A fan can be useful for cooling PLA prints to improve bridging and overhang performance. It also means that you don't need to insert a minimum layer time in your slicing profile. An example cooling fan arrangement is: {{:image017.jpg?600|}} However there are a number of points to remember: - The fan must not blow onto the hot end. - Do not use the fan for ABS prints (they will crack). - The fan shouldn't be used for the first few layers as it reduces adhesion to the bed surface. If you connect the fan to the correct pins on the Azteeg controller then it can be automatically controlled by Slic3r and Repetier-Host through the M106/M107 commands. For instance, Slic3r can be configured to automatically turn the fan on after the first layer. For the Azteeg X3 controller you simply connect the fan to the D4 low power switched output pin (this is the left-hand-most set of pins on the block of pins to the left of the thermistor connectors). The red fan lead connects to the 12V or 5V pin (depending of you fan's voltage) and the black lead connects to the middle D4 pin. The X3 Marlin firmware requires no modification as it already assumed that D4 is assigned to the M106/M107 cooling fan command. For the Azteeq X1 controller, there is a single 12V switched fan output on the board. Connect the fan to this. Unfortunately the Marlin firmware doesn't automatically use this pin (D4 again) for the FAN_PIN and so you need to modify the X1 Marlin firmware to do so. In the //Marlin/pins.h// file, search for a line which says "#if MOTHERBOARD == 62 || MOTHERBOARD == 63", then search for the next occurrence of "#define FAN_PIN -1" and change it to "#define FAN_PIN 4". Recompile and upload firmware as described in [[software-to-install]] Then in Slic3r change your PLA filament profiles to "Enable cooling" You can also test that the fan is working properly using the Repetier-Host //Manual Control// tab (which has a fan control button and slider).