Applying a constant force to belt sander

nick_kiedaisch

Hello, 
What is the easiest way to use the FT300 to apply a constant force while sanding a part on a belt sander? We have attempted to use the force wizard with some interesting results where the robot moves randomly in the x and y planes rather than holding the force in the z direction as desired
Thank you,
Nick Kiedaisch

matthewd92

Are you allowing the robot to be compliant in those axes?  Also, one thing we have found with the force wizard is to really reduce the angular velocities of any of the axes.  We generally start with maybe 5-10 deg/sec for the rotational axes and 10-20 deg/sec for the linear axes.  Are you just wanting to hold the part in a specific location and apply a steady force in the Z-Axis? 

If you want to stay in a specific spot you could always write a small loop that allows you to correct the motion either in or out based on the force you are seeing, as the material is being removed you would want to slowly move inward, if the force goes up to far you move slightly outward.

Something like

loop
 if (Fz < 2):
   movel(pose_trans(get_actual_tcp_pose(),p[0,0,0.0001,0,0,0]))
else if (Fz >3):
   movel(pose_trans(get_actual_tcp_pose(),p[0,0,-0.0005,0,0,0]))
end
end


This would allow the robot to move in towards the belt when the force is less than 2 N and move away from the belt if the force is greater than 3N if it's between those values then it would hold the current position.  In this example I have it moving away from the belt faster than going in so that you can drop the force quickly but that could be adjusted

nick_kiedaisch

@matthewd92 Thank you for the response! Very good idea. We were using something similar to the loop you detailed in the second half of your post with great success.
When using the force wizard we were not allowing compliance in the x and y axis. The robot does what we want when we use the "test and freedrive" function, but when running the program it does strange things. We will try with the velocities reduced on the other axes. Thanks again for the quick help!