Combination Turning-Spindle/C-Axis - HOW?

[kmckenn]

I've been around and programmed a "C-Axis" on a turning center... and it's never dawned on me as to "How its Made" (Works) before.

Can someone point me in the direction to find information on how thats done? What drives 1000's of RPM's and can function as a rotational milling axis?

Just CURIOUS...

[Al_The_Man]

Its usually done one of two ways, if the spindle is driven by a regular non servo spindle drive, when using it in a C axis fashion, the spindle is de-activated and a C axis servo motor is enabled to position the chuck.
The other method requires a spindle motor and drive system that is capable of servo control.
The problem with the second method is that it requires an encoder on the final spindle shaft and if there is a multi-change gear box between the motor and the chuck, then this can cause problems in positioning.
If there is no gearbox (direct drive), then the latter method can be used.
Al.

[kmckenn]

It's actually kinda odd as to how the proverbial "?" finally came to floating over my head...

The background...

Not long ago, I provided MILL fashion programming on 7-Axis machining center, where a good bit of that was engraving type work accessing the C-Axis after turning operations were complete on the parts (obviously knowing that single spindle performed both purposes). I'd also provided similar programming to a Lathe with a C-Axis and live tooling.

And, I'd supplied programming for a 5-Axis Mill (X-Y-Z and B-C)... an awesome experience! Once you've had 5-Axis's available, it's hard to go back!

Today...

I own a couple of little used, nice Table/Bench Top CNC machines (EMCO PC-Mill55 and PC-Turn55 ( http://i1016.photobucket.com/albums/...ll-Lathe55.jpg )). Like most guys that have a 3-Axis mill, ya want MORE... (ToolTime/Tim Taylor comes to mind) at least an A-Axis.

I've been doing a lot of homework on researching ways to add at least an A-Axis to the EMCO Mill-55.. be it by retro fiting all new components in, or even scavenging components off of the Turn55 to feed additional capability to the Mill55. THEN my eyes started crossing (conceptually) and my two machines that are sitting beside each other started turning into overlapping ghost images... the spindle on the Turn-55 started looking alot like the A-Axis I was wanting to upgrade onto the Mill-55... I even began having visions of a Mill/Turn55 "Machining Center" coming to mind.

OBVIOUSLY problems arise from thinking that I could MILL on the Lathe spindle, or Turn parts on a worm driven "A-Axis"... Then my semi recent experience(s) of C-Axis programming on turning centers come to mind... and it naturally leads to the Cable TV show type question.... "How'd they do that?", "How it's Made".

I know just enough to be dangerous, and not nearly enough to answer my questions, or even waiving the notion that it could reasonably accomplished... how to even GOOGLE the right question on how its accomplished. I thought it was a good question, this is the only place I know to ask it, so here I am! :-D

[Al_The_Man]

I just CNC'd a 9"x30" LatheMaster, I used a direct drive Fanuc servo motor for the spindle, with a 2500 pulse encoder, which gives me 10,000 pulse resolution after x4.
This can be used as a spindle or 360° positioning as a C axis.
Al.

[keebler303]

Al

The spindle is driven by a toothed belt pulley? Is this rigid enough for C axis milling?

Matt