Sunlu PA6-CF Filament 1.75mm

Nylon 6 with 20% chopped carbon fibre. This is the strongest, stiffest thing we stock — 112 MPa tensile, 192 MPa in bending and an 8600 MPa flexural modulus. It is a step up in capability from PLA or PETG and a step up in demands on your printer, so read the temperatures before you buy.

The headline is heat. Under a light 0.45 MPa load it holds shape to around 203°C, which puts it in a different class from anything PLA-based. Made for functional parts that actually get hot or loaded: brackets, gears, jigs, engine-bay mounts, tooling.

At a glance

Worth knowing

270–290°C means an all-metal hotend. That is fine on a Bambu X1, P1 or A1, but it rules out any printer with a PTFE-lined hotend. Check yours before ordering.

Two heat figures that look contradictory, and both are real. Glass transition is 65°C but heat deflection is 203°C. They measure different things: nylon 6 is semi-crystalline, so the crystal structure plus the carbon fibre carries load long after the amorphous regions have softened. Design to the 203°C figure, but note it is measured at a light 0.45 MPa — under real load, expect less.

A hardened nozzle is not optional, and it needs glue on the plate. 20% carbon fibre will chew through brass. Sunlu specify a textured PEI plate with solid glue stick or LAC spray — nylon does not bond to bare PEI reliably, and you will get a part coming loose mid-print without it.

Stiff, so not very stretchy. 12% elongation at break and 6.5 kJ/m² notched impact — this resists bending hard but will crack rather than flex if you overload it. It is strong, not tough. Sunlu also rate it well for warping and cracking resistance, which is unusual for nylon and the main reason to pick a CF-filled PA6 over a plain one.

Nylon is the most moisture-hungry material in the range by a distance, and a wet spool prints visibly badly — see storage below. Chemically it shrugs off petrol, ether and weak alkali, handles water well, and is only middling against alcohol and acetone. Strong acid will attack it.

Storage

Sunlu specify drying at 80–110°C, and say plainly to keep it dry throughout the print, not just before it. A filament dryer you can print straight from is close to essential with nylon. Store sealed with fresh desiccant.

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 and it usually comes back.