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ERROR: "CIRCULAR_ARC_WITH_INFINITE_RADIUS"
#1
Question 
Background Info: I'm running a Universal Robot (UR5) for a dispensing application.   I've had a lot of success thus far, that is...prior to this latest issue stated in the subject.   I've been at this for the past year now.   Still learning as I go.

Anyways...I've had the post processor tweaked by a RoboDK tech a few times prior for similar errors.   Those tweaks to the limits surely should've prevented the error that I'm getting now.   The problem is...for this latest project, I was successful at first where I was able to have a "basic" program to run fine.   However, subsequent changes to it eventually lead to the error I'm faced with now.   Funny thing is, the changes I made had nothing to do with what the error is associated with.

What's weird is if I took a known good program that would run just fine on the UR5, and through RoboDK make just a change to the file name prior to generating the program...it would then no longer work right.   The "CIRCULAR_ARC_WITH_INFINITE_RADIUS" error would come up.

Can anyone out there help me with this?
Any help would be much appreciated!
#2
I believe the error "CIRCULAR_ARC_WITH_INFINITE_RADIUS" can occur on the Universal Robots controller for one of the following reasons (at least):
  1. The arc/circle radius is too large: In that case it is better to replace the circle for a line.
  2. The circle is too small: Two of the three points that define a circle are too close to each other and creates problems on the robot controller side.
  3. A large rounding radius (blend radius): The rounding parameter allows the robot to "take shortcuts" (smooth the corners) by a certain radius.
  4. The speed can have an influence. I believe that moving at higher speeds you are more likely to see this error. This is probably related to the blend radius.
  5. You may experience different behaviors with different versions of the UR Polyscope.
The default RoboDK post processor for UR tries to filter reasons 1 and 2 by checking if the radius is in the range between 1 mm and 10m. If it is not in this range, RoboDK will just generate a linear movement. These values can be easily updated in the post processor.

I would say that if you see this error using a program that you generated with RoboDK, the problem is likely to be a permissive blend radius or rounding radius (reason 3). A large blend radius can alter the arc/circle or even make it disappear! (the robot controller will skip it).

For your information, there have been some modifications recently with the default UR post processor that comes with RoboDK to avoid this issue (reason 3). The latest version (file attached) should work better as it is more strict with the blend radius, however, it might show jerky movements. You can just update RoboDK or copy this PY file to:
C:/RoboDK/Posts/Universal_Robots.py

.py   Universal_Robots.py (Size: 30.58 KB / Downloads: 126)

If you still have issues with this post it would be great if you can send a sample project and we can look at a specific case or set of parameters. We look forward to finding the right set of parameters/filters that make it work on the controller under any conditions.
  




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