I used the amazing design by Cursed Magician who has made a very easy to use openscad file. However for those who are afraid to try openscad, here's a version that can fit 70mm fans from old cpu heatsinksPrinted with .4 mm layers for a quick print. Snaps on to the printrbot LC ubis hotend mount. Fan gets pretty close to touching the heated bed, but still manages to clear it.