Make a silicone mold from an STL with the Mold Maker
Load a master model, choose a mold type, and the Mold Maker builds the parts you print: a jacket for silicone, a box, a tray or a rigid two-part mold, with registration keys, a pour port and vents. It highlights possible air traps and previews the fill before you print anything.
The Mold Maker is open to every Printara account. Sign in, or create an account, and the editor opens at printara.co/lab/mold and in the Mold tab of Printara Studio. Building a mold on your own computer is free. A build on our server costs credits, from 10 per mold, and after a server build, rebuilding the same model as the same mold type within 24 hours is free, up to 3 times.
Eight mold types for different jobs
Each type is a different way to reproduce a master. Pick the one that matches the shape and the material you cast.
Adaptive shell
A printed jacket that follows the model at silicone thickness: a base plate plus two to four wedges, and one pour through the spout. For figures, minis and anything with undercuts.
One-piece cut mold
The open box poured as one silicone block, with molded guide grooves that show where to slit it open after curing, so it keys back together on its own. The hobby standard for figures and minis.
Open box
A box or cylinder around the master: a base plate and two wall halves that key into each other, held by a rubber band in its own channel. Drop the master in and pour.
Two-part silicone box
A printed parting bed, frame and sprue for two pours with release agent between them. For masters whose parting line has to sit on an edge.
Tray
One open-top cup for flat masters such as coins, tiles, bases, chocolate or soap. Pour from the top and flex the cup to demold.
Printed two-part mold
A rigid printed negative with no silicone, for wax, plaster or resin. Only for masters with almost no undercuts, with 2 degrees of draft by default. Not food-safe as printed.
Press mold or stamp
One printed tool you press into clay, dough, soap or leather, from a shallow stamp of the design to the model's full depth.
Vessel with inner core
Vases, planters, cups and candle holders cast hollow: a shell for the outside plus a printed core for the inside. For concrete, plaster, resin, wax or soap.
How to make a mold from an STL
- Load your master as an STL (under 95 MB) and check its dimensions. Scale it to the size you want to cast.
- Choose the mold type and set the silicone thickness and the shell wall. The shell can close with bolts through tabs, spring clamps on a parting flange, a flange with bolts, printed clips or hooks and rubber bands.
- Add a fill and drain opening, registration keys and vents. Keys are sized and placed automatically, or you place them yourself. Shrink compensation has presets for platinum and tin silicone, resin and wax.
- Build the mold, free on your own computer or on Printara servers for credits. A simple master takes seconds, a detailed one up to a few minutes. Both use the same engine.
- Inspect it. Make the master or the shell transparent, check the highlighted air traps, move through the fill preview and pull the parts apart.
- Download and save. The print files come as a ZIP with one STL per part, together with a report and the list of hardware to buy. Save the mold set to your Library to open it again later.
Check the mold before you print it
Screens from the Academy lesson Make a printable mold shell for silicone casting.
The full lesson from Printara Academy, 5 minutes 5 seconds, also on the lesson page.
What is in the download
Print files
A ZIP with one STL per printed part, named by its role: shell wedges, base plate, fill-port plug or core. Each part in the list shows its volume and overhang so you can plan the print.
Report and hardware
A report of the build and the hardware the mold needs, such as the number and size of bolts and nuts. Your master is a separate download and stays unchanged.
Silicone, resin and other materials
The printed parts shape and hold the mold; the material you pour decides the rest. Platinum-cure silicone shrinks less and lasts longer; tin-cure silicone is cheaper and shrinks a little more. The Mold Maker's shrink presets cover both, plus resin and wax. The printed two-part mold and the press mold skip silicone and go straight into wax, plaster, resin, clay, dough or leather. For anything that touches food, use a food-grade silicone and follow its maker's instructions: printed plastic is not food-safe as printed.
What it costs
A mold computed on your own computer costs nothing, so the 0 credits a new account starts with are enough. If your computer is not up to a model, our server builds it for credits. All you need is a Printara account. Filament, silicone and hardware are up to you.
| What you do | Credits |
|---|---|
| Create a Printara account (no card needed) | No charge |
| Build a mold on your own computer, inspect it and download the parts | 0 |
| Build a press mold or stamp on our server | 10 |
| Build a tray, an open box or a one-piece cut mold on our server | 20 |
| Build an adaptive shell, a vessel with a core, a two-part silicone box or a printed two-part mold on our server | 30 |
| Rebuild the same model as the same mold type within 24 hours of a server build (up to 3 times) | 0 |
| Save the mold set to your Library and reopen it | 0 |
| AI product photo of a saved mold set | 5 per photo |
Prefer a ready-made or hand-made mold?
Mold Maker FAQ
Who can use the Mold Maker?
Anyone with a Printara account. Sign in, or create an account, and the Mold Maker opens at printara.co/lab/mold and in the Mold tab of Printara Studio. Signing up is free.
Does the Mold Maker cost credits?
Not when the mold is computed on your own computer: that build is free, and so are saving it to your Library and downloading the parts. If your computer is not up to a model, our server can build it for credits: 10 for a press mold, 20 for a tray, an open box or a cut mold, 30 for an adaptive shell, a vessel with a core or a two-part mold. Rebuilding the same model as the same mold type within 24 hours of a server build is free, up to 3 times. New accounts start with 0 credits.
Can my computer build the mold?
Most desktops and laptops can, in a current Chrome, Edge, Firefox or Safari. The Mold Maker picks your computer whenever it can run the engine. It suggests our server only when your computer is slow (a touch device, fewer than 4 processor cores or less than 4 GB of memory) or the model may not fit in its memory, and only if you have the credits for it. You can always choose. Both use the same engine: in Chrome and Edge the print files come out the same as a server build, in other browsers they can differ very slightly.
What file do I need as a master?
An STL of the object you want to cast, under 95 MB. After loading, check the dimensions and scale the master to the size you want to cast.
Which mold type should I choose?
Figures and minis with undercuts: the adaptive shell or the one-piece cut mold. Flat pieces such as coins, tiles and soap: the tray. Clay, dough or leather: the press mold. Vases and candle holders cast hollow: the vessel with an inner core.
Do I still need silicone?
For the adaptive shell, the open box, the cut mold and the two-part silicone box, yes: the printed parts hold and shape the silicone. The printed two-part mold and the press mold are used directly, without silicone.
Is a printed mold food-safe?
Not as printed. For chocolate or other food, cast a food-grade silicone mold with the printed parts and follow the silicone maker's instructions.
Will my cast be free of bubbles?
The air trap highlight and the fill preview help you spot problems before you print, but they are a check, not a guarantee. Degassing, pour speed and vents still decide the result.
Can Printara make the mold for me?
Yes. Printara Atelier in Prague makes silicone molds and casts in resin and plaster by hand. Ask for a quote on the Atelier page.
Related tools and guides
- AI Mold MakerA real mold, from the silicone pour to the resin cast.
- STL SplitterCut a big master into parts before molding.
- Academy: make a mold shellThe full video lesson.
- How to make a silicone mold from an STLBox or shell, thickness, vents and silicone math.
- How to prepare a model for a split moldParting line, draft, keys, clearances and vents.
- Browser mold makers comparedMeshcast, MoldStudio3D, Mold Studio and Printara.
- All Printara toolsClicker, ornament maker and more.
- PricingPlans, credit packs and the marketplace fee.
Ready to build your first mold?
Sign in, or create an account, and build your first mold. Building it on your own computer is free.