Free concrete mold maker
Design a printable mold for concrete, cement or Jesmonite in your browser, preview it in 3D, and download a print-ready STL or 3MF in seconds. Coasters, trays, dishes, planters and candle vessels - no account, no software to install.
Free · runs entirely in your browser · STL & 3MF download
How it works
- Pick a shape or upload your own STL - coasters, trays, trinket dishes, planters, candle vessels and logo pieces all work.
- Set the size in true millimetres and choose an open one-piece mold for flat-backed pieces or a two-part mold for shapes with undercuts.
- Preview the mold on a virtual print bed, then download the print-ready STL or 3MF and cast your concrete or Jesmonite.
What you get
A watertight, print-ready STL or 3MF sized in real millimetres, with a flat base and sensible wall thickness. Two-part molds include alignment keys so the halves register cleanly under the weight of a full pour. Everything is generated on your device - your model never leaves the browser.
Materials & casting tips
- Filament: PETG is the best all-round choice - it shrugs off the alkalinity and heat of curing cement over many pours. PLA works for a few casts but degrades faster in wet concrete.
- Wall thickness: concrete is heavy, so use 3-4 mm walls with 4 perimeters to stop bowing on larger pieces.
- Release: printed molds release cleanly with a wipe of vegetable oil, a spray mold release, or a thin coat of paste wax. A little draft angle on the walls makes demolding much easier.
- Mixes: a fine sand-free mix (or Jesmonite / cement-all) captures printed detail best; vibrate or tap the mold to knock out air bubbles before it sets.
- Watertight prints: print at 100% infill (or seal with a wipe of the same filament's solvent) so the wet mix can't weep through the layer lines.
Who it's for
Makers casting concrete coasters, catch-all trays, ring dishes, candle vessels and small planters, plus crafters working in Jesmonite and cement-all who want a custom shape without CAD. For a hollow pot or planter with an inner cavity, use the vase & planter mold instead. For fine detail or long production runs, print this master and cast a flexible silicone mold from it.
FAQ
Is the concrete mold maker free?
Yes. Designing and downloading a concrete mold is free and runs entirely in your browser - there is no server render and no account required to start.
Can I pour concrete straight into a printed mold?
Yes. Concrete, cement-all and Jesmonite all cast fine in printed PETG or PLA molds. Coat the inside with oil or a spray release first, and add a little draft so the piece lifts out cleanly. For repeat production or crisp detail, cast a silicone mold from a printed master.
Will the concrete stick or crack the mold?
Not with a release agent and enough wall thickness. Concrete gives off heat and expands slightly as it cures, so 3-4 mm walls and a two-part design with alignment keys handle the pressure. PETG lasts longest across many pours.
What file format do I get?
A standard STL or 3MF that loads straight into any slicer - Cura, PrusaSlicer, OrcaSlicer and others.
What's the difference between this and the plaster mold?
This makes a mold you pour concrete or Jesmonite into. The plaster slip-casting mold makes a reusable plaster mold that absorbs water from liquid clay - a different casting process for ceramics.