Uses the heat sink fan of the MK8 extruder to also do active cooling of the print. This is a remix of http://www.thingiverse.com/thing:22297 because my extruder head orientation and dimensions were somewhat different and the original design would not fit.
This version is 11mm thick, which is the same thickness as the heat sink.
The fan needs to be reversed from the original mounting so it blows across the heat sink (and then across the print area) rather than sucking air from the heat sink.
This shroud is designed to replace the two cylindrical aluminum spacers that fit between the heat sink and fan on the M3 bolts. The heat sink should snap into the shroud. You may need to sand the shroud interior edges slightly to get a proper fit with the heat sink depending on your printer's tolerances.
I was originally skeptical that this would improve print quality, but it has made a huge difference. I can now print single small items without them getting all oozy from excess heat from the molten plastic and extruder.
Currently, the fan duct provides more cooling to the print area towards the higher Y-axis. I plan on redesigning to provide more even cooling coverage both in front of and behind the extruder nozzle. Also, there is only about 1.5mm clearance of the printed part in the Z direction with the fan duct. The duct has not yet hit anything while printing, but it is rather close and in another revision I plan on raising it another millimeter or so.