Slightly More Parametric Prusa Z Screw Isolator

Needed a bit more adjust-ability for use with differently sized threaded rod from the smooth rod, and differently spaced smooth rod from threaded rod.

Basically just made it more parametric and set the variables to my needs.

UPDATE: Uploaded new copies of the SCAD and STL. I had an error in the scad where the flat to flat measurement of the nut was not calculated properly for the true diameter of the 6 sided cylinder.