Rotation of the frames to define the path for Robotic Arm

[ArchEssi]

When I want to define a circular path and the frames follow the slope of the curve, I always have errors, but when all frames are in the same direction, there is no error. I put some photos here to make it clear. I need it for 3d printing. if the profile of the extruded layer is circular maybe there is no difference whether the frames follow the direction of the path or not but if the section of the layer is rectangular for example a layer with the height of 1 cm and the width of 5 cm, then there is a difference in thickness of the wall if the extruder rotates in accordance with the path or not. I would be grateful if you suggest me a solution. Thanks.

[Johannes @ Robots in Architecture]

Hi,

Well, this is more of a general hardware problem as the robot by design has got axis limits that bite you at some point. You can mitigate it in software, but only to a point.

In your case, if it's only about a single circle, you can try to check which axis is winding up - probably A4 or A6 - and then start the process at the limit of the axis, so that you can then move until the limit on the other side. However, once you have multiple circles or a helix, you will quickly encounter axis limits again.

On most KUKA robots you can set A6 to infinite rotation, but note that any cables will still wrap themselves around the robot, even if the simulation of the robot looks clean.

For a clay or concrete extruder, you could potentially mount the non-symmetrical nozzle to the A6 and connect it to the rest of the extruder via a rotating connector. I guess that wouldn't work for plastic extrusion as it will harden too quickly.

Finally, more of a general remark: Do not use PTP motions for accurate toolpaths. Use PTP for the large motions and LIN for the accurate motions.

Best,
Johannes