This washer fits between one of Emmett's Gear Bearings and a power-drill chuck, ensuring that the planetary gears avoid unnecessary collisions.
While not critical, this primarily helps keep the gear's surface looking nice, and secondarily avoids the generation of PLA-dust.
Print out a washer (1-2 minutes!), and stick it between the chuck and gear as pictured.
P.S. This is yet another simple OpenSCAD STL-butchering, as the washer was generating in extremely little time by intersecting the entire bearing STL with a small cylinder. Even though the implementation is dirty, it worked extremely well to generate the needed geometry. :)