Direct Drive NEMA17 extruder block, spring loaded, fully compatible with Replicator 2X extruder lever

Update 19-DEC-2015
- Guide block for bowden tube has parametric length now
- Added a hole for bowden tube fixing screw, parametric diameter

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For my 3D DIY cartesic printer I wanted to use an simple direct drive extruder concept like the Replicator 2X, but with bowden tube, a 4 hole motor mount and a side flange.

This one is completely re-modelled in Openscad from scratch, but still compatible to the Replicator 2X type, it also uses the original Makerbot lever wh