g33 syncronized motion without spindle speed?

I have not posted a while. Been using my converted CHNC lathe for a few years without any trouble.... Anyway I was playing with rigid tapping lately which make me wonder something else.

Can I put a feed per revolution (lathe) say .050 per rev on the z axis but not command a spindle speed. I would like to do this in mdi then be able to rotate the spindle by hand and have the z axis move in sync with the spindle.

The application would be cleaning up threads similar to the way you can do it on a manual lathe. Seems entirely possible because I can use spindle speed override while taping and the feedrate is automatically adjusted.

Seem from the literature that it expects spindle speed. Is there anyway around this?

Thanks!

Justin

I think (have not tested):

set spindle running with M and S code
have spindle-at-speed true

So you would need to be able to set M and S code without the spindle drive actually responding.
You would need to be able to force the spindle-at-speed signal True (could already be that way)

You could also try setting the spindle override down to zero.
That usually requires a INI setting to be changed if using AXIS screen : MIN_SPINDLE_OVERRIDE

Chris M

Thanks for the tips. I can indeed fake it out by turning the spindle override to zero. This worked while in the middle of a g76 threading cycle as well. (that seems like what was going on in the youtube video)

The only thing is it will only feed one direction. If you spin the spindle in reverse it will not feed the opposite direction. It is actually pretty interesting. Say I spin the spindle 3 revolutions in reverse then start spinning it forward it will not have any movement until it has rotated the 3 revolutions back to where it started and then it will start feeding again.

I am guessing this is because it has either m3 or m4 as well as a z axis destination already programmed in.


I can't find anyway around this little problem. However I can probably do most of what I after feeding in one direction only. Just be careful to not rotate backward at all.


Justin