The quality and state of your filament plays a vital role to the success and quality of your prints. Here are some common issues with filament to look out for:

If your filament diameter is not consistent, you’ll notice it in your prints. Sections that are too thin will produce under-extrusions or fail to get gripped and transported by the drive gear. Parts that are too thick will over-extrude or even get stuck somewhere along the filament path. High quality filament has a consistent diameter from beginning to the end of the spool.

There could be a thin section on a spool with inconsistent diameter. Or maybe your extruder’s feeder idler pressure is not high enough or possibly the drive gears teeth are worn or gunked up.

Filament will absorb moisture, Nylons and PVA especially, but it can also happen with ‘normal’ filament, even PLA, it just takes longer. Make sure you store your filament in sealed bags with freshly charged desiccant.

Filament can go stale, especially after it absorbs moisture or was exposed to UV/sunlight for quite a while. Generally once exposed to the air, we suggest replacing filament over 6 months old. However, if stored correctly it can last much longer and if unopened and stored in a cool, dry space may last indefinitely

Brittle filament, breaking or snapping may mean stale filament. There are also some of the more brittle formulas, especially for PLA or PMMA, which might snap when passing the drive gear or is bent for example in a Bowden tube at a higher angle.

A good test for the ‘freshness’ of PLA filament is to bend it to 90 degrees (at room temperature ~20°C) with your fingers. If it snaps, it is stale. Pull 10-15 meters off the reel and try again. You might be lucky – it may only be the top layers that have gone stale.