Mould Design Generator — User Guide
The Navi3D Mould Design Generator turns a 3D model into a print-ready mould. Upload your part, choose a few options, and download the mould halves as STL files — ready to print on your FDM or resin printer and cast in resin, silicone or plaster of Paris. Everything runs on our servers, so there is nothing to install.
How it works
You upload a model. Our servers measure it precisely, build a cavity in the exact shape of your part, add the pour hole, air vents and alignment keys, and return the finished mould as STL files inside a ZIP. The whole process takes about 10 to 60 seconds.
You do not need any CAD software. You do not need to repair your file first. The generator is built to handle real-world models, including 3D scans and sculpted meshes.
What a mould is made of
Every two-part mould has the same parts. Knowing their names makes the options easy to understand.
- Cavity — the hollow in the exact shape of your part, where the casting material sits.
- Sprue — the pour hole you pour resin or plaster into.
- Parting line — the flat plane where the two halves meet and separate.
- Registration keys — small bumps on one half that fit sockets in the other, so the halves line up perfectly every time.
- Air valves — thin vertical channels that let trapped air escape while you pour.
- Wall — the solid mould material around the cavity.
Step-by-step quick start
Follow the six cards on the page from top to bottom. The sections below explain each choice in plain language.
1. Upload your model
Drop an STL, STEP or 3MF file onto the upload area, or click to browse. Files up to 200 MB are accepted.
- The free plan handles models up to 1.5 million triangles.
- Premium handles models up to 4 million triangles.
- If your file is larger, the tool tells you and you can simplify it in your slicer, or upgrade to Premium.
2. Mould setup
This is where you choose the overall shape of the mould.
Mould type
- Two-part — two halves that clamp together for a closed pour. Best for full 3D shapes like murtis and figures.
- One-part (open pour) — an open-topped mould you pour straight into. Best for reliefs, coasters and flat-backed items.
Mould style
- Block — a solid rectangular mould. Strong and easy to clamp. Recommended for most parts.
- Conformal shell — follows the shape of your part, using less material and printing faster. Good for large simple shapes.
Pull direction (parting axis)
This is the direction the two halves separate. Pick the axis along which your part has the fewest overhangs. For most upright parts this is Z. If in doubt, leave it on Z and check the report after generating.
Parting plane
- Auto — the tool finds the widest cross-section and splits there. Recommended.
- Center — splits through the middle.
- Offset — you set the exact split height yourself.
3. Cavity and fit
These settings control how the casting fits and releases.
- Wall thickness — how much mould material surrounds the cavity. 6 to 10 mm is typical. Thicker is stronger but uses more filament.
- Cavity clearance — a small uniform gap around the part for a clean fit and easy release. 0.10 to 0.15 mm works well.
- Shrinkage compensation — grows the cavity slightly to allow for casting material that shrinks. Use 0% for plaster, around 1% for resin.
- Draft angle — see below.
Draft angle
Draft is a slight taper on the walls so the casting slides out easily.
- Use 0° when your part has holes that must stay perfectly round, or when casting flexible material like silicone.
- Use 1° to 2° for rigid casts in rigid moulds, so they release cleanly.
- Important: draft also tapers the pins that form holes in your part. If your part has holes that must stay cylindrical, keep draft at 0°.
Undercut relief
Leave this on. It sweeps each half so the mould always separates cleanly, even if your part has overhangs. The report tells you how much extra material this added, if any.
4. Feed system (the pour hole)
The sprue is where you pour the casting material in.
- Gate type — Top pours straight down into the cavity. Side places the pour hole beside the part with a channel feeding in along the parting line. Top is simplest.
- Sprue profile — Straight, Tapered (wider at the top for easier pouring) or Funnel (a wide mouth). Tapered or funnel help with thick materials like plaster.
- Sprue diameter — 6 to 8 mm for most parts. Use the larger end for viscous plaster.
Placing the pour hole
By default the pour hole sits at the center of your part. If the center of your part is a raised feature or a hole, move the sprue onto a nearby flat area using the Sprue offset X and Y fields. These values are in millimetres — for example, 11 mm in X and 5 mm in Y. After generating, check the report: if it warns that the pour hole may be blind, adjust the offsets and generate again.
5. Venting and air valves
Air valves are thin channels that let trapped air escape as you pour, so the casting fills completely.
- Air valves — None, Straight or Tapered. Straight is fine for most work.
- Count — how many valves. 4 gives good coverage on round parts.
- Diameter — 4 mm is a good default.
- Ring position — how far from the center the valves sit. 0.1 is near the center, 0.9 is near the edge. Use 0.8 for parts where air collects near the rim.
- Parting-line vents — shallow channels along the parting line for closed pours. Keep the vent width at least twice your voxel size.
6. Registration keys
Keys keep the two halves aligned. One half gets small bumps, the other gets matching sockets.
- Key shape — Dome (rounded, easy to align) or Cone (self-centering).
- Count — 4 is standard.
- Diameter — 8 mm works for most moulds.
- Socket clearance — the gap so the halves fit without forcing. Use 0.15 mm for FDM prints, 0.10 mm for resin prints.
7. Resolution
Resolution controls how much fine detail the mould captures.
- Draft (0.8 mm) — fastest, for large simple shapes.
- Standard (0.5 mm) — balanced, the default for most parts.
- Fine (0.3 mm) — sharpest detail, for small holes and sharp edges. Available on Premium.
As a rule, a feature needs to be about five times the voxel size to come out accurately. A 3 mm hole needs Fine (0.3 mm) resolution to stay round.
Reading the report
After generating, the summary panel shows the part size, mould size, casting volume and other numbers. Always read the Warnings section — it flags things like undercuts, a pour hole that may be blind, or features too small for the chosen resolution. Warnings do not stop you downloading; they tell you what to check before printing.
Downloading and printing
Your download is a ZIP file containing:
- The mould halves as STL files (two files for a two-part mould, one for an open-pour mould).
- A report file with all the measurements.
Import the STL files into your slicer as usual. Print the halves, clamp them together with the registration keys aligned, and pour your casting material slowly. Tap or vibrate the mould gently so material flows around fine features without trapping air.
Recommended settings by part type
| Part type | Mould type | Draft | Resolution | Notes |
|---|---|---|---|---|
| Murti or sculpture | Two-part block | 1° | Standard or Fine | Add 4 air valves near the rim |
| Engineering part with holes | Two-part block | 0° | Fine | Keep draft at 0 for round holes |
| Relief or coaster | One-part open pour | 1° | Standard | No keys needed |
| Large simple shape | Two-part conformal | 1–2° | Draft or Standard | Saves filament |
Free plan and Premium
- Free — two moulds per day, standard 0.5 mm resolution, models up to 1.5 million triangles. No login needed.
- Premium — unlimited moulds, fine 0.3 mm resolution, custom voxel size down to 0.15 mm, and models up to 4 million triangles. Linked to your account, so it works on all your devices.
Common questions
The pour hole does not reach my part
Move the sprue onto a flat area of your part using the Sprue offset X and Y fields, then generate again. Check the report for the blind-hole warning.
My holes came out as cones
Draft tapers the pins that form holes. Set the draft angle to 0° for perfectly cylindrical holes.
Sharp edges look rounded
Use Fine (0.3 mm) resolution. Smaller voxels capture sharp corners more closely.
My file was rejected as too large
The free plan allows 1.5 million triangles. Simplify the mesh in your slicer, or upgrade to Premium for up to 4 million.
Can I edit the mould in CAD afterwards
Yes. The STL imports into SolidWorks, Fusion 360 or Blender as a mesh body, where you can cut, combine and modify it. It is not a parametric feature tree, but practical edits like enlarging the pour hole or adding clamp holes work well.