I've got some of them, not actually ball screws but they do look interesting

After you decide to go to ball screws you then realise double nuts are a good idea, then it's sprung double nuts. I even spring the axial bearings together on the Y/Z and hold the X screw in tension. No measurable backlash, not a sausage, or tiny fraction of a sausage even :heehee:

Not sure what comes after that because I haven't got there yet :naughty: