UR5 force mode for contour following

Hi! I have a UR5 robot arm, and I want to program it to follow a contour in x-y plane while applying a constant force in z direction. To elaborate, I want the robot arm to apply a force in z direction NOT more than 2 N, while it is moving in predefined direction in x- and y-axis? I am trying to use the force mode, but I am unable to get the behavior I want. Could some please help me program this behavior? Also, is maintaing a force less than 2 N in the z-direction a realistic value, or do I need to have a higher value than 2 N? If yes, the how much?

Welcome to the URcommunity Radhen,

In the Force Node command you check boxes to allow compliance in rx/ry directions, I would set speed and torque values very low to start and work your way up until it suits your needs. Also you can select Features or Simple/Frame/Point/Motion to change robot forcemode() behavior. Press the ‘Test’ button and you can use Freedrive button to get a feel of how the robot will react to different forces.

I’ve noticed this as well, the lower the force sometimes the robot can give itself a false reading and wander off the part. This can happen during sudden changes of direction or drastic changes of tool orientation (90 degree turns). Not sure how drastic of a contour you are working with just things to be aware of. Also I would zero the force-torque sensor right before entering forcemode() and before you make contact with the surface to ensure you are getting proper readings from the sensor. I use around 5N on most projects where i quickly need to move using forcemode()

Note: there is some variance in the actual force/torque values, I believe UR10’s are +/-10N and UR3’s are +/-5N (I forgot the Torque values, but they are noted somewhere in UR’s documentation)

Anyways, other URcommunity members may have a better solution or be able to help more but hope that helps and best of luck!