Follow up to my last reply.

Mach 3 is sending 8.3 - 9.4 volts DC to the VFD when I have commanded 6000rpm in Mach3, It definitely fluctuates. . This may be a Mach 3 or possibly a ESS smooth stepper issue/setting. Not sure where to go from here, but I can get the full 6000 RPMs if I control the VFD myself.