build123d-cad
# build123d CAD
Parametric 3D CAD via [build123d](https://build123d.readthedocs.io). This skill provides Python scripts for generating and measuring 3D solids. Run them with the `exec` tool.
## Setup (first time only)
```bash
cd {baseDir}
uv venv --python 3.12
uv pip install build123d
```
## Commands
All scripts use the venv Python at `{baseDir}/.venv/bin/python`. All output JSON to stdout.
### Generate — export STEP/STL/SVG
```bash
{baseDir}/.venv/bin/python {baseDir}/scripts/cad_generate.py \
--script 'from build123d import *
with BuildPart() as result:
Box(100, 60, 40)' \
--format step \
--filename my_box
```
Output: `{ "success": true, "artifact_path": "...", "format": "step", "file_size_bytes": N, "bounding_box_mm": {...} }`
### Measure — dimensions, volume, mass
```bash
{baseDir}/.venv/bin/python {baseDir}/scripts/cad_measure.py \
--script 'from build123d import *
with BuildPart() as result:
Cylinder(10, 50)'
```
Output: `{ "success": true, "bounding_box_mm": {...}, "volume_mm3": N, "surface_area_mm2": N, "center_of_mass_mm": {...}, "face_count": N, "edge_count": N }`
### Section — 2D cross-section SVG
```bash
{baseDir}/.venv/bin/python {baseDir}/scripts/cad_section.py \
--script '...' \
--plane XY \
--offset 5.0
```
Output: `{ "success": true, "artifact_path": "...", "plane": "XY", "offset_mm": 5.0 }`
### API Reference — build123d cheatsheet
```bash
{baseDir}/.venv/bin/python {baseDir}/scripts/cad_api.py
```
Output: JSON with primitives, operations, selectors, export functions. Call this first if you need to learn what's available.
### Validate — interference, clearance, swept-volume collision
Check an assembly of multiple parts for interference, minimum clearance, and moving-part collisions.
```bash
{baseDir}/.venv/bin/python {baseDir}/scripts/cad_validate.py \
--script '...' \
--mode full \
--min-clearance 1.0
```
Modes: `static` (Boolean intersection between all pairs), `clearance` (bounding box gap), `sweep` (rotate moving parts through angular range, check collisions), `full` (all three, default).
The script must define `parts = {"name": solid, ...}` dict. Optionally define `sweeps` list for moving parts:
```python
from build123d import *
with BuildPart() as enclosure:
Box(100, 80, 50)
offset(amount=-3, openings=enclosure.faces().sort_by(Axis.Z)[-1:])
with BuildPart() as pcb:
with Locations((0, 0, 5)):
Box(60, 40, 2)
with BuildPart() as servo_arm:
with Locations((30, 0, 25)):
Box(5, 20, 3)
parts = {
"enclosure": enclosure.part,
"pcb": pcb.part,
"servo_arm": servo_arm.part,
}
sweeps = [
{
"name": "servo_arm",
"axis_origin": (30, 0, 25),
"axis_direction": (0, 1, 0),
"angle_start": -45,
"angle_end": 45,
"angle_step": 5,
},
]
```
Output: `{ "verdict": "PASS|WARN|FAIL", "static_interference": {...}, "clearance": {...}, "swept_volume": {...} }`
- **PASS** — no interference, clearance OK
- **WARN** — clearance below threshold but no hard collision
- **FAIL** — parts intersect or moving parts collide during sweep
Swept volumes are exported to `~/.openclaw/workspace/cad-output/swept_<name>.step` for visualization.
## Script Format
All single-part scripts must assign the final solid to `result` via a `BuildPart` context:
```python
from build123d import *
with BuildPart() as result:
Box(100, 60, 40)
fillet(result.edges().filter_by(Axis.Z), radius=5)
with Locations((0, 0, 40)):
CounterBoreHole(radius=5, counter_bore_radius=8, counter_bore_depth=3, depth=40)
```
For validation scripts, define `parts` dict (and optionally `sweeps` list) instead of `result`.
All dimensions in millimeters. Exported files go to `~/.openclaw/workspace/cad-output/`.
## Workflow
1. If unsure about build123d API, run `cad_api.py` first for the cheatsheet.
2. Write a parameterized script (no magic numbers).
3. Run `cad_measure.py` to verify dimensions before exporting.
4. **For multi-part assemblies: run `cad_validate.py --mode full` before exporting.** Fix any FAIL/WARN before proceeding.
5. Run `cad_generate.py` with the desired format (step for CAD, stl for 3D printing).
6. For clearance visualization, run `cad_section.py` at relevant planes.
7. Report artifact paths and validation verdict.
## Design Rules
- Parameterize all dimensions for reusability.
- Add fillets to stress concentrations (min 1mm for plastic, 0.5mm for metal).
- Include mounting features (bosses, standoffs, screw posts) where applicable.
- Specify material and process assumptions in comments.
- Output both the script and the exported file.
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skill
ai
