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 linear bearings.As with all other solutions of this kind, it gets rid of the Z-Stage wobble. It even has a springy suspension on the threaded rod end, to dampen the last bit of wobble.The extruder mount has an integral fan and air ducts. The airflow cools the extruder motor, the thermal barrier tube heat sink and the object being printed. It also cools the load bearing ABS parts from the inside, because I'm a little paranoid about the ABS right next to the hot end.The achievable build height with this Z-Stage is about 150mm with the standard Cupcake build platform.Parts recycled from original Z-Stage assembly:Additional parts (vitamins):A picture is allegedly better than a thousand words, and a thousand pictures (using a week of CPU time) make a short movie:http://www.youtube.com/watch?v=PDC4pM5bYRIThe instructions are in PDF format, please download below.http://www.thingiverse.com/download:33161