After many iterations, I finally finished making air vents for both extruder on my Craftbot 3 machine. It fits a 5/8" O.D. hose. All STL files are oriented for printing and only minimal supports are needed (check against photo 3). When I used S3D for slicing the default 2 wall setting behave as a 4 wall layer for many of the thin sections. The upper halves have a usage hole and a non-usage hole to control which extruder get to be vacuumed.

Craftbot 3

No

Yes

.3 MM

30%

As the support picture shows the lower halves only need support at the encircled "interface" areas. So long as you set bridging/infill overlap to anchor on the perimeter you should be good to go for not trying to support the entire length. I placed a tight skirt to help anchor the upper pieces.

If the snap fit interface seems loose at all, add a layer of tape to the tip of the upper halve. Or if it's tight, sand it down.

With Autodesk Inventor utilizing Iparts and assembly mode. Many iterations to get the sizing right.