3D printers filament - usually almost robust - is pulled by the extruder while the roll is placed nearby to the printer, free to rotate. I have observed meaningful differences in the material behaviour depending on the usage level, referred to 1Kg filament rolls. A new (full) filament spool flows almost well but the force applied by the extruder should be relatively relevant: the weight is at least 1.5 Kg. The extruder motor (most of the cases a Nema17 stepper) ha sufficient power to do the job but the two gears of the extruder pushing the filament to the hot-end side while working collect particles of the filament due the applied forces; this requires frequent extruder maintenance to avoid the nozzle clogging. These particles tends to detach and mix with the clean filament while it is feeding, increasing nozzle problems and a more frequent nozzle wear; this occurs more frequently with 0.3 mm diameter nozzles. When the filament roll is half used or more its spirals become smaller and in some environmental conditions the filament tend to break too frequently. Long print jobs become less reliable and stressful; I can't leave the printer working alone for an entire night without controlling it. Thus controlling the filament feed by motor figures solving a series of issues.
Participated in the
Design for Robotics Contest 2017