Flashforge left side fan

[rodsaylor]

what is it for?

[CompoundCarl]

There are 2 small fans on the front of each extruder. Those are used to keep the mechanical parts of the extruder cool, so that the hotend does not melt the plastic near the drive gear. On some newer FF Creator Pros, there is also a third fan on the side that is used for cooling your part. It can be very useful for printing small parts or with some materials that melt easily like PLA.

[giantpune]

That extra fan on the left helps when printing PLA, but its generally not used when printing ABS. Its the same reason you'd print with the door open and the top removed for PLA but the door closed and the top on for ABS.