JPH08206834A - Groove width copying method - Google Patents

Abstract

PURPOSE: To provide the groove width copying method capable of preventing welding quality from lowering. CONSTITUTION: A root gap G1 at welding start point is detected, weaving is executed while a weaving width W1 is controlled corresponding to the root gap G1. The reference value G0, which is corrected so that the increase of root gap G2 is difficult to detect at increasing the weaving width W and the increase of root gap G2 is easy to detect at decreasing weaving width W, is compared with the electric quantity at weaving, thus, increase/decrease of root gap is detected, the groove width copying is executed with controlling weaving width corresponding to increase/decrease of root gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groove width copying method for controlling a groove width by controlling a weaving width so as to cope with an increase or decrease in a root gap.

[0002]

2. Description of the Related Art When performing butt welding or fillet welding by arc welding, the welding electrode is usually weaved in the left-right direction with respect to the welding line in order to form the weld metal flat and reduce internal defects. While weaving welding is adopted.

In the above-mentioned weaving welding, a welding start point, a welding end point, and welding conditions (for example, groove information such as weaving width, surplus height, reference route gap, etc.) are taught to an arc welding robot in advance. The teaching data is reproduced to operate the arc welding robot.

The groove state fluctuates due to factors such as groove machining of workpieces, variations in tacking accuracy, and thermal strain during welding, and often does not match the groove information from the beginning or the middle of welding. By simply reproducing the groove information and performing the weaving welding, it is not possible to stably obtain good welding quality with a constant extra height. Therefore, conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-293675, an opening for controlling the weaving width so that the electric quantity (current / voltage) of the arc at both ends of the weaving becomes a predetermined reference value. By the tip width copying method, the weaving width is changed in response to the change in the groove state.

[0005]

However, in the above-described conventional groove width copying method, as shown in FIGS. 15 (a) and 15 (b), it is more practical than the reference root gap G0 of the groove information at the welding start point. When the root gap G1 of the workpieces 51 and 51 is larger, a deviation occurs until the weaving width corresponding to the reference root gap G0 follows the root gap G1, and the welding quality in the region near the welding start point There is a problem that it will be lowered.

Further, if the weaving width is made to follow the root gap, there is also a problem that the excess height related to welding quality is reduced. Therefore, by adopting the method of controlling the welding speed according to the variation of the weaving width, it is possible to make the surplus height constant, but in this case, the change of the welding speed depends on the detection of the root gap. And the groove width control becomes unstable, and as a result, there is a problem that the welding quality deteriorates in the region during welding.

That is, as shown in FIGS. 16 (a) to 16 (c), when the weaving width W1 is increased, if the welding speed is reduced so as to prevent the reduction of the extra height, the arc point is welded. Welding torch 53 is located at the rear of the pool.
The state exists from the position to the B position. Therefore, at the position B, since the apparent root gap is increased, the weaving width W1 is further increased. In the worst case, the weaving width is increased and the welding speed is decreased. This causes the control of the welding electrode to diverge.

[0008] Therefore, in Japanese Patent Laid-Open No. 245636/1993, the relationship between the excess height and the root gap is analyzed, and the range in which the change in the welding speed does not affect the detection of the root gap is specified. A method for performing width copying control is disclosed. However, in this case, there is a problem that the groove width profile becomes unstable and the welding quality is deteriorated when the work exceeds the above range due to thermal deformation of the work, provisional attachment error, or the like.

Therefore, the present invention is intended to provide a groove width copying method capable of preventing deterioration of welding quality.

[0010]

In order to solve the above-mentioned problems, a groove width tracing method according to a first aspect of the present invention detects a root gap at a welding start point and sets a weaving width corresponding to the root gap, The groove width is controlled by controlling the weaving width so as to correspond to the increase or decrease of the root gap.

According to the groove width tracing method of the second aspect, an increase / decrease in the root gap is detected by comparing the electric quantity during weaving with a reference value, and the weaving width is adjusted so as to correspond to the increase / decrease in the root gap. The above reference value is corrected so that it is difficult to detect the increase in the root gap when the weaving width is increased, while the weaving width is decreased. It is characterized in that it is corrected so that it is easy to detect an increase in the root gap.

[0012]

According to the first aspect of the invention, since the root gap at the welding start point is detected and the weaving width corresponding to the root gap is detected, the groove width is traced. The route gap in
Even if it is larger than the expected route gap,
It is possible to prevent the deterioration of the welding quality in the region near the welding start point.

According to the second aspect of the present invention, the reference value is corrected so that it is difficult to detect the increase in the root gap when the weaving width is increased. Even if the apparent root gap increases due to constant control, this increase can be subtracted by correcting the reference value, and as a result it is possible to prevent deterioration of the welding quality in the region during welding. Has become. In addition, even if the increase or decrease in the root gap becomes noticeable due to the thermal deformation of the workpiece or a mistake in tacking, the increase or decrease in the root gap is detected based on the reference value. There is no loss of quality.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the groove width copying method according to the present embodiment, the arc welding robot 1 uses the robot control panel 2 as shown in FIG.
It is designed to be carried out during welding while being controlled by. The arc welding robot 1 is fixed to the base 6, and is provided on a swivel base that swivels about a vertical axis, a swivel base, a vertical arm that swings in a vertical plane, and a tip end of the vertical arm. It has a horizontal arm that oscillates in the same vertical plane and a wrist portion that is provided at the tip of the horizontal arm and holds the welding torch 3. The welding torch 3 is welded from the wire feed motor 7 to the welding torch 3. The electrodes 8 are supplied.

As shown in FIG. 3, the robot control panel 2 has an attitude control unit 10 and a copying control unit 11, and the attitude control unit 10 stores a teaching data storage unit 16 in which teaching data is stored. And a position calculation unit 12 that calculates the position of the welding torch 3 based on teaching data such as a weaving width,
A servo control unit 13 that drives a servo motor (not shown) provided in the arc welding robot 1 and a start point gap sensing unit 17 that detects a root gap at a welding start point.
It has and.

On the other hand, the copying control section 11 weaves based on the A / D conversion section 14 for converting the welding current into a digital welding current value, the welding current value and the weaving end signal from the position calculation section 12. The scanning calculator 15 is provided for transmitting a correction command signal to the position calculator 12 so as to change the width to an appropriate width. As a result, as shown in FIG.
The robot control panel 2 associates the weaving width with the root gap of the welding start point, and then changes the weaving width from the welding start point to the welding end point to an appropriate weaving width according to the root gap, and then the posture of the arc welding robot 1 is changed. And the position is controlled to perform welding.

A groove width copying method will be described through the operation of the arc welding robot 1 having the above structure.

First, the teaching operation when it is assumed that the workpiece 9 shown in FIGS. 4A and 4B is welded will be described. As shown in FIG. 5, the arc welding robot 1 is equipped with a teaching pendant.
When the welding electrode 8 is operated, the welding electrode 8
It is moved to 1 and this position is stored (S
1). After that, welding conditions such as current / voltage, reference welding speed V0, weaving frequency, reference weaving width W0, reference root gap G0, surplus height H and groove angle θ are input (S2) to generate an arc. Arc on
After the command is input (S3), the welding electrode 8 is moved to the welding end point P2, and this position is stored (S3).
4). Then, the arc OFF command for stopping the generation of the arc is input (S5), and the teaching operation is ended.

Next, the reproducing operation will be described. As shown in FIGS. 6A to 6C, the actual work 9 has a wider root gap G0 from the welding start point P1 to the welding end point P2 than the same reference root gap G0 as the work assumed at the time of teaching. It is assumed that the taper is expanded from G1 to the root gap G2.

First, as shown in FIG. 3, the attitude control unit 10
Starting point gap sensing unit 17 and position calculation unit 1
By executing the robot control process in 2, the starting point gap sensing is performed.
That is, as shown in FIGS. 7 and 8, after the tip of the welding electrode 8 is positioned at a predetermined height distance D (about 2 mm) above the welding start point P1, the welding electrode 8 contacts the groove wall 9a. The movement distance GU is obtained by the parallel movement in the A direction and the B direction until they come into contact with each other. The moving distance GU and the height distance D are G = GU-2Dta.
By substituting for nθ, the root gap G1 at the welding start point P1 is obtained (S
8).

After this, the gap difference dwo between the root gap G1 and the reference root gap G0 is obtained (S9). This gap difference dwo will be added to the reference weaving width W0, and as shown in FIG. 6C, the reference weaving width W0 is corrected to the weaving width W1 corresponding to the root gap G1 of the welding start point P1. In addition, the welding speed V corresponding to the root gap G1 is corrected by the surplus height control process described later (S10).

Next, when the weaving operation is started with the above weaving width W1 and welding speed V, it is judged whether or not the welding electrode 8 is located at the end of the weaving operation (S11). ). When it is determined that the welding electrode 8 is not located at the end, S16 is executed, and after the target position is obtained by the trajectory calculation using the current weaving width W1 and welding speed V. (S16), this target position is output to the servo control unit 13 (S17).

On the other hand, when it is determined that the end portion is located, as shown in FIG. 1, the weaving end indicating whether the end portion is located at the right end or the left end with respect to the welding direction. The signal is output to the copying control unit 11 (S12). After this, when the correction command signal dw from the scanning control unit 11 is received (S13), the correction command signal d
By substituting the data content of w into W = W1 + Σdw, the weaving width W is updated (S
14).

Next, a surplus height control process is executed, and the welding speed V corresponding to the current route gap G is corrected (S15). Specifically, as shown in FIG. 9, weaving width W · W1 and root gap G1
Is substituted into G = G1 + (W-W1),
The current route gap G will be calculated (S2
1). After this, as shown in FIG.
Using the surplus height H and the groove angle θ, the cross-sectional area S of the groove formed in the root gap G is obtained (S22),
This cross-sectional area S and the reference cross-sectional area S0 of the groove assumed at the time of teaching
And the reference welding speed V0 are substituted into V = V0 × (S0 / S) and corrected to a new welding speed V (S2
3). As a result, as the root gap G increases, the cross-sectional area S of the groove increases, and the corrected welding speed V decreases.

When the correction to the welding speed V is completed, as shown in FIG. 8, the target position is obtained by the trajectory calculation using the corrected welding speed V and the weaving width W (S1).
6) Then, this target position is output to the servo control unit 13 (S17). Then, the posture control unit 10 performs the above robot control processing from the welding start point P1 to the welding end point P.
The reproduction operation is repeated until the number of times reaches 2.

On the other hand, as shown in FIG.
In the above, while the posture control unit 10 executes the robot control process, the copying calculation unit 15 waits for the weaving end signal from the posture control unit 10 while executing the copying control process.

That is, in the copy calculation section 15, FIG.
As shown in, it is determined whether or not the weaving end signal is received (S31), and S31 is repeatedly executed until it is determined that the weaving end signal is received. If it is determined that it is received, it is determined whether or not the weaving operation is from the left end to the right end (S32), and if it is determined that the weaving operation is from the left end to the right end, the A / D of FIG. The welding current value is fetched from the conversion unit 14, this welding current value is stored as the current value IR1, and the current minimum value is stored as the current value IR2 (S3).
3). On the other hand, when it is determined that the welding current value is going from the right end to the left end, the welding current value is stored as the current value IL1 and the current minimum value is stored as the current value IL2 (S34).

After that, it is determined whether or not the half cycle has ended depending on the presence or absence of the input of the weaving end signal, and the above S32 and S33 or S34 until the end of the half cycle is confirmed.
And will be repeated. As a result, S3
When the end of the half cycle is confirmed in 5, if the weaving operation is toward the right end, the current value IR1 at the right end
And the minimum value IR2 during the half cycle are detected, the current value IL1 at the left end and the current value IL2 during the half cycle are detected in the case of the weaving operation toward the left end (S35). ). After this, it is determined whether it is the first half cycle, and if it is the first half cycle,
It is re-executed from S31 described above (S36).

On the other hand, when it is not the first half cycle, the left and right current values IL1, IL2, IR1 and IR2 are in a uniform state, and therefore the respective current differences (DELL / DELR).
Is calculated (S37), and these current differences (DELL ・ D
By comparing the ELR) with the reference value K, it is determined whether the route gap is increased or decreased. That is, both current difference (DELL
It is determined whether or not (DELR) is greater than the reference value K (S38), and if both are determined to be greater, the current difference (DELL.DEL
It is recognized that R) has increased, and the weaving width is increased by a predetermined amount D.
The correction command signal (dw = -D) is formed so as to decrease (S39).

On the other hand, if it is determined in S38 that at least one is less than or equal to the reference value K, it is subsequently determined whether or not the current difference (DELL / DELR) is smaller than the reference value K. (S41). If both are determined to be small, it is recognized that the current difference (DELL / DELR) has decreased due to the increase in the root gap, and the correction command signal (dw = + D) to increase the weaving width by a predetermined amount D. Will be formed (S
42). If it is determined in S41 that at least one of them is small, it is recognized that the root gap has not changed, and the correction command signal (dw = 0) is formed so as to maintain the current weaving width. (S43).

The predetermined amount D for correcting the weaving width may be a constant value of about 0.1 mm to 1 mm, and the difference between the current difference (DELL / DELR) and the reference value K (DELR-K, It may be a value proportional to DELL-K). Generally, the predetermined amount D, which is a constant value, is effective when the change in the root gap is not so large, the welding current fluctuates largely under the welding conditions, and the copying control becomes relatively unstable and hunting may occur. Yes, proportional amount D
Is effective when the scanning control is relatively stable and the change in the root gap is large.

After this, as shown in FIG. 1, S39, S
42 and the correction command signal (d
After w = -D, + D or 0) is output to the attitude control unit 10 (S40), the reference value correction process is executed (S44).

When the reference value correction processing is executed, as shown in FIG. 12, it is judged whether or not the correction command signal dw is larger than "0" (the weaving width is increased) ( S51), if it is determined that the value is larger, a new reference value K obtained by subtracting the reference value correction amount dK (> 0) from the current reference value K is obtained. On the other hand, S51
If it is determined that the correction command signal dw is smaller than "0" (the weaving width is decreased), it is determined (S53). In this case, the reference value correction amount dK (> 0) is added to the current reference value K to obtain a new reference value K. If it is determined in S53 that the current reference value K is not smaller than the new reference value K.
(S55).

Thus, for example, when the weaving width is increased, the arc speed is set to the rear of the molten pool in order to decrease the welding speed V as shown in the extra height control process of FIG. 9 described above. In the prior art, when the variation of the root gap is detected, even if there is no variation, it is easy to detect the increase of the root gap, and it is difficult to make a correct determination. Is increased, the reference value K is decreased by a predetermined amount (reference value correction amount dK) to make it difficult to detect the increase of the root gap, so that the increase of the root gap can be correctly determined.

The reference value correction amount dK may be a constant value or a value proportional to the magnitude of the correction command signal dw. The initial value of the reference value K may be a preset value, or may be a value proportional to the difference between the reference weaving width W0 and the reference root gap G0 as shown in the following formula. Reference current value: K0 = α × (W0-G0) α: Constant according to welding conditions (A / mm)

As described above, in the groove width tracing method of this embodiment, as shown in FIG. 6, the root gap G1 at the welding start point P1 is detected, and the weaving width W1 corresponding to this root gap G1 is set. After that, the groove width is imitated.

As a result, even if the root gap G1 at the welding start point P1 is larger than the reference root gap G0, it is possible to prevent the deterioration of the welding quality in the region near the welding start point P1. .

Further, the groove width copying method of this embodiment is shown in FIG.
As shown in 2, while the reference value K used when detecting the increase / decrease of the root gap is corrected so that it is difficult to detect the increase of the root gap when the weaving width is increased (width positive correction). , When the weaving width is decreased (width negative correction), the increase of the root gap is corrected so as to be easily detected.

As a result, the reference value K is corrected so that it is difficult to detect the increase in the root gap when the weaving width is increased. Even if the root gap of No. 2 increases, the increase can be subtracted by correcting the reference value K, and as a result, it is possible to prevent deterioration of the welding quality in the region during welding. Further, even when the increase / decrease in the root gap becomes noticeable due to the thermal deformation of the work or a mistake in the temporary attachment, the increase / decrease in the root gap is detected based on the reference value K, and the groove width copying becomes unstable. Welding quality does not deteriorate.

In this embodiment, the correction command signal d
The reference value K is corrected by determining the increase or decrease of the weaving width based on w, but the invention is not limited to this. That is, as shown in FIG. 13 and FIG. 14, the welding speed V corrected so as to correspond to the increase or decrease of the weaving width W in the posture control unit 10 is taken in, and the welding speed V and the reference value K0 and the reference welding at the time of teaching are taken. Speed V0 and K = K
The reference value K may be corrected by substituting it into 0 × (V / V0).

[0041]

As described above, according to the first aspect of the present invention, the root gap at the welding start point is detected, the weaving width corresponding to the root gap is set, and then the weaving width is adjusted to increase or decrease the root gap. The groove width is controlled by performing the above control.

As a result, even if the root gap at the welding start point is larger than the assumed root gap, it is possible to prevent the deterioration of the welding quality in the region near the welding start point. .

According to the second aspect of the present invention, an increase / decrease in the root gap is detected by comparing the quantity of electricity during weaving with a reference value, and the weaving width is controlled so as to correspond to the increase / decrease in the root gap. The height is controlled to be constant, and the reference value is corrected so that it is difficult to detect the increase in the root gap when the weaving width is increased, while the reference value of the root gap is reduced when the weaving width is decreased. The configuration is such that the increase is easily detected.

As a result, the reference value is corrected so that it is difficult to detect the increase in the root gap when the weaving width is increased. Even if the root gap is increased, the increased amount can be subtracted by correcting the reference value, and as a result, it is possible to prevent the deterioration of the welding quality in the region during welding. further,
Even if the increase or decrease in the root gap becomes noticeable due to the work's thermal deformation or temporary attachment error, etc., the increase or decrease in the root gap is detected based on the reference value. It has the effect of not lowering.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a signal transmission timing between an attitude control unit and a copying control unit.

FIG. 2 is a block diagram of a control system that operates an arc welding robot.

FIG. 3 is a block diagram of an attitude control unit and a copying control unit.

FIG. 4 is an explanatory diagram showing a state of a work at the time of teaching,
(A) is an explanatory view of the whole and (b) is an explanatory view at a welding start point P1.

FIG. 5 is a flowchart of teaching operation processing.

FIG. 6 is an explanatory diagram showing a state of an actual work,
(A) is an explanatory view of the whole, (b) is an explanatory view at a welding start point P1, and (c) is an explanatory view at a welding end point P2.

FIG. 7 is an explanatory diagram showing the operation of the welding torch at the welding start point P1.

FIG. 8 is a flowchart of a robot control process.

FIG. 9 is a flowchart of a surplus height control process.

FIG. 10 is an explanatory diagram showing a state of a groove cross section.

FIG. 11 is a flowchart of a scanning control process.

FIG. 12 is a flowchart of reference value correction processing.

FIG. 13 is an explanatory diagram showing a signal transmission timing between the attitude control unit and the copying control unit.

FIG. 14 is a flowchart of reference value correction processing.

FIG. 15 is an explanatory view showing the locus of the welding electrode, (a)
Is a plan view and (b) is a front view.

16A and 16B are explanatory views showing the position of the welding torch when the welding speed is changed, FIG. 16A is a side view, FIG. 16B is a front view at the A position, and FIG. 16C is a front view at the B position. is there.

[Explanation of symbols]

 1 Arc Welding Robot 2 Robot Control Panel 3 Welding Torch 4 Welding Power Supply 5 Current Detector 6 Basic 7 Wire Feeding Motor 8 Welding Electrode 9 Workpiece 10 Attitude Control Section 11 Copy Control Section 12 Position Calculation Section 13 Servo Control Section 14 A / D Conversion unit 15 Copying calculation unit 16 Teaching data storage unit 17 Starting point gap sensing unit

Claims (2)

[Claims] 1. A root gap at a welding start point is detected, a weaving width corresponding to the root gap is set, and then the weaving width is controlled so as to correspond to an increase or decrease of the root gap, and a groove width is traced. A groove width copying method characterized by. 2. An increase / decrease in the root gap is detected by comparing the amount of electricity during weaving with a reference value, and the surplus height is made constant while controlling the weaving width so as to correspond to the increase / decrease in the root gap. In the groove width copying method to control, while the reference value is corrected so that it is difficult to detect an increase in the root gap when the weaving width is increased,
A groove width tracking method, wherein correction is performed so that an increase in the root gap can be easily detected when the weaving width is decreased.