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Home > Troubleshooting > Unwanted robot movement when spot welding with UR10e
tor_odigo

Hello!
I am integrating a spot weld application with a UR10e at the moment. The weld head is mounted on the robot, and weld nozzle (mounted on a spring) needs to be pushed down about 10 mm for the weld to be successful. However, when the robot is rectracting from the surface, it makes an unwanted horizontal movement which causes a scratch to the copper plate underneath.

Here is a video of the movement: Dropbox - 20210608_105945.mp4 - Simplify your life

My guess is that the force needed to push down the nozzle is too large and the torque it causes makes the robot become slightly offset when it makes the rectrating move. Is there a way to fix this unwanted movement or is the force too much for the the robot to stay accurate?

Best,
Tor

matthewd92

How much force does it take to compress that spring in the head?  When are you seeing that horizontal motion, is it when the robot is retracting or while it’s still pushing?  Hard to tell from the video
tor_odigo

It is when the robot starts moving up again. When I go down 10 mm the force applied by the spring is 4.6kg which is about the same as the whole weld head weighs. So maybe the robot doesn't like that the real payload shifts to being 0 kg momentarily.
matthewd92

That’s most likely what you are seeing. If you press down on the head while the robot is sitting still and then let go you will see it jump up. This is due to the sudden decrease in “gravity” when it’s sitting still. You may be seeing the same phenomenon here
matthewd92

I’ve seen similar motion before when we have to press hard against something with the robot and then the force goes away when we lift off.