cupholder end knob

Simple end knobs for a badly-designed cupholder -- to stop cups from falling off. Tapered so they slide on easily. The hole itself is **9.5mm**.

A previous version included text on the end. It didn't print well, so I removed it.

Composed using _openscad_. This version uses a dxf profile created in _inkscape_ for the shape of the end itself. A previous version used minkowski on an annular disk & sphere (but took 5 hours to render :-/)