how much resolution do I need?

[jrz126]

I've been wanting to build my own CNC for a few years now, and I've slowly begun to collect parts.
I just got these ball screws:


They are 1/2" per turn, about 26" long. Problem is, the encoders are coupled to the ball screw and only 250PPR. So the best case I can do is 0.0005" if I sample the encoders at 4X.

Will my actual resolution be anywhere close to 0.0005"?

[mike_Kilroy]

u sure those are 1/2" per turn? sure look cruder. r they 1/2 diameter screws?

if so, quadrature is indeed .0005" so yes your resolution is .0005". and depending on your control you can expect anything from +/-1 count best case to +/-10 counts stopping and holding position. If designing new system we try to get enough res to have 10+ counts for the final position res wanted to be safe. that said, we have lots os systems that spend their life bouncing +/- 1 count.

I would use what you have until you find it is not good enough then change it. for now starting out it is good start if that is enough resolution for your job.