This is an original design of an extruder that has the following features:- Symmetrical load on stepper axis;- Adjustable filament pressure without spring;- Simple & open design (easy to see what's happening inside);- No need for a geared reducer, direct drive;- Support flexible filament (anti-buckling support on both extrusion and retraction);- Best bang for your buck;See it in action:*https://www.youtube.com/watch?v=F3HcuB7CWsAFiles for modification are publicly available and with a free Onshape account here:* https://goo.gl/ESpfDwFor details about fitting the coil on the stepper motor, you can find them by looking for #bicgear , #saintflint or #flintfeeder on Google Plus.05-09-2015 Uploaded some variation on the current design, namely:- MK8 gear based version- NEMA14 based version (uses smaller 625 bearings). This last version should perform very well as a "suspended" extruder on a delta with a short bowden. Very light yet powerful enough to get along with the speed.