ball nuts grinding? why

[replicapro]

I put brand new ball nuts on, and they are grinding so much that its faulting the servo. I put white lithium grease on the ball screw and sometimes its ok other times it is horrible sounding.

Could this be to many bearings in the nut? not enough? I don't get it.

[posix]

Usually people find that when it's noisy then their ball nut is not 100% paralell to the ballscrew. So I guess the first thing would be to check that

I've seen bits of paper used as shims to get them to align properly.

[replicapro]

ok Ill try adjusting it

[NC Cams]

DId you check the ball sizes??? Keep in mind that balls are selectively fit so as to match the nut and the screw.

A couple of tenths oversize ball could tighten them up quite a bit - like in serious preload. Rotation force goes up quickly as you go into negative clearance.

Also, it is not uncommon to stagger the ball sizes ala OoOoOo etc when you load the nuts/screws. This helps keep them from binding as they roll thru the nut and screw.