Your steps per unit are determined by your motors, any reduction you have beteen the motors and ballscrew/leadscrew, the pitch of the ballscrew/leadscrew and finally if your drives are microstepping.

For example, say you had 0.2 inch pitch screws, normal 1.8 degree (200 steps per rev) stepper motors, 2:1 reduction and 10 microstep drives it would be as follows.

Amount of steps to turn the motor 1 rev is 200

Amount of microsteps is 10 so that means the drive needs 2000 steps to rotate the motor one revolution.

You have 2:1 gearing so it takes two revs of the motor to turn the screw one revolution so that means 2000 steps x 2 =4000 steps to turn the screw one rev.

Finally your screw is 0.2 pitch or 5tpi so it takes 5 revolutions of the screw to move 1 inch (which is one Unit to Mach) so 5 x 4000 = 20,000 steps per unit.

If your machine is moving one inch when you tell it to move one inch then the steps per unit you have set will be correct.

Hood