serdarvaran/datumsmith

A mechanical CAD skill for coding agents that checks its own work.
English · Türkçe
Datumsmith teaches Claude Code, Codex, Hermes, LM Studio and other skill-aware agents to design parametric parts in
CadQuery and then prove them. Every design rule it applies comes from a cited source, and every delivered STEP is
measured by deterministic checkers before the agent is allowed to call the job done.
> An agent that writes a CAD script is not the same as an agent that delivers a part you can print, machine or mould.
> Datumsmith closes that gap with numbers, not adjectives.
## Contents
Why Datumsmith
How it works
What it checks
Rule library
Technical drawings
Install
Usage
Tools reference
Repository layout
Testing and evaluation
Limits
License
## Why Datumsmith
| Without it | With Datumsmith |
| The agent picks "about 3 mm" for an M3 hole | ISO 273 clearance (3.4 mm, medium series) or the CNC Kitchen insert hole (4.0 mm) from a sourced table |
| "Looks fine" after the script runs | checkfeatures measures every hole, boss and cut-out on the BRep against the contract |
| Walls, overhangs and draft are eyeballed in a render | checkdfm measures them on the real geometry for the chosen process and orientation |
| Lid and PCB collide on the first print | checkfit reports interference volume and minimum gap between parts |
| A drawing is a screenshot | An ISO first-angle sheet with a title block, dimensions from a datum and ISO 286 fit callouts |
## How it works
mermaid
flowchart TD
A[Request text, sketch, STEP] --> B[Inspect existing CAD, units, datums]
B --> C[Specify process, contract JSON, sourced rules]
C --> D[Build parametric CadQuery script]
D --> E{Validate gates}
E -->|BRep, features, DFM, fit, mesh| F[Visual review renders, sections]
E -->|any error| D
F --> G[Deliver STEP / STL / 3MF, drawing, report]
1. Inspect the request and any existing model; record units, datums and what must not change.
2. Specify the manufacturing process first, because it sets every limit. Write a small JSON contract of the
features that matter (holes, bosses, cut-outs, keep-outs).
3. Build an editable, parametric CadQuery script. Neutral CAD (STEP) stays the source of truth; meshes are derived.
4. Validate with the gates below. A failed gate sends the agent back to the script, not to the report.
5. Deliver the files, a drawing when requested, and a report that lists what was checked and what was assumed.
Agents follow twelve hard rules in SKILL.md. Examples: never invent dimensions of purchased parts when a drawing
exists, never claim PASS without the gates, keep design intent editable.
## What it checks
### Design for manufacturing on the real geometry
checkdfm.py tessellates the BRep and measures, for the chosen process and build or pull direction:
| Check | What it measures |
| minwall | Wall thickness by inward ray casting; only faces that really oppose count, so drafted walls and acute edges are not false alarms |
| overhang, bridge | Downward faces steeper than the process limit, and flat ceilings short enough to bridge |
| fdmhorizontalhole | Horizontal holes over 5 mm, unless they have a teardrop or flat-top roof pointing up |
| minhole, minpin, minfeature | Smallest holes, pins and features against the process minimum |