Fan shroud for the Hexagon hot-end, to suit a vanilla Prusa i2 x-carriage. Fits a 25mmx25mmx10mm fan.
I had trouble finding a shroud that would fit the i2 x-carriage. The designs I was able to find had the top of the fan level with the collar that interlocks with the metal mounting plate for the Hexagon, but for the i2 it needs to project down a bit further in order to fit in below the carriage body. It also threatened to interfere with the screw that fixes the extruder to the carriage.
I'd already printed http://www.thingiverse.com/thing:796756 before I realized any of this, and was impressed by how well it fit the hexagon otherwise. So I cut it in two and added an extra 8mm of angled ducting to fit where I needed it to go.
Screw holes are deliberately slightly undersized. I tapped them to M3, but you could also clean them up with a drill bit and use small self-tapping screws.
Mount over hexagon heat-sink fins from the top. The rounded end will rest on the topmost fin. Put together your extruder/hot-end assembly on the carriage before mounting the 25mm fan or it will obstruct access to the mounting screws.