200 ipm seems dreadfully slow when in production. I would like to see if I can get this machine in the 400 ipm rapid area. The current setup is Mach4 -- Hicon Integra controller -- Viper 200 servo drives -- Anilam DC servo. I am running about 90vdc on the power supply. I can get up to 250ipm but not as reliably. I am looking to switch to AC servos, possibly something from DMM, but I am finding it difficult to determine what is equivalent to what I have, and what is better.

Current servo specs are:
3.5Nm
140 Max V.
30A Peak
31 in-lbs
6.5 Cur-A
2400 Max RPM

Screw is 5 tpi, pulley ratio is 2:1. This results in .0001" resolution with the current setup.

So, end goal is 400ipm with the same resolution. This is a decent sized bed mill, 7.5hp spindle. 20 x 40 x 20 travels.
Is direct drive an option on the screws?
I would like to start with just the z-axis (biggest bang for the buck).
Thanks!
Joe