I'm using the Hexagon all-metal hot end, and it requires a cooling fan blowing on the fins to maintain the temperature gradient. The fan shroud that comes with the hot end touches the hot end block, which melts it. It also directs the air back into an enclosed space, where it then blows down on the bed, interfering with adhesion.

I designed a replacement deck and a fan shroud that uses a 25mm fan to pull air across the hot end fins and vent it out the top, behind the extruder. This keeps all of the airflow away from the bed and also makes it easy to see what
s going on because the hot end isn't buried behind a fan.

The shroud is very close to the heat block because there isn't much space. I have found that wrapping the plastic in Kapton tape keeps it from melting. I went a step further and made a thin insulator pad out of fiberglass tape and Kapton because I am experimenting with higher temperature materials.

The parts and instructions are here: http://www.thingiverse.com/thing:335613

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