4th Axis Question.

I just saw on ebay a shaper attachment that is powered by the spindle of a VMC. Nifty. Might have been a Volstro, but I can't be sure.

I forgot about that trick yup works great for soft jaws and emergency collets you'll be dead nuts concentric....

Also this works on the manual indexers, use light cuts and lock out the indexing latchpin so that the table simply freewheels...circular feed ( mostly conventional cutting ) by hand via a large crescent wrench or a chunk of barstock clamped onto one of the jaws as a handle.

I ground the taper on a CAT 50 adaptor for our rotary indexing table directly on the machine. Easy to hit the right angle when you can just program it - and runout was perfect.

Not sure my indexer can be programmed via the controller for continuous rotation but your concept certainly should work fine if table were to be disabled at the cnc leaving only dc power supply and tach loop to the amp ( velocity mode ) ( also BRAKE OFF ) The +/-10 analog 10vdc speed sig would be easy enough to supply using some selection of one or more 1.5 v dry cells in series. Fact is I have a possible app for some "mill turning" that involves small diameter ( a few thousandths dia ) in brass and likely will do some R&D using this concept really soon.

Well, our table can't do continuous rotation as such either. I programmed all three axis in the same line, like milling a tapered thread using G91. Something like this:

G91 X10 Z-100 A999

At one point the control would bark and stop if the accumulated A value became too large, so a bit of fiddling was involved. It would be nice if this "rev counting" could be bypassed. It would then be just a matter of running a simple loop while the table kept doing it's thing.

Gary:

You mean compressor scrolls like these?