Didn't have a small fan so I designed a shroud for a fan I had on hand so in true hackerdom I salvaged a fan from a gateway all-in-one computer and started to design a mount. This the the 5th generation and final design that works very well.
My first OpenSCAD project and seemed a simple hack was all that was needed to move the current fan that mounted to the right around to the front and open the fan mount opening to match my fan. I added legs that extended on ether side and mounted fan in front of the extruder and bolted to the existing mount holes. New to 3D printing I quickly learned about de-laminating. The design was flawed. The spindly legs would snap with any pressure.
Back to the drawing board.
2 more designs mounted the fan to the side and one in front of motor exhausting to the right. while this mounted fine and was printable, it turns out the added weight was enough to torque the extruder just enough to chatter when passing over the print.
Design 4 located the fan above the extruder head. This eliminated the torque issue. The fan laid flat just above the extruder gear. This required a wide duct down to the nozzle.
The final design. The fan is mounted above the extruder head and exhausting to the right through a slim duct to the nozzle. All clearance is maintained with no loss for print volume.
The nozzle was shamelessly stripped, hacked and modified from the original TAZ3 fan upgrade source files included with the machine. The nozzle's basic shape and bolt mount locations is all that remains of the original.
OpenSCAD file included so it can be modified for other similar fans. I tried my best to keep it all parameterized, but to be honest, there are quite a few tweaks here and there. Is my first real project in OpenSCAD so YMMV.
Prints on a fan less TAZ3 with PLA in 4 hours. I included my .35 layer sliced gcode.
Will update with wiring instructions once I have worked that out, just manually switching fan on atm.
1 - salvaged fan from a gateway all-in-one computer
2 - M3-20 machine screws.