About this 3D model
The idea came from http://www.thingiverse.com/thing:65997 which was too small for the PrintrBot Plus 12mm z rods. If your printer settings are out of wack you may have to (SLOWLY) drill out the rod holes. I find a rotozip works best at slow speeds. Take your time and it'll come out well. This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/2xI2G0z2rQb Updated STL to the new version that uses less plastic. I