Eccentric spacer for Raise3D N2 extruder

UPDATE 03/02/16: I have replaced the original with a new version that can be used with a spring to dynamically tension the pinch pressure. This version requires that the original M3 12mm screw be replaced by an M3 18mm one. I replaced the acrylic cover thumbscrew with a longer cap screw and added a printed grooved spacer, also included here, to hold the spring. This version of the eccentric spacer also has a thinner shoulder that sits on the bearing inner ring and a bevel coming up from the bear