Autodesk team changed the post, and then messaged me to ask if I wanted to test it! Which I have just been doing. All looks good from their side, but I am seeing some slightly odd behaviour from UCCNC. I did a shape below, so it started at D5mm and progressed along until moving to D10mm and then D20mm. It runs OK at 100% feedrate, however, when I reduce the feedrate down low with the override to say 10%, it gets buggy. The feedrate is then not constant, in that it will suddenly increase, then go back down again, with sudden and seeming random jumps forward. Sometimes the jumps are quite large, like a whole rotation. Also, on the other end of the scale, there seems to be a cap regarding the maximum speed I can make it rotate at - even though the axis itself is capable of going at 2000rpm, when running with G93 it maxes at around 60rpm. This seems to be irrespective of whether I increase the feedrate in fusion, or if I increase feedrate manually above 100% with the override. I have checked the gcode, and copied sections of the A co-ordinates with F numbers, then run them through excel to calculate the rotational deg/ms speed, and the output from fusion seems to be constant. Also, although the behaviour is most noticeable when I set the feed override low, I can put my finger on the axis and feel it doing tiny little jumps as it progresses when at normal speed. Sometimes it also sticks a little once per turn.
There is a slight oddity from the fusion produced code that could be related, in that the cylinders are simple in the model, but the gcode has tiny movements in the Z position up to 0.004mm. I cannot see it is an issue with my Z axis feedrate, as the axis is capable of going fast enough, and the moves are really really tiny. I can put my finger on the axis, and feel the stepper making tiny adjustments, but these seem to be unrelated to the random A axis movements. Also I can see on screen, each time it jumps forward the feedrate likewise jumps upwards, and UCCNC jumps through multiple lines of code. Finally, I just tried running the code on my desktop in demo mode and offline (latest version), and set the Z axis to the max speed and acceleration that I could, and that doesnt give me a constant rotational speed either. It would be interesting to strip all these tiny Z moves out the code and see if it still does it, but I am unfamiliar with the type of programming that would be required to go through a text file and do that. Also, I only copied small sections of the code over into excel to check, so it is still possible that the problem is there, but I dont think so.
I've attached a picture of the model and toolpath, the nc file wouldnt upload but I've made a link to it here if you want to check:
https://1drv.ms/u/s!Auwy2_XWmERmm3mR3e6iFo8Lj_Od - can also upload a video of the behaviour if helpful.
Anyway, I'll try running an actual carving file tomorrow. Maybe it wont have so much of an effect, so long as I dont try to override the feedrate. Above looks like a bug to me, but apologies if I have missed something obvious. Still learning!