JPH0318478A - Method for controlling weld line profile - Google Patents

Abstract

PURPOSE:To perform just enough weaving welding and to improve welding quality by obtaining the position of a next weaving end point at an n-th weaving end point. CONSTITUTION:A welding current and the welding voltage at the position in the vicinity of the weaving end point are obtained as reference values. The welding current and the welding voltage in the vicinity of the n-th (n>=2) weaving end point are then measured and the weaving width from an (n-1)th weaving end point to the n-th weaving end point is corrected based on the difference between the measured values and the reference values. Based on the corrected weaving width, the (n+1)th weaving end point position is then obtained and weaving welding from the n-th weaving end point to the (n+1)th weaving end point is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a welding line tracing control method, and particularly to a welding line tracing control method when causing a welding robot to perform weaving welding.

(Conventional technology and its issues) One of the important functions of welding robots is weaving welding. As is well known, this weaving welding involves swinging the welding torch in a direction approximately perpendicular to the welding line.
This is a welding method in which the weld is moved along the weld line.

By the way, the work to be welded (in this specification, "
The two welded bodies to be welded to each other are expressed as "first" and "second", respectively. ), the butt interval between the first and second objects to be welded, the groove width, etc. (this In the specification, these are collectively referred to as the "mutual spacing" of the objects to be welded), which are often non-uniform in the weld line direction. Therefore, even though the mutual spacing is uneven as described above, if welding is performed while keeping the swing width of the welding torch, that is, the weaving width, constant, over- or under-welding may occur depending on the location. Welding quality will be significantly reduced.

In order to solve this problem, we developed a welding line tracing control method that automatically responds to changes in the mutual spacing during weaving welding and can always perform good welding.
For example, Japanese Patent Application Laid-open No. 62-254979 has been proposed.

According to these proposed examples, welding voltage and welding current are simultaneously measured while weaving welding, and weaving end points are detected based on changes in the welding voltage and the like. For example, if the arc of a welding torch is controlled at a constant voltage, the current flowing through the welding torch during welding, that is, the welding current, is
It decreases as the distance between the tip of the welding torch and the groove surface widens, and conversely increases as the distance narrows.

Therefore, the welding current was continuously set at a total of 71 pI L, so
The position where the current suddenly changes is determined and determined to be the weaving end point.

However, in the above proposed example, as explained below, welding that always maintains a constant welding height even when the groove width changes (hereinafter referred to as "constant welding height control") is performed well. The problem is that it cannot be done. Generally, it is known that the amount of welding wire melted per unit time is proportional to the welding wire feeding speed. In other words, when a power source with constant voltage characteristics is used, such as in conventional consumable electrode type shielded welding, when the welding wire feed speed is increased, the amount of welding wire melted per unit time is increased in order to maintain a constant arc voltage. becomes larger, and as a result, the welding current increases. Conversely, when the welding wire feed speed is decreased, the amount of welding wire melted per unit time decreases in order to maintain a constant arc voltage, and as a result, the welding current decreases.

Therefore, two methods can be considered for controlling the welding height to be constant. The first method is a method of changing the welding wire feed speed according to the groove width while keeping the welding progress speed constant. When controlling the welding height to be constant using this method, the welding current changes greatly as the welding wire feed speed changes, and defects such as poor penetration are likely to occur.

On the other hand, the second method is a method of changing the welding progress speed according to the groove width while keeping the welding wire feeding speed constant (keeping the melting amount per unit time constant). In carrying out the second method, it is necessary to know at least the position of the next weaving end point relative to the current position of the welding torch in order to perform speed control. However, in the proposed example, the next weaving end point is detected while the weaving operation is being performed, so it is impossible to perform constant welding height control using the second method.

(Objective of the Invention) An object of the present invention is to solve the problems of the prior art described above, and to ensure that even when the mutual spacing between objects to be welded is uneven along the welding line direction, the welding material can be welded with just the right amount or too little. To provide a welding line tracing control method capable of performing welding welding and excellently controlling the welding height to be constant while keeping the welding wire feed rate constant.

(Means for achieving the object) The present invention is a welding line tracing control method for weaving welding a first and a second welded object along a welding line based on teaching data given prior to welding. Therefore, in order to achieve the above object, the welding current and/or welding voltage at a position near the weaving end point is determined as a reference value, and the welding current and/or welding voltage at a position near the nth (n≧2) weaving end point is further determined. After each actual measurement value δII L, the nth
The weaving width up to the weaving end point is corrected, and based on the corrected weaving width, the (nth
+1)th weaving end point position is determined, and weaving welding is performed from the nth weaving end point to the (n+1)th weaving end point.

(Example) FIG. 1 is an overall schematic diagram of an (x, y, z) rectangular coordinate system welding robot RO employed as a welding robot that forms the background of the present invention.

A vertical shaft 1 formed at the terminal of this welding robot RO (details not shown) supports a first arm 2 so as to be pivotable around the shaft 1 (in the direction of arrow α).

Further, a second arm 3 is provided at the tip of the first arm 2 and supported so as to be pivotable around a diagonal link 3a (in the direction of arrow β).

A welding torch 4 (an MIG welding torch in this embodiment) as an end effector is attached to the tip of the second arm 3.

The central axes of the shaft 1, the support 3a, and the torch 4 are at one point P.
It is constructed so that it intersects at.

Furthermore, the torch 4 is set so that its welding operating point can coincide with the point P. In such a structure, by controlling the rotation angle in the directions of arrows α and β, the torch 4
The attitude angle θ and the turning angle ψ (so-called Euler angle) with respect to the vertical axis 1 can be controlled by fixing the point P.

Device 5 is a welding power supply device. This device 5 includes a torch 4
A spool 6 winding up a consumable electrode (welding wire) 4a of
Although details are not shown, the electrode 4a can be drawn out by rotating a feed roller, and a welding power source 5a can be connected between the electrode 4a and the workpiece WK. The welding power source 5a is equipped with an energization state detector (current sensor).
5e are connected in series. The device 5 also includes a detection power source 5b. The detection power supply 5b is limited to a voltage of approximately 100 to 2000 V and a current limited to a small current, for example. An energization state detector (current sensor) 5c is connected in series to the detection power supply 5b, and 1! The source 5a and the current sensor 5e can be switched by a switching means 5d.

A known computer 7 serving as a control device for the entire embodiment includes a CPU and a memory, and a bus line B of this computer 7 is connected to current sensors 5c, 5e and switching means 5d.

The bus line B is further connected to an X-axis servo system Sx of the robot RO, and this servo system SX includes an X-axis power MX and an encoder EX that outputs its position information. Similarly, a similarly constructed Y-axis servo system SY, Z-axis servo system SZ, α-axis servo system Sα, and β-axis servo system Sβ are connected to the bus line B.

Further, a remote control panel 8 is connected to the bus line B.

This operation panel 8 has numbers "0" to "9" keys as well as
It is equipped with a group of keys for inputting various information assigned in advance, and a display 8a for displaying necessary messages and information according to key operations so that teaching work can be performed in an interactive manner. has been done.

A predetermined procedure for teaching, which will be described later, is preprogrammed in the memory of the computer 7, and the computer 7 controls the display 8a based on this program and the operator's key operations. In addition, soft label selection keys are used so that functions can be easily added or deleted without changing the number of keys. Ru. Which key is to be used is determined by the computer 7 according to the pre-programmed procedure described above, and is clearly indicated to the operator on the display 8a. That is, for example, when the above-mentioned predetermined processing procedure comes to a soft label selection procedure and a soft key label is displayed on the display 8a, it is used as a soft label selection key, and the cursor is displayed on the display 8a instead of a soft key label. For example, if it is blinking, it can be used as a numerical key.

The data taught by the operator is stored in the memory of the computer 7 as a user program, and when welding is performed, the computer 7 controls the welding robot according to this user program.

On the other hand, as shown in FIG. 1, the workpiece WK in this embodiment is two horizontal plates Wl and W2 serving as first and second objects to be welded, each provided with grooves Bl and B2, respectively. It is assumed that these horizontal plates Wl and W2 are butted and welded. However, as shown in the same figure and Figure 2, the spacing between the butts is uneven for some reason, and although they touch each other at the lower end in the figure, they open slightly upward (distantly). It is assumed that it is stored away. Note that FIG. 2 shows a state in which the groove portion of the workpiece WK in FIG. 1 is viewed from above.

Next, the processing in the embodiment of the present invention will be explained, focusing on the parts related to the features of the present invention.

Of these, the first process is teaching, and in addition to the above Figure 1, the second process shows the positional relationship of teaching points, etc.
The explanation will be made with reference to the figure and FIG. 3 showing the steps of the program. The teaching process is proceeded by the operator operating the numeric keys on the operation panel 8 in accordance with messages displayed on the display 8a, as described below.

(1) First, when this device is powered on, an initial screen (not shown) is displayed on the display 8a according to a program previously stored in the memory of the computer 7. After seeing this screen, the operator selects manual mode M from among the three modes (manual mode M, test mode TE, and auto mode A) by operating the numeric keys from "0" to "9". select. Correspondingly, a message appears on the display 8a prompting you to set the moving speed V, Vo of the torch 4 in manual mode and auto mode, and to select either linear interpolation rLJ or circular interpolation "C". messages are displayed respectively. In accordance with this message, the operator operates the numeric keypad numbers "0" to "9" to store the moving speed V in the memory of the computer 7, as well as the moving speed V. and linear interpolation rLJ are set respectively. After that, by operating the key group corresponding to the operation of each part of the welding robot RO (hereinafter referred to as "operate key group 8bJ"), the electrode outlet end of the torch 4 is moved to the surface G of a certain conductor. Move the computer 7 to the position of the dimension (the Po position indicated by the one-dot chain line in Fig. 1). Then, by operating the "teach" key 8C, the computer 7 moves to the point Po.
Orthogonal information (X, Y, Z, θ. and ψ.), 0
0 0 Linear interpolation rLJ and velocity V. Each piece of information is imported as the content of the first step of the program. Note that the movement of the torch 4 to point Po is point P. The position information may be stored in the computer 7 in advance and called up to automatically control the position.

(2) Next, according to the message displayed on the display 8a, the operator selects "0" to "9".
Operate the numeric keys to set the sensing command "S", and then select the sensor menu number S E M No. Select "9" as the And "Teach" key 8C
If you operate , you will get to point P. location information, sensing rsJ and SEM No. r99J is imported as data regarding Step Demon 2.

At the same time, the computer 7 has SEM No. A command is output by r99J, the switching means 5d is switched (solid line shown), and electricity i4a is output. When the tip of the protruded electrode 4a comes into electrical contact with the surface G, the circuit is closed and a detection signal is output from the sensor 5C. Upon receiving this, the computer 7 stops protruding the electrode 4a (this process is (referred to as extension alignment). In this state, torch 4
In contrast, the welding operating point is the tip position of the electrode 4a. Then, the switching means 5d is returned to its original state.

(3> Next, operate the operation key group 8b to move the torch 4 to the first sensing start point P near the welding start point P4.
Move it to 1. And menu number SEMNa. r9
Clear 9J and set the linear interpolation rLJ by operating the numeric keys "0" to "9". Then, by operating the "teach" key 80, the position information of point P1, the linear interpolation "L"
”, and the speed Vo is the step No. It is taken in as information regarding 3.

<4) Next, according to the message displayed on the display 8a, the operator selects "0" to "9".
Operate the numeric keys to set the sensing command "S" and further set SEMN (L to "01").

When the "teach" key 8c is operated, the computer 7 takes in the sensing information by the SEMkrOIJ as data regarding step Nll4. This sensing will be described later.

(5> Operate the operation key group 8b to set the torch 4
is positioned at an arbitrary point P2 close to the welding start point P3. Next, linear interpolation rLJ is set by operating the numeric keys "0" to "9". Then, by operating the "teach" key 8C, the computer 7 transfers the position information of point P2 and the information of linear interpolation rLJ to step No. Import as data related to 5.

(8) Next, by operating the operation key group 8b, the torch 4 is positioned at the welding start point P3 in a posture suitable for welding. Then, arc sensing rAJ, SS EMNo. Select r01J, welding condition "01" and correction method "98". Of these, “01” indicates the welding conditions.
” is a number set in accordance with conditions suitable for weaving. Also, arc sensing rA
By setting J and the correction method "98" to S, it means that it is taught that the subsequent welding will be performed in the amplitude variable weaving mode using arc sensing. SEM No. rOIJ
means that the position of point P3 and the amplitude of the first cycle of weaving are corrected by the correction amount based on the above-mentioned first point sensing result when processing is executed. Through these operations, data regarding step N (L6) has been input.

(7) Position the torch 4 at an arbitrary intermediate point P4 (referred to as a dummy point) by operating the operation key group 8b. Next, set arc sensing rAJ, SEMS N housing r01J, FN range "7", and correction method "02" using the number entry keys "O" to "9". Among these, FNo. r7J is the designation of a dummy point, and the correction method "02" is the designation of a downward fillet as the weld joint shape. Then, when the "teach" key 8c is operated, the computer 7 displays the position information of the dummy point P4, the arc sensing "AS", and the SEM No. ro iJ, FN
o. r7J and correction method "02" in step NO. 7
Import as data regarding.

(8) By operating the operation key group 8b, the torch 4 is positioned at the welding end point P5 in a posture suitable for welding. Next, arc sensing "A" and S correction method "98" are selected using the numerical input keys "0" to "9". The meanings of the arc sensing rAJ and the setting S of the correction method "98" are as described above. Then, by operating the "teach" key 8C, the computer 7 transmits the position information of the welding end point P5, the arc sensing "A", and the correction method "98" to step NQ. Import as data related to 8S.

(9) Finally, by operating the operation key group 8b,
The torch 4 is positioned at an arbitrary retreat point P6 that can be moved linearly from the welding end point P5. Next, by operating the "teach" key 8C after setting the linear interpolation rLJ using the numeric keys from rOJ to "9", the position information of the point P6 and the linear interpolation rLJ are taken in as data regarding step k9.

This completes the teaching. Next, the operator
” to “9” to switch from manual mode M to test mode TE, and then operate the “Start” key 8d, the welding robot RO performs the same operation as the welding operation described later. Execute without doing. The operator monitors the operation and corrects any errors in the data during teaching.

As described above, teaching and correction of the data are completed, and preparations for welding are completed.

When actually welding, the operator operates the operation key group 8b to newly position the torch 4, and then operates the number entry keys "0" to "9" to switch from test mode TE to auto mode. Switch to mode A and operate the "start" key 8d.

In response to this, various command signals are output from the computer 7, and welding is performed by the welding robot RO main body. Here, prior to explaining the actual weaving welding operation, the processing executed by the computer 7 and the operation of the welding robot RO main body based on the command output from the computer 7 will be explained below with reference to the flowchart in FIG. 4. do.

First, in process 101, the computer 7 determines whether the step in question (the corresponding step in FIG. 3) is sensing rSJ, and if YES, the process proceeds to process 102, and if NO, proceeds to process 103. In process 103, it is determined whether the step in question is arc sensing rAJ. If YES, the process proceeds to process 104, and if No, the process proceeds to process 105. In processing 105, sensing rSJ
Processing other than arc sensing rA J is executed, but if you follow the programming (teaching) content shown in Figure 3, will it be possible to do this directly? Interpolation rLJ
Movement of the torch 4 by (step N (L1, 3, 5.9
) is executed.

In process 102, SEM No. It is determined whether or not is "99". If YES, process 106;
When the answer is No, the process proceeds to process 107. In process 106, extension alignment is performed, and the protruding length of the electrode 4a of the torch 4 is regulated to a predetermined length 1. On the other hand, in process 107, sensing is executed. That is, first, the switching means 5
d is switched to the side of the current sensor 5C, and then the torch 4
Sensing is performed using electrical contact between the tip of the electrode 4a and the workpiece WK. For example, the torch 4 is swung horizontally from the first sensing starting point P1 (horizontal direction in FIG. 2), and the point of contact with the horizontal plate W1 on the left (assumed SP1) and the point of contact with the horizontal plate W2 on the right The position information of (SP1■) is imported. Then, the computer 7 calculates the rainwater 1l, the mutual distance D between the flat plate materials Wl and W2, and the information included in the welding condition "01" of the midpoint P of these l2° based on the above-mentioned captured position information of SP and SP 12. calculate the difference ΔP from the position information of point P, and 1
1 and the amplitude information included in welding condition "01". Sensing position information ΔP, sensor 12
t-sing amplitude information ΔDl2
are SEMNQ. It is stored as data related to 01. Then, in process 108 following process 107, sensing position information ΔP and sensing amplitude information Δt D1 obtained in this way are obtained. Correct the teaching data. That is, SEMN (34 position information of the designated point P.P of LOI is corrected by the sensing position information ΔP1, and the amplitude information of the first cycle of weaving is corrected by the sensing amplitude information ΔD12. This sensing correction is This is effective for correcting individual differences in objects to be welded and individual installation errors.

When the determination in process 104 is YES, process 109, N
When o, the process proceeds to process 110. In process 110, normal arc sensing is executed. On the other hand, in process 109, variable amplitude weaving using arc sensing according to the present invention is executed. Note that this will be explained in detail later.

Above processing 105, 106, 108, 109 or 110
When the step is completed, it is determined in process 111 whether or not the step is the final step. If it is the final step, the series of processes is completed, but if it is not the final step, the step is updated in process 112, and the process returns to process 101 to repeat the above-described process.

Next, the actual weaving welding operation performed according to the flowchart of FIG. 4 based on the teaching of FIG. 3 will be explained in order. When the step data shown in FIG. 3 is applied to the above-described processing flow, the tip of the torch 4 follows the trajectory F (excluding the sensing portion) shown in FIG. 2. That is, the tip of the torch 4 is
Step No. Point P according to the data of 1. (FIG. 1), and then the above-mentioned extension alignment is executed based on the data in step NllL2.

Next, the tip of the torch 4 is placed at step No. The sensor moves to the first sensing start point Pl by linear interpolation according to the data in step Na4, and the above-described sensing is executed there based on the data in step Na4.

Next, the tip of the torch 4 moves to point P2 according to the data in step lll[L5, and then steps! llo. 6
It moves to point P3 by linear interpolation according to the data. From point P3, welding is started based on the data from steps 6 to 8, and weaving welding is performed while changing the amplitude as described later, following the change in the mutual spacing of horizontal plates Wl and W2 in the welding line direction. Let's do it. Point P4 is Fl
Since the dummy point is designated by lla r7J, the torch 4 is advanced ignoring this point. In this way, the tip of the torch 4 performs weaving welding while gradually increasing the amplitude in FIG. Move by interpolation and complete a series of welding processes.

Next, arc sensing performed in the process 109 will be described in detail with reference to FIG. 5. FIG. 5 is a flowchart showing the amplitude varying method in this case. First, in response to a command from the computer 7, welding is performed from the welding start point P3 toward the first weaving end point W P t (process 201). At this time, weaving welding is performed based on the teaching data corrected in process 108. Then, it is confirmed that the torch 4 has reached the first weaving end point WP1 (
In step 202), the computer 7 samples the welding current measured by the current sensor 5e in FIG. 1 in the vicinity of the first weaving end point WP1 within a certain period of time, and obtains an integral welding current l1 corresponding to the added value. (Processing 203)
, stores the current value I1 in its memory. Here, the reason for determining the integral value of the welding current is that even if the value measured at the weaving end point WP1 contains errors such as noise, it can be calculated by integrating the current value actually measured near that end point WP1. This is to reduce the influence of noise.

Next, the advancing direction of the torch 4 is changed to the opposite direction, and welding is performed from the first weaving end point WPl to the second weaving end point WP2 in accordance with a command from the computer 7 (process 204).

Weaving welding at this time is performed based on the corrected teaching data, similar to process 201. Then, when it is confirmed that the torch 4 has reached the second weaving end point WP2 (process 205), the computer 7 performs the welding process near the second weaving end point WP2 measured by the current sensor 5e, similarly to the above. Integrate the current to obtain the integrated welding current I2 (process 206), and calculate the value l2
is stored in memory. Note that the welding up to this point has been performed based on the data corrected in process 108, so the positions of the torch l2 4 and the horizontal plates Wl, W2 at the first and second weaving end points wp, wp are The relationship is always shown in Figure 6 (a
), and good welding can be obtained.

Next, the computer 7 reads the integrated welding current 1 from the memory.
, I and 12 reference current I according to the following formula. is obtained (process 207) and stored in the memory of the computer 7.

1 - (1, +12)/2 ... (1
)O Let us now consider the meaning of the reference current lo.

As can be seen from the above description, at the first and second weaving end points WPl and WP2, as shown in FIG. 6(a), the torch 4 and the welded objects W1 and W2 are in a good positional relationship, The integral welding current at that time is the current ■l. '! 2, so if the integrated welding current l near a certain weaving end point is the average value of the current 1.12, the reference current! . and the same value l, then the torch 4 and the welded object Wl,
It can be said that there is a good relationship with W2 (Fig. 6(a)).

Also, the integral welding current l is the reference current! .

This means that if the value is smaller than (1<!.)
It can be seen that the torch 4 is very far away from the objects to be welded Wl, W2 (FIG. 6(b)). On the contrary, the reference current! .

This means that (1 > Io
), the torch 4 is connected to the object to be welded W1. It can be seen that the welding current is very close to W2 (Fig. 6 (C)). In other words, the integral value of the welding current that is actually δll1 near the weaving end point (
Integral welding current ■) and reference current I. The positional relationship between the toe sen4 and the objects to be welded Wl, W2 can be derived from the size relationship between the two.

Therefore, in process 208, the amount of deviation of the torch 4 at the weaving end point (hereinafter referred to as "correction amount Δ") is determined from the following equation.

...(2) However, dl-(io-1n) I0: Actual +1P at the n-th weaving end point wp + welding current n: Natural number kl: Constant Note that in this example, the correction amount Δ is approximated by equation (2). However,
It is not limited to this. Also, from various experiments,
(2> Instead of formula (2), the correction amount Δ is calculated using the first-order approximation of formula (2).
It has been verified that sufficient accuracy can be obtained even when calculating .

When the correction amount Δ is determined, the correction amount Δ is added to the weaving width in step 204, and the weaving width of the next welding (welding from the second weaving end point WP2 to the third weaving end point WP3) is determined. Corrected. For example, as shown in FIG. 7, the welding from the first weaving end point WPl to the second weaving end point WP2 (solid line in FIG. 7) has a weaving width L. 12 is executed based on the pitch p, and when the correction amount Δ (positive value) is found in process 208, the weaving width L23 is found in the computer 7 according to the following equation.

L23''=''12+Δ Furthermore, the position of the third weaving end point W P 3 is determined geometrically based on the weaving width L23 and the pitch p.

Then, welding (dotted line in FIG. 7) from the second weaving end point WP2 to the third weaving end point WP3 is performed according to this position data (process 209).

Then, when it is confirmed that the torch 4 has reached the third weaving end point WP3 (process 210), the third weaving end point WP determined by δp1 by the current sensor 5e
The integrated welding current I3 is obtained by integrating the welding current near 3 (process 211). Then, in the same manner as the above process 208, a correction amount Δ is obtained (process 212), and the correction amount Δ is added to the weaving width in process 209, and the next welding (from the third weaving end point WP3 to the fourth The weaving width of welding to the weaving end point W P 4 is corrected. Then, the position of the next weaving end point WP4 is determined based on the width, and welding is performed toward the next weaving end point WP4 (process 213).

The above processes 210 to 213 are executed until the torch 4 reaches the final weaving end point WP (process 2l4) e . In addition, the final weaving end point WP
Welding from to welding end point P5 is performed based on the teaching data corrected in process 1e08.

As mentioned above, in this embodiment, the position of the next weaving end point with respect to the current position of the welding torch 4 is always known (for example, if the current position of the welding torch 4 is the second weaving end point WP2, (the position of the third weaving end point W P s is obtained), it is possible to appropriately control the moving speed of the welding torch 4 during welding from the current position to the next weaving end point (i.e. welding progress speed). It's easy. Therefore, by controlling the welding progress speed while keeping the welding wire feeding speed constant (keeping the melting amount of the consumable electrode (welding wire) 4a constant per unit time), welding height can be controlled to be constant. can be done. Furthermore, as described above, since the positions of all weaving end points are known, the weaving amplitude can be correctly changed to follow the change in the mutual spacing between the horizontal plates Wl and W2 in the welding line direction.

Therefore, even if the mutual spacing between the objects to be welded is uneven along the welding line direction, weaving welding can be performed without excess or deficiency.

Furthermore, the integrated welding current corresponds to the sum of the welding currents sampled within a certain period of time near the weaving end points! , I , I , . . . 123 and the positional information of the weaving end point is determined based on these values. This prevents erroneous detection of the weaving end point due to noise, etc., and enables accurate welding. However, if it is not necessary to take into account the influence of disturbances such as noise, it is not necessary to use an integrated welding current for determining the reference current (■), but instead use the welding current sampled at the weaving end point. May be used directly.

In the above embodiment, the reference current I is based on the integral welding current I1, (2). was calculated (process 2027), but the reference current I. The settings are not limited to this. For example, the integral welding current ■ is the reference current I. It is also possible to do 1. Also, the reference current I. was determined by a simple average of the integral welding current of 1.12, but a weighted average or the like may also be used. Also, the integral welding current ■ is the reference current I. It may be set to

2 Furthermore, since it is possible to have the reference current independently at the left and right ends of the weaving, it is also applicable to asymmetrical joints such as a rectangular groove. While welding from point P3 to second weaving end point WP2 is performed based on the teaching data corrected in process 108, in welding from second weaving end point WP2 to welding end point P5, the correction amount Δ is first Find (processing 208, 212),
Based on this, the next weaving width is corrected, and the position of the next weaving end point is determined based on the width, and then welding is performed. In the present invention, the present invention is not limited to the above embodiment, and the welding start point P3 to the first weaving end point W
Welding up to P t is performed by the former (process 108),
The integral welding current ■ is the reference current I. However, welding from the first weaving end point WP1 to the welding end point P5 may be performed by the latter method. Also, a welding from the welding start point P3 to the m-th weaving end point WP (where m≧3) is performed by the former, while welding from the m-th weaving end point WP to the welding end point P5 is performed by the latter. It may also be done by.

In addition, in the above embodiment, as shown in FIGS. 1 and 2, we considered a change in which the mutual spacing becomes uniform as it goes forward, but for example, as shown in FIG. 8, the mutual spacing becomes uneven. The present invention can also be applied to workpieces that change.

It is also applicable to works other than horizontal plates.

Further, in the above embodiment, the correction amount Δ was determined by focusing on the welding current, but it goes without saying that the correction amount Δ may be determined based on the welding voltage instead of the welding current. Furthermore, the welding current and welding voltage may be measured simultaneously and the correction amount Δ may be determined from these.

Further, in the above embodiments, the present invention is applied to single-layer welding, but it can also be applied to multi-layer welding. For example, while weaving welding the first layer as described above, the position data of each weaving end point is stored in the memory of the computer 7, and when weaving welding the second and subsequent layers, the data stored in the memory is used. It may also be done based on this. In this case as well, the same effect as above can be obtained.

(Effect of the invention) As explained above, according to this invention, the nth (n
≧2) Since the position of the next weaving end point, that is, the (n+1)th weaving end point, can be found at the weaving end point of Even if welding occurs, it is possible to perform weaving welding with just the right amount of welding, thereby ensuring high quality welding accuracy. Also, the (n
+1. ) based on the position data of the weaving end point, from the nth weaving end point to the (n+1)th weaving end point.
Since welding is performed at the end point of the weaving, the welding speed can be easily controlled, and since the welding wire feed speed is kept constant, the welding height can be well controlled to be constant.

[Brief explanation of the drawing]

Fig. 1 is an overall view of a welding robot which is the background of an embodiment of the present invention, Fig. 2 is a diagram showing how to take a teaching point and the trajectory of a torch in an embodiment of this invention, and Fig. 3 is a diagram showing the trajectory of a torch in an embodiment of this invention. A step diagram of a program used in the embodiment, FIG. 4 is a flowchart showing the operation of the embodiment of the present invention,
Fig. 5 is a flowchart of the amplitude variable method according to the present invention, Fig. 6 is an explanatory diagram of the positional relationship between the torch, the opening, and the tip at the welding end point, and Fig. 7 is the position of the next weaving end point relative to the current position of the welding torch. FIG. 8 is an explanatory diagram for explaining a method of calculating , and FIG. 8 is an explanatory diagram of a variation of the present invention. Io... Reference current, 1, I, I2, I3... Integral welding current, l LI2' L23... Weaving width, Wl. W2
...Horizontal plate material, WL...welding line, wp, wp
, wp , wp , wp1. 2
3 4 e...Weaving end point

Claims (1)

[Claims] (1) A welding line tracing control method for weaving welding a first and second workpiece along a welding line based on teaching data given prior to welding, the welding current at a position near the weaving end point. and/or the step of determining the welding voltage as a reference value, and after actually measuring the welding current and/or welding voltage near the nth (n≧2) weaving end point, respectively.
Based on the difference between the actual measurement value and the reference value, the (n-1)th
The weaving width from the nth weaving end point to the nth weaving end point is corrected, and the (n+1)th weaving end point position is determined based on the corrected weaving width, and the (n+1)th weaving end point position is determined from the nth weaving end point to the ( Welding line tracing control method comprising the step of performing weaving welding up to the (n+1)th weaving end point.