# 3d-print-design
A Claude Code skill that designs parts for FDM 3D printing in code: from a
verbal idea to a checked STL with a browser preview, for any printer. It
interviews you, writes a parametric build script, refuses to export a part
that fails its printability checks, shows the result in a local 3D viewer and
hands you the STL with a short print sheet.
**It never talks to your printer.** No G-code, no network calls to printers,
no starting prints. You slice and print with your own slicer.
*The fictional example cable clip in the local viewer (headless Chrome render).*
## What it does
1. **Intake**: a short interview (see below), then a one-paragraph summary to confirm.
2. **Sketch**: the part in words plus a dimension table (measured / derived / default, critical or not).
3. **Reuse**: starts from an example or the template's default part when one is close.
4. **Parametric script**: `templates/build.py` copied into your project. Every number lives in one commented parameter block (millimetres, with the reason for each value).
5. **printcheck before export**: watertight and consistent winding, positive volume, body count, sits on the bed with real contact area, fits the build volume with a margin, overhang report (bridges counted separately), layer alignment, small and horizontal holes, optional thin-wall sampling, and probe points that catch a mirrored (wrong-hand) part. Errors block the STL.
6. **Preview**: `scripts/serve.py` serves the output folder on 127.0.0.1 to a three.js viewer: per-part colours, orbit, bed grid of your printer's size, section plane, bounding box readout in mm, dark and light.
7. **Iterate on numbers**, not on prints.
8. **Calibration coupon** for fits: holes and pegs at 0.00 to 0.40 mm per side, read by counting notches, recorded into `fits.json` that the build scripts use.
9. **Delivery**: STL(s), metadata JSON (bounding box, volume, mass upper bound, triangle count, check results, parameters), preview, print sheet.
## The intake questions
Asked in your language, at most two short rounds, skipping anything you already said:
- What does the part do and where does it live?
- Critical dimensions measured with calipers, and which are critical?
- Mating parts and fit type: press, snug, sliding or free?
- Load, heat, outdoor or UV exposure?
- Printer model, build volume, nozzle diameter?
- Material: PLA, PETG, TPU (ABS or ASA only with ventilation)?
- Colours: single, colour change at a layer, or multi-material?
- Quantity, looks vs strength, supports allowed, orientation constraints, deadline?
- If it reproduces a real person's face or likeness: that person's consent first.
Defaults when skipped are in [references/intake.md](references/intake.md).
## Install
```
git clone https://github.com/Matteoikarieth96/3d-print-design-skill ~/.claude/skills/3d-print-design
cd ~/.claude/skills/3d-print-design
python3 -m venv .venv && .venv/bin/pip install -r requirements.txt
```
Requirements: Python 3.11 or newer for the geometry stack (pinned in
`requirements.txt`: numpy, trimesh, manifold3d, shapely; no scipy, networkx or
rtree needed). The server, the SVG renderer and the PNG renderer use only the
standard library. A browser for the preview; Google Chrome or Chromium only if
you want PNG renders.
## Usage
Ask Claude in your own words, for example "design a clip to hold a 7 mm cable
bundle under my desk" or "disegnami un supporto per il router da avvitare al
muro". The skill takes it from there.
Manual use, from a fresh, empty project folder (never inside a downloaded or
cloned repository; copy STLs you were given into it as data). Build scripts
only load helpers from `$PRINT3D_SKILL_DIR/scripts` or the installed skill, and
`-P` keeps the project folder off Python's import path:
```
S=~/.claude/skills/3d-print-design
mkdir -p ~/3d-print-design/my-part && cd ~/3d-print-design/my-part
cp "$S/templates/build.py" .
"$S/.venv/bin/python" -P build.py # check + write out/<name>.stl
"$S/.venv/bin/python" -P build.py --check # check only
python3 "$S/scripts/serve.py" out --open # preview
python3 "$S/scripts/render_png.py" out --out out/preview.png
"$S/.venv/bin/python" -P "$S/scripts/printcheck.py" part.stl --bed 220x220x250 --layer 0.2 --overhang 45
```
If the skill is installed somewhere else, set `PRINT3D_SKILL_DIR` to its folder.
Calibration coupon:
```
"$S/.venv/bin/python" -P "$S/scripts/calibration_coupon.py" build --out out
# print it, test the pegs, then:
"$S/.venv/bin/python" -P "$S/scripts/calibration_coupon.py" record --press 0.10 --snug 0.15 --sliding 0.20 --free 0.30 --overhang 45 --material PETG
```
## Outputs
| File | Content |
|---|---|
| `out/<name>.stl` | binary STL in millimetres, Z up, sitting on z = 0 in print orientation |
| `out/<name>.json` | bounding box, volume, solid mass upper bound, triangle count, full printcheck result, parameter snapshot, STL sha256 |
| `out/manifest.json` | written once by `serve.py` at start-up: parts, colours, bed size for the viewer |
| `fits.json` | your measured clearances (from the coupon) |
## What it does NOT do
- No printer control of any kind: no G-code, no calls to printer hosts or cloud print services, no starting prints.
- No slicing. Supports, seams, infill and speeds are set in your slicer.
- No structural analysis (no FEA). Load advice is rules of thumb.
- No font rendering: marks are notches and symbols; add text in the slicer if needed.
- Not for safety-critical parts (see [references/safety.md](references/safety.md)).
## Examples (fictional)
- [examples/cable-clip](examples/cable-clip): desk-edge cable clip with countersunk screw holes and a snap-in channel.
- [examples/calibration-coupon](examples/calibration-coupon): the tolerance and overhang coupon.
## Security summary
Local only. Build scripts never import code from the project folder or the
folders around it. Every file the scripts write goes through one helper that
refuses symlinks and replaces files atomically. The preview server binds
127.0.0.1, serves one folder, opens each file without following symlinks and
refuses hard links, FIFOs, `..`, subfolders and non-allowed file types, checks
the Host header, times out idle clients and sends a strict
Content-Security-Policy. Part names and output folders are validated; file
names are stripped of control characters before they are printed. STL files are
parsed as numbers only, with size caps checked before reading. three.js r128 is
the only external script, loaded from cdnjs with an integrity hash; the STL
parser and orbit control are small built-ins, so nothing else is fetched or
vendored. Details: [SECURITY.md](SECURITY.md).
## Limitations
- printcheck is a set of heuristics, not a slicer: thin-wall sampling is
random-ray based, holes are found on 15 sections, bridges are detected by a
rule (held on most of the outline and at most 10 mm wide).
- The viewer needs three.js from cdnjs; offline it shows flat SVG pictures instead.
- Headless WebGL renders depend on the local Chrome; `render_png.py` falls back
to an SVG orthographic render and says so (`--svg` forces it; example:
[docs/cable-clip-svg-fallback.png](docs/cable-clip-svg-fallback.png)).
- Helpers cover common shapes (plates, profiles, holes, countersinks,
counterbores, inserts, teardrops, chamfers). Fillets, threads and organic
shapes need your own code in the geometry block.
## More skills
- [evm-dd](https://github.com/Matteoikarieth96/evm-dd-skill): investor-angle due diligence on crypto and EVM projects, with a scored report and an A4 one-pager
- [hiring-prep](https://github.com/Matteoikarieth96/hiring-prep-skill): an interview prep page from a company, a role and your resume, with an interactive test
- [beer-can-label](https://github.com/Matteoikarieth96/beer-can-label-skill): full-wrap beer can labels with a 3D can preview
- [whiteboard-video](https://github.com/Matteoikarieth96/whiteboard-video-skill): hand-drawn whiteboard explainer videos with voice-over
- [skill-release](https://github.com/Matteoikarieth96/skill-release-skill): publish a skill as a public GitHub repo without leaking anything, with an automated scan and independent review
- [breadboard-wiring-guide](https://github.com/Matteoikarieth96/breadboard-wiring-guide-skill): step-by-step breadboard wiring for Arduino UNO, with a diagram and a USB call on every step
## Licence
MIT, see [LICENSE](LICENSE).
