Multiple Independant Z and C Axis Control Possible?

 Most Pick and Place machines have multiple placing heads so a new question is can you control multiple Z and C  axis?
I know LinuxCnC can control 9 simultaneous axis but am I stuck with X, Y, Z, A, B, C, W, U,  and V ?
Or can I rename them X, Y, Z1, Z2, Z3 C1, C2, and C3 or more?

 I could see numbering them could cause a problem and confusion in the system so I figured I would ask first.

If you want to control them independently and simultaneously in g-code you will need to have a axis letter assigned for each degree of freedom you intend to control in g-code. Possibilities would be XYZABCUVW and you would be limited to those 9 in g-code. So if you are wanting to have your multiple Z and C axis do different things at the same time you are going to have to use the drive letters. Where things get grey are if you don't need simultaneous independent control. Then you can do things with changing which joints are slaved to what axis letters, but this will add an order of magnitude of complexity to your machine configuration. So if your multiple Z and C axis are either doing the same thing together (slaved) or not simultaneously, then you could possibly use Z1, Z2... and be changing which joint is obeying the axis command using M-codes. Not sure what is the current practical limit for joints in Linuxcnc, last I checked I thought maybe it was 16.  Another possibility is to set joint position commands directly for joints unpaired with axis letters using M-code commands.  This could make synchronized motion difficult or impossible for those joints, but that might not be an issue for your machine design.

The machines I have two Z axis on, are configured as Z and W, and I have a set of custom M-codes that can slave/unslave the W axis to the Z axis and when slaved they move together with the Z commands. This lets me have different offsets for the Z and W. For example the start of the g-code file will move both Z and W so the tools in each are the same height above the material, then the axis slaving M-code slaves them together, the milling g-code is ran (with Z and W moving together with only Z commands), then the unslaving M-code is issued, the Z and W are sent to their machine zero positions and the g-code file ends.

 I guess independent was a bit misleading on my part. On any PnP that I have seen even multi headed ones, they still
put down one part at a time, but with multi heads you don't have to go back to a feeder every time a part is placed.
So M-codes to slave and un-slave would probably work best . Fortunately the machine I am currently working on
doesn't have true multi-heads. Just 1 placing head and one air actuated glue dot or solder paste dispensing head. 
However if I build another PnP in the future I would go the true multi-headed route.

tommylight post=237251 userid=17274 later you can kick me out!
Waiting for the wrath of internet to be bestowed upon me !

tommylight  you don't have to worry about me ever kicking you out .
I am still wrapping my brain around using Linuxcnc to my will.
I have seen some I believe called a turret head where they have mutiple nozzles mounted
on a rotor set at a 45 degree angle and it just rotates the appropriate nozzle into place to
deposit the part. Very complex obviously. A lot of th Charm High machines use a dual head and
a rack and pinion Z control so full + makes the one head place the part or full - make the other
head place the part.
 

a turret head style PnP

Often the com with peripherals such as Smartserial on a Mesa Card is going to be the bottleneck with about 4 or 5khz being the practical limit. (At least that is what I found with my 5i25 hardware trying to run torque mode servos.)

Holy crap, that was fast. (I don't see that working with Linuxcnc)

But back to reality, on a more normal pick and place with a half dozen pneumatic placer "heads" (is that really the right term?) I would not use them as axis or joints. Simply tool numbers, each with their own XYZ offsets, Calling each individual tool number lowers it and raises the others and changes the position offset. easy peasy, no wonky joint or axis magic required.