Burr

Burr is a design-rule linter for CAD-as-code workflows.

It checks generated design data and artifacts for mechanical mistakes before they become prints, prototypes, or expensive debugging sessions.

design file -> generated part -> burr-design-data.json -> Burr checks -> receipt

Burr is not a constraint solver, FEA engine, or universal CAD brain. It does not design the part. It checks whether generated CAD violates known mechanical rules.

Why

Image review is useful, but not enough. A screenshot can show that something looks suspicious; it cannot reliably prove exact hole distances, hidden clearances, source/STEP freshness, or rule-specific pass/fail.

Burr turns design data into measurable receipts:

M3 loaded mounting hole
measured center-to-edge = 8.0 mm
required center-to-edge = 10.2 mm
result = fail by 2.2 mm

Install

See INSTALL.md for current crates.io and uv install paths.

For local development:

cargo test
uv sync --all-packages
npm run check

Install the Rust CLI from crates.io:

cargo install burr
burr --version

Run the CLI from a local checkout:

cargo run -- --version
cargo run -- init my-part
cargo run -- check examples/linear-actuator-bad
cargo run -- check examples/linear-actuator-good

Run the build123d adapter examples:

uv sync --all-packages
npm run check:build123d

The build123d examples commit only design.py. actuator.step and burr-design-data.json are generated by the example scripts and ignored by git.

Start a build123d part:

burr init my-part
cd my-part
uv run python design.py
burr check .

Commands

burr --version
burr init <folder>
burr check <folder|burr-design-data.json>...
burr stamp <folder|burr-design-data.json>...

init creates a minimal build123d project with design.py, pyproject.toml, and .gitignore. Until burr-build123d is published to PyPI, the generated project depends on the helper from the burr-build123d-v0.5.0 Git tag.

check finds burr-design-data.json, runs freshness checks and rulepack checks, then writes burr-receipt.json beside each design data file.

stamp computes sha256 and size_bytes for declared source and generated artifact files.

Build123d Helper

Burr does not replace build123d. The optional helper records design data while your normal build123d file creates geometry.

from build123d import Box, BuildPart, Locations, export_step
from burr_build123d import BurrDesignData, DESIGN_DATA_FILE, m3_clearance_hole

design = BurrDesignData(
    artifact_id="my-actuator",
    artifact_type="actuator_mount",
    process={"kind": "FDM", "material": "PETG", "nozzle_mm": 0.4},
)
design.source("design.py")
design.artifact("actuator.step")
design.part("housing", bbox_min=(-42, -16, 0), bbox_max=(42, 16, 26))

with BuildPart() as housing:
    with Locations((0, 0, 13)):
        Box(84, 32, 26)

    m3_clearance_hole(
        design,
        feature_id="m3_lower_left",
        part="housing",
        center=(39.5, -8, 8),
        axis=(1, 0, 0),
        role="loaded_mount",
    )

export_step(housing.part, "actuator.step")
design.write(DESIGN_DATA_FILE)

That one helper call cuts the hole in build123d and records the feature Burr checks. Burr core still reads only burr-design-data.json, so other CAD tools can use the same contract.

Design Data

A lintable CAD artifact folder contains burr-design-data.json.

This file is the language-agnostic contract. It can be emitted by build123d, CadQuery, OpenSCAD, JavaScript CAD, Rust CAD, Fusion scripts, or any tool that can write JSON.

{
  "schema_version": "burr.design-data.v1",
  "artifact_id": "linear-actuator-bad",
  "artifact_version": "0.1.0",
  "artifact_type": "actuator_mount",
  "units": "mm",
  "source": {
    "path": "source.py",
    "sha256": "..."
  },
  "artifacts": [
    {
      "kind": "step",
      "path": "actuator.step",
      "sha256": "..."
    }
  ],
  "parts": [
    {
      "id": "housing",
      "bbox_mm": {
        "min": [-42, -16, 0],
        "max": [42, 16, 26]
      }
    }
  ],
  "features": [
    {
      "id": "m3_lower_left",
      "part": "housing",
      "kind": "clearance_hole",
      "fastener": "M3",
      "diameter_mm": 3.4,
      "center_mm": [39.5, -8, 8],
      "axis": [1, 0, 0],
      "role": "loaded_mount"
    }
  ]
}

Rulepacks

The included actuator mount rule checks loaded M3 clearance holes:

{
  "schema_version": "burr.rulepack.v1",
  "id": "actuator_mount",
  "version": "0.1.0",
  "rules": [
    {
      "id": "m3_loaded_hole_edge_distance",
      "kind": "hole_edge_distance",
      "applies_to": {
        "kind": "clearance_hole",
        "fastener": "M3",
        "role_any": ["loaded_mount", "mount", "housing_mount"]
      },
      "min_center_to_edge_diameter_multiple": 3.0
    }
  ]
}

Versioning

Burr has three versioned surfaces:

Burr package version       -> CLI/library behavior
Design data schema version -> JSON shape Burr can read
Rulepack schema version    -> rule syntax Burr can execute

Receipts include all three:

{
  "schema_version": "burr.receipt.v1",
  "burr_version": "0.6.0",
  "artifact_version": "0.1.0",
  "rulepack_version": "0.1.0",
  "compatibility": {
    "design_data_schema_version": "burr.design-data.v1",
    "rulepack_schema_version": "burr.rulepack.v1"
  }
}

Unsupported design data or rulepack schemas fail lint instead of silently producing untrustworthy receipts.

Legacy fray-cad.json files with schema fray.cad.artifact.v1 are still read for transition, but new integrations should emit burr-design-data.json.

Example Result

Bad actuator:

FAIL examples/build123d-actuator/bad/burr-design-data.json -> <not written>

1 problem:
1. M3 loaded hole m3_lower_left is too close to the edge.
   Measured center-to-edge: 8 mm
   Required center-to-edge: 10.2 mm
   Short by: 2.2 mm
   Try moving the hole inward or increasing the surrounding part size.

Fixed actuator:

{
  "status": "pass",
  "measured": {
    "center_to_edge_mm": 12,
    "wall_to_edge_mm": 10.3
  },
  "required": {
    "center_to_edge_mm": 10.2,
    "wall_to_edge_mm": 8.5
  },
  "margin_mm": 1.8
}

Status

Early prototype. Current checks are design-data-based. Future versions may derive more facts directly from STEP topology.