Printable Z-Stage for Makerbot / Cupcake CNC

This is an alternative Z-Stage for Makerbot/Cupcake with MK5/MK6 extruder. It's heavily inspired by MiseryBot's "MiZ Rider" ( http://www.thingiverse.com/thing:7954 ). I even copied MiseryBot's stepper motor coupler verbatim.

I was considering building MiseryBot's Z-Rider and was looking for a source for the small ball bearings. Turned out that for my neck of the world, those bearings would have been significantly more expensive than real linear bearings, so I designed this Z-Stage based on li