I have a configuration where UR-5 robot is mounted with 2f-185 finger and FT-300 sensor. My task is to uncap a threaded cap. Since the last axis of UR robot is not having infinite rotation, after every 180 degree turn I am opening the gripper and moving up and going back to initial configuration and again repeating the same. Since the cap is threaded I need to move robot a little bit up along its tool axis after every turn so as to not to damage the gripper or cap. I have two options: One is to move robot a little up (along z axis of its tool) programmatically or setting the gripper (robot) in compliance mode along z axis. I am considering to go by option 2 as it looks more logical. Now I want to know how to achieve this? I have tried using FT mode but it didn't help or maybe I am doing something wrong. Please help.

Here is the solution found:
"I think it worked for now. I guess the issue was in setting the force along z. Earlier I was setting it to zero as you have mentioned. This time I made it a little higher around 40N. So now in every turn the grip still holds it. Previously when set to zero somehow the robot was not even going back to the grip point. At every successive iteration, it was holding back a little. Now after setting the force value to nonzero robot gripper reaches the surface of the cap and grips it properly."