This post is just a placeholder for now, but I finally bit the bullet and bought a rf-45 clone machine that I have been wanting for a while. I have a G0704 that works fine,but have wanted the Grizzly G0762 ever since I saw one while visiting the Grizzly showroom while on vacation about 3 years ago. This machine already has a vfd and 3 phase motor and I believe with re-programming of the vfd could be made to go a bit faster. We'll have to see on that though. The trigger for finally buying it was when I saw that the machine is aon closeout at Grizzly for $2195 from its list price of $3493. The machine is essentially the same as the G0761, but with the vfd and 3 ph motor. I won't need the power feed it comes with but the price of the G0762 is actually less than the G0761 right now and only a little more than I could find any other rf-45 clone for..
Anyway, the plan for this machine is 20mm ballscrews with double nuts on each axis. The drive type for the axes is still a little up in the air, but will be closed loop of some type. I haven't ruled out closed loop steppers but am leaning toward either DC servos with gecko drives, or DMM AC servos. I'll have to weigh the pros and cons before I make up my mind. I'm hoping I can eek out 9" y-axis travel From one youtube video I've seen it appears that is possible as the limiting factor on the travel as it comes from Grizzly is the big switch box for the power feed. It sounds like just removing that gets you 9" travel with a modest amount of overhang of the base. I'll know in about a week once it gets here.
The first things I'll be doing are building a temporary wood stand to get it to a comfortable working height, then disassembly of everything for measurement for the conversion, and also to verify that the head internally is clean. I've read too many horror stories about rf-45 clones that had grit in the gearbox. Then it will take some time for me to design my conversion. I figure each brand of the rf-45 clones probably has enough variation that other designs would at least need verification.
I'm going to try to hold onto my G0704 long enough to make the conversion pieces for the G0762, but in order to avoid sleeping in my workshop I promised Mamma that I would be selling the G0704. I'll have to see how long I can hold her off.
Here is a stock picture of the machine I bought.