Bambu Lab PETG-CF Filament 1.75mm 1kg

PETG with chopped carbon fibre through it. The fibre stiffens the material and kills the warping and stringing that plain PETG is known for, and it leaves a matte, faintly speckled surface that hides layer lines well.

This is the pick for functional parts that also need to look finished — jigs, drone frames, brackets, tool holders, enclosure panels.

You need a hardened nozzle. Carbon fibre is abrasive and will wear out a standard brass nozzle quickly. Bambu specifies 0.4, 0.6 or 0.8mm hardened steel — 0.2mm is not supported, as the fibres will block it.

At a glance

What the carbon fibre buys you

It is worth being precise about this, because "carbon fibre" is often read as "stronger across the board" and that is not what the numbers say.

What improves: impact strength is the best in the whole PETG range at 41.2 kJ/m² against PETG Basic's 34.2 — parts absorb a knock rather than cracking. Heat resistance improves markedly too, with Vicat softening at 85°C against Basic's 69, which matters for anything living in a car or sitting near a motor. And the finish and dimensional behaviour are better: matte, low-gloss, and far less prone to warping.

What does not: tensile strength is 35 MPa against Basic's 51, and stiffness in tension 2460 MPa against Basic's 2780. Short chopped fibre reinforces the surface finish and toughness, but it interrupts the polymer chains that carry a pulling load. For a part loaded in pure tension — a hook, a strap, a clip that stretches — plain PETG Basic is the stronger material.

Worth knowing

Layer bonding is the weak axis, more so than usual. Stiffness drops from 2460 MPa in plane to 1340 across layers, because the fibres align with the extrusion and do nothing to bridge between them. Orient the part so load runs along the layers, not across them.

Annealing works here, unlike the rest of the PETG range — but it is slow: 55–60°C for 65 to 70 hours. Larger or thin-walled parts may warp, so it is worth a test piece before committing a long print.

Storage

Bambu specifies under 20% RH, sealed with desiccant, and 65°C for 8 hours before printing. Carbon-filled filaments pick up moisture readily, so treat drying as routine rather than a fix for when things go wrong.

As filament takes on moisture you'll hear popping or hissing at the nozzle, then see stringing and rough surfaces, and eventually the strand goes brittle enough to snap in the tube. That's almost always moisture, not technique. Dry it at 65°C for 8 hours and it usually comes back.