Strong friction will be generated between the extruder gears and the filament during printing, due to which
lots of small shavings will be ground away from the filament. If not cleaned regularly, the teeth of the extruder gears may be flattened by the accumulated shards and particles, which will inhibit the gears from gripping and pushing the filament through the hot end and finally affect the printing results.
At least once every two weeks.