I have a program that has been working well for a while now, and twice when I have turned the robot on it fails.
The program moves to a position (given by a camera) and then searches down until tool contact is made. Normally it stops and then makes a few more moves and picks up the item.
Twice now we have powered up the robot and started the program, and it has got to this point in the code, moved to the position given by the camera and started moving down until it hits the parts.. and then continued until a protective stop happens. Both times starting the program from the start again resulted in the same error.
Restarting the whole robot and the problem goes away. I haven’t been there myself either time the robot was started with the problem, so I can’t be sure there wasn’t something strange about how it was started… but I can’t figure it out.
Thanks, I’ll add that in and see if it happens again… although I didn’t think that the move until tool contact actually used the sensor (just tracked robot position to detect the contact).
Did you ever end up finding a fix for this? Running into the exact same issue recently with a program that had been running fine for close to a year, and this protective stop thing has been coming up more and more frequently. We tried running the until contact node in force mode too, but no dice.
The “Until tool contact” does indeed use the force/torque sensor. As is written in the program node, it’s a good idea to lower the speed to 100 mm/s at most (or lower than that if it’s a sturdy surface that needs registering).
Also, as mafa mentions, try doing a reset of the sensor before using the “Until”. And insert a Wait 0.5 seconds before doing the reset to make sure the robot arm and tool have stopped moving/vibrating from earlier movements.
If the force on the tool increases gradually, e.g., when approaching with a “soft” gripper or a “soft” part, a better approach would be to wait for force X (which can also be done in the “until… contact” node).
Waiting for tool contact works best when the change in force is sudden and occurs at a low speed.