Router will not go up and down all the way

So i did only 1 cut with my router and now the router lifts up twice or goes down twice and makes a grinding nois . Any ideas?


We need more details to be able to help you adequately. What kind of router? Does it move sideways at all? Does the sound come from the router or from the stepper motor?

I have over tightened the belt at the top of the z axis to the stepper binding it against the bearing, you may also of cross threaded the delrin nut but as Robert says there are several other items of info that may help in a diagnosis.