How to make a mold from a Tinkercad design
This guide was drafted with AI assistance.
To make a mold from a Tinkercad design: group your shapes, choose Export > .STL, then either subtract the model from a box with a Hole shape (fine for flat shapes, one piece only) or drop the STL into a mold generator, which adds the parting line, keys, pour spout and vents and checks undercuts. The whole thing takes a few minutes.
Drop in an STL and get a printable mold in about a minute. Free, in your browser, nothing to install.
Open the mold generator →Before you start
Tinkercad is Autodesk's free, browser-based 3D editor. It builds everything from simple solids, which is good news for molds: a Tinkercad design is almost always a clean, closed shape, so it rarely fails the checks that trip up scans and sculpts. You need a free Autodesk account, a finished design, and nothing else.
- Scale. Tinkercad's grid is in millimetres by default, and one grid square is 1 mm unless you changed it. STL files carry no units, so an exported 40 mm figure is just the number 40 to the next program, which then reads it as millimetres.
- One solid. Group everything that belongs to the model (select all, then Ctrl+G, or the Group button). Loose, overlapping pieces cast badly and slice badly.
- No other object on the plane. Delete rulers, notes and spare shapes before you export, or they land in the STL too.
Export your design as an STL
Group and check the size
Select the model, press Ctrl+G to group it, and click the model to read its width, depth and height in millimetres. Note the numbers: you will check them again after the mold is generated.
Export
Click Export at the top right of the editor, then choose .STL. Pick Everything in the design (or just the selected shapes, if you only want one part). The file lands in your downloads folder.
Keep it oriented how you want it cast
Tinkercad exports the model exactly as it sits on the workplane. If the model has a flat back, lay it flat; a mold generator lets you rotate it later, but starting with a sensible orientation saves a step.
The Tinkercad way: a mold with a Hole shape
You can make a basic one-piece open mold inside Tinkercad itself, and for a flat-backed shape such as a coin, a letter or a simple tile it works fine.
Build a block
Drag in a Box and size it so it is at least 8 to 10 mm larger than the model on every side, and taller than the model by the same margin. For a rigid mold you pour wax or resin into, 3 to 5 mm of wall is enough.
Turn your model into a Hole
Select the model and change it to Hole in the shape panel. It turns striped and see-through.
Position and group
Lower the Hole so its flat back sits at the top face of the box and the rest of it sinks into the block. Select both and Group. The hole cuts a cavity out of the box.
Export the block
Export the grouped block as an STL, and print it with the open cavity facing up.
Where this stops working
The Hole method has hard limits, and they are the reason most people end up generating the mold instead.
| Limit | What happens |
|---|---|
| One piece only | Anything with an overhang or undercut gets trapped in a one-piece mold, so a 3D shape such as a figure, a fruit or a bust cannot be demolded. |
| No parting line | Splitting a block into two halves means more Holes, more alignment, and halves that do not register unless you model keys by hand. |
| No pour spout or vents | You build them as extra Holes and place them yourself, with no check that air can escape. |
| No undercut or wall check | Nothing tells you a thin wall will tear or a shape will lock into the mold until you have printed it. |
The faster way: let a generator do the mold
Take the STL you just exported and drop it into Meshcast's two-part box mold. It builds the block, the split along the parting line, registration keys, the pour spout and vents from sliders, and gives you both halves ready to print. It also checks undercuts and can fill them in one click, which is the thing the Hole method cannot do.
Because Tinkercad exports clean solids, the upload usually goes through at once. If a file is ever rejected as not watertight, the popup offers Fix it for me, which rebuilds the model as a closed solid and generates in the same click. The reasons a file gets rejected are listed in why was my model rejected.
Choose the generator for what you pour:
| You are casting | Use |
|---|---|
| Candles and wax | Candle mold maker: two printed halves, keys and a pour spout |
| Resin, soap, detailed figures | Silicone mold maker: a printed box to pour silicone into, or a contoured shell that uses less silicone |
| Ice, wax melts, gummies | Tray mold, runs entirely in your browser |
| Concrete planters and vases | Vase and planter mold with a tapered core so the cast comes out hollow |
| Plaster and slip casting | Plaster mold, multi-part housings with clay-shrinkage presets |
Making Tinkercad models cast better
- Add draft. Tinkercad's Cone, Roof and Paraboloid shapes give you tapered sides. Vertical walls grip the silicone or the cast; a degree or two of taper lets it release. See draft angles and undercuts.
- Avoid knife-thin features. Keep details at 1 mm or more, or the mold will not capture them.
Questions
Can you make a mold in Tinkercad?
Yes, for simple shapes. Turn your model into a Hole, place it in a box and group them to cut a cavity, then export the block as an STL. It only gives you a one-piece open mold with no keys, spout or undercut check, so shapes with overhangs need a two-part mold instead.
How do I export an STL from Tinkercad?
Click Export at the top right of the editor and choose .STL. Group your shapes first with Ctrl+G so they export as one solid, and delete any helper shapes you do not want in the file.
Is Tinkercad free to use for making molds?
Yes. Tinkercad is free with an Autodesk account and runs in your browser. Meshcast's mold generators are free to try as well, with 2 downloads a week on a free account and no card.
Will my Tinkercad STL work in a mold generator?
Almost always. Tinkercad builds models from closed solids, so they are usually watertight. If one is rejected, the Fix it for me button in the popup rebuilds it as a closed solid and generates straight away.
What size are Tinkercad exports?
The workplane grid is in millimetres by default, so a 40 unit shape is 40 mm. STL files carry no units, so check the dimensions on the generated mold against your design before you print.
Made by meshcast.app. Menu names are from Tinkercad as of November 2026 and can move between releases. Got stuck? Email a photo and I'll help you debug.