thx for the link and replies.
But what happens if the stepper misses one or more steps (or oversteps)?
I feared this would be a reply. yesterday evening a read a datasheet of a stepper and it said "stepping accuracy 5%" and i was like omg pleaaase dont -why cant this be just plain simple. 
Is the "forward" and "reverse" movement of steppers/gearmotors usually done with relays?