Review DTG vidieos he explains it it one of his ox builds
No ball screws then AFAIK mach4 is not to good yet on backlash
But use a jo block and a dti to measure your movement.
There is a good right up in the Mach 3 manual , m4 does not have the auto tune though
It is explained in the m4 manual as well it's just a simple maths problem