Universal Robots Forum

Using Force Mode the Robot Bounces in One Program, Not Another

I’m using Force to hold a part down while I close a vise. Sometimes it bounces up and down, sometimes it does not.

I have 2 programs, a Left and a Right (opposite parts). I created a program for the Lefts and ran 300+ parts then saved the program as Right and moved relevant waypoints to new positions. I did not change anything do do with the force mode.

At this point in the program the part is in a closed vise. In the below code the gripper is positioned above the part and moves down to contact the part in the vise. I apply a force model then open and close the vise to allow the part to sit flat, with the force from the gripper helping to push it down.

  • Direction Z- Until contact
  • zero_ftsensor()
  • Force
    • Wait: 1.0
    • Set chuck2 = On
    • Wait: 0.5
    • Set chuck2 = Off
    • Wait: 0.5
  • zero_ftsensor()

Now in this new (Right) program the robot bounces up and down while in the Force() mode. This is causing my parts to not sit flat in the vise and when machined the parts taper by .01 to .02 inches.

The other parts (Left) were almost all within .001" and the gripper did not bounce during Force() mode.

I double checked the COG and tool weight, they are identical to the Left parts.

What else might be causing this bouncing in one program but not the other?

Help!!! :upside_down_face:

I’m losing close to 10% of parts on this order order now because of the bouncing while in Force mode. It was closer to 0.5% on the opposite parts.

I tried timing the bouncing with closing the vise but it’s not bouncing the same every time.

The bouncing cycle is roughly up and down one time every 1.5 seconds.

I went through both programs again and everything is the same except the waypoints are about 1/2" apart from Left to Right parts.

Any idea what’s causing the bouncing in one program and not the other?