Drew's Planetary Geared Extruder

After running my Rostock printer for a while, I've determined that the extruder motor really needs a geared reduction. It's not that the motor doesn't have enough torque, but that producing the required torque causes the motor to run hot, which can affect the ability to grip the filament or even deform the motor mount. It also causes the motor driver board to overheat and cut out. I'm only running a 0.5mm nozzle, but these problems only get worse with a 0.35mm nozzle.

Some people have switched to a stepper motor with an integrated planetary reduction. That works, but the gearbox on that has a shaft which is larger than the 5mm hole in the MK7 drive gear I'm using. I don't have access to the required machine tools to safely modify my drive gear for a larger shaft. So instead I decided to make my own gear reducer using stuff from my junkbox.

The gear assembly itself is based on gear code from Emmett's Automatic Transmission Model: http://www.thingiverse.com/thing:34778

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