Part Cooling Fan Settings for Carbon Fiber Nylon: What a Print Tech Actually Runs

You sliced your first carbon fiber nylon part and left the cooling fan on full blast, the same way you do with PLA. The result: a part that cracked right along the layer lines under finger pressure. So you tried the opposite and shut the fan off completely to keep it strong, and the overhangs sagged into a stringy mess. Both moves cost you parts. Here is what actually works, straight from the print room.

What the Fan Does to Nylon

Nylon does not set like PLA. When PA6-CF or PA12-CF comes out of the nozzle, it needs time at temperature for the layers to weld together. Hit it with 100% fan and you freeze the interface before that weld forms. The part looks fine on the outside and fails at the layer lines. Carbon fiber makes this worse, not better: it stiffens the part, so when a layer bond lets go, it lets go hard and fast.

That does not make the fan your enemy. Overhangs and bridges sag without any cooling because the material stays soft too long. The trick is using the fan for the geometry, not for the whole part.

Fan Settings We Actually Run

On our X2D and QIDI Plus 5, with the chamber held at 45-55 C, these settings work for PA6-CF and PA12-CF every time:

• First 3-5 layers: 0% fan. You want that first layer to stick and stay warm.
• Solid walls and infill: 0-15% fan. Let the layers weld.
• Overhangs past 45 degrees and bridges: 30-40%, and only for those sections.

OrcaSlicer and Bambu Studio can do this automatically with the fan-only-on-bridges or per-feature fan control. Use that instead of one flat percentage. If your slicer cannot do per-feature fans, slow the speed down 20-30% on the overhang sections rather than cranking the fan.

Signs Your Cooling Is Wrong

Too little cooling: sagging overhangs, drooping bridges, and a rough top surface on flat spans. Too much: matte, powdery top layers, layer separation when you flex the part, and cracks that follow the layer lines. If a part delaminates, check the fan first, right before moisture, because wet nylon produces the exact same failure.

What We Use

Most of our structural test parts run on TINMORRY PA6-CF. It is the spool we grab when a part has to carry load, and the tested settings page has the full profile we print with. When we drop the fan to zero on tall builds, the BIQU Cryogrip Pro plate keeps the first layer planted without glue stick or tape.

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