Best print settings for 3D printed molds

The best settings depend on what the print is for. A rigid mold you pour into needs to be watertight and stiff: a fine layer height around 0.12–0.16 mm, 3–4 walls, a 5–6 layer floor and the cavity facing up. A master for a silicone mold needs to be smooth more than strong, because silicone copies every layer line. Here are the settings for both.

Step 1 — Know which part you're printing

• Rigid mold (direct pour): you pour wax, soap, plaster, concrete or resin straight into the print. It must hold liquid without leaking and survive demolding.
• Master (for silicone): the print is the shape you want to copy; silicone is poured around it, and you cast into the silicone. Strength barely matters — the surface finish is everything.
• Mold box: the printed walls that hold liquid silicone around a master. It needs to be watertight at the seams, but its finish doesn't transfer to anything.

I generate all three in 3DGEN — a two-part rigid mold with the mold maker, a mold box around a master with the silicone mold box generator — in the browser in seconds, no CAD. The slicer settings below apply to files from any source.

Step 2 — Settings for a rigid mold

• Layer height: about 0.12–0.16 mm. Finer layers mean smoother casts and fewer paths for liquid to seep through; 0.2 mm is fine for shallow molds and wax.
• Walls (perimeters): at least 3; use 4 for deep molds, resin and concrete. Walls do most of the sealing.
• Bottom and top layers: 5–6 solid bottom layers so the floor of the cavity doesn't leak.
• Infill: moderate — roughly 15–20% gyroid is a common starting point, more (30–50%) for heavy pours like concrete, and 100% for small molds.
• Orientation: cavity facing up, the parting face flat on the bed, and no supports inside the cavity.
• Extrusion: a few degrees hotter than usual and a slight flow increase (+1–3%, checked on a test cube) help layers fuse into a sealed wall.
• Ironing on the top face of the cavity, if your slicer supports it, gives a smoother surface for the cast.

In the mold maker, the mold's own Wall thickness (5 mm by default) sets how much plastic surrounds the cavity — thicker walls are stiffer and give your slicer more room for perimeters.

Step 3 — Pick the filament for the pour

• PETG — the usual default for molds: tougher and more heat tolerant than PLA, and good with resin, plaster and concrete.
• PLA — fine for room-temperature pours (plaster, concrete, resin) and for masters; avoid it for hot wax, because it softens around 60 °C.
• ABS/ASA — more heat tolerant still, if you can print them.

The full comparison is in best filament for 3D printed molds.

Step 4 — Seal and release a rigid mold

FDM prints are slightly porous between layers. For resin and other sticky materials, seal the cavity with a thin coat of epoxy, sanding sealer or clear spray, then smooth it. Always use a release agent — paste wax, PVA release or a release made for your casting material — and reapply it between casts; a cast that sticks on the third or fourth pour is usually a worn-off release. A sealed, released FDM mold typically lasts for a modest run of casts rather than hundreds. To check a mold before the first pour, follow how to make sure your mold prints watertight.

Step 5 — Settings for a silicone master

• Layer height: as fine as your patience allows — 0.08–0.12 mm. Every visible step will appear on every cast.
• Orientation: put the most important faces on vertical sides or the top, not on curved shallow slopes where layer stepping is most visible, and keep supports off show surfaces.
• Walls and infill: 2–3 walls and light infill are enough — the master only has to hold its shape.
• Resin printers: excellent for detail, but wash and fully post-cure the print and let it rest before use — uncured resin can stop platinum silicone from curing. Test a small patch of silicone on the print first.

Step 6 — Smooth the master

1. Sand through progressively finer grits — start coarse enough to knock down layer lines and finish fine (wet-sanding at the end gives the smoothest surface).
2. Fill remaining steps with a filler primer, sanding between coats.
3. Coat with a brush-on epoxy coating or a clear gloss finish if you want glossy casts — let it cure fully.
4. Test the silicone on the finished master. If it stays tacky where it touched, add a barrier coat — why silicone won't cure covers the fixes.

Step 7 — Print the mold box

A mold box isn't seen by the cast, so print it for speed and tightness: 0.2 mm layers, 3 walls, and good first-layer adhesion so the base seals. In the silicone mold box generator, Fit tolerance (joints) controls how snugly the printed parts lock together — tune it to your printer so the seams don't leak silicone. After Build the box, the Material estimate panel shows how much silicone to mix.

FAQ

What layer height should I use for a 3D printed mold?

About 0.12–0.16 mm for a rigid mold, and finer (0.08–0.12 mm) for a master you'll copy in silicone.

How do I get rid of layer lines on a 3D printed mold?

Print finer layers, iron the cavity face, then sand and seal it. For a silicone master, sand, prime and coat before you pour the silicone.

How many walls does a mold need?

At least three, four for deep molds and resin, plus 5–6 solid bottom layers so the floor doesn't leak.