Ultimate 3D printing guide for PETG CF
Get strong, clean prints from PETG-CF
Everything you need to dial in Numakers PETG-CF — from first-layer setup to functional, load-bearing parts.
PETG-CF reinforces PETG with 10% chopped carbon fiber for stiffness and dimensional stability — without the brittleness of PLA-CF. It prints reliably on any FDM machine, but a few things matter more than they do with standard PLA. Here's how to get it right.
Before you start
Use a hardened steel nozzle
The carbon fiber is abrasive and will wear out a brass nozzle fast. Use hardened steel or ruby, 0.4mm or larger. Avoid 0.2mm — the fiber can clog it.
Dry the filament
PETG absorbs moisture from the air. Wet filament causes stringing, popping, and a rough surface. Dry at 65°C for 6–8 hours if the spool has been open a while.
Nail the first layer
PETG-CF rewards a slow, well-squished first layer. Get good plate adhesion early and the rest of the print follows.
Recommended print settings
One rule you can't skip: hardened nozzle
PETG-CF contains 10% chopped carbon fiber. It's abrasive. A standard brass nozzle will wear out quickly, and worn nozzles ruin dimensional accuracy. A hardened steel or ruby-tipped nozzle is required, not optional.
Dialing it in
Temperature
Hotter (250–260°C) = stronger layer bonding for functional parts.
Cooling
Run part cooling, but don't overdo it — too much fan weakens layer adhesion, the whole point of a CF filament. Ease off for maximum strength on structural parts.
Stringing
Fine hairs between parts usually mean wet filament (dry it), temp too high (drop 5°C), or retraction needs a small bump.
Bed adhesion
PETG sticks aggressively to smooth PEI — sometimes too well. Use textured PEI, or a thin glue-stick layer on smooth PEI as a release agent.
Stiffness without the brittleness
The chopped carbon fiber locks into the PETG matrix to resist bending under load, raising rigidity and modulus so parts hold their shape under stress — while keeping enough give to absorb impact without cracking.
That balance is what makes PETG-CF a smarter frame material than PLA-CF for parts that actually take a beating.
Tight tolerances, every print
Carbon fiber lowers shrinkage and resists warping as parts cool, so prints come off the bed true to spec and stay that way. Ideal for fitted hardware where a repeatable fit is the difference between a part that works and one that doesn't.
It also shrugs off the oils, greases, fuels, and solvents that degrade other materials — dependable around fluids and stress.
What PETG-CF is best for
Drying & storage
Quick troubleshooting
| Problem | Likely cause | Fix |
|---|---|---|
| Stringing / hairs | Wet filament; temp too high | Dry filament; drop nozzle 5°C |
| Weak, splitting layers | Too much cooling; temp too low | Reduce fan; raise nozzle temp |
| Poor bed adhesion | Surface or first layer | Slow first layer; clean bed; adjust Z-offset |
| Clogging | Nozzle too small; wet filament | Use ≥0.4mm hardened nozzle; dry |
| Rough / fuzzy surface | Moisture; worn brass nozzle | Dry filament; switch to hardened steel |