JP3243390B2 - Groove width copying method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art When performing butt welding or fillet welding by arc welding, in order to form a flat weld metal and reduce internal defects, a welding electrode is usually weaved in a lateral direction with respect to a welding line. Weaving welding is performed while welding.

In the above-mentioned weaving welding, a welding start point, a welding end point, and welding conditions (for example, groove information such as a weaving width, a margin height, and a reference route gap) are previously taught to an arc welding robot. The teaching data is reproduced and operated by operating the arc welding robot.

[0004] The state of the groove varies depending on factors such as a variation in groove processing of the work, a variation in tacking accuracy, and thermal distortion during welding, and often does not match the groove information from the beginning or during welding. By simply reproducing groove information and performing weaving welding, it is not possible to stably obtain good welding quality with a constant extra height. Therefore, conventionally, as disclosed in Japanese Patent Application Laid-Open No. 61-293675, for example, 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. The weaving width is changed according to the fluctuation of the groove state by the tip width copying method.

[0005]

However, in the conventional groove width copying method described above, as shown in FIGS. 15A and 15B, the groove information at the welding start point is actually larger than the reference route gap G0 of the groove information. When the root gap G1 of the workpieces 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 is reduced. There is a problem that it becomes lower.

Further, when the weaving width is made to follow the root gap, there is another problem that the height of the extra portion related to the welding quality is reduced. Therefore, by adopting a method of controlling the welding speed in accordance with the fluctuation of the weaving width, it is possible to keep the extra height high.However, in this case, the change in the welding speed causes the detection of the root gap. , The groove width scanning control becomes unstable, and as a result, there is a problem that the welding quality is reduced in a region in the middle of welding.

That is, as shown in FIGS. 16 (a) to 16 (c), when the welding speed is reduced so as to prevent a decrease in the extra height when the weaving width W1 is increased, the arc point is increased. The welding torch 53 is located at the back of the pool and is A
A state exists from the position to the position B. Therefore, at the position B, the apparent root gap is increased, so that the weaving width W1 is further increased. In the worst case, the increase in the weaving width and the decrease in the welding speed are repeated. This causes the control of the welding electrode to diverge.

Therefore, Japanese Patent Application Laid-Open No. 5-245636 discloses an analysis of the relationship between the height of a margin and a root gap to identify a range in which a change in welding speed does not affect the detection of a root gap. A method for performing width scanning control is disclosed. However, in this case, there is a problem in that when the above-mentioned range is exceeded due to thermal deformation of the work, erroneous tacking, or the like, the groove width scanning becomes unstable and welding quality is deteriorated.

Accordingly, an object of the present invention is to provide a groove width copying method capable of preventing a decrease in welding quality.

[0010]

To solve SUMMARY OF to the above objects, a method copying groove width of claims 1, conductive during weaving
By comparing the air volume with the reference value, the route gap
Detect increase / decrease and respond to increase / decrease of the route gap
The height of the extra height is controlled while controlling the weaving width
The reference value increases the weaving width.
It seems difficult to detect an increase in route gap when it is increased
Is reduced while the weaving width is reduced.
It is easy to detect the increase of route gap when it is reduced
The correction is increased .

[0011]

According to the above arrangement, the reference value is corrected so that it is difficult to detect an increase in the root gap when the weaving width is increased. Therefore, the extra height is controlled to be constant. As a result, even when the apparent route gap increases, it is possible to subtract the increase by correcting the reference value, and as a result, it is possible to prevent a decrease in welding quality in a region in the middle of welding. Furthermore, even if the increase or decrease in the root gap becomes significant due to thermal deformation of the work or mistake in tacking, the increase or decrease in the root gap is detected based on the reference value, so the groove width scanning becomes unstable and welding is performed. There is no quality degradation.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the groove width scanning method according to the present embodiment is configured such that the arc welding robot 1 uses the robot control panel 2.
Is performed at the time of welding while being controlled by. The arc welding robot 1 is fixed to the foundation 6 and pivots around a vertical axis, a vertical arm that is provided on the pivot table, and swings in a vertical plane, and is provided at the tip of the vertical arm. It has a horizontal arm oscillating in the same vertical plane, and a wrist provided at the tip of the horizontal arm and holding the welding torch 3. An electrode 8 is provided.

As shown in FIG. 3, the robot control panel 2 has a posture control unit 10 and a copying control unit 11, and the posture control unit 10 has a teaching data storage unit 16 storing teaching data. A position calculator 12 for calculating 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.
And

On the other hand, the scanning control section 11 includes an A / D conversion section 14 for converting the welding current into a digital welding current value, and a weaving based on the welding current value and the weaving end signal from the position calculation section 12. And a scanning calculator 15 for transmitting a correction command signal to the position calculator 12 so as to change the width to an appropriate width. Thereby, as shown in FIG.
After making the weaving width correspond to the root gap of the welding start point, the robot control panel 2 changes the posture of the arc welding robot 1 while changing the weaving width to an appropriate weaving width according to the root gap from the welding start point to the welding end point. And the position is controlled to perform welding.

In the above configuration, a method of following the groove width through the operation of the arc welding robot 1 will be described.

First, a description will be given of a teaching operation on the assumption that the workpiece 9 shown in FIGS. 4A and 4B is welded. As shown in FIG. 5, the arc welding robot 1 is operated by the teaching pendant.
Is operated, the welding electrode 8 is moved to the welding start point P.
1 and this position is stored (S
1). Thereafter, welding conditions such as current / voltage, reference welding speed V0, weaving frequency, reference weaving width W0, reference root gap G0, extra 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, an 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 root gap wider than the same reference route gap G0 as the work assumed at the time of teaching from the welding start point P1 to the welding end point P2. It is assumed that G1 is tapered to a root gap G2.

First, as shown in FIG.
Starting point gap sensing unit 17 and position calculating unit 1
By executing the robot control process in 2, the start 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. By moving in parallel in the directions A and B until they come into contact with each other, the moving distance GU is obtained. Then, the moving distance GU and the height distance D are G = GU−2Dta.
By substituting into nθ, the root gap G1 at the welding start point P1 is determined (S
8).

Thereafter, a gap difference dwo between the root gap G1 and the reference root gap G0 is obtained (S9). This gap difference dwo is 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 at the welding start point P1. At the same time, the welding speed V is corrected to the welding speed V corresponding to the root gap G1 by the surplus height control processing described later (S10).

Next, when the weaving operation is started with the above-described weaving width W1 and welding speed V, it is determined whether or not the welding electrode 8 is positioned 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 the 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 is located at the end, as shown in FIG. 1, the weaving end indicating whether the end 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). Thereafter, when the correction command signal dw from the copying control unit 11 is received (S13), the correction command signal dw
By substituting the data content of w into W = W1 + Σdw, it is updated to the weaving width W (S
14).

Next, a margin height control process is executed, and the welding speed V is corrected to the welding speed V corresponding to the current route gap G (S15). Specifically, as shown in FIG. 9, the weaving width W · W1 and the root gap G1
Is substituted into G = G1 + (W−W1),
The current route gap G is calculated (S2
1). Thereafter, as shown in FIG.
The cross-sectional area S of the groove formed by the root gap G is calculated using the height of the bulge H, and the groove angle θ (S22).
This sectional area S and the reference sectional area S0 of the groove assumed at the time of teaching are described.
And the reference welding speed V0 are substituted into V = V0 × (S0 / S), and the new welding speed V is corrected (S2).
3). Thereby, as the route gap G increases, the cross-sectional area S of the groove increases, so that the corrected welding speed V decreases.

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

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

That is, in the copying calculation unit 15, FIG.
As shown in (1), it is determined whether or not the weaving end signal has been received (S31), and S31 is repeatedly executed until it is determined that the signal has been 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). 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, and 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 vehicle is moving 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).

Thereafter, it is determined whether or not the half cycle has ended based on the presence or absence of the input of the weaving end signal.
Are repeatedly executed. Thereby, S3
5, when the end of the half cycle is confirmed, if the weaving operation is to the right end, the current value IR1 at the right end
And the minimum value IR2 during the half cycle is detected, while in the case of the weaving operation toward the left end, the current value IL1 at the left end and the current value IL2 during the half cycle are detected (S35). ). Thereafter, it is determined whether or not it is the first half cycle, and if it is the first half cycle,
The processing is executed again from S31 described above (S36).

On the other hand, if it is not the first half cycle, the left and right current values IL1, IL2, IR1, and IR2 are aligned, so that the respective current differences (DELL and DELR) are obtained.
Is calculated (S37), and these current differences (DELL · D
ELR) is compared with the reference value K to determine the increase or decrease of the route gap. That is, both current differences (DELL
(DELR) is larger than the reference value K (S38), and if both are larger, the current difference (DELL · DEL) is reduced due to the decrease of the root gap.
R) is recognized to have increased, and the weaving width is increased by a predetermined amount D
A correction command signal (dw = -D) is formed so as to decrease the value (S39).

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

Incidentally, 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 (DELR-K, difference between the current difference (DELL / DELR) and the reference value K). DELL-K). In general, the predetermined amount D, which is a constant value, is effective when the root gap does not change so much, the welding current fluctuates greatly due to welding conditions, and the scanning control becomes relatively unstable and hunting may occur. Yes, proportional predetermined amount D
Is effective when the scanning control is relatively stable and the root gap changes greatly.

Thereafter, as shown in FIG.
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 processing is executed (S44).

When the reference value correction processing is executed, as shown in FIG. 12, it is determined whether or not the correction command signal dw is larger than "0" (weaving width is increased) (see FIG. 12). S51) If it is determined to be larger, a new reference value K is obtained by subtracting the reference value correction amount dK (> 0) from the current reference value K. On the other hand, S51
If it is determined that the correction command signal dw is not large, it is determined whether the correction command signal dw is smaller than “0” (weaving width is reduced) (S53), and it is determined that the correction command signal dw is small In this case, a new reference value K is obtained by adding the reference value correction amount dK (> 0) to the current reference value K. If it is determined in S53 that the current reference value K is not smaller, the current reference value K is changed to the new reference value K.
(S55).

Thus, for example, when the weaving width is increased, as shown in the surplus height control processing of FIG. 9, the arc point is located behind the molten pool in order to decrease the welding speed V. Conventionally, when detecting a change in the root gap, the increase in the root gap is easy to detect even if there is no change, and it is difficult to make a correct determination. Since the reference value K is decreased by a predetermined amount (reference value correction amount dK) when the increase in the distance makes it difficult to detect the increase in the root gap, it is possible to correctly determine the increase in the root gap.

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

As described above, in the groove width scanning method of the present 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 the root gap G1 is determined. Later, groove width copying is performed.

Thus, 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 a decrease in welding quality in a region near the welding start point P1. .

The groove width copying method of the present embodiment is shown in FIG.
As shown in FIG. 2, the reference value K used for 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 (correction of the width). When the weaving width is reduced (negative width correction), the correction is made so that the increase in the root gap can be easily detected.

Thus, the reference value K is corrected so that it is difficult to detect an increase in the root gap when the weaving width is increased. Even if the root gap increases, it is possible to subtract this increase by correcting the reference value K, and as a result, it is possible to prevent a decrease in welding quality in a region in the middle of welding. Further, even if the increase or decrease of the root gap becomes remarkable due to thermal deformation of the work or a mistake in tacking, the increase or decrease of the root gap is detected based on the reference value K, so that the groove width scanning becomes unstable. There is no deterioration in welding quality.

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 FIGS. 13 and 14, the welding speed V corrected by the posture control unit 10 so as to correspond to the increase or decrease of the weaving width W is taken in, and the welding speed V, the reference value K0 at the time of teaching and the reference welding Speed V0 and K = K
The reference value K may be corrected by substituting it into 0 × (V / V0).

[0039]

The invention of claim 1 according to the present invention, as described above, Wie
By comparing the amount of electricity at the time of
Detect the increase or decrease in the root gap, and
Margin while controlling the weaving width to correspond to
The height is controlled to be constant.
Increase the root gap when increasing the
While the correction is reduced so that it is hard to detect,
Increase the root gap when the
In this configuration, the correction is increased so as to be easily detected .

[0040] This ensures that, because adapted reference value as hard detection is corrected in increased root gap when increased c Ibingu width, controlling the excess prime height constant Thus, even if the apparent root gap increases, the increase can be subtracted by correcting the reference value, and as a result, it is possible to prevent a decrease in welding quality in a region in the middle of welding. further,
Even if the increase or decrease of the root gap becomes noticeable due to thermal deformation of the work or incorrect tacking, etc., the increase or decrease of the root gap is detected based on the reference value, so that the groove width tracing becomes unstable and the welding quality becomes poor. There is an effect that it does not decrease.

[Brief description of the 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 the arc welding robot.

FIG. 3 is a block diagram of a posture 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 diagram of the whole, and (b) is an explanatory diagram at a welding start point P1.

FIG. 5 is a flowchart of a teaching operation process.

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

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

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

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

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

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

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

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc welding robot 2 Robot control board 3 Welding torch 4 Welding power supply 5 Current detector 6 Foundation 7 Wire feed motor 8 Welding electrode 9 Work 10 Attitude control unit 11 Copying control unit 12 Position calculation unit 13 Servo control unit 14 A / D Conversion unit 15 Tracking calculation unit 16 Teaching data storage unit 17 Start point gap sensing unit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 9/12 B23K 9/095 B23K 9/127

Claims (1)

(57) [Claims] 1. An increase / decrease in a root gap is detected by comparing a quantity of electricity at the time of weaving with a reference value, and a margin height is kept constant while controlling a weaving width so as to correspond to the increase / decrease in the root gap. In the groove width scanning method to be controlled, while the reference value is corrected so that the increase in the root gap is hardly detected when the weaving width is increased, the root value is reduced when the weaving width is reduced. A groove width tracing method, wherein a correction is increased so as to easily detect an increase in a gap.