JP2766244B2 - Automatic welding method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic welding method having means for advancing a welding torch along a scheduled welding line. In particular, the present invention provides one countermeasure when an arc does not occur at a welding start scheduled point. 2. Description of the Related Art When the surface of a workpiece is covered with an oxide film, an arc may not be generated at a scheduled welding start point. When the welding torch is moved along the scheduled welding line, and an arc is generated at a point different from the scheduled welding start point, that becomes the actual arc start point. Welding is possible from the arc start point to the welding end point, but welding in the section from the welding start point to the arc start point is not completed. If the scheduled welding end point coincides with the scheduled welding start point and the scheduled welding line is in a closed circuit shape, then the welding to the scheduled welding end point (scheduled welding start point) is followed by the arc start point. The welding up to may be performed. However, it is troublesome when the scheduled welding line is not closed, for example, a straight line. It is not clear whether or not the arc is cut again at the welding end point, and again when the welding is to be performed again between the welding start scheduled point and the arc start point where welding has not been completed. [0003] An object of the present invention is to weld all sections of a scheduled welding line at once without breaking an arc even when the scheduled welding line is not a closed circuit. An object of the present invention is to provide an automatic welding method. The present invention utilizes a step of moving a welding torch for arc welding from a scheduled welding start point on a workpiece along a scheduled welding line starting therefrom. This step is executed by, for example, a program arranged in a control panel for controlling the robot body.
The present invention has a step of determining whether or not an arc has actually occurred. If no arc has occurred, the arc start is repeated. This execution is repeated until an arc actually occurs. However, when the arc has not been generated even after the arc has been repeated a specified number of times, it is preferable to determine that welding is impossible. If no arc is generated at the welding start scheduled point and an arc is generated at a stage slightly advanced from that point, that arc becomes the actual arc start point. The present invention includes a step of causing the welding torch to proceed in reverse while maintaining the arc from the arc start point to the welding start point. This step is also executed by the program of the control panel that controls the robot body, but is different in that a program that advances the welding torch in the reverse direction is executed instead of the program that advances the welding torch in the forward direction.
The present invention includes a step of moving the welding torch again from the scheduled welding start point along the scheduled welding line while maintaining the arc. As the welding progresses again, the welding torch goes beyond the previous arc start point while welding and proceeds to the welding end point. As a result, the section from the welding start point to the arc start point is double-welded. However, since the welding is performed over the entire planned section without cutting off the once generated arc, undesired welding is not performed. There is no end section. In order to reduce the section of double welding, at the arc start point, it should be judged whether it is better to advance to the welding end point and then return, or to return to the welding start point and advance again. However, since the return distance is smaller in practical use, the latter method may be specified uniformly. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, a robot as shown in FIGS. 2 and 3 is used. A welding torch 2000 for arc welding is attached to the wrist of the robot body 1000,
Control its position and orientation. For this control, a control panel 3000 wired to the robot body 1000 or a teaching pendant 3500 attached thereto is used. FIG. 4 shows the state of arc welding, in which a welding torch 20 is used.
00 is positioned at the scheduled welding start point S on the workpiece 4000, and proceeds from there to the scheduled welding end point E along the scheduled welding line l starting from the scheduled welding start point S. Also,
At the same time, arc welding using the arc 2500 is performed. Such an operation is taught in advance for the work 4000,
According to the program stored in the memory of the control panel 3000. FIG. 1 is a flowchart showing a main part of a program, particularly a part relating to an arc retry function. Hereinafter, description will be given along this flow. In step 10, the robot main body 1000 is driven to position the welding torch 2000. It is checked whether or not the point positioned in step 11 is registered as the welding start point S. If it is not the scheduled welding start point S, the routine shifts to the normal operation of step 12, and the arc retry function is not used. If it is the welding start scheduled point S, the retry counter N is set to −1 in step 13. In step 14, the welding conditions are set to pilot arc conditions. The condition of the pilot arc is a condition in which the generated arc is narrowed down from that of the rated welding condition determined in advance at the time of teaching the applicable work, and the arc voltage and / or current is set to a lower value. Set to. Further, the protrusion amount or the feeding speed of the welding wire and the moving speed of the welding torch 2000 are set to lower values so as to correspond to this. In step 15, an arc-on command is issued to a welding machine (not shown). In the subsequent step 16, the process waits for 0.5 seconds and advances the retry counter by one. At step 17, the position data of the welding torch 2000 at that time is stored. If necessary, the posture data at that time is also stored. In step 18, it is checked whether an arc answer has been returned. The reason for waiting for 0.5 seconds in the previous step 16 is to give time required for returning the arc answer from the welding machine to the robot control panel 3000. The arc answer is generated when a current flows through the welding torch 2000 and the work 4000. If the arc answer does not return,
In step 19, the wire feed signal is stopped. This is to prevent the welding wire from being excessively extended. Step 20
It is determined whether the count value N of the retry counter has exceeded a predetermined Nmax. If not, step 2
In step 1, the welding torch 2000 is advanced by one sampling distance, and the processing from step 14 is repeated thereafter. One sampling distance is a length that advances in one unit of time under sampling control, and is about 1 to 2 mm. If an arc answer is returned in step 18, the process proceeds to step 22. In this step 22, the welding conditions are returned to the original rated values. Further, the mask of the wire feed signal performed in step 19 is also released. In step 23, the welding torch 2000 is returned to the original welding start point S while maintaining the arc. When the welding start point S becomes the arc start point, the length of the return is 0 and it does not actually return. The reason why the arc is maintained without returning when returning is to prevent re-failure of the arc start. Step 23
In step 17, the position data stored in step 17 is read out and used in the reverse order of the storage order. This is to save the trouble of calculating the return path again. In the next step 24, the accumulated value M of the retry counter N is calculated as M = M +
N is obtained and stored. If the arc start is always performed in one try, the retry counter N
Becomes 0 and the cumulative value counter M does not advance. When the failure of the arc start is repeated, the cumulative value counter M is steadily increased. Although the step of resetting the cumulative value counter M to 0 is not shown, the cumulative period of the cumulative value counter M is, for example, one day. It is reset at the start of the welding work on that day, and the accumulated value M of the accumulated value counter M is checked at the end of the work on that day. If the accumulated value at this time is small, there is not much problem. However, if the accumulated value is large, it is necessary to reconsider the welding operation itself such as re-teaching. This is because, in the near future, an undesired situation in which an error will occur in step 27 later and the operation is interrupted will be foreseen. In step 25, a normal welding process is executed. Thus, scheduled arc welding is performed while the welding torch 2000 is advanced from the scheduled welding start point S to the scheduled welding end point E along the scheduled welding line l. The comparison constant N used in step 20
max is 8, for example. The retry counter N increments from 0, but if the arc cannot be started even after reaching the 9th time of 9th, it is determined that welding is impossible, and the subsequent retry is stopped. During this time, the welding torch is 10-20
mm, since it has moved from the welding start scheduled point S, the position is returned to the original position in the next step 26. At this time, the position data stored in step 17 is used. In step 27, the robot body 1000 is stopped, and the control panel 300
An error message indicating that the arc start has failed is displayed on the display screen of 0. Here, we wait for manual restoration. A welding torch 20 according to the program of FIG.
FIGS. 5 to 9 exemplify the movement of 00 and the like. When the count value N of the retry counter is 0, the arc start fails. It also fails when the retry counter N is 1 or 2. When the count value N of the retry counter becomes S,
When the arc 2500 is generated as shown in FIG. 5, the position of the arc 2500 becomes the arc start point AS. The welding torch 2000 is returned from the arc start point AS to the welding start scheduled point S as shown in FIG. During this time, welding to the work 4000 is accompanied in order to maintain the arc 2500. Thereafter, as shown in FIG. 7, the welding process from the welding start point S to the welding scheduled line 1 starting from the welding start point S is executed again. Arc start point AS from scheduled welding start point S
Is welded twice before and after. On the other hand, even when the count value N of the retry counter reaches 9, as shown in FIG. Retrying while shaving the surface with a welding wire is still useless. In addition to pushing the welding wire forward while pushing the welding wire, it is conceivable to project the welding wire that has been pulled back each time. The purpose is to expose the conductive surface. In the case of FIG. 8, it is determined that welding is impossible, and the welding torch 2000 is returned from the position of the retry counter N = 9 to the welding start scheduled point S as shown in FIG. In FIG. 6, arc start point A
The arc 2500 is maintained when returning the welding torch 2000 from S to the scheduled welding start point S, but this is not for welding. Therefore, it is desirable to reduce the arc as much as possible, as long as the arc 2500 does not go out. This is because, for example, in step 22 of FIG.
Then, the welding conditions can be returned to the rated values. The present invention is characterized by maintaining the arc generated by the arc retry, returning the welding torch to the welding start point as it is, starting welding again from there, and so on. is there. According to this, even when the scheduled welding line is open without closing, there is an effect that an undesired section where welding is not completed does not occur.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a processing program of an automatic welding apparatus according to the present invention. FIG. 2 is a front view of a main body of a robot used for this. FIG. 3 is a front view of the control panel. FIG. 4 is an explanatory diagram showing the progress of welding. FIGS. 5 to 9 are explanatory views for explaining the movement of the welding torch and the like in each step in FIG. [Description of Signs] 1000: Robot body, 2000: Welding torch,
3000 ... control panel, 21 ... means to advance welding torch, 14-15 ... means to execute arc start,
23: Means to advance the welding torch in reverse, 25 ... Means to advance the welding torch again.

Claims (1)

(57) [Claims] An industrial robot is provided with a welding torch attached to a tip of an arm thereof, wherein the industrial robot is moved by teaching data pre-taught, thereby automatically welding a workpiece. Moving, issuing an arc-on command to the welding machine, determining whether an arc answer has returned from the welding machine, and if the arc answer does not actually return without actually generating an arc. An arc retry execution step of repeatedly issuing an arc-on command along a scheduled welding line starting from the scheduled welding start point and, if an arc is actually generated and an arc answer is returned, from the point to the scheduled welding start point. Advance the welding torch in the reverse direction while maintaining the arc, and then move the welding torch from the welding start point while maintaining the arc. Automatic welding method characterized by comprising the steps of advancing again along the tangent scheduled line. 2. And determining whether reaches the Akuritora IgaTadashi value, the steps if the count value is not reached the specified value to perform overlapping arc retry until the specified value automatic welding method claims paragraph 1, wherein in that example Bei. 3. Stores welding torch position data from the welding start point to the arc start point where the arc actually occurred
And, wherein the patent automated welding process ranging first claim of claim that advancing the welding torch the position data from the use ear over click start point to the welding start scheduled point in reverse. 4. 2. The method according to claim 1, further comprising the step of accumulating and storing the number of executions of the arc retry.
Automatic welding method described in the item. 5. The welding robot attached to the tip of the arm of the industrial robot
And the industrial robot has a teaching taught in advance.
Moved by data, thereby automatically moving the workpiece
In the automatic welding equipment for welding, the robot is scheduled to start welding.
A moving means for moving to a fixed point, and
Means for issuing an arc-on command when a fixed point is reached,
Depending on the presence or absence of an arc generation signal according to the arc-on command
Means for determining whether or not an arc has actually occurred;
If there is no arc generation signal, start robot welding
Hand to execute arc retry operation by moving from the scheduled point
And performing the arc retry operation.
If there is a generation signal, from the actual arc generation position
Keep the arc and move the robot to the welding start point
Means for reversing, and the robot reaching the welding start point
After reaching, the robot is moved from the welding start point to the melting point.
Means for proceeding along the tangent line.
And an automatic welding robot.