E3D v5 30mm Fan Duct

HJK14's fan duct *almost* worked for my printer (T-MAX 2.0, a Mendel Max 1.5i derivative), but the screws for the pillow blocks were in the way and pushed it down a little, so it wouldn't seat nicely.

I added an indentation in the top of that design to allow it to clear the pillow blocks.

The pictures show the original 30mm fan that came with my E3D mounted to the duct, and combined, they provide enough cooling to run even higher temp materials (e.g., 250+ degrees) without heat issues