EDIT: I've now included an extended model without the switch slot, for those who just want to direct the airflow over the aluminium block and have no need for the switch. This is a remix of the blank fan mount. It has been extended about 10mm to make room for a switch slot and to cool the aluminium direct drive assembly of the extruder. Behind the switch I've wired a tiny basic circuit with a diode to prevent flyback damage to the bot when the fan is turned off. The cabling runs under the extruder and joins the rest of the extruder cabling back to the underside of the bot, where it is wired directly to the 12V pins on the power supply barrel connector. Cooling has been running very well even at higher extruder voltages! (Had to increase voltage for the extruder to prevent skipping)Printed on a Printrbot Simple metal using Slic3r. PLA, 2 perimeters, 30 infill, 0.3969mm layer height. I also printed with a heated bed at 65 degrees. Printed in about 8 minutes. The odd layer height is calculated to be perfectly divisible by the whole number of steps the Simple Metal's Z axis rod can move. Not strictly necessary!