JPH0245954B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a welding detection method in a spot welding robot.

(Prior Art) Conventionally, in a spot welding robot placed on a work line in a factory, the welding gun of the robot and a workpiece may become welded together during the work. If such a welding error occurs, if you send the robot welding completion signal and move the robot to the next step, there is a risk that the machine will be destroyed. It was necessary to take action.

Considering such situations, conventionally, for example, the fourth
The welding detection method shown in the figure is adopted.

That is, in FIG. 4, when spot welding starts (step 51), a flag is set during welding (step 52), and while the flag is set, contact between the tip of the welding gun and the workpiece is not detected. do. When the spot welding is completed (step 53), the flag is reset (step 54),
A timer is started (step 55). While this timer is operating, contact between the tip of the welding gun and the workpiece is not detected by the detection means, and the robot continues to stand by at its original position. When the timer times up (step 56), it is determined whether the chip and the workpiece are in contact (step 5).
7) is performed by the detection means, and if contact between the chip and the workpiece is not detected, the robot starts moving to the next step position (step 58). On the other hand, if contact between the chip and the workpiece is detected, this is considered a welding error and the robot is brought to an emergency stop (step 59).

(Problems to be solved by the invention) In the conventional welding detection method as described above,
If the timer setting time is too short, contact between the tip and workpiece will be detected while the robot's spot welding gun is being opened from the workpiece (separating the tip from the workpiece), and the welding burr on the workpiece and the tip will be detected. There was a problem in that contact was detected and the robot had to make an emergency stop very frequently due to welding burrs. On the other hand, if the timer is set longer, contact will not be detected until the welding gun is completely separated from the workpiece, and the frequency of emergency stops due to contact between welding burrs and chips will be reduced. However, the longer the timer is set, the longer the robot will have to wait at every spot where spot welding is to be performed.
There was a problem that the overall work time was long and work efficiency was poor.

(Means for Solving the Problems) The present invention has been devised in view of the above-mentioned conventional problems, and is designed to avoid emergency stoppage of robots due to welding burrs, and to improve spot welding work by spot welding robots. The purpose is to provide a welding detection method that can improve efficiency, and its gist is to detect contact between the welding tip of a welding gun and a workpiece in a spot welding robot and to make an emergency stop of the robot. The welding gun is provided with a first timer and a second timer that start operating after the spot welding operation is completed, and the time-up time of the first timer is set while the welding gun is being opened, and the time-up time of the second timer is set to a time when the welding gun is opened. The time-up time is set longer than the time-up time of the first timer, and after the time-up of the first timer, the contact between the welding tip and the workpiece is detected by the detection means, and if there is no contact, the robot is moved to the next step. In addition, if there is contact, a second
The structure is configured so that an emergency stop signal is sent to the robot as a welding error only if there is still contact after the timer times out.

(Function) Since the time-up time of the first timer is short, the time-up time is short while the welding gun is being opened.
At that stage, contact between the chip and the workpiece is detected. If there is no welding between the chip and the workpiece and no welding burrs are generated on the workpiece, contact between the chip and the workpiece will not be detected and the robot will immediately start moving to the next step position. Additionally, if welding burrs have occurred and the welding burrs are in contact with the chip, the robot will not come to an emergency stop until the second timer times up, and the welding gun will open further during that time. When the welding burr and the chip are no longer in contact with each other, the robot starts moving to the next step position. Even after the second timer times up, the robot is brought to an emergency stop only when there is still contact between the chip and the workpiece, that is, when the chip and the workpiece are in a welded state.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart showing the first embodiment. In the figure, TIM1 is a gun weight timer, and after the spot welding robot completes welding work at a certain welding point, it starts at the next step position (welding point). ) This is a timer for setting the waiting time until the movement starts. Further, TIM2 in the figure is a welding ignore timer for setting a certain period of time after the completion of welding work, during which contact between the tip of the welding gun and the workpiece is not detected.

Note that in this example, TIM1 is set to about 0.1 to 0.3 seconds. This set time is the minimum time after the completion of spot welding, during which the welding gun opens slightly relative to the workpiece (the welding tip slightly separates from the workpiece). Further, TIM2 is set to about 3 to 5 seconds. This set time is longer than the time required for the welding gun to fully open relative to the workpiece after spot welding is completed.

To explain the flowchart here, the step position (dot point) where the spot welding robot is located
When the welding gun is closed and spot welding is started on the workpiece (step 1), the welding flag is set (step 2). While the flag is set, contact (welding) between the chip at the tip of the welding gun and the workpiece is not detected by the detection means. Next, it is determined whether the spot welding is completed (step 3), and if it is not completed, welding is continued, and if completion is confirmed, the welding flag is reset (step 4). At the same time as the welding flag is reset, TIM1 and TIM
Timer 2 starts (step 5) and TIM
While TIM 1 and TIM 2 are operating, the robot waits at its original position and does not detect contact between the chip and the workpiece. Also, during the operation of TIM1, the welding gun opens slightly with respect to the workpiece (the tip slightly separates from the workpiece). Next, it is determined whether or not TIM1 has timed up (step 6).
When TIM1 times out, the detection means detects whether there is contact between the chip and the workpiece (step 7). If there is no welding between the tip and the workpiece, and if there is no contact between the welding burr and the tip, contact is not detected and the spot welding robot starts moving to the next step using the moving means ( Step 8). On the other hand, if contact between the welding burr and the chip is detected, conventionally this would be considered a welding error and the robot would come to an emergency stop.
In this example, the welding robot continues to stand by while TIM2 is in operation, and during that time the welding gun is completely opened from the workpiece. If the tip and welding burr have come out of contact by the time it is determined whether TIM2 has timed up (step 9), the robot immediately starts moving to the next step (step 8). On the other hand, even when TIM2 timed up,
If contact between the chip and the workpiece is detected, it is assumed that welding has occurred, and the robot is brought to an emergency stop (step 10) as a welding error. In this case, an emergency stop and an alarm may be issued. Furthermore, even after the robot starts moving to the next step using the moving means (step 8), for safety reasons, contact is detected (step 13), and if there is contact with the chip, an emergency stop is triggered (step 1).
0) to be done.

In this way, in the welding detection method of this example,
Two timers TIM1 and TIM with different setting times
By using Timer 2 and setting the time-up time of one timer TIM1 short, if contact between the welding burr and the chip is not detected, the robot can immediately move to the next step, reducing the robot's standby time. can be made extremely short. Also, only when contact between the welding burr and the chip is detected, the robot waits until the other timer TIM2 times up, and the TIM
Even after the time-up in step 2, we decided to make an emergency stop of the robot only if there is still contact.
By the time TIM 2 times up, the welding gun is completely separated from the workpiece, and the welding burr often loses contact with the chip, which greatly reduces the frequency of the robot having to make an emergency stop. In other words, short-term contact between the welding burr and the chip will not be detected as a welding error and an emergency stop will not occur. Therefore, the overall speed of welding work by the robot is increased and work efficiency is improved.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2 and 3.

In this example, a detection procedure using TIM3 is added after the means of step 8 in the first example. That is, in addition to the timers TIM1 and TIM2 in the first embodiment, a new timer TIM3 is set.

To explain the flow based on the flowchart in Figure 2, when contact between the chip and the workpiece is not detected and the timer starts moving to the next step (step 8), the set TIM3 starts. (Step 11). This timer TIM3
The contact between the welding burr and the chip is not detected and ignored during the operating time until the time-up occurs. While TIM3 is operating, the robot continues to move toward the next step, and when TIM3 times out (step 12), it is detected whether there is contact between the welding burr and the chip (step 1).
3). If there is no contact, the robot continues its moving operation (step 14). On the other hand, if contact is detected, the robot is brought to an emergency stop (step 10).

That is, at the time when the contact between the welding burr and the chip is detected in step 7 by the method of the first embodiment,
Because the TIM1 setting time is short, the welding gun is only slightly open to the workpiece.
In this state, when the robot starts moving toward the next step (step 8), the welding gun tip T hits the welding burr B on the workpiece, which is formed in the robot's moving direction G, as shown in Fig. 3. may come into contact with each other (step 13), and in such a case, there is a possibility that the robot will be brought to an emergency stop as a welding error (step 10). By the way, in this example, while TIM3 is in operation, the contact between welding burr B and tip T is not detected and ignored, so if the robot moves out of this contact area before TIM3 times up, the robot will make an emergency stop. This will occur less frequently.

In this way, the method in this example does not require an emergency stop even for burrs B that occur in the direction of movement of the robot, and improves work efficiency by reducing the frequency of emergency stops even more than in the first embodiment. be able to.

(Effect of the invention) As is clear from the above explanation, the present invention has the following effects:
A detection method for detecting contact between a welding tip of a welding gun and a workpiece, etc. in a spot welding robot and causing an emergency stop of the robot, the detection method comprising a first timer and a second timer that start operating after completion of spot welding work. The time-up time of the first timer is set while the welding gun is being opened, the time-up time of the second timer is set longer than the time-up time of the first timer, and the time-up time of the second timer is set to be longer than the time-up time of the first timer. Contact between the welding tip and the workpiece is detected by the detection means, and if there is no contact, the robot is moved to the next step, and if there is contact, the second timer is activated only if there is still contact after time-up. Since the configuration is configured to send an emergency stop signal to the robot as a welding error, even if the welding burr generated on the workpiece comes into contact with the tip of the welding gun during spot welding work by the spot welding robot, the contact will be temporary. If this were the case, the robot would not have to make an emergency stop, and it would be possible to avoid the conventional situation where the robot would have to frequently make an emergency stop due to welding burrs. Therefore, it is possible to eliminate delays in welding work and poor work efficiency due to emergency stops, and the robot can be activated only for welding between welding chips and workpieces that truly require an emergency stop, or for extremely large welding burrs. This produces the effect that it can be stopped.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the first embodiment of the present invention, FIG. 2 is a flowchart showing the second embodiment, FIG. 3 is an explanatory diagram showing the relationship between welding burrs and chips, and FIG. 4 is a flowchart diagram showing a conventional example. 1-14...Step, T...Tip, B...
Welding burr.

Claims (1)

[Scope of Claims] 1. A detection method for detecting contact between a welding tip of a welding gun and a workpiece, etc. in a spot welding robot and causing an emergency stop of the robot, the first detection method starting operation after completion of spot welding work. A timer and a second timer are provided, the time-up time of the first timer is set while the welding gun is being opened, and the time-up time of the second timer is set longer than the time-up time of the first timer, After the first timer times up, the detection means detects contact between the welding tip and the workpiece, and if there is no contact, the robot moves to the next step, and if there is contact, the second timer starts again after the timer times up. A method for detecting welding in a spot welding robot, characterized in that it is configured to send an emergency stop signal to the robot as a welding error only when there is contact with the spot welding robot. 2. A third timer is provided, which starts operation when there is no contact between the welding tip and the workpiece after the first timer times up and the robot starts moving to the next step, and the welding tip starts operating after the third timer times up. A patent claim characterized in that the robot is configured to detect contact between the workpiece and the like, and if there is no contact, the robot continues to move, and if there is contact, an emergency stop signal is sent to the robot as a welding error. A method for detecting welding in a spot welding robot according to item 1.