Universal Robots Forum

Error Code C157A1 and C204A7 after increasing the speed

Hello all,
I have a little problem with our UR5e and I hope you can help me.
I am studying the accuracy of laser cutting with a UR5e in my bachelor thesis. For this, I have to run a test track (similar to DIN EN ISO 9283) in the XY, YZ and XZ plane with an absolute accuracy as high as possible. The Laser Optic is attached to the flange (weight: 4,22kg, TCP displacement X:0mm, Y:-120,4mm, Z:178,34mm, center of gravity displacement X:-21,3987mm, Y:-46,3453mm, Z:-41,7088mm, all Parameters are stored in the TCP File). Because of the Lasercutting we need to use the movep command.
Among other things, the test track has 2x 30° peaks and 2x 1cm squares (see picture). I have to test the whole thing in 3 different speeds. At 16,67mm/s and 83,33mm/s I have no problems in any plane. But as soon as I increase the speed to 166,67mm/s, I get the error message: C204A7 path sanity check failed: Robot Approaching singularity - Acceleration threshold failed. I could avoid this by increasing the blend radius to 2mm (which I don’t really want because of the high absolute accuracy). Then the next error message appears for the squares: C157A1: Collision detected by joint: Shoulder. Check payload, center of gravity and acceleration settings. Although the robot was not blocked in any way.
I have a bit of a hunch that I need to change the safety settings. But I don’t want to do this without asking here first.

Thanks for your help



movep commands are designed to maintain constant tool (TCP) velocity throughout the motion. When sharp or near sharp corners are encountered, the motion that the robot arm needs to perform to maintain the TCP velocity could be quite extreme from a joint motion perspective. If this motion is beyond the capability of the robot to perform whether due to safety settings or total torque capacity of the joints, a fault can occur.

Thanks for your reply @pho .

And if I wanted to force the robot to go this way, what safety settings should I change? And is it reasonably safe to change these?

There is no standard here, what is considered “reasonable” is very much situation dependent.
the safety settings for a robot with a gripper, is usually not reasonable for a robot with a welder, as the welder is considerably more dangerous.
The same think is true for robot that could be within reach of a person when running and one that is enclosed.
So you really have to study up on the regulation in your area, to answer this question.

Best Regards Casper
PS: You could try increasing the blend radius at the sharp corners, this will result in more rounded corners though.
, which might not be desirable.

I agree with the making sure it is safe comment.from cg1.

Tool speed will probably not be a major factor if your TCP is defined properly to be at the location of the laser focal point…

Elbow speed will be an important factor as it affects how fast the robot can change orientations as the TCP goes around a corner.

Joint speed will also be a factor but they are likely already set at maximum.

Momentum could also affect the maximum speed but like tool speed it probably is not a factor.