MakerFarm i3v Z rod support - Improved

This improves on kkessler's Z axis protectors by adjusting various dimensioning such as hole spacing and hole sizes, allowing for a corner radius that better matches the MakerFarm style, and by providing additional options regarding use of a bearing.

Only a single support bracket design is provided that is intended to be used on both Z axis threaded rods. I don't plan to provide a version that includes mounting provisions for the MakerFarm top-side spool mount.

The openSCAD file allows many parameters for the support bracket to be customized.

Three predefined STL files are included. File Zrod_support_bearing_none.stl has no recess for a bearing. File Zrod_support_bearing_top.stl has a recess for a 625 bearing (same as on the V-rail wheels) on what will be the upper side of the support. File Zrod_support_bearing_bottom.stl has a recess for a 625 bearing on what will be the lower side of the support.

FYI - The knob shown in the gallery picture is Grainger #3GFJ3.