moldgen

Turn any 3D model into a ready-to-print (or CNC) mold for carbon fiber work.
Runs locally in your browser — upload a part, drag the parting plane, download the mold halves.

---

• What it does
• Setup on Windows
• Setup on Linux / macOS
• Using the app
• Optional: STEP / IGES input
• Troubleshooting
• For developers

What it does

Upload a part (STL / 3MF / OBJ), pick a mold style, and moldgen generates watertight, printable mold geometry — with the mold-making details already engineered in, following Easy Composites' published guidance. Every setting in the app has a hover tooltip explaining what it does and where the default number comes from.

Whichever way you spell it — carbon fiber or carbon fibre, mold or mould — this covers the three tool types home and small-shop composite work actually uses: forged carbon compression moulds, prepreg/vacuum-bagging laminating tools, and open layup tools.

Mold style	What you get
Compression / forged carbon	Two-part telescoping mold — the male plug pistons into the female pocket so chopped fiber can't jam the seam. Registration pins, clamp bolt holes, pry slots, jack screws, resin overflow channels, optional ejector hole.
Prepreg / laminating tool	Single-sided female tool with a trim-allowance run-out (witness line to trim to), bagging flange, sealant-tape guide line, optional split-mould bush holes.
Open layup	Basic single-sided female tool with a flat bagging flange.

Before you commit plastic, the built-in demolding check highlights faces that will lock (red) or drag (amber) during demolding, and the parting height is auto-suggested. Printer presets (resin / FDM / CNC) set all fit clearances in one click.

Setup on Windows

You need Python 3.11 or newer — tick "Add python.exe to PATH" in the installer. Then in PowerShell or Command Prompt:

git clone https://github.com/cauliflowermossgrape/moldgen.git
cd moldgen

py -m venv .venv
.venv\Scripts\pip install -e .
.venv\Scripts\python -m uvicorn moldgen.main:app

Open http://localhost:8000 in your browser. That's it — next time, only the last command is needed.

Setup on Linux / macOS

You need Python 3.11+ (python3 --version to check). Then:

git clone https://github.com/cauliflowermossgrape/moldgen.git
cd moldgen

python3 -m venv .venv
.venv/bin/pip install -e .
.venv/bin/python -m uvicorn moldgen.main:app

Open http://localhost:8000. (If you have make: make dev does all of the above, make test runs the test suite.)

Using the app

1. Pick your process at the top — resin print, FDM print, or CNC. This sets all the fit clearances.
2. Drop your model into the viewport (STL, 3MF or OBJ, in millimeters). You'll see dimensions, a watertightness check, and a warning if the model looks like it was exported in meters.
3. Set the parting plane with the slider (it starts at the auto-suggested height) and click Analyze undercuts — red faces will lock in the mold, amber faces will drag. Adjust until it's clean.
4. Pick a mold style and tweak settings — hover anything to see what it means.
5. Generate mold — inspect the halves with the explode slider and ghost-part toggle, read any warnings (they tell you what was shrunk, moved or skipped, and anything about your part that will fight demolding).
6. Download the STL per half and slice it like any other print.

Uploaded parts and generated molds are stored in the local workdir/ folder — nothing leaves your machine.

Optional: STEP / IGES input

To upload CAD files directly (STEP/IGES instead of meshes), install the step extra — it pulls OpenCascade, whose wheels are several hundred MB:

# Windows:   .venv\Scripts\pip install -e ".[step]"
# Linux/mac: .venv/bin/pip install -e ".[step]"

Surfaces are tessellated on upload with adjustable precision; IGES files are sewn into closed shells automatically. The app detects support at startup and enables the formats. On minimal Linux installs you may also need sudo apt install libgl1.

Troubleshooting

Problem	Fix
python / py not found	Install Python 3.11+ and re-open the terminal; on Windows make sure "Add to PATH" was ticked.
Page loads but the 3D view is blank	The viewer loads three.js from a CDN — the first page load needs internet access.
Port 8000 already in use	Add --port 8080 to the uvicorn command.
STEP upload says "not installed"	Install the step extra (see above); on Linux also sudo apt install libgl1.
"mesh is not watertight" error	Your model has holes/open edges. moldgen attempts repair automatically; if it still fails, fix the export in your CAD tool (export as a solid, not surfaces).
Mold seems too big/thick	Wall margin is horizontal (flange room for pins/bolts); Base thickness is the vertical shell — lower it for thin parts.

For developers

.venv/bin/pip install -e ".[dev]"
.venv/bin/python -m pytest        # 48 tests, a few seconds

moldgen/
  core/            pure-geometry engine (no web imports)
    engine.py        generate_mold(mesh, params) -> MoldResult
    forged.py        telescoping compression construction
    prepreg.py       laminating-tool construction
    hardware.py      pins, bolts, pry slots, jack screws, overflow, scribes
    undercuts.py     demold + drape analysis, parting-plane suggestion
    step_io.py       optional STEP/IGES tessellation (cadquery/OCP)
  main.py          FastAPI app: JSON API + static frontend
frontend/          vanilla JS + three.js viewport (no build step)
tests/             pytest — geometry verified by exact volume arithmetic

All booleans run through manifold3d (watertight-guaranteed); trimesh handles I/O and analysis. The frontend talks to a small JSON API (POST /api/upload, /api/analyze, /api/generate, GET /api/download/{id}/{half}.stl) — script it directly if you prefer. Units are millimeters everywhere.

Known limitations: the undercut check is first-order (won't catch silhouette-occluded undercuts like tilted bores), the parting surface is a flat plane, and fillets can't be added to your part automatically — the drape check tells you where they're needed.

License

MIT