Inspired by http://www.thingiverse.com/thing:5756 I wanted a ducted fan that would use an older CPU fan I had laying around.I designed this to fit on a thing-o-matic and rest on the extruder platform.By adjusting how much of the arms are hanging over the edge around the extruder the airflow can be controlled.Print the TOM_fan_duct.stl and hopefully find a fan that slides over the pegs.I you wish to edit the file I have also included the .prt file created in NX6. If you can't convert it or want a different file type I can see what I can do.