Printrbot Top Joinder w Nut Retainer & Y offset

edit/ Added SCAD file /edit

Based on http://www.thingiverse.com/thing:23038, but with retained nut, and clearance for high-Z.

TheGrum's version was fine, and I liked the Printrbot logo.

A while ago I was learning OpenSCAD so decided to do a version for 8mm threaded rod and with the nut retained (also has no bridging). See the v3 stl & the red one in the photos.

It did improve the smoothness of the prints. See the close-up, the red one was printed without a joinder, the white one with the red fitted, much crisper edge, but I found the stepper crashed into it at high Z.

So I did another design moved back on the Y axis, see the v4 stl, the white ones in the photos.