motor tuning

[trucks1948]

I have an old practical cnc table with stepper motors.How do i tune my Z axis motor correctly?For that matter how do i tune all axis correctly? I mean i know where to do it,how do i determine the correct settings?.I have a problem with the Z axis losing motors occasionally.I thought it was the slides binding up so we rebuilt(freed up) those.Still having the problem ,so i'm wondering if the wrong settings in the tuning could be causing it.Any help would sure be appreciated.Thanks Jim