Double Pivot Parametric Filament Guide for P3Steel or Prusa i3 6mm frame

This is a redesign of the Filament Guide for the Prusa Mendel by tosjduenfs (thing #34133). I liked the idea of an oscillating arm holding the filament guide but it wouldn't have worked as such with my 3D printer setup: the top of my P3Steel is already way too crowded with a filament spool holder, the bundle of cables for the extruder, and an LCD controller mount. I needed a more flexible solution.

I designed this double-pivot filament guide so that it tracks the X-carriage motion without get