Himy, I just reread your posts to me and I've still got some questions, I'll try and make this simple. I haven't done any grounding yet, I've kept the machine under 10 IPM and these days that's too slow so I'm going to do the wiring today.
120V Ground = Lug on Metal Housing Box
12VDC Negative From PS Side One = Lug on Metal Housing Box
12VDC Negative From PS Side Two = Lug on Metal Housing Box
Lug on Mill = Lug on Metal Housing Box
220V Ground on OUTPUT of VFD = Lug on Metal Housing Box
12VDC Negative Power Supply for VFD from it's circuit board = Lug on Metal Housing Box
5VDC Negative Power Supply from BOB = Lug on Metal Housing Box
Shield Wire from Signal Cables for Limits Switches and Accessory Wires = Lug on Metal Housing Box
Shield Wire from Each Stepper Cable = Lug on Metal Housing Box
If the above is correct then the only thing I don't get is where you say to ground the Stepper Drivers, the Negative 72V going into it is from the Powersupply and I mention that above as grounded, do I need to tie in the A- and B- of the drivers that go to the steppers? Thanks.