JPH06312274A - Welding gun position correcting method - Google Patents

Abstract

PURPOSE:To suppress deformation of materials to be welded generated by displacement of a pressurized point to the minimum, to optimally keep an interval between electrodes, to prevent increase of the cycle time by increase of the opening and closing time, to preferably confirm the wear quantity of electrodes and to directly control the exchange time of electrodes. CONSTITUTION:The average wear quantity Sav is used after welding of the next time and the position of a robot 1 is shifted backward for the operating direction of an electrode 6. Namely, a C type gun is lifted up by the average wear quantity Sav. In addition, the command position of the electrode 6 moved by a servomotor 3 is shifted by the average wear quantity Sav forward for the operating direction. Consequently, even when the electrodes 6 and 7 are worn away, the same set interval L between electrodes as the state where there is not no wear quantity at the time of opening can be kept. In addition, at the time of closing, the tip position of the electrode 7 is kept at the same position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding technique utilizing servo control, and is particularly suitable when a servo motor is used as an electrode drive source of a spot welding gun attached to an industrial electric robot. Welding gun position correction method.

[0002]

2. Description of the Related Art In a conventional resistance welding gun, an electrode is operated by a driving source such as an air cylinder and a motor, and a pair of electrodes scissor an object to be welded, pressurize and hold it, and weld a large current. Was going on. Due to the pressure and welding heat during welding, the counter electrode gradually wears. In the conventional technology, it is possible to detect the wear amount of this electrode while the robot is operating, and to correct this wear amount. There wasn't.

[0003]

Therefore, in the conventional resistance welding gun, firstly, in order to perform the pressurization, the electrode on the side connected to the drive source is pushed out more than in the state without wear. It is necessary to stick out. For this reason, the pressure point at which the counter electrodes meet at the time of welding changed, and most of them deformed the objects to be welded, which were thin laminated plates. Secondly, when the electrodes are worn, the gap between the electrodes becomes large, and the time required for the opening / closing operation of the electrodes is extended, and thus the working time is extended. And thirdly, there was a problem that the electrode was consumed to such an extent that it was not suitable for welding, and welding was continued with an unsuitable electrode.

An object of the present invention is to obtain welding caused by displacement of a pressurizing point by grasping the electrode position in real time, detecting the wear amount of the electrode, and freely positioning the electrode position in consideration of the wear amount. The deformation of the object is minimized, the electrode interval is kept optimal, the cycle time is prevented from increasing due to the increase of the opening / closing time, and preferably the electrode consumption is confirmed, and the electrode replacement time is directly set. It is to provide a welding gun position correction method that can be managed.

[0005]

Therefore, the present invention has solved the above-mentioned problems of the prior art by providing a welding gun position correcting method as set forth in the claims.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the attached FIGS. FIG. 1 is a block diagram showing the configuration of an apparatus used in a welding gun position correcting method according to an embodiment of the present invention,
FIG. 2 shows the C-shaped welding gun of FIG. 1 (which may be a welding gun having two pairs of electrodes, such as an X-shaped welding gun), and scissors and pressurizes the object to be welded with the pair of electrodes. FIG. 3 is an explanatory view showing a holding state, and FIG. 3 is a flow chart showing a welding gun position correcting method according to an embodiment of the present invention. In the embodiment of the present invention shown in FIG. 1, another electrode position detector 4 is attached to the robot tip which is the arm tip coordinate of the robot controlled by a servo motor (not shown) with a position detector (not shown).
C-type welding gun 2 having a built-in servo motor 3 as a drive source of the electrode 6 and only one electrode 6 is opened and closed.
The case of attaching is described. For convenience of explanation, it is assumed that the heights of the electrodes 6 and 7 at the start of welding and the amount of wear of the electrodes due to welding are equal.

The electrode 6 is driven by the servo motor 3 via the ball screw 5. The electrode 7 is attached to the fixed side of the C-type welding gun 2, and is vertically moved by moving the C-type welding gun 2 attached to the tip of the arm of the robot up and down. The robot 1 has previously reached the target command position data Pi, which is the coordinates of the tip of the robot tool,
A program 13 including a welding position including the pressure point a of one of the electrodes taught in advance and the welding object plate thickness ti is given. The robot uses a program data reading circuit 12 to read command position data Pi, pressure point a, and plate thickness ti taught by the program 13. The robot tip coordinate position is commanded by the robot position command circuit 15 and is positioned by driving the robot via the robot drive circuit 14.

The electrode position data of one of the electrodes is represented by a one-dimensional value in the tool tip coordinate system where the robot tool tip coordinate is 0. The electrode position data detected by the electrode position detector 4 is input to the electrode position amount calculating circuit 9 via the electrode position amount detecting circuit 8, and the electrode position amount calculating circuit 9 causes the program data reading circuit 12 to execute the program 1
The electrode position amount is calculated based on the pre-taught pressure point a data read from No. 3. A target pressurizing point b (FIG. 2d) is created from this electrode position amount and the command pressurizing point a data created by the electrode position command creating circuit 10 in which similarly the pre-taught pressurizing point a data is input. Output as the electrode command position. This causes the electrode 6 of the gun 2 to move to the servo motor 3
Thus, the operation is performed toward the target pressurizing point position b. The electrode position amount output from the electrode position amount calculation circuit 9 is simultaneously added to the output of the robot position command circuit 15.

The welding gun position correcting method of the present invention will now be described with reference to FIG. In the figure, the reference position of the electrodes 6 and 7 is the base of the electrode (attachment port to the gun arm). Further, the set electrode spacing is L (FIG. 2A). Regarding the operating direction of the electrode 6, the closed side is normal and the open side is reverse. When the electrodes 6 and 7 are in the initial state (= wear amount 0), the pressure command position b to the electrode 6 is b = a-ti, and the command position b and the stop position c are almost equal (Fig. 2d. ). As wear progresses, a difference ΔL occurs between a and c (Fig. 2e). Considering the plate thickness, and assuming that the amount of wear of the electrode due to welding is equal, the wear amount Sj and
When the average Sav of n times is calculated,

[0010] the Sj = (ΔL + ti) / 2 Sav = (Σ n Sj) / n (Σ n denote the display bearing the lower case n on the sigma shown in FIG. 2). This average wear amount Sav is used from the next welding onward to shift the position of the robot 1 in the opposite direction to the operation direction of the electrode 6. That is, the C-shaped gun is lifted by the average wear amount Sav (Fig. 2f). Further, the command position of the electrode 6 moved by the servomotor 3 is shifted positively with respect to the operation direction by the average wear amount Sav (FIG. 2f). This allows
Even when the electrodes 6 and 7 are consumed, the set electrode spacing L can be maintained similar to the state where there is no wear amount when opening (FIG. 2).
F). Further, the tip position of the electrode 7 can be kept at the same position when closed (Fig. 2g).

Next, a more detailed welding gun position correcting method according to an embodiment of the present invention will be described with reference to FIG. The robot reads instructed command position data Pi, pressure point a, and plate thickness ti from the program 13 (step 21). In this, the command position Pi 'is calculated by subtracting the previously detected electrode wear amount Sav as the wear amount of the electrode 7 (lower electrode) from the arrival target Pi of the robot 1 (step 22), and this is used as the position command. Output and lift the C-shaped gun by the average wear amount Sav (step 23). The current position P of the robot body is fetched (step 24), and read / monitored until P = Pi '(step 25). If P and Pi 'match, it is judged that the robot 1 has reached the welding point, and the wear amount Sav and the plate thickness ti detected up to the previous time from the position command data a of the electrode 6 by the electrode position command creating circuit 10 are determined. Subtracting, the target pressurization point b is created (step 26), and output as a command position (step 27). This causes the electrode 6 of the gun 2 to move toward position b.

The current position of the electrode 6 fetched by the electrode position detection circuit 8 is p, the value fetched one time before is p-1, and p-1 = 0 (step 28) for initialization. Import current value data p of gun axis (step 29), p = p
Continue monitoring while p-1 = p until -1 (step (step
30), if they match, it is assumed that the electrode 6 has stopped, and its position c
Is obtained (step 31). The position c is regarded as the actual pressurization point, and the electrode displacement amount calculation circuit 9 obtains the displacement amount ΔL of the electrodes 6 and 7 from the difference between this position and the teaching pressurization point a. Further, considering the plate thickness ti given by the program 13, the sum 2Sj of the wear amounts of the electrodes 6 and 7 is obtained. Considering that the wear amounts of the two electrodes are equal, the wear amount Sj per electrode is obtained (step 32). When the wear amount Sj exceeds the specified value (step 34), a message notifying the electrode replacement time is displayed, a signal is output, etc. (step 38). The wear amount Sj (j = 1 to n) obtained by pressurizing n times before this time is averaged to obtain the average wear amount Sav (step 35). A welding start signal is output to the welder (step 36), and the process waits until a welding completion signal is input. When the welding completion signal is input, it moves to the next point (step 37).

[0013]

As described above, according to the present invention, the electrode position is grasped in real time to detect the wear amount of the electrode,
Since it is decided to freely position the electrode in consideration of the amount of wear, the deformation of the welding object caused by the displacement of the pressure point is minimized, the electrode interval is kept optimal, and the opening / closing time is increased. It has the effect of preventing an increase in cycle time, and preferably the amount of electrode wear can be confirmed, the time to replace the electrode can be directly controlled, and the loss of the electrode can be detected by detecting an abnormal amount of wear. It has become possible to provide a welding gun position correction method that achieves the above.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus used in a welding gun position correcting method according to an embodiment of the present invention.

FIG. 2 is a pair of electrodes supported by the C-shaped welding gun of FIG. 1 (which may be a welding gun having two pairs of electrodes such as an X-shaped welding gun) and scissors the welding object. Hold pressure,
An explanatory view showing a state showing a welding gun position amendment method of one example of the present invention.

FIG. 3 is a flowchart showing in detail the welding gun position correction method shown in FIG.

[Explanation of symbols]

 1. ． Robot 2. ． C-shaped welding gun 3. ． Servo motor 4. ． Position detector 6, 7. ． electrode

Claims (5)

[Claims] 1. A C-type welding gun, an X-type welding gun, etc., in which one electrode is operated by a driving source such as a servomotor having a position detector to scissorly hold a welding object with the other electrode forming a pair and pressurize the welding object. Using a welding gun having two pairs of electrodes, the average wear amount S when the electrodes wear during the welding operation
By using av from the next welding onward, the robot supporting the welding gun is shifted in position by the average wear amount Sav in the direction opposite to the operating direction of the one electrode, that is, the welding gun is moved by the average wear amount Sav. The command position of the one electrode electrode which is lifted and moved by the drive source such as the servo motor is shifted by the average wear amount Sav in the operation direction,
As a result, even when the two paired electrodes are consumed, the set electrode spacing is maintained at the same level as when there is no wear amount when the electrodes are opened, and the tip positions of the two paired electrodes are the same when the electrodes are closed. Welding gun position correction method characterized in that it can be kept in position. 2. A C-type welding gun, an X-type welding gun, etc., in which one electrode is operated by a drive source such as a servomotor having a position detector to scissorly hold the object to be welded with the other electrode forming a pair. Using a welding gun having two pairs of electrodes, the robot position data Pi, which is the coordinates of the tip of the robot tool, the pressure point a previously taught on one of the electrodes, and the plate thickness ti of the welding object are read. , The robot command position Pi ′ obtained by subtracting the wear amount Sj previously detected as the wear amount of the other electrode from the robot position data Pi.
Is calculated and output as a position command, and the robot current position P, which is the coordinate of the tip of the robot tool, is fetched, and P =
It is read and monitored until it becomes Pi ', and when P and Pi' match, it is judged that the robot has reached the welding point, and the electrode position command preparation circuit causes the teaching pressure point position a of one of the electrodes.
Is subtracted from the wear amount Sj and the plate thickness ti detected up to the previous time to create a target pressurizing point b, which is output as the command position of one of the electrodes, and is operated toward the target pressurizing point position b.
The current position of one of the electrodes captured by the electrode position detection circuit is set to p, and the value captured one time before is set to p-1, and first, p-1 = 0 is initialized, and the current value data p of one of the electrodes is set. Monitoring is continued while setting p-1 = p until = p-1, and when the coincidence occurs, one of the electrodes is stopped, and the electrode reaching pressurizing point position c of the one of the electrodes is obtained. The point position c is regarded as the actual pressurization point, the welding start signal is output to the welding machine, the welding completion signal is waited for, and when the welding completion signal is input, the set position toward the next point is detected. A welding gun position correcting method, wherein the displacement amount of the electrode is calculated from a value obtained from a position detector. 3. The wear amount Sj detected up to the previous time
Is the displacement amount ΔL of the pair of electrodes from the difference between the electrode reaching pressure point position c and the taught pressure point position a, and the wear of the pair of electrodes is considered in consideration of the plate thickness ti taught in advance. Sum of quantity 2S
The welding gun position correcting method according to claim 2, wherein the position is calculated as j. 4. The wear amount Sj detected up to the previous time is repeatedly repeated n times to obtain an average wear amount Sav from the average value, and the average wear amount Sav is used instead of the wear amount Sj detected up to the previous time. The welding gun position correcting method according to claim 3, wherein 5. The method according to claim 2, wherein when the wear amount Sj detected up to the previous time becomes equal to or more than a specified value, a message or a signal for notifying the replacement time of the electrode is displayed. Welding gun position correction method.