About two years ago bought an old mid eighties VMC, stripped off everything except the servos, and installed a Galil ethernet 4********* controller with the Mach3 plugin. Got everything to work, but my machine had .003 backlash on x and y axis. Found out that Mach3 compensation doesn't work with Galil. I read about Galil dual loop and decided to put some 1um scales on my x and y axis. I couldn't be happier. I get amazing accuracy, within a couple tenths. It's so nice to be able to machine separate parts and dowel pin them together and have them fit perfectly. Thanks to the Galil plugin that makes it possible.

FYI anyone setting up a dual loop system, one thing that is odd and interesting. When I originally started using dual loop, I couldn't get mach3 to settle at the exact commanded position. For instance if the command was G0 X0.3 the machine would go to X0.2997. It would usually be +/- .0005. What I found, and I can't remember how I discovered it, was that if i put a coordinate system command in front of the move I get a move that settles at the exact commanded position, or at worst, +/- .0001. For example:

G01 X.3000 will go to X.3000 plus or minus .0005

G54 G01 X.3000 will go to X.3000 or at worst plus or minus .0001