Re: Z axis backlash of around 0.2mm could it be a worn ballnut ?
I decided to making a mounting and install a new motor that would crank the spindle up to 20krpm
Hopefully you don't mean spinning the stock spindle 20,000 RPM , that won't work for long.
what I have suddenly found is that each pass the tool seems to be dropping very slightly.
If the error isn't greater than commanded position +/- backlash maybe you're on to the problem. If it's greater than that start looking further.
do I need to replace the entire nut or can i just repack it with larger balls
cncfusion used to repack with larger balls for an extra fee. Worth a try.
Anyone who says "It only goes together one way" has no imagination.