[WesM]

I'm a real fan of the GS units. I had a GS2 on my mill for years, and later installed a GS3 when I went to direct drive and eliminated the vari-drive.

I am also a real fan of linear encoders, glass or magnetic. I have 1 micron magnetic linear encoders on all of my machines. About $120 / axis. Putting the encoder on the axis rather than the lead screw automatically compensates for backlash and leadscrew errors.

EDIT: Your other question about the interface with the Acorn controller, no they won't. The Acorn system is step & direction, the drives you currently have appear to be analog control. And in that case, the encoders won't do you any good. The only encoder input on the Acorn is the spindle encoder. I like the ClearPath SD ''servos'', they seem to work well. There are a number of closed loop stepper options also.

Ah ok, that answers that question, I should have figured they were analog. I don't know if there would be any point in just replacing the encoders and drives, but at this point I think I am looking at a full DMM servo/driver replacement. I do plan on pricing out a closed loop stepper system, but from my initial research it seemed like they were going to end up costing pretty much the same as, or close to the DMM AC servo system. The more I look the more it seems like the DMM setup is a great value.

On the subject of closed loop system, from what I understand the DMM systems are closed loop at the encoder? Not sure I completely understand that, any pros/cons vs closing the loop via controller?

You always want bigger than the motor rating, 5Hp is fine and what you need when going to single phase, don't worry if the VFD drive says it is for 3ph input they work fine on single phase, any good quality VFD will work fine, just some are more confusing than other to set up, but out of the box for your motor, yours would run, as the default parameter settings would be at 60Hz, you can adjust some of the Parameters to suit after you get it running

As Jim said, just the encoders won't help you, you want the complete Dmm package if you are to use there system

Sounds good, at this point I will plan on using a GS2 5HP VFD. For the DMM package do you have any recommendations on the DYN2 vs DYN4 drives? The main difference I can find seems to be the DYN2 are used on drives up to 750w while the DYN4 go up from there. Are there quality and or performance differences? Assuming I want to hit a max of 300 ipm rapids with normal probably being closer to 200 ipm on this machine.