Filament guideCarbon fiber nylon is strong, but it soaks up moisture and loses strength when it does. That's a problem for parts that live in a damp basement, a humid workshop or near heat. PET-CF is Bambu Lab's answer for those jobs. Here's what it is and when we'd pick it.
Quick answer
The short answer
PET-CF is a carbon fiber reinforced PET filament for stiff, heat-resistant functional parts. Its standout trait is very low moisture absorption: Bambu measures 0.37% at saturation, against 2.35% for its PA6-CF nylon.
Bambu rates its heat deflection temperature at 205°C (401°F). It positions PET-CF as a better choice than nylon for parts used in humid or high-temperature environments.
01
What is PET-CF?
PET is the same family of plastic used in drink bottles and polyester fiber. PET-CF mixes it with short chopped carbon fibers. The fibers add stiffness and help the part hold its shape.
It isn't the same as PETG-CF, which is easier to print and suits lighter-duty parts. PET-CF prints hotter, at 260–290°C (500–554°F), and Bambu recommends an enclosed printer for strong layer bonding. It needs a hardened-steel nozzle and drying before use.
02
PET-CF vs carbon fiber nylon
| Bambu's data | PET-CF | PA6-CF |
|---|---|---|
| Water absorption (saturated) | 0.37% | 2.35% |
| Heat deflection temperature | 205°C (401°F) | 186°C (367°F) |
| Bending strength | 131 MPa | 151 MPa (dry) |
| Bending modulus (stiffness) | 5,320 MPa | 5,460 MPa (dry) |
| Tensile strength | 74 MPa | 102 MPa (dry) |
| Impact strength | 36.0 kJ/m² | 40.3 kJ/m² (dry) |
Dry nylon is stronger on paper. But Bambu's PA6-CF drops to about 95 MPa bending strength when wet, while PET-CF barely takes on water. For damp settings, that steadiness is the point. See our nylon composites guide for the full comparison.
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What PET-CF is good for
- Load-bearing brackets and structural parts
- Functional parts used in humid spaces
- Parts that sit near heat sources
- Mechanical assemblies, automotive accessories and fixtures
- Parts that need to keep tight dimensions over time
04
Limits to know about
- Layers are the weak direction. Bambu's impact strength is 36.0 kJ/m² along the layers but 4.5 kJ/m² across them. Orientation matters.
- Black only. Bambu offers PET-CF in black. It's a functional finish, not a display one.
- Stiff, not flexible. Bambu lists a breaking elongation of 4.5%, so it snaps rather than bends. For parts that need to flex, ask us about TPU or nylon.
- Overkill for light jobs. For a desk organizer or a prop, PETG or PLA-CF is simpler.
05
Designing for PET-CF
Tell us the direction of the main load. We'll orient the part so force runs along the layers.
Add fillets to sharp inside corners and avoid very thin walls on load-bearing areas. Overhangs can be supported with Bambu's Support for PA/PET, which comes off by hand.
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PET-CF at IMPRESO
We print PET-CF in-house at our studio in Ridgewood, Queens. Tell us how the part will be used and where it will live, and we'll recommend the right material for it. Every job is quoted individually.
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