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G95 spindle sync on Hurco


Sep 15, 2015
London, UK
I'm trying to run something similar to a tapping cycle, where the spindle rotation is synced to the Z feed, but I don't want to reverse out of the hole. It's for a decorative knurling application.

My understanding is that I should be able to use G95 before a G1 move, but It's not syncing. Machine is a Hurco VM10i and the Hurco manual lists G95 in there, but with not a lot of info.

Am I missing something from this code or is what I 'm trying to achieve not possible with this control?
S100 M3
G95 M29 G1 Z-2 F1

M29 enable rigid tapping, which I thought would help, but no luck so far.

Perfect synchronization is possible only in rigid tapping which is an option.
Why you do not want to reverse out of the hole?
Retraction can be 20x faster on Fanuc. Something similar on your control, possibly.

M29 is not for G01.
Thanks for the reply

Yeah, i have rigid tapping, i can use G84.2, but obviously have no control beyond the parameters.

As i understand fanuc controls allow tapping using G95 as part of an expanded tapping cycle, and the Hurco mill controller documents G95. I'm just trying to work out how to use it.

My immediate use is for a knurling pattern. It would be a neat solution, but i can work around it if I can't get G95 to work.

I dont have a cnc lathe so do a bit of spindle mounted turning. I would like to be able to do threading in this configuration, which I'm pretty sure would need the rigid tapping synchronisation to be possible.

I know it's a pretty unusual use, but the possibility is tantalising.

G84.2 and M29 G84 are the same thing on Hurco.

G95 has nothing to do with synchronisation, it only allows you to program the pitch directly in a rigid tap cycle.

In short, it's not going to do what you want to do.
Rigid tapping is the only way to get Z-spindle synchronisation on most mills (yours included), and there is no way to have it not reverse out of the hole.

You also have no control over starting orientation with rigid tapping.

The only way to do what you want to do is to have the part mounted in a 4th or other indexer oriented around Z and have a cutter that will tolerate being dragged back through the cut on retract so that you can use the rigid tap cycle and index the part between passes.
OK thanks, I thought it may be the case.

Regarding starting orientation, my understanding is that rigid tapping performs a spindle orient at the top position before the cycle. The documentation describes being able to re-enter a previously tapped hole (I've never actually done this) but it would be needed for peck tapping which my machine can definitely do. To change the thread orientation in the hole, just vary the top plane across the distance of 1 pitch.

rigid tapping performs a spindle orient at the top position before the cycle. The documentation describes being able to re-enter a previously tapped hole
That is correct.
I have no idea about your control, but Fanuc has made spindle orientation at R-point parameter-dependent. If rework is desired, this parameter would need to be appropriately set. Of course, once the job is unclamped/reclamped, rework would not be possible using usual methods, as the thread orientation would change.