LinuxCNC S-Curve Accelerations

These are in inches.

So my understanding would be:

So 20 IPS max Velocity
200 Max accel (~1/2g) so 1/10 second to maxvel with no jerk limit (old TP)
2000 Max jerk  so 1/10 second to full accel

Which (jerk=2000) actually sounds a bit low

Those ini values do not cause an issue with the old TP (0)

I'll check your suggestions in a bit...
 

PCW wrote:

These are in inches.

So my understanding would be:

So 20 IPS max Velocity
200 Max accel (~1/2g) so 1/10 second to maxvel with no jerk limit (old TP)
2000 Max jerk  so 1/10 second to full accel

Which (jerk=2000) actually sounds a bit low

I was doing some math to create paths (not real time) a little while back and on my machine with 0.5G (5000mm/s/s) a jerk of like 50000mm/s/s/s was the starting point of usefulness, and 500000 would probably be where I end up. So your 10:1 seems a logical place to start.

BUT, it shouldn't matter. Jerk should never create a following error, it should be mathematically precise, even if its comically low for real life machines.
 

OK so the bad ini values seem to be LinuxCNC defaults (they were not specified in my ini file)
With more reasonable values set the errors are of much smaller magnitude bu there are still accel violations: 







Note that the acceleration (green) which has a constraint of 200 IPS/S sometimes obeys this constraint
(right side of screen) but sometimes ignores it (spikes toward center of screen reaching more than 1500 IPS/S)


ini file settings: 



 

 

Could you try again with arc blend enable to true?

Which G-code did you use for the test? I'd like to try it myself.