SlicerDial

Carbon- and glass-fiber filaments: hardened nozzles, nozzle size and the stiffness trade-off

Published October 15, 202631 sources

Short answer

Fiber-filled filaments are stiffer and more dimensionally stable but usually less tough, and they wear out soft nozzles [1, 8]. Bambu Lab says never to use brass or stainless steel with CF/GF filaments, and recommends a 0.6 mm hardened steel nozzle as the first choice [2]. Polymaker estimates a brass nozzle lasts about 9 hours with its PA6-CF20 [14]. Avoid 0.2 mm nozzles, which clog easily with fibers [2].

Published ranges at a glance

The span of values that makers publish for 19 products (carbon-fiber filled, glass-fiber filled) in the filament database, by grade. Every product, with its source, is listed in the full table below the guide.

GradeProductsNozzle °CBed °CDrying °CHDT at 0.45 MPa, °C
PA-CF7 from 6 brands260–32040–12070–10084.5–215
PETG-CF4 from 4 brands240–27560–10055–8068.6–96
PLA-CF2 from 2 brands190–24035–605553–55
ABS-CF1 from 1 brand250–270100–11070–8099
ABS-GF1 from 1 brand250–270100–11065not published
ASA-GF1 from 1 brand250–270100–11070–8098
PC-CF1 from 1 brand275–295100–12090114
PET-CF1 from 1 brand280–32060–809086.7
PET-GF1 from 1 brand30080100–12078

What the fibers do

Composite filaments mix carbon, glass or kevlar fibers into a base polymer [1]. Prusa’s Knowledge Base summarizes the effect: better dimensional stability, lower weight, less warping, higher heat resistance and higher tensile yield strength, but usually lower Charpy impact resistance and weaker layer-to-layer adhesion [1]. Print temperatures are slightly higher than for the unfilled base, and cheap composites can clog, ooze or break more often [1].

Not every CF product is about strength. Prusa’s composites article says the carbon fiber in Prusament PETG Carbon Fiber is there for appearance only [1], while the product page still credits it with better dimensional stability, a higher modulus and less stringing than plain PETG [11].

Stiffness up, toughness down: the published pairs

The clearest way to see the trade-off is to compare a base filament with its CF version from the same maker and test lab.

Pair (same maker) Flexural modulus, base → CF Unnotched impact, base → CF
Bambu PLA Basic → PLA-CF (XY) 2750 → 3950 MPa 26.6 → 23.2 kJ/m²
Prusament PETG → PETG CF (horizontal) 1.7 → 2.3 GPa no break → 29 kJ/m²
Prusament PC Blend → PC Blend CF (horizontal) 2.1 → 3.5 GPa no break → 32 kJ/m²

Sources: [7, 8, 9, 10, 12, 13].

In all three pairs the part gets stiffer, and in the two Prusament pairs the unnotched specimens go from not breaking at all to breaking. Prusa’s PETG CF page lists lower toughness than plain PETG as a con [11].

Layer adhesion is less consistent than the general rule suggests. Prusa’s in-house interlayer test gives 18 MPa for both PETG and PETG CF, and 21 MPa for PC Blend against 23 MPa for PC Blend CF [9, 10, 12, 13]. Bambu Lab’s engineering-filament table shows a wide spread in Z-direction impact strength: 4.5 kJ/m² for PET-CF and 2.8 kJ/m² for PPS-CF, but 15.5 kJ/m² for PA6-CF, against 7.4 kJ/m² for ABS [4]. The base polymer matters as much as the fiber.

Fibers also raise heat resistance [1]; the heat resistance comparison and the nylon guide show the jump for PA.

Nozzle material

Fibers are abrasive, so the nozzle bore wears. The sources agree on the rule, and Bambu Lab applies it to glass-fiber (GF) grades as well as carbon fiber [2]:

  • Prusa: a hardened nozzle is necessary [1].
  • Bambu Lab: always use hardened steel; do not use stainless steel or brass, which wear quickly and degrade print quality [2]. Its nozzle guide lists hardened steel for abrasive filaments such as PA-CF, PLA-CF, PETG-CF, glow-in-the-dark and wood, and stainless steel for non-abrasive ones [3].
  • Polymaker: with Fiberon PA6-CF20, a brass nozzle lasts about 9 hours; it recommends hardened steel or ruby [14].

Bambu Lab also sells tungsten carbide nozzles for its newer printers and says they show significantly less wear than hardened steel after many kilograms of filament [3].

Nozzle size and speed

Fibers also clog narrow nozzles. Bambu Lab’s guidance is specific [2]:

  1. Do not use a 0.2 mm nozzle; the clogging risk is very high.
  2. First choice: a 0.6 mm hardened steel nozzle.
  3. Second choice: a 0.4 mm hardened steel nozzle, with 0.15–0.3 mm layers and a maximum of about 100 mm/s.
  4. Exception: for Bambu’s own PLA-CF and PETG-CF, the 0.4 mm hardened nozzle is the recommended first choice.

Prusa sets the floor at a 0.4 mm nozzle and 0.2 mm layers, and notes that larger nozzles and taller layers lower the clogging risk [1]. Bambu’s PLA-CF data sheet lists 0.4, 0.6 and 0.8 mm nozzles only [8]. High-flow hotends have their own limits: Bambu Lab does not recommend its 0.4 mm High Flow nozzle for PLA-CF, PETG-CF, ASA-CF, PAHT-CF or PA6-CF, while the 0.6 and 0.8 mm versions are compatible [5].

Speeds are lower than for unfilled grades. Bambu Lab’s suggested limits include below 100 mm/s and 8 mm³/s for PET-CF and PAHT-CF, below 130 mm/s and 10.5 mm³/s for PA6-GF, and below 250 mm/s and 18 mm³/s for ASA-CF [4]. The volumetric speed calculator converts these for other line widths.

Before printing composites, Prusa recommends a cold pull to make sure the nozzle is clean [1]. Bambu Lab suggests heating the nozzle to 280 °C and clearing residue with a needle first [2]. If a clog happens anyway, see clogged nozzle.

Feeding paths and multi-material units

Fiber-filled filament is often stiff and brittle. Bambu Lab sorts problem filaments for its AMS into three groups: too soft, too brittle (some PET-CF and PA-CF) and too hard and rough (some PET-CF, PA-CF and PLA-CF), the last of which wears the internal PTFE feed tubes [2]. It says its own PLA-CF, PETG-CF and PAHT-CF are optimized to work in the AMS [6]. Polymaker tells users not to run its abrasive Fiberon grades through an AMS and to keep the filament path free of sharp bends [15].

Bambu Lab’s engineering guide gives the same advice for PET-CF, PPA-CF and PPS-CF: they break easily, so the feed angle must be adjusted to avoid tight bends [4].

Handling and safety

Safety: Bambu Lab warns that carbon-fiber filaments may carry hard, microscopic barbs on their surface and cut ends. It recommends puncture- and cut-resistant gloves and safety goggles when handling the filament, removing supports or sanding parts [4]. The same guide asks for a well-ventilated area or air filtration while printing [4].

For the base materials themselves, see the polycarbonate guide and the nylon guide.

All 19 products in the database

Values as each manufacturer publishes them (carbon-fiber filled, glass-fiber filled). Filter by grade or brand, or click a column heading to sort; "not published" sorts last.
Source
Bambu LabPLA-CFPLA-CF210–24035–451.2255 °C, 8 h55 °C @ 0.45 MPa
54 °C @ 1.8 MPa		not published[8]
Bambu LabPETG-CFPETG-CF240–27065–751.2565 °C, 8 h74 °C @ 0.45 MPa
68 °C @ 1.8 MPa		not published[16]
Bambu LabPAHT-CFPA-CF260–29080–1001.0680 °C, 8–12 h194 °C @ 0.45 MPa
170 °C @ 1.8 MPa		not published[17]
ElegooPAHT-CFPA-CF260–29090–1101.0875–85 °C, 8 h194 °C @ 0.45 MPanot published[18]
eSUNPLA-CFPLA-CF190–23045–601.21not published53 °C @ 0.45 MPanot published[19]
eSUNPA-CFPA-CF260–30045–601.2470 °C, ≥ 12 h155 °C @ 0.45 MPanot published[19]
PolymakerFiberon PA6-CF20PA-CF280–30040–501.17100 °C, 10 h215 °C @ 0.45 MPa
173 °C @ 1.8 MPa		not published[14]
PolymakerFiberon PETG-rCF08PETG-CF240–27060–701.3065 °C, 3 h68.6 °C @ 0.45 MPa
65.7 °C @ 1.8 MPa		not published[20]
PrusamentPETG Carbon FiberPETG-CF255–27580–1001.2755 °C, 6 h96 °C @ 0.45 MPa
80 °C @ 1.8 MPa		not published[10, 21]
PrusamentPC Blend Carbon FiberPC-CF275–295100–1201.2290 °C, 4 h114 °C @ 0.45 MPa
106 °C @ 1.8 MPa		not published[13, 21]
PrusamentPA11 Carbon FiberPA-CF280–290100–1201.1190 °C, 6 h192 °C @ 0.45 MPa
152 °C @ 1.8 MPa		not published[21, 22]
Siraya TechFibreheart PET-CFPET-CF280–32060–801.3090 °C, 4–6 h86.7 °C @ 0.45 MPa
76.6 °C @ 1.8 MPa		20[23]
Siraya TechFibreheart PETG-CF ProPETG-CF250–27070–801.3070–80 °C, 4–6 h75 °C @ 0.45 MPa
69 °C @ 1.8 MPa		25[24, 25]
Siraya TechFibreheart PET-GFPET-GF300801.30100–120 °C, 4–6 h78 °C @ 0.45 MPa
74 °C @ 1.8 MPa		not published[26]
Siraya TechFibreheart PPA-CFPA-CF280–32070–901.20100 °C, 4–6 h84.5 °C @ 0.45 MPa
82.5 °C @ 1.8 MPa		12[27]
Siraya TechFibreheart PPA-CF CorePA-CF280–320801.2380–100 °C, 4–6 h97 °C @ 0.45 MPa
84 °C @ 1.8 MPa		not published[28]
Siraya TechFibreheart ABS-CFABS-CF250–270100–1101.0670–80 °C, 4–6 h99 °C @ 0.45 MPa
94 °C @ 1.8 MPa		not published[29]
Siraya TechFibreheart ABS-GFABS-GF250–270100–1101.0865 °C, 4–6 h93 °C
97 °C		not published[30]
Siraya TechFibreheart ASA-GFASA-GF250–270100–1101.1070–80 °C, 4–6 h98 °C @ 0.45 MPa
94 °C @ 1.8 MPa		not published[31]

Questions

Can I print carbon-fiber PLA with a brass nozzle?

Bambu Lab's filament guide says not to use brass or stainless steel nozzles with CF/GF filaments because they wear quickly and affect print quality; use hardened steel [2]. Prusa likewise says a hardened nozzle is necessary because the fibers are highly abrasive [1].

Can carbon-fiber filament go through a Bambu AMS?

Only some. Bambu Lab says its own PLA-CF, PETG-CF and PAHT-CF are formulated to work with the AMS, while many third-party fiber-filled filaments are too brittle or too abrasive for its feed tubes. PETG-CF is not recommended for the AMS lite, and PET-CF, PPA-CF and PPS-CF are not compatible with any AMS [2, 6].

Sources

  1. Composite materials filled with carbon, kevlar or glass. Prusa Knowledge Base. Manufacturer documentation. Effect of fibers on properties, hardened nozzle, cold pull, minimum 0.4 mm nozzle and 0.2 mm layer. Accessed October 12, 2026.
  2. Filament guide: printer, nozzle, AMS, build plate, glue compatibility and required parameters. Bambu Lab Wiki. Manufacturer documentation. CF/GF nozzle rules, nozzle size choice, AMS limits for brittle and abrasive filaments. Accessed October 12, 2026.
  3. Introduction to Bambu Nozzles. Bambu Lab Wiki. Manufacturer documentation. Hardened vs stainless steel, nozzle size trade-offs, tungsten carbide wear. Accessed October 12, 2026.
  4. PET-CF / PPA-CF / PPS-CF / PA6 CF Carbon Fibers Filament Usage Guide. Bambu Lab Wiki. Manufacturer documentation. Fiber splinters and protective gear, Z impact data, speed and flow limits, brittle feeding. Accessed October 12, 2026.
  5. Bambu High Flow Hotend (H2/P2S/X2D) product page. Bambu Lab. Product page. 0.4 mm high-flow nozzle not recommended for several CF filaments. Accessed October 12, 2026.
  6. Notes for AMS. Bambu Lab Wiki. Manufacturer documentation. Third-party fiber-reinforced filaments in the AMS. Accessed October 12, 2026.
  7. Bambu PLA Basic Technical Data Sheet (V3.0). Bambu Lab. Technical data sheet. Bending modulus and impact strength for comparison with PLA-CF. Accessed October 12, 2026.
  8. Bambu PLA-CF Technical Data Sheet (V2.0). Bambu Lab. Technical data sheet. Bending modulus, impact strength, nozzle sizes 0.4–0.8 mm. Accessed October 12, 2026.
  9. Prusament PETG Technical Datasheet (v1.1, 16-02-2022). Prusa Polymers. Technical data sheet. Flexural modulus, Charpy impact, interlayer adhesion. Accessed October 12, 2026.
  10. Prusament PETG Carbon Fiber Black Technical Datasheet (v1.0, 20-12-2022). Prusa Polymers. Technical data sheet. Flexural modulus, Charpy impact, interlayer adhesion. Accessed October 12, 2026.
  11. Prusament PETG Carbon Fiber. Prusament. Product page. Lower toughness, hardened nozzle, not suitable for small parts. Accessed October 12, 2026.
  12. Prusament PC Blend Technical Datasheet (v1.1, 16-02-2022). Prusa Polymers. Technical data sheet. Flexural modulus, Charpy impact, interlayer adhesion. Accessed October 12, 2026.
  13. Prusament PC Blend Carbon Fiber Technical Datasheet (v2.0-OY, 19-04-2023). Prusa Polymers. Technical data sheet. Flexural modulus, Charpy impact, interlayer adhesion. Accessed October 12, 2026.
  14. Fiberon PA6-CF20 Technical Data Sheet (V1.1). Polymaker. Technical data sheet. Brass nozzle life about 9 hours; hardened steel or ruby nozzle recommended. Accessed October 12, 2026.
  15. Polymaker Material Print Tips. Polymaker Wiki. Manufacturer documentation. No AMS for abrasive Fiberon grades, avoid sharp bends for brittle filaments. Accessed October 12, 2026.
  16. Bambu PETG-CF Technical Data Sheet (V3.0). Bambu Lab. Technical data sheet. Recommended printing settings, drying, physical, thermal and mechanical properties. Accessed October 12, 2026.
  17. Bambu PAHT-CF Technical Data Sheet (V3.0). Bambu Lab. Technical data sheet. Recommended printing settings, drying, physical, thermal and mechanical properties. Accessed October 12, 2026.
  18. ELEGOO PAHT-CF product page: Specifications. ELEGOO. Product page. Specifications section: drying, recommended printing settings, physical properties (density, Vicat, HDT at 0.45 MPa) and X-Y/Z mechanical properties; no test standards named. Accessed October 12, 2026.
  19. Product Comparison. eSUN (official store). Product page. Values appear after choosing a product in the comparison tool: density, HDT at 0.45 MPa, melt flow index, Z tensile strength, X-Y flexural and Izod values, extruder and bed temperature, fan, print speed, build surfaces and printing recommendations; no test standards named. Accessed October 12, 2026.
  20. Fiberon PETG-rCF08 Technical Data Sheet (V1.0). Polymaker. Technical data sheet. Physical, thermal and mechanical properties of printed specimens; recommended printing conditions incl. drying. Accessed October 12, 2026.
  21. Drying filament. Prusa Knowledge Base. Manufacturer documentation. Drying temperature and time table for Prusament materials; spool temperature limits. Accessed October 12, 2026.
  22. Prusament PA11 Carbon Fiber Technical Datasheet (v1.0, 29-06-2022). Prusa Polymers. Technical data sheet. Recommended print settings, typical material properties and mechanical properties of printed test specimens. Accessed October 12, 2026.
  23. Siraya Tech Fibreheart PET-CF TDS. Siraya Tech. Technical data sheet. Print settings, drying, unannealed and annealed property data, max extrusion volumetric speed. Accessed October 12, 2026.
  24. Fibreheart PETG-CF Pro TDS. Siraya Tech. Technical data sheet. Print settings, drying, property data with test methods. Accessed October 12, 2026.
  25. Fibreheart PETG-CF Pro Filament (product page). Siraya Tech. Product page. Flow rate up to 25 mm³/s; HDT 76 °C claim; product specifications. Accessed October 12, 2026.
  26. Fibreheart PET-GF TDS. Siraya Tech. Technical data sheet. Print settings, drying, unannealed and annealed property data, annealing procedure. Accessed October 12, 2026.
  27. Siraya Tech Fibreheart PPA-CF TDS. Siraya Tech. Technical data sheet. Print settings, drying, unannealed and annealed property data, max extrusion volumetric speed. Accessed October 12, 2026.
  28. Siraya Tech Fibreheart PPA-CF Core TDS. Siraya Tech. Technical data sheet. Print settings, drying, unannealed and annealed property data. Accessed October 12, 2026.
  29. Siraya Tech Fibreheart ABS-CF TDS. Siraya Tech. Technical data sheet. Print settings, chamber temperature, drying, property data. Accessed October 12, 2026.
  30. Fibreheart ABS-GF Filament TDS. Siraya Tech. Technical data sheet. Print settings, drying, property data. Accessed October 12, 2026.
  31. Siraya Tech Fibreheart ASA-GF TDS. Siraya Tech. Technical data sheet. Print settings, chamber temperature, drying, property data. Accessed October 12, 2026.