Pellet Extruder with Auger + Moineau screws

v0.8, Monday 22 August 2016.
UPDATE, 31 Oct 2016: a new improved version has been published as: http://www.thingiverse.com/thing:1861347

This is a very first attempt to design a (full-parametric, customizable) prototype extruder for plastic pellets that can work for common 3D printers. The real extruder should be obviously printed out of metal (stainless steel, probably) at a smaller scale and many parts will have to be added/improved (for example: the head should be able to accept "standard" screw-in nozzles; the axis should be coupled with a stepper motor, possibly with a geared reduction; a controlled heating system should be applied around the stator for melting the pellets; different types of flange should be added for connecting the extruder to common 3D printers; etc...). Anyway, this prototype can already be printed in plastic and it may be hopefully good for some preliminary tests with "soft" pellets (chocolate granules? Play-Doo???), extruding "by hand" and without a heating system. We still haven't tested it, really... But we plan to do it soon, and to post here the results and an improved version of the design.