3D-printed carbon fibre molds (hand wet layup)
The carbon fibre mold maker carves your part out of a block, leaving an open female cavity to lay fabric into. Print it in PETG, sand and wax the cavity, wet the fabric out with epoxy, cure, then lift the part out and trim.
What this mold is for
Carbon parts are made against a surface: you press wet fabric into a dish and the side touching it becomes the smooth show face. The generator carves that dish out of a block, adds a flat flange rim to trim against and a 5° release draft so the part lifts out, and splits the mold if it is too big for your bed. Background: the draft angles guide.
Print & lay up in 3 steps
Generate the mold
Upload the finished part, not a mold, turned so the open side faces up: that is the direction it pulls out. Set the draft, flange width and base thickness. An overhang warning means the part traps itself, so re-orient or split it.
Print it
Cavity opening upward, so no supports. PETG, 0.2 mm layers, 4 walls, 20% infill: a stiff mold keeps the part accurate. Glue printed halves with epoxy and let it set fully. Full profile in the print-settings guide.
Smooth, wax and lay up
Whatever texture is in the cavity transfers onto your part, so sand the layer lines out. Then several coats of release wax, buffed between each, and a film of PVA release.
Cut the fabric oversize, brush a wet layer of epoxy (mixed by weight) into the cavity, lay a ply in and stipple it down: dab, never drag, or the weave distorts. Add plies, chasing out the air, which otherwise cures as a white void. Gloves and ventilation. Cure at room temperature for the full time, usually overnight, then wedge the edge free and trim to the flange.
What a printed mold can't do
A printed mold is a low-temperature tool for hand layup.
| Works well | Don't |
|---|---|
| Room-temperature layup with laminating epoxy | Prepreg or oven cures, the mold sags |
| Open shapes: panels, covers, dishes, fairings | Closed hollow boxes, split those in CAD |
| Thin laminates that cure gently | Thick one-shot laminates, exotherm heat distorts it |
Carbon fibre mold FAQ
What filament should I print a carbon fibre mold in?
PETG. It takes the warmth of a curing epoxy better than PLA and needs no heated chamber. PLA works for one small part, but softens early.
Can I use a printed mold for prepreg or an oven cure?
No. Prepreg cures far above the temperature at which a printed mold softens, so the tool sags and takes your part with it.
Do I upload the mold or the part I want to make?
Upload the finished part, the thing you want in carbon. It is carved out of a block, so the cavity reproduces your part's outer surface.
Made by meshcast.app. Got stuck? Email a photo and I'll help you debug.
If the generator refused your file, the message is explained here: why was my model rejected. Almost every rejection is the same thing, a mesh with holes, and the “Fix it for me” button in the popup resolves most of them in one click.