Hybrid Manual/Stepper Control

Hi Folks,

I have a bit of an odd use case. I have an RF45 clone machine, and given the position of my z crank, I don't ever want to touch it, and would prefer to use the Z controls of LinuxCNC. However, I want to maintain manual control of my X and Y crank for the occasional manual operation.

Is there a reasonable way to make LinuxCNC control my Z, without getting unhappy about following errors on my X and Y, without having some kind of "modal" behaviour, where it "snaps back" to the commanded position when I exit that mode?

 
One option is MPGs, you could install two MPG encoders.

timo wrote:

 
One option is MPGs, you could install two MPG encoders.

That is a very good idea as it eliminates many issues caused by other methods regarding feedback and jumping to position and ...
There is another similar topic going on here on the forum but i do not think this idea was presented there, i will double check if i bump into it.

forum.linuxcnc.org/27-driver-boards/4698...7i96s?start=0#252760

I made a lathe with manual control of two axes simulatively, although apart from the servo motor as the main spindle I didn't have another axis as in your Z that could do its thing while these two are moved manually as I understood. maybe something in this topic can help.

Thanks for the replies! I have considered putting independent x/y MPGs somewhere on the machine, but it doesn't quite scratch the itch I'm trying to scratch. 
My background is a manual machinist, and I wanted to add some CNC capability to my arsenal, even if that came at the cost of being able to do manual machining the way I used to. That said, there's no substitute from the feedback you get from turning the cranks, when you just need to make a quick slot, face a part, etc.
It seems like LinuxCNC (appropriately) is really intended almost exclusively for the CNC use case. 

I am pretty sure something can be done with some hal or tailor made component, but i never had the need for such thing.
Should be possible with encoder feedback to LinuxCNC as it will continue to monitor position even when drives are disabled, but i do not recall if it also adjusts the output position while disabled (i think not).
That also has the advantage of using the LinuxCNC as a DRO when using it manually.