This fan shroud allows you to mount a 40mm fan to cool your NEMA 17 extruder motor without blowing air on the bed or printed parts. It's specifically designed to fit on the MakerFarm Prusa i3 and i3v, but it should fit any printer that uses Greg's Hinged Accessible Extruder.
It will print unsupported on most printers with the fan attachment plate face-down down on the bed.
The shroud has eight internal channels that pull air in through the ports on the bottom, smoothly across two sides of the motor and exhaust it out the top, away from the bed.
It mounts to the motor with a single zip tie, passing through the air channels and the provided hole in the center divider.
Some fans create tubulence and a loud whine as the leading edges of the blades pass across the edges of the partitions in the shroud. If yours does this, a spacer plate is also provided to mount between the fan and the shroud.
See the instructions for details.
This fan shroud is sized to fit the standard motors that ship with the MakerFarm Prusa i3 and i3v kits. If you're using different motors, the fit may vary.
The mount is designed for a 40mm fan. Attach it with the air flow exhausting upward using four M3 screws. The holes are sized to be tapped with an M3 tap. No drilling should be necessary. The holes are only 10mm deep, to avoid disturbing the air flow in the interior. If your screws are longer, you can always drill the holes through to the interior air passages.
Snap the shroud over the motor as shown in the photos. Attach it with a zip tie passed through the second port from the wire side of the motor. There's a small opening in the center air divider to the zip tie to pass through.
Once the shroud is mounted, use a zip tie to attach your extruder motor and hot end wires to the tab. There's a notch in the back side of the tab opposite the hole to keep the zip tie from slipping off. I've provided a generous amount of space to accommodate extra wires for a motor, heater, thermistor, Z probe, servo, fans, lights, etc.
You will want a fan that can move plenty of air. If your fan makes a loud whining noise, you may wish to print out a spacer to put between the fan and the shroud to allow the airflow to consolidate and reduce turbulence. An output funnel is also provided to decelerate the air exiting the fan and reduce the chances of air off the edges of the fan making its way back down to the bed.