Around-the-nozzle cooling ring

This is another cooling design, inspired by (but not directly based on) thing 5756.

I wanted to use Iwo's design, but I just upgraded to a MakerGear stepper plastruder on my Thing-o-Matic, and there wasn't enough clearance around the extruder nozzle to mount any fan ducts on the top side of the Z-stage. So, this design is a circular cooling nozzle that mounts around the extruder nozzle, just under the Z-stage.

It is fed by two 1/4" PVC hoses, attached to a fan mount that sits on top of the Z-stage, near the rear of the bot. This mount holds a 40mm fan salvaged from an old graphics card.

The overall airflow is very subtle- it's detectable with your hand, but just barely. But it makes a huge difference in print quality for small parts. In the attached image of two single-wall calibration boxes, both boxes were printed consecutively using the same g-code. The only difference is that one box had the cooling fan intake blocked.

This design is in parametric OpenSCAD, so it should