SK-Tank 120mm Broad Part Cooling Duct

This is a duct and mount for a 120mm fan, to provide broad/gentle part cooling for the Seckit SK-Tank. The idea is that for certain parts, the regular part cooling fans can't cool some places sufficiently because the print head is moving around too quickly. This duct allows a pair of large fans (or four, maybe!) to wash air across the whole XY printing plane, and provide additional cooling. I can report that for me, even blowing from only one side, this has made a noticeable difference in benchy quality.

Ernest designed something like this already, but I wasn't able to find it, and in any case I wanted a shorter duct.

The duct has an integrated mount that goes on the underside of the Y braces (see pics). This is a first stab and it's not super rigid, but it'll do for now :-/ At some point I will add ribs to strengthen it, raise the outlet opening a little bit, add fins to help ‘laminarize’ the airflow, and fine-tune the shape to get more consistent airflow across it.

The other issue is that the design currently requires supports (in its default orientation anyway) which leaves a rough surface on the interior. I put easily-removable integrated supports into the slots for the Y brace mount, so you can get by with supports on the bed only, but I will probably also want to add integrated supports under the duct itself, so it will print more cleanly.

Credits: 
- Thanks to @TeachingTech for his video about the loft tool in OnShape… I used Fusion360, but it worked similarly.
- The hex grill in the pic is here.