Printrbot Simple Bind-Resistant Filament Guide

My printed filament guide was bad about catching the filament and binding it, because the hole was too small. I realized that the filament only needed to be restricted from side to side, so I combined the two OEM filament guide parts (E12 and E13), and changed the hole to a rectangle in a bit of a "hopper" shape to resist filament binding.

Dreadpirate15 greatly improved on this design by turning the filament guide into an insert for the extruder. Unlike my design, it's not able to fall off of the extruder body, so I am now using it full-time. I highly recommend checking it out at http://www.thingiverse.com/thing:163991.