caxis.comp - spindle reverse

@Andy,

As you might have noticed, I've resurrected NoJo's thread regarding the work you and he (and others) did on his live-tool c-axis DIY lathe in 2021.  My own lathe is nearing completion - axes & spindles are moving reasonably well - and it's time to work on the C-axis function.

While waiting for a reply from him, I've been re-reading the multiple threads and trying to digest everything - specifically caxis.comp.  If you don't mind revisiting the topic, I have a few questions you may be able to clarify - perhaps better than NoJo as you appeared to be the primary author.

NoJo's last posted config (5/2023) looks like he added a switchkins function, via G12.1/13.1 and some m-code bash commands, to your basic caxis.comp component.

However, the last caxis.comp file you posted (5/30/2021) looks like it doesn't contain any reference to polar interpolation.  If my thread-reading skills aren't complete garbage, it appears that the control scheme you intended was:

• lathe turned on
• all axes homed, including C-axis
• lathe is in C-axis mode until a spindle command is given
• spindle command executed
  • PID switch handled by caxis.comp
• spindle stopped
• Resume C-axis mode automatically
  • switch back to c-axis PID
  • C-axis moves to last position prior to spindle engagement
  • Does not need to unwind more than 360 degrees

To paraphrase a comment PCW made in one of the threads: it's a C-axis with spindle capability... not the other way 'round.  Have I got it right?

Assuming I'm not way off base, here's my question, or at least my concern...

My lathe is a gang-tool setup, and I know I'll (eventually) have tools that are front, back, M3 as well as M4.  I'm concerned that if I have an M3 tool followed by an M4 tool, each spindle direction change will need to wait for the C-axis to return to the last position.

Is there any way to stop the automatic C-axis mode resuming after a spindle-mode stop?  Perhaps a modification of caxis.comp where some pins are added that can be tied to motion.digital-in pins or M-codes that stop the C-axis mode from forcing a re-home until triggered in g-code?

I guess what I want is a spindle with non-automatic C-axis capability...

Am I even in the right ballpark?

Thanks,
R
 

andypugh wrote:

• Is that a major problem? I think I would suggest trying it out first to see if you even notice.
  
  (Also, if the spindle remains on, it will probably just reverse without going back into C mode)

Wise suggestion, as usual.  I'll have a go at it and see if it behaves.

@Andy,

Thank you - M3 to M4 works as you suspected.  Spindle reverses without returning to the last c-axis position.

At M5 it stops and returns to last c-axis position before spindle mode.

(sorry for fiddling with the thread title)