Filament can break for a variety of reasons:
Moisture: Moisture in filament can weaken it and make it more susceptible to breakage. Moisture can be absorbed through inadequate storage or storage in a humid environment.
Aging: Filament can become brittle and more prone to breakage due to aging.
Incorrect tension: incorrect tension of filament in the extruder can cause it to twist or become twisted, resulting in breakage.
Wear: Filament can become worn and more prone to breakage due to frequent use.
Incorrect settings: Incorrect settings such as too high a compression force or too high an extrusion rate can cause filament to break.
Undersized hardware: Undersized hardware can cause the filament to be overstressed and break.
It is important to dry the filament before use, store it in a dry environment, and ensure that the tension of the filament in the extruder is set correctly to minimize the risk of filament breakage.