You should also check your encoders as the problem with limited speed and faulting drives may stem from the encoders being mismatched.
Mach3 has a limit on how many pulses it can put out. If you have high count encoders then your motor speed is going to be slow no matter what the power supply is.
From your first post using those motors and a power supply of 75v at 30 amps you should have a half decent setup.
To get any kind of speed and resolution out of Mach3 from the printer port setup, you'll need a max of 2000 pulses per 1mm travel.
More pulses per mm = less speed
John |