Owen's Bowden clamp: tightening cone improvement (parametric + inner rings)

Update: tweak your own according to your printer and setup: http://www.thingiverse.com/apps/customizer/run?thing_id=25636 !

I had some trouble printing an acceptable cone for the two bowden clamp things: they were a bit slippy on the inside unless I destroyed them in the riser by screwing them too much...

This one:
- features inner rings to add radial but non-uniform clamp force on the tube, which works really nicely
- is (still) fully parametric so you can tune it to your tube diameter,