[solved] Rehoming Lathespidle / Rotary-Axis from inside GCode

smc.collins wrote:

excellent thread guys, I'll look at caxis.comp and see if i can figure it out
 

NoJo's responded in his original thread I drug up... I suspect he will be able to shed some light on the whole shebang.  Might want to pay attention to that one, too.

Your insights are also, as usual, most welcome.  I tend to grab my popcorn and thinkin' cap when I see you post something.

I am thinking about handling the c axis and spindle by controlling the encoder signal by using the enable for each, and then using macro's to force the rehoming of the axis or spindle orient on each enable. IE if spindle is enabled, call orient from a macro and  then have the output sent to the spindle encoder , when in c axis, the encoder output is sent out to C axis then macro calls home and resets encoder. at least, that what I have worked out in theory. This functionality really needs to be integrated into linuxcnc at it's core.

smc.collins wrote:

 IE if spindle is enabled, call orient from a macro and  then have the output sent to the spindle encoder , when in c axis, the encoder output is sent out to C axis then macro calls home and resets encoder.
 

Do you think you need to orient the spindle?  I gather the C-axis homes every time it's enabled (like my Fanuc), but I don't see the need for spindle orient once a C-axis is available.

And, looking back through NoJo and Andy Pugh's discussion while they were working out the bugs, resetting the encoder on C-axis enable results in the C-axis immediately homing. 

I think this takes place in caxis.comp.

Maybe.

well, the index iirc is used by c and spindle, for m19 etc.

I'll try to get to testing in near future, busy working on my slv40 mill currently.

resetting the encoder on C-axis enable results in the C-axis immediately homing.

As I see it the problem when switching from spindle mode back to rotary mode is to get the motor to match the commanded position of the rotary axis before the encoder was disconnected in the switch to spindle mode. If the commanded position does not match the encoder feedback a joint following error will occur when the encoder is reconnected. That is at least how I understand it.

Thus, in my opinion, just resetting the encoder count to the index is not enough since there is still a difference between the commanded position (which has not changed during spindle mode) and the newly reconnected encoder position simply because the motor is in a different position.
Using M19 in spindle mode seems the logical solution to orient the motor to where it was in rotary mode.
The question is, how accurate can the spindle be oriented using M19?
 

So it does seem that the caxis.comp is the component that I had remembered. Here is the whole saga, unfortunately the thread title is misleading:
forum.linuxcnc.org/10-advanced-configura...and?start=140#210682