This is a ducted fan mount for a Makerbot/Cupcake with MK5 Extruder. It seems to successfully stop small objects from turning into molten blobs.
The whole thing clips into the extruder mount. It uses an old fan from the junk box, I think it was from a graphics card or similar.
Mostly cools the current top layer of the printing object without pushing the platform heater into desperation. I'm running the fan through a 200 Ohm potentiometer, to control the airflow.
The air flow is down and towards the nozzle, roughly 45 degrees. The air follows the extruder hot end and reaches about 60 degrees by the time it hits the object.
The thing prints without support.
The ducts have a designed central support that helps with the bridging for the top layers.
The outlet support pillars can be cut away or left standing. Mine broke off while cleaning the ducts.
The fan is 'mounted' with 3 drops of superglue.