@dc42 Five axis painting machine and foam milling machine, my senior work in college. Attached is an image and video of the plastic prototype making a test painting of line-based moves if you are interested (it still isn't working how I want it to but getting there).
Essentially it has a continuous rotation axis that rotates parallel to the z. So certain circular moves with the brush following tangent end up sending the head on an "unnecessary" rotation which is due to the IK sending it a G0 A1 when it is at position A355. All GCode being generated in python and rhino/grasshopper, and right now I have a post processor checking for this extra rotation and sending a G92 to set A to -5 before the above mentioned G0 Move. This creates delays in the movement and can get messy.
Duet 2 and rrf have been the key drivers behind this machine and amazing so far. Also built this thing on a cnc running duet 3. Very exited to have this continuous rotation feature now.