Print Tip: Brittle Materials (Carbon Fibre/Glass Fibre/Sparkle/Glow in Dark)

Why Is My Filament Brittle?

Understanding Speciality Filament Behaviour and How to Prevent Breakage

Some speciality filaments such as carbon fibre filled, glass filled, sparkle, glow in the dark, and UV reflective types can be more prone to brittleness. This is often caused by the additives blended into the material, which can reduce the flexibility of the base polymer. For some materials 

Tips to Prevent Brittle Filament

1. Dry before use and dry during use: It is recommended to dry these speciality filaments prior to printing. A filament dryer can help restore performance, you can see our drying guide on our filament or this drying guide. We do recommend printing from dry box or active dryer for these materials. 

2. Store properly: Keep filament in an airtight container (drybox) with desiccants when not in use to reduce moisture exposure over medium-long term.

3. Check the filament path: Ensure that filament guides or reverse Bowden tubes do not have tight bends. Smooth paths help reduce breakage during printing. May not be suitable high speed printing depending on your filament pathway setup, above 5k+ some more brittle materials some more brittle materials like PC CF you may need reduce printing speed. 

Causes of Brittle Filament

• Moisture absorption: These filaments absorb moisture from the air much quicker and easily, which can lead to brittleness and printing issues.

• Material additives: Reinforcing additives like carbon or glass fibres can reduce the natural flexibility of the filament.

• Tight filament paths: Sharp bends or tight reverse Bowden tubes can cause brittle filament to snap, especially after moisture exposure.

Over-Drying Warning

While drying is essential, over-drying can also lead to brittleness, especially in filaments that contain flexible polymers or sensitive additives.

Signs of Over-Drying:

• Filament becomes chalky or snaps under light bending

• Loss of colour or sheen

• Diminished layer adhesion or surface quality

TPU, PLA blends, PC CF and glow/specialty filaments are particularly sensitive to extended high-temperature drying.

Solution:

We’ve found that some filaments can regain a degree of flexibility and therefore improved printability by being left out in the open to slowly reabsorb moisture. We recommend checking the filament every hour to assess brittleness. Once the filament has softened slightly, use the remaining spool from a dry box or filament dryer on the lowest setting, and ensure it is properly stored and labelled afterward.

As noted in our drying guide, repeating this drying and reconditioning process multiple times may lead to material degradation, at which point the above solution may no longer be effective.

If problems continue, please reach out to our support team for further advice. We're happy to help troubleshoot and get you back to printing smoothly.