Brady Watson posted the following on the SB Forum as an answer to this same question. It appears that all variations of a rotary axis have the same issues. Whether you buy from mfgr X, Y or Z, build your own, or buy one online, the following seems true.
Many of the challenges I had early on are still true today. Thought I'd chime in from memory - although things have gotten WAY better over the course of time where kids today don't know how good they've got it when it comes to indexing....
1) No instructions on how to mount the indexer and hook it up in software.
Long, long ago in a land far far away, I bought my first indexer from SB. It came with a single sheet of paper that showed the difference between a cove and a bead. There were no instructions on how to mount it. How to set it up in SB2 or later SB3....The head and tail stocks were too tall to mount on top of the bed and clear the Z, so you were guaranteed failure right out of the box. Mine sat for a few years before I messed with it. I wound up mounting it off the table and later, just bought a lathe, converted it to an indexer and welded another 18" onto the end of my table just for the indexer. This way it was always setup. In more recent times, SB has provided mounting options for the indexer. It only took like 20 years, but hey...they do it now.
2) I've got it mounted, now what?
Early on there were NO gadgets, tutorials or help (even from SB because even THEY didn't really know how to run the indexer, aside from a simple MB move). There were a few guys doing 3D incremental indexing (not really) using ArtCAM combined with calculating the 'magic number' using a function of Pi and your Unit Value to basically wrap a 3D toolpath around the indexer. There were secret handshakes involved and there were still plenty of questions. Documentation has gotten WAY better in more recent times, although it still leaves a bit to be desired. I suppose you must prove yourself worthy by tracking down all the info from SB and Vectric and then understand it all - which is 1000x easier than it was for me.
3) What kind of file do I need for the indexer and how do I make it?
Depending on the desired outcome, the kind of model needed for the indexer was a source of confusion. Does it need to be 'full 3D'? Could I make in in ArtCAM/Aspire, a 2.5D program? What about models that dipped in the center that couldn't be unwrapped? What then??? What about if I wanted to miter/fishmouth a tube so I could weld it to another on an angle? How about just engraving on the surface? Can I do a statue and get full coverage? How about machining something on 2,4 or more sides using conventional 3-axis toolpaths? How do you do those barley twist things with the form cutters? Can I use this thing as a lathe? What's the difference? The answers to these questions only came after doing a ton of research, playing around and actually trying things out - there wasn't anybody out there to ask...
4) How do I make money with this thing?
(crickets chirping...) Still trying to figure that one out.
The indexer is one of those things...you just gotta have one. It has a certain mystique to it...it can cut out ANYTHING!!! (or at least that's what we believed when we bought it) - It's interesting in the sense that, for those that bought one, it seemed to represent a level of skill we all aspired to reach at some point in our CNC 'career' or whatever. It represented possibility - whether real or imagined.
CNC Technology & Training
The Ultimate Woodworking Machine
GCnC411 (at) gmail.com