What stepper controllers are you using, with what current limit, and what power supply voltage? Limited current, or low voltage will seriously degrade high speed performance. Even with steppers, properly setup you should get at least 100 IPM, though using leadscrews instead of ballscrews will decrease performance significantly, due to the greatly increased friction. You will also likely find the nuts wear, and develop backlash, very quickly.
Regards,
Ray L.