Great stuff, thanks! You might want to check the small gear stl is valid. First attempt, I printed both and the small gear was a little distorted (poss too fast/hot). So only needing the small gear, downloaded it and slic3r complained big time. And nothing showed up in the Pronterface gcode preview window. I didn't bother trying a netfabbing repair, just split the two gear stl with Meshlab.