Carbon fibre filament: stiff, but demanding

What carbon fibres do in plastic

Short pieces of carbon fibre are mixed into the base polymer, usually a few percent up to around fifteen. The result is labelled CF, for example PLA-CF, PETG-CF or PA-CF. It is a simplified version of the composites you know from bicycles and cars, but the fibres here are short and chopped, so the strength comes nowhere near a real composite.

The part is stiffer, holds its shape better, has a matte dark surface and shrinks less when printed. In return it is more brittle and breaks rather than bends under impact.

Why it is hard to print

• It wears out the nozzle. The fibres are hard, and an ordinary brass nozzle widens within a few hundred hours, so you need a hardened nozzle.
• It wears the extruder too. The fibres scuff the toothed gear that pushes the filament, see extruder.
• The base polymer. If it is nylon, for example, it has to be kept dry, see filament moisture.

Carbon filament and our range

We do not print this kind of material. We offer PLA (€8 per kg) and PETG (€9 per kg), which is only the material share of the price. If you need a stiff part, design usually helps: thicker walls, ribs and a strong infill (40%) give PETG or PLA the stiffness you need for ordinary work. See wall thickness.

Have a different requirement, such as a drone or a beam? Write to jakub.novak@boostello.com and we will assess it, but we will not promise to print it.

What you usually need for stiffness

Design solves most cases where people look for carbon. Enlarge the cross-section of the part, add ribs, round off sharp corners (fillet) and raise the infill to a strong 40%. Each of these steps is cheaper than a special material.

The direction of the layers matters too. A part is weaker across its layers, so turn it so the force does not act against them, see model orientation. You will see the price for light (10%), standard (15%) and strong (40%) infill in the calculator right after uploading.