This is a clip-on mount for attaching a brushless blower fan to a Printrbot+ extruder. Assuming the extruder dimensions are constant, this will likely work for all Printrbots with laser-cut wooden extruders.
It was designed to work with a 5015S blower fan purchased from eBay for $4.89, which is 50mmx15mm high, runs at 3800rpm, and puts out 20CFM. It runs circles around the 40mm PC fans I'd tried previously to use to cool filament.
In the photo, it looks as though the bottom edge of the blower is lower than the tip of the extruder nozzle, but that's due to the angle at which the photo was taken. The bottom edge of the fan housing is at least 1mm higher than the end of the nozzle, which is plenty.
Here are the more interesting settings I used, which worked fine:
.35mm extruder nozzle
3mm black PLA plastic
overhang threshold: 60Âº
Pattern spacing: 40mm
Pattern angle: 0Âº
Fill density: .1
Fill pattern: rectilinear
Top/bottom fill pattern: concentric
Infill every: 2 layers
Fill angle: 45Âº
I printed using Repetier-Host Mac 0.53, and had to rotate the object 90Âº on its X axis in order to place it flat on the print bed.
This mount takes inspiration from http://www.thingiverse.com/thing:29565, but aims to be more minimal. I designed the mount such that it holds itself in place using friction and also has little arms that poke through holes in the sides of the extruder platform and extend to its back to provide even more support for the weight of the fan. If you print this in PLA, the object may be too brittle to bend enough to fit both arms into the holes, and one may snap. This happened to me, and I just glued it together in-place using a drop of cyanoacrylate. It'll likely hold in place without those arms, but they provide just a little more support.
This is my first attempt at a semi-complicated CAD project, and I expect many of you who might benefit from such a mount can probably improve upon this design and make a nice derivative. So in addition to the printable STL file, I've uploaded the original .f3d file (object was designed in Autodesk Inventor Fusion), and an exported STP file.
Here's the link to the blower fan I'm using: