you need to set the steps per unit correctly. If you are using imperial (Inch) then this is what you need to work out.
If its steppers are they 200 step per rev or 400, they will most likely be 200.
What stepping or microstepping are your drives? this could be full, half or 8 or 10 or?
Do you have any reduction between motor and screw?
What is the pitch/tpi of the screw?
When you know that you can work it out, I will give an example of 200 step motor 10 microstepping drive, 2:1 gearing and 10 tpi screw.
200 x 10 =2000 ( pulses for one motor rev)
2000x 2 =4000 (2 motor revs for one rev of screw)
4000 x 10 = 40,000 (10 turns of the screw to move 1 inch)
So your steps per inch would be 40,000
Hood