Lathe C axis homing

The commanded C position should come directly from LinuxCNC, It should not have steps
nor be affected in any way by PID settings.

Can you post your HAL/INI files?

 

It does make some sense to me that the commanded position would stay ahead by some bit so that it doesn't instantly get massive following error, but am not sure at this point. It comes from joint.n.motor-pos-cmd. I've attached the config files here

OK I guess I got too swayed by the "homing" in the title when in fact this looks like a C axis
programmed path where the "steps" are real.

It basically looks like  the acceleration is too high to the spindle to follow. This may just be physics
(inertia vs spindle motor torque) or programming (some acceleration limit set in the drive)

Yeah, the title is a bit misleading at this point, but not sure it's worth making another thread for this.

I see what you mean but I've tried vastly different acc/vel values on the joint and stepgen sections and it still has the same kind of behaviour.

If it was a physical issue that should be ruled out when using stepgen.position-fb instead of encoder feedback, I'm thinking so? But that makes no difference still...

I tried to figure out how the joint comes up with the position command but with no luck either.

With open loop, (stepgen feedback) you need to have a _much_ higher P term
(typically 1000 with a 1 ms servo thread period)

 

I've tried that too. Now I've noticed that I have pid.c.feedback-deriv connected. Maybe getting rid of it will help, Guess I'll try that next.

A little update as I've found the issue. It was the spindle-at-speed signal. Connected to encoder feedback it would go off in axis mode and I assume it's Gmoccapy behavior that it halts all motion if that signal is false.

Still took me embarrasingly long to figure that out.