JPH0459072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic processing method after a temporary stop occurs due to abnormal arc current in a welding robot.

This type of welding robot has a configuration as shown in FIG. This welding robot is
A wrist part 2 is equipped with a welding torch 1 and has a rotation axis S and a rotation axis B (see FIGS. 2 a and b) for controlling the attitude of the welding torch 1, and a horizontal feed X, a horizontal Y, and a vertical Z. The robot body is composed of an arm 3 having an orthogonal coordinate system, a welding robot control device 4, a teaching box 5, a welding current supply device 6, and a welding wire box 7.

When welding workpieces using such a welding robot, it is necessary to flow a predetermined arc current depending on the thickness of the workpiece, leg length, etc., in order to obtain the desired welding quality.

Normally, in order to maintain the above-mentioned predetermined arc current during welding, axis control is performed to keep constant the distance between the welding torch 1 and the workpiece, that is, the wire protrusion length L (FIG. 3). However, due to errors between the taught welding line and the actual welding line and various other influences, the wire protrusion length L changes significantly, and as a result, the graph showing the relationship between the wire protrusion length L and arc current shown in Fig. 4. As is clear from the above, the arc current value may exceed the allowable range.

If the wire protrusion length becomes too short and the arc current exceeds the maximum allowable current, there is a risk of melting the torch, nozzle, etc. due to radiant heat from the molten iron.
There is also a risk of penetration of the workpiece.On the other hand, if the protruding length of the wire becomes too long and the current falls below the minimum allowable current, the effect of the gas shielding, which is used to shield the welding area during welding, will weaken. , the welding quality of the workpiece deteriorates because the welding point is exposed to outside air (plow hole).

Therefore, conventionally, for the above-mentioned reason, when the arc current value exceeds a permissible range, the arc current is temporarily stopped. In order to restart the robot, the operator must operate a pause release button after performing appropriate processing, which increases the burden on the operator and hinders unmanned operation of the robot.

The present invention was made in view of the above circumstances, and
An object of the present invention is to provide an automatic processing method after a sudden stop occurs due to an arc current abnormality, which can automatically remove the cause and restart when the arc current exceeds the maximum allowable current and temporarily stops. .

According to this invention, a case where the arc current exceeds the maximum allowable current and is temporarily stopped is detected, and at this time the welding torch is retreated by a predetermined amount in the direction in which the welding torch is facing, and then the welding torch is moved back to the position at the retreated position. The above purpose is achieved by automatically restarting the system based on the data.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 5 is a flowchart showing an embodiment of an automatic processing method after a temporary stoppage occurs due to abnormal arc current according to the present invention. In the figure, in order to start welding, preparations for starting welding are first performed such as detecting the starting end of the welding line (not shown), and then welding is started from the starting end position of the welding line. During this welding,
The movement of each axis of the robot is controlled so that the welding torch 1 follows the actual welding line using movement commands and tracing control based on teaching data, and the arc current value is determined to be within a preset allowable range. Constantly monitor whether or not it is inside.

If the arc current value is normal, it is determined whether or not there is still a weld line, and the welding is continued until there is no more weld line, and the welding is terminated at the weld line terminal position. If the arc current value is abnormal, the process is temporarily stopped and then the process according to the present invention is executed.

When the arc current value becomes abnormal and a temporary stop occurs, the arc current value may be below the minimum allowable current value or above the maximum allowable current value, so first, check whether the arc current value is abnormal. Determine whether

If the arc current value is less than the minimum allowable current value,
The welding quality may be poor because the arc and torch are too far apart and the gas shielding effect is weakened. It will display that it has changed and remain in a paused state, waiting for processing by the operator. Note that this is the same as before.

If the arc current value is greater than the maximum allowable current value,
Based on the processing function prepared in advance, the welding torch is moved back a predetermined amount in the direction in which the torch is facing, and after moving the torch away from the workpiece (after performing the processing enclosed by the one-dot chain line), it is automatically restarted. let

Now, as shown in Figure 6, teaching points P _i and
A case where the arc current value exceeds the maximum allowable current value at position P _i ' while welding between P _i+1 will be explained. In addition, X regarding the above teaching point P _i ,
Let the teaching data of the Y, Z axes and rotational axes S and B be (X _i , Y _i , Z _i , θ _S , θ _B ), and similarly, the teaching data regarding the teaching point P _i+1 be (X _i+1 , Y _i+1 , Z _i+1 , θ _S , θ _B ). That is,
As is clear from these teaching data, it is assumed that there is no change in the attitude of the welding torch when the welding torch is moved between the teaching points P _i and P _i+1 .

Now, if the arc current value exceeds the maximum allowable current value at position P _i ', the welding robot is temporarily stopped as described above, and the welding torch 1 is retreated by a predetermined amount △L in the direction in which the torch is facing. .

Here, a method for retracting the welding torch 1 by a predetermined amount ΔL will be explained with reference to FIG. In order to move the welding torch 1 in the direction that the welding torch 1 is facing, three orthogonal axes are driven simultaneously, and the amount of movement of each axis X, Y, and Z is △X, △Y, △, respectively.
It should be Z. Here, if the distance between position P _i ' and position Q is △L, and the angles of the S axis and B axis of wrist part 2 are θ _S and θ _B , respectively, then each axis X, Y,
The moving amounts △X, △Y, and △Z of Z are as follows: △X=△Lsinθ _B sinθ _S △Y=△Lsinθ _B cosθ _S △Z=△Lcosθ _B ... (1).

Therefore, each axis X calculated using the above formula (1),
By retreating the welding torch 1 by the moving amounts ΔX, ΔY, and ΔZ in Y and Z, the welding torch 1 can be retreated by a predetermined amount ΔL in the direction in which the torch is facing.
In addition, in order to move the torch back in the direction of arrow A to avoid interference between the torch and the workpiece, each axis X,
It is sufficient that the speed ratio of Y and Z satisfies the ratio on the right side of the above equation (1).

In this way, the torch retraction amount ΔL is read out (FIG. 5), the amount of movement per unit time is calculated, and the command value is output to each axis to simultaneously control each axis. Then, when the torch retreat amount reaches ΔL, the movement is stopped.

Next, the welding torch 1 is automatically restarted from the retreated position. In this case, a movement command is calculated based on the position data at the retreat position and the teaching data at the teaching point P _i+1 , and the movement of the welding torch 1 during subsequent welding is controlled.

Note that the torch retraction amount △L is, for example, 3 mm, 5 mm,
It is also possible to set different values such as mm and 7 mm, and to set the arc current value back by different values depending on the number of times the arc current value exceeds the maximum allowable current value and is temporarily stopped.

As explained above, according to the present invention, when the arc current value exceeds the maximum allowable current value during welding and the welding is temporarily stopped, the welding torch is moved away from the workpiece in order to reduce the arc current, and then automatically Since the restart is performed, the operator's operations can be reduced and the robot can be operated unmanned.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram showing an example of a welding robot to which the present invention is applied, Fig. 2 a and b are respectively a plan view and a side view of the wrist of the welding robot, and Fig. 3 defines the wire protrusion length. FIG. 4 is a graph showing the relationship between wire protrusion length and arc current, and FIG. 5 is a graph showing an example of the automatic processing method after a temporary stoppage occurs due to arc current abnormality according to the present invention. Flowchart, Figure 6 is an explanatory diagram when an arc current abnormality occurs during welding between teaching points P _i and P _i+1 , and Figure 7 is a method for moving the welding torch in the direction the welding torch is facing. FIG. 2 is a diagram used to explain. 1... Welding torch, 2... Wrist part, 3... Arm part, 4... Welding robot control device.

Claims (1)

[Claims] 1 Consists of a wrist part with a rotation axis that controls the posture of the welding torch, and an arm part with multiple axes that move and control the position of the wrist part, and temporarily stops when the arc current value falls outside the allowable range during welding. In the welding robot that performs welding, a processing function is prepared in advance to move the welding torch back by a predetermined amount in the direction in which the welding torch is facing, based on the orientation of the welding torch during a pause, so that the arc current value during welding is adjusted to the maximum allowable current. The arc is characterized in that it detects a temporary stop when the value exceeds the value, executes the prepared process at this time, and automatically restarts the arc from its retreated position based on the position data of each axis after the process is executed. Automatic processing method after a temporary stop occurs due to current abnormality.