Use CasesMedium Impact·Monday, March 30, 2026

Dad Uses Codex to Skip CAD, Generate 3D-Printable Pegboard Pieces

A maker used OpenAI Codex to convert a hand sketch and two dimensions into parametric Python generators for a printable kids' pegboard system.

What happened

A developer/maker shared a Hacker News project where they photographed a sketch, pasted it into Codex with just two measurements (40mm hole spacing, 8mm peg width), and got working Python geometry generators in about a minute. The result: a 40mm pegboard system with 7 play pieces, 4 gears, and 2 printable boards — all defined as small Python scripts rather than hand-modeled meshes. The repo includes an AGENTS.md file explicitly designed to let coding agents extend the system safely. The project demonstrates a sketch-to-3D-print pipeline with minimal manual CAD work.

Why it matters to you

personalized

This project demonstrates a concrete agentic loop: image input → dimensional constraints → parametric Python generators → iterable physical output. The key architectural insight is keeping geometry as code (Python functions) rather than binary mesh files, which makes agent-driven iteration trivially fast. The AGENTS.md pattern — a machine-readable spec file for safe extension — is a reusable convention worth stealing for any generative design or config-heavy project.

What to do about it

Clone the repo, run the three generator scripts locally, then prompt Codex to add a new piece variant (e.g. a T-shaped connector for 3-peg intersections) by pointing it at AGENTS.md — measure how many lines of manual code you wrote vs. generated.

Put it to workPython · 10 min

A new .stl file for the 3-peg bar piece, generated without touching CAD software — ready to slice and print

Suggested exercise · not independently tested. Access requirements and costs may vary.

1
Clone the repo and run: python3 -m venv .venv && . .venv/bin/activate && pip install -r requirements.txt
2
Run: python scripts/generate_pegboard_shapes.py to generate the base STL outputs
3
Open Codex or Claude and paste the contents of AGENTS.md plus this prompt: 'Add a new piece: a straight bar connecting 3 pegs in a row at 40mm spacing, 8mm peg width, same wall thickness as existing pieces. Output as a new generator function matching the existing file style.'
4
Drop the output function into generate_pegboard_shapes.py and re-run to see the new STL

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