Cad Partcad Repository

PartCAD — Public CAD Repository for build123d

Prerequisite: Load cad-build123d-general first if the user is going to consume PartCAD parts in a build123d script.

Sibling skill: cad-build123d-bd-warehouse covers Gumyr's bd_warehouse part library directly (and is what an agent should reach for first for nuts/bolts/bearings). PartCAD's repository includes bd_warehouse parts, but is much broader — load this skill when the user wants a community part outside the bd_warehouse scope, wants to publish their own CAD package, or wants to use PartCAD's AI-generated part workflow.

Purpose

PartCAD is a package manager and public repository for parametric CAD models. It treats CAD parts and assemblies the way npm treats JavaScript packages or pip treats Python packages: a versioned namespace, a CLI to install/inspect/export, and a public catalog at https://partcad.org/repository with hundreds of community-published items.

This skill covers:

• Installing PartCAD and using the CLI (pc list, pc info, pc inspect, pc export).
• Browsing the public repository (online and from the CLI).
• Importing PartCAD parts into a build123d script — pc.get_part_build123d(...) and pc.get_assembly_build123d(...).
• Authoring your own PartCAD package: partcad.yaml, .assy files, the supported part type: values (file formats, CAD scripts, AI generation).
• Publishing a package to the public index.

When to Use This Skill

• The user asks for a community CAD part that isn't a basic fastener (e.g. "an OpenVMP robot arm", "an IKEA-like desk", a published electronics enclosure model).
• The user wants to browse the catalog at https://partcad.org/repository.
• The user wants to install and use PartCAD's CLI to inspect or export models without opening a CAD GUI.
• The user wants to import a PartCAD part into a build123d script.
• The user wants to publish their own build123d/CadQuery/OpenSCAD models as a PartCAD package.
• The user wants AI-generated CAD models (CadQuery or OpenSCAD) as a starting point.

For just a hex bolt or socket-head cap screw, do NOT load this skill — use cad-build123d-bd-warehouse instead. PartCAD has more setup overhead.

Install

pip install partcad

PartCAD is a real PyPI package (unlike bd_warehouse which is git-only). The install brings the pc CLI plus the partcad Python module.

Optional configuration for the AI-part-generation feature (type: ai-cadquery / type: ai-openscad):

# ~/.partcad/config.yaml
googleApiKey: <...>
openaiApiKey: <...>

Browse the public repository

The web UI groups packages by top-level category:

A part path looks like //pub/<package-tree>:<part-name>, for example //pub/std/metric/cqwarehouse:hexhead-din931.

CLI Reference

# Initialize a new PartCAD package in the current folder (creates partcad.yaml)
pc init

# List things across all available packages
pc list packages -r
pc list parts -r
pc list assemblies -r
pc list sketches -r
pc list interfaces -r
pc list mates -r            # known matings of interfaces

# Inspect a single part — prints info without opening a viewer
pc info //pub/std/metric/cqwarehouse:fastener/hexhead-din931

# Display in the OCP CAD Viewer (in VS Code)
pc inspect //pub/std/metric/cqwarehouse:fastener/hexhead-din931

# Display with parameters
pc inspect \
    -p length=30 \
    -p size=M4-0.7 \
    //pub/std/metric/cqwarehouse:fastener/hexhead-din931

# Render projections to image files
pc render -t svg <part-path>
pc render -t png <part-path>

# Export to a file
pc export -t stl  <part-path>
pc export -t step <part-path>
pc export -t 3mf  <part-path>
pc export -t step -a <assembly-path>

Supported export targets: STEP, BREP, STL, 3MF, ThreeJS, OBJ, GLTF, IGES.

Consuming PartCAD parts in build123d

This is the entry point most CAD-Builder agents need.

# part.py
import build123d as b3d
import partcad as pc

part = pc.get_part_build123d(
    "//pub/std/metric/cqwarehouse:hexhead-din931",
)
show_object(part)

# assembly.py
import build123d as b3d
import partcad as pc

assembly = pc.get_assembly_build123d(
    "//pub/furniture/workspace/basic:imperial-desk-1",
)
show_object(assembly)

The returned part is a regular build123d Part (or Compound for assemblies) — fuse it, position it, integrate it with your own geometry the same way you would any other build123d part.

Passing parameters

Many parts in the repository are parametric. The CLI -p key=value and the Python API's keyword arguments serve the same purpose. Check the part's repository page for valid parameters.

Generic Python API (no CAD framework)

import partcad as pc
part = pc.get_part("//pub/std/metric/cqwarehouse:hexhead-din931")
part.show()

CadQuery API (when not on build123d)

import cadquery as cq
import partcad as pc
part = pc.get_part_cadquery(
    "//pub/std/metric/cqwarehouse:fastener/hexhead-din931",
)
show_object(part)

Authoring your own package

Every PartCAD package is a folder with a partcad.yaml manifest.

Parts from a CAD file

# partcad.yaml
parts:
    part1:
        type: step          # part1.step is used
    part2:
        type: brep          # part2.brep is used
    part3:
        type: stl           # part3.stl is used
    part4:
        type: 3mf           # part4.3mf is used
    part5:
        type: obj           # part5.obj is used

Parts from a Python script (build123d / CadQuery)

PartCAD intercepts show_object() calls (CQGI) — your script just calls show_object(part) like normal:

# partcad.yaml
parts:
    optional-path/part1:
        type: build123d     # optional-path/part1.py is used
    part2:
        type: cadquery      # part2.py is used

Parts from OpenSCAD

# partcad.yaml
parts:
    part1:
        type: scad          # part1.scad is used

OpenSCAD parameters are not yet propagated by PartCAD as of the current docs. If you need a parametric SCAD part, factor parameters into a wrapper build123d/CadQuery script.

AI-generated parts (Google / OpenAI)

The fastest "from scratch" bootstrap:

# partcad.yaml
parts:
    part1:
        type: ai-cadquery   # part1.py is created by the AI
        desc: A cube
        provider: google
    part2:
        type: ai-openscad   # part2.scad is created by the AI
        desc: A flat screen TV
        provider: openai
        images:
          - product_photo.png

Workflow: generate → empty the file and re-generate with refined prompts → at some point drop the ai-* prefix and continue improving the script manually.

Assemblies (.assy)

A partcad.yaml lists assemblies that point to .assy files.

# partcad.yaml
assemblies:
    logo:
        type: assy

# logo.assy — hierarchical composition with positioning
links:
  - part: /produce_part_cadquery_logo:bone
    location: [[0, 0, 0], [0, 0, 1], 0]
  - part: /produce_part_cadquery_logo:bone
    location: [[0, 0, -2.5], [0, 0, 1], -90]
  - links:
      - part: /produce_part_cadquery_logo:head_half
        location: [[0, 0, 2.5], [0, 0, 1], 0]
      - part: /produce_part_cadquery_logo:head_half
        location: [[0, 0, 0], [0, 0, 1], -90]
    location: [[0, 0, 25], [1, 0, 0], 0]
  - part: /produce_part_step:bolt
    location: [[0, 0, 7.5], [0, 0, 1], 0]

Each location is [[x, y, z], [axis_x, axis_y, axis_z], angle_degrees].

Publishing to the public repository

1. Push your package as a public GitHub repo.
2. Open a pull request against partcad/partcad-index adding a reference to your repo.
3. Once merged, your package is browsable at https://partcad.org/repository and importable via pc.get_part(...).

Caching

PartCAD aggressively caches intermediate and final compilation results. First fetch of a part triggers a download + build; subsequent runs return instantly from the local cache. See https://partcad.readthedocs.io/en/latest/features.html#caching.

When NOT to use PartCAD

• For a single hex bolt / nut / washer in a personal project → bd_warehouse.fastener is one pip install and one import; PartCAD adds package-manager overhead that isn't worth it for one bolt.
• For pure GUI workflows in FreeCAD/Fusion → there's no PartCAD plugin for these GUIs yet. Export the model to STEP/3MF first (pc export -t step ...) and import the file.
• For your own one-off model that won't be shared → build123d alone is simpler. Reach for PartCAD when you're publishing or when you're consuming a published part.

Quick Reference

See Also

• PartCAD docs: https://partcad.readthedocs.io/en/latest/
• Use cases: https://partcad.readthedocs.io/en/latest/use_cases.html
• Public repository: https://partcad.org/repository
• Source: https://github.com/partcad/partcad
• Index repo (for publishing): https://github.com/partcad/partcad-index
• VS Code extension: https://marketplace.visualstudio.com/items?itemName=OpenVMP.partcad
• Sibling skill: cad-build123d-bd-warehouse (use first for standard hardware)
• Sibling skill: cad-build123d-tools — references PartCAD as one of many ecosystem tools; this skill is the authoritative deep-dive