to the front layer or welding thermal deformation. In this case, optimal welding can be performed, and high-quality automatic multi-layer welding can be performed.

In the present embodiment, the image processing device 9 detects when the left end or right end of the welding torch 3 is stopped based on the weaving position signal.
It is not limited to this. That is, as shown in FIG. 8, for example, a signal Sw (both ends stop signal) indicating when the left end and the right end of the welding torch 3 are stopped is sent to the control device 1.
And causes the image processing device 9 to capture an image based on the both-ends stop signal.
Correction calculation processing may be performed.

Third Embodiment Next, a third embodiment will be described with reference to FIGS. The third embodiment is different from the second embodiment in that a trigger signal generator 11 is further provided, and the other configurations are substantially the same as the second embodiment. In the third embodiment, the same portions as those in the second embodiment are denoted by the same reference numerals, and detailed description is omitted.

Hereinafter, the operation of the present embodiment will be described.

When the automatic welding operation is started, the control device 1
Outputs the weaving position signal and the above-described both-ends stop signal (see the second embodiment) to the image processing apparatus 9.

On the other hand, the welding power source 4 always outputs a signal (welding monitor signal) indicating the welding current (or welding voltage) supplied to the welding torch by the welding power source 4.
Since the welding current is usually supplied in the form of a pulse current as shown in FIG. 10, the welding monitor signal also takes the form of a pulse signal.

The trigger signal generator 11 detects a peak portion and a base portion of the welding monitor signal, and outputs a trigger signal Tr which is turned on at the base portion to the image processing device 9. The detection of the peak portion and the base portion is determined by the magnitude relationship between the welding monitor signal and the threshold value Is of the preset detection level.

When both of the above-mentioned both-end stop signal and the trigger signal are ON, the image processing device 9
Capture the image of Then, the weaving operation of the welding torch is controlled based on the captured image in the same manner as in the third embodiment.

As described above, in the present embodiment, the image is taken in while the base current is being supplied, so that the CCD camera 8 always keeps the vicinity of the tip 3a of the welding torch 3 under the condition of a constant light quantity level. Can be captured. For this reason, image analysis can be performed more accurately. Therefore, it is possible to more accurately control the welding conditions.

[Fourth Embodiment] Next, a fourth embodiment will be described with reference to FIGS. Speaking of the configuration of the automatic welding apparatus, the fourth embodiment is different from the second embodiment in that a slit laser generator 10 for irradiating a slit laser beam on a groove of a welding work is further provided. However, the rest is substantially the same as the second embodiment. In the fourth embodiment, the same parts as those in the second embodiment are denoted by the same reference numerals, and detailed description is omitted.

Hereinafter, the operation of the present embodiment having the above configuration will be described with reference to the flowchart of FIG. 13 while referring to FIG. 11 and FIG. FIG. 12 is a groove sectional shape diagram showing the condition correction according to the shape of the welded laminated bead. FIG.
3 is a flowchart showing automatic welding operation control, measurement processing, and condition data correction.

First, as shown in FIG. 13 (a), when the welding of the n-th pass is completed, the control device 1 determines the welding conditions of the next pass (the (n + 1) -th pass) from the welding database (not shown). Is read (step S200). These welding conditions are obtained in advance by calculation corresponding to the design shape of the welding work. The control device 1 transmits the welding condition data to the image processing device 9.

Next, the image processing device 9 measures the shape of the weld bead formed in the welding process up to the n-th pass,
The welding condition data read from the welding database is corrected (step S210).

Hereinafter, the processing in step S210 will be described in detail with reference to FIG.

First, the slit laser generator 10 irradiates the slit laser beam in the groove cross-sectional direction so as to cover the entire width direction (Y-axis direction) of the groove of the welding work, and the projected image of the slit laser beam is formed. An image is captured by the CCD camera 8. (Step S211).

Next, the image processing device 9 sets the groove position and groove cross section (groove width, groove depth, groove angle, melting to the front layer) based on the shape of the projected image of the slit laser beam. Part width) is detected. This detection step is performed by the welding work 7
Is performed at preset intervals in the groove longitudinal direction (X-axis direction). From the groove cross-sectional shape, FIG.
(A) Groove depth T, groove angle θ, lamination bead width W shown in FIG.
b is detected (step S212).

Next, the image processing device 9 receives the data of the groove position and the groove cross-section that are sequentially detected, and corrects the welding condition data read from the welding database based on these data.

FIG. 12B shows a lamination pattern based on welding condition data set in advance. The setting condition is 1 pass / layer, and the bead height h for the second and subsequent layers has a constant value.

Based on the detected data, first, the number of remaining paths PN is calculated by the following equation (step S213). The decimal places are rounded off. PN = (T + 2) / h Next, the bead height hr of the next pass is calculated by the following equation (step S214). hr = h + {(T + 2) -PN · h} Next, as the correction conditions, the welding speed Vs, the amplitude W of the weaving operation, and the weaving speed Vw are calculated by the following equations (step S215). However, it is assumed that the wire speed Vf, the wire diameter d, and the stop time ts at the left and right ends of the weaving operation are set in advance as welding condition data.

[0055]

(Equation 1) The calculated corrected welding condition data is transferred from the image processing device 9 to the control device 1 as shown in FIG. 13A (step S220).

Based on the transferred corrected welding condition data, the control device 1 operates the welding head 2 and outputs welding arc instruction data to the welding power source 4 to perform welding.

During welding, as in the second embodiment,
The operation range of the welding torch 3 is controlled based on the analysis result of the image around the tip of the welding torch 3 so as to always be at the groove center position, and both ends of the weaving operation are always at a fixed distance from the groove wall surface. The control is performed as follows.

As described above, multi-layer welding is performed while similarly correcting the condition data for all the passes (steps S230 and S240). During the welding of each pass, the second
Alternatively, the same weaving operation control as in the third embodiment is performed.

As described above, according to this embodiment, the groove cross-sectional shape is detected by the slit racer light before or after welding, and the welding conditions of the next pass are corrected. Image capturing and image processing are performed to detect the welding torch position, welding work groove position, and weld pool shape, and process the detected data with an image processing device.
Calculates the deviation of the welding torch tip position from the center position of the welding work groove, controls the welding torch operation range to always come to the groove center position, and both ends of the weaving are always at a fixed distance from the groove wall Thus, even when the groove shape changes due to variations in groove processing before welding or thermal deformation during welding, high-quality multi-layer welding at an appropriate welding torch position can be performed.

[0060]

As described above, according to the present invention,
Even when lamination cannot be performed according to the set conditions or when welding thermal deformation occurs, high-precision, high-quality automatic multi-layer welding can be easily performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an automatic welding device according to the present invention.

FIG. 2 shows a welding torch position in a groove of a welding work,
It is a figure which shows a welding arc shape and a bead shape, FIG.2 (a) is a figure which shows the case where welding is performed normally, FIG.2 (b) is a position of a welding torch and the groove of a welding work. The figure which shows the case where welding is performed in the state shifted from the center of FIG.

FIG. 3 shows a welding torch position, a welding arc shape, and a welding arc within a groove of a welding work when welding is performed normally.
3A and 3B are views showing a bead shape, FIG. 3A is a perspective view, and FIG.

FIG. 4 is a diagram showing a welding torch position, a welding arc shape, and a bead shape within a groove of a welding work when normal welding is not performed; FIG. 4 (a) is a perspective view, FIG. 4B is a sectional view.

FIG. 5 is a flowchart illustrating a flow of a welding condition correction process according to the first embodiment.

FIG. 6 is a diagram showing a welding torch position, a welding arc shape, and a bead shape within a groove of a welding work according to a second embodiment, and FIG. 6 (a) shows a welding torch in a weaving operation. FIG. 6B shows a state where the welding torch is swung to the right end in the weaving operation, and FIG.

FIG. 7 is a diagram showing a temporal change in a position of a tip end of a welding torch in a Y-axis direction in a second embodiment.

FIG. 8 is a view for explaining a both-ends stop signal transmitted from the control device to the image processing device.

FIG. 9 is a block diagram showing the configuration of a third embodiment of the automatic welding device according to the present invention.

FIG. 10 (a) is a view showing an output current (or voltage) waveform of a welding power source in a third embodiment;
FIG. 10B is a diagram illustrating a trigger signal output by a trigger signal generator based on an output current of a welding power source.

FIG. 11 is a block diagram showing a configuration of a fourth embodiment of the automatic welding device according to the present invention.

FIG. 12 is a groove sectional shape diagram for explaining condition correction according to a welded lamination bead shape in the fourth embodiment;
FIG. 12A shows groove welding condition data.
(B) is a diagram showing a lamination pattern based on welding condition data set in advance.

FIG. 13 is a flowchart showing automatic welding operation control and measurement processing and condition data correction in the fourth embodiment. FIG. 13A is a flowchart showing automatic welding operation control, and FIG. 9 is a flowchart showing details of the measurement processing and condition data correction of a).

FIG. 14 is a block diagram showing a configuration of a conventional automatic welding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Welding head 3 Welding torch 4 Welding power supply 7 Welding work 8 CCD camera 9 Image processing device 10 Slit laser light generator 11 Trigger signal generator

Claims (8)

[Claims] An image around the tip of a welding torch is taken during welding, and a groove position of a welding work is determined based on the taken image.
Detects the tip position of the welding torch, the shape of the welding arc and the shape of the weld pool, and based on the detected shape and position data, the tip of the welding torch is located at the center of the groove in the width direction and the weld pool shape is appropriate An automatic welding method, wherein a predetermined welding condition is automatically corrected so as to have a shape, and multi-layer welding is performed. 2. An automatic welding method for performing multi-layer welding by weaving a welding torch, wherein an image around the tip of the welding torch is taken in synchronization with the stop of the weaving operation at both ends of the weaving operation range of the welding torch. Based on the captured image, the welding torch operation is automatically corrected so that the amplitude of the weaving operation and the center of the weaving operation are within a predetermined appropriate range, and the multi-layer welding is performed. Method. 3. The automatic welding method according to claim 2, wherein when the arc current or the arc voltage is at a low level, an image around the tip of the welding torch is taken. 4. After one-pass welding is completed, a slit light is applied to the groove position of the welding work to capture a projected image of the slit light, and a sectional shape of the groove is detected based on the projected image. 4. The automatic welding method according to claim 1, wherein welding conditions for welding in the next pass are determined based on the detected cross-sectional shape of the groove. 5. An automatic welding apparatus for performing multi-layer welding, comprising: a welding head for holding and moving a welding torch; a welding power supply for supplying electric power for generating a welding arc to the welding torch; An imaging device that images the periphery of the torch tip, and based on an image taken by the imaging device, detects the groove position of the welding work, the tip position of the welding torch, the shape of the welding arc light, and the shape of the molten pool. An image processing device that calculates a correction welding condition such that the tip of the welding torch is located at the center of the groove and the shape of the molten pool is an appropriate shape, based on the detected data, And a controller for controlling the welding head and the welding power source based on the corrected welding conditions. 6. An automatic welding device for weaving a welding torch to perform multi-layer welding, comprising: a welding head for holding and moving a welding torch; and supplying electric power for generating a welding arc to the welding torch. A welding power source, an imaging device for imaging the periphery of the welding torch tip, and an image from the imaging device taken in synchronism with the stop of the weaving operation at both ends of the weaving operation range, and the opening of the welding work is performed based on the image. An image processing device that determines a correction welding condition such that the width of the weaving operation and the center of the weaving operation are within a predetermined appropriate range based on the detected position data and the tip position of the welding torch and the tip position. The welding head and the front based on the corrected welding conditions calculated by the image processing device. Automatic welding apparatus characterized by and a control device for controlling the welding power supply. 7. The image processing apparatus further comprises: a trigger signal generator for generating a trigger signal when a current or voltage output from the welding power source becomes equal to or less than a predetermined threshold value. 7. The automatic welding apparatus according to claim 6, wherein a correction welding condition is calculated based on an image obtained by the imaging device when the image is output. 8. A slit light generator for irradiating a slit light to a groove position of the welding work, wherein the image pickup device is configured to emit the slit light irradiated by the slit light generator after one-pass welding is completed. A projection image is taken, and the image processing device detects a cross-sectional shape of a groove based on the projected image, and determines welding conditions for a next pass based on the detected cross-sectional shape. 8. The automatic welding apparatus according to 6 or 7.