Hardened Nozzles and Abrasive Filaments

Why some filaments eat nozzles

A filled filament is a plastic carrying hard particles: chopped carbon or glass fiber, mineral or metal powder, glitter, or the phosphorescent pigment that makes glow-in-the-dark filament glow. Those particles scrape the inside of the nozzle on every millimeter of extrusion. Prusa says carbon, glass and Kevlar fibers are highly abrasive, so a hardened nozzle is necessary. Bambu Lab says stainless steel and brass nozzles are not hard enough for these materials and wear out quickly, affecting print quality and nozzle life.

Which filaments count as abrasive

Check the filament maker's data sheet or product page first; many state the nozzle requirement directly. As a guide, the makers' own lists include:

Filler	Examples named in maker documentation	Source
Carbon or glass fiber	PLA-CF and GF, PETG-CF and GF, ABS-CF and GF, PA-CF and GF, PAHT-CF and GF, PET-CF and GF	Bambu Lab filament guide
Kevlar (aramid) fiber	Kevlar-filled composites	Prusa composite guide
Glitter, mineral and glow particles	PLA Sparkle, PLA Marble, PLA Glow, glow-in-the-dark	Bambu Lab filament guide and nozzle guide
Wood and metal fill	Wood-filled and metal-infused filaments: makers disagree. Prusa's Nextruder table marks them hardened at 0.4 mm, while Bambu Lab's filament table and Prusa's Woodfill guide say a standard nozzle works. Follow your spool's own requirement.	Prusa Nextruder nozzle guide, Bambu Lab filament guide

Bambu Lab's definition of standard PLA is useful here: it means PLA without hard, large-particle fillers such as carbon fiber, glass fiber, or metallic or inorganic fillers. Silk, matte and similar finishes count as standard; CF, GF, Sparkle and Marble do not. For the materials themselves, see Carbon, Glass and Wood-Filled Filaments.

Nozzle choices for abrasive filament

• Hardened steel. The standard answer. Bambu Lab lists it for any abrasive filament with hard particles. Prusa notes its thermal behavior differs from brass, so on its E3D V6 hardened nozzle you may need to raise the hotend temperature by about 5 °C Maker spec, and some materials, such as ABS, cannot be printed as fast as with brass.
• Plated or coated hardened steel. Prusa describes a nickel-plated hardened nozzle as suited to frequent switching between abrasive and non-abrasive materials, and coated hardened nozzles designed for abrasive materials at high temperatures. Prusa warns that cold pulls can tear off some of these coatings, and that acupuncture needles and brass brushes can damage them.
• Harder tips. Prusa lists a solid polycrystalline diamond tip for metal and ceramic-filled engineering filaments, and a ruby-tipped nozzle that resists wear but is brittle and can crack if the nozzle hits the bed. It also notes that one coated nozzle handles glass, Kevlar and carbon fillers but not harder fillers such as boron carbide or tungsten carbide. Very aggressive fillers can wear even premium nozzles.

No nozzle is wear-proof. A harder nozzle lasts longer; it does not make the filament gentle.

Nozzle size: go bigger

Filled filaments also clog more easily, because fibers and particles can bridge across a small opening. The makers agree on direction:

• Bambu Lab: do not use a 0.2 mm nozzle with these materials, as clogging risk is extremely high. Its first choice is a 0.6 mm hardened steel nozzle, with 0.4 mm as a second choice for better detail Maker spec. For some of its own specially designed filaments it recommends 0.4 mm hardened steel as the first choice.
• Prusa: the higher the layer height and the wider the nozzle, the lower the chance of clogging. Its lowest recommended values for composites are a 0.4 mm nozzle and 0.2 mm layers Starting point.
• Prusa also notes that composites with particles approaching 0.4 mm Maker spec risk clogging smaller nozzles.

Both makers give their own temperature recommendations for their own composite filaments. Use the range printed on your spool or data sheet, not another brand's number.

The rest of the feed path wears too

The nozzle is not the only part touched by abrasive filament. Bambu Lab says the nozzle and extruder gears need more frequent maintenance with these materials, and warns that rough or abrasive filaments such as carbon fiber or glow filaments can grind down the PTFE feed tubes inside its automatic material system over time. If you print abrasive filament often, inspect gears and feed tubes on a schedule, not just when something fails; see Maintenance Schedule.

How to set up and check

1. Read the filament maker's nozzle requirement. If it says hardened, wear-resistant or "not for brass," treat it as abrasive.
2. Fit a hardened or wear-resistant nozzle of 0.4 mm or larger, and select the matching nozzle profile in the slicer.
3. Start from the filament maker's printed temperature range; with hardened steel, check whether your printer maker suggests a small temperature increase.
4. Prusa suggests a cold pull before printing composites so the nozzle starts clean, unless your nozzle's coating rules cold pulls out.
5. If you have already run abrasive filament through a brass or stainless nozzle and print quality has dropped, replace the nozzle rather than tuning around it.
6. Label nozzles that have run abrasive material, so a worn one does not go back into service for detail work.