How do you deal with backlash???

You probably have to take the motor off, but I would put an indicator on the end of the leadscrew and turn it back and forth. Total indicator reading is the amount of backlash from your thrust bearings. You can assume any remaining backlash is in the nut. You can check the nut directly as well by putting a mag base indicator on the table and pressing its tip against the side of the screw thread. Rock the screw back and forth and any relative movement you see there is backlash in the nut.

Found the problem on the Y axis. The retaining bolt that held the ball nut in the housing was not tight. Never assume that something is done right, if you haven't checked it. Backlash is now cured on both X and Y axis.

thanks,
Ken

There is most certainly a mechanical problem! Ball screws can minimize backlash to at least 0.0001"
if configured correctly. My mill beds lash is below the detection of a 1/10 reading Mitutoyo dial
indicator.

Are your ball screw suspension bearings angular contact thrust type? Are they correctly pre-loaded using
bearing shims? Are you using a dual ball screw bearing nut so that you can also pre-load the nut assembly?
Are the bearing housings and ball screw bearing attachments secure? Any one of these could be the
cause of your problem.

Good hunting