Hi All

I'm new to the forum and the CNC'ing and am currently building my 2nd iteration machine - it's a steep learning curve!

I need to achieve 0.01mm accuracy and precision on my machine and are building based on Hiwin 15mm rails, two rails per axes, duel carriages per rail and 1605 ballscrews, C7 grade and aluminium extrusions. I've build a first version and am getting the following accuracy and backlash (measured using a dial indicator):

X: 0.15mm (800mm rails/ballscrew)
Y: 0.04mm (800mm rails/ballscrew)
Z: 0.04mm (125mm rails/ballscrew)

I'm investigating why the X is worse than the other two axes, checking the fittings, plates, etc. But I do want to improve the overall accuracy and want to know whether fitting a second ballnut will improve accuracy and reduce backlash? If so, does the second ballnut need to be tensioned relative to the first ballnut?

Also to add, I know that accuracy depends on a lot more that just the ballscrew and ballnut, but I want to get clarity on this.

Shared knowledge, experience and constructive critique are welcomed!