Ballscrews correct pitch

[justingro]

Building a new router and am trying to get some idea on the correct pitch for the Ballscrews to get a reasonable amount of speed and some repeatability and if I should drive the Ballscrews direct or by stepping it down I'll be using a closed loop 8nm motors any advice will be appreciated​

Justin

 

[madscientist]

Hi Justin,

from what I have gathered so far in my research (I ve only been really going in depth the last few weeks) it seems that the finer the pitch in the ball screw the better the resolution, generally for CNC applications a pitch of 4-6mm is preferable. It will also depend on the tolerance the screw is made to and what kind of nut the screw has. The screw will have a C or T rating along with it. C0 being extremely precise and T4 being a little more sloppy. Generally a C3 with a circulating nut are more than suitable. Generally you can reduce the amount of error by also stepping down with a 2:1 ratio so the stepper is spinning twice as fast as the ball screw, this effectively halves the error again. THK have quite comprehensive catalogues you can download and go through. So far I ve decided on the BNFN-V type.
hope this helps

 

[justingro]

Hi mad

Thanks for that this was helpfull I'm also trying to find out what is a respectable speed for the axis still trying to learn all these duel pitch or twin starts ECT and how they effect speed and accuracy and resulution massive learning curve

Justin