About this 3D model

This guide keeps the filament centered on the hobbed gear as it is drawn in to the extruder. This resolves occasional issues with the filament riding up off the ridged part of the gear. The part is simply wedged in place. It is easily removed in order to change filament or make other adjustments. It may work free if the fit is not tight when the extruder retracts - try boring out the hole or tightening the fit. Intended for 1.75 mm filament and the late 2013 Printrbot Simple wood extruder. (Earlier versions had a different extruder design.) (See also this alternative, which better resists working free from retraction: http://www.thingiverse.com/thing:265814)