PartCAD

PartCAD is the first package manager for CAD models, and a Python package to consume these packages in CAD scripts (cadquery and build123d). It brings the same power to CAD scripting as pip to Python, npm to JavaScript, maven to Java etc. Though it aims to achieve the integrity and security properties of bazel which makes PartCAD quite distinct from pip and npm.

Join our Discord channel!

PartCAD allows to maintain information about mechanical parts, how they come together to form larger assemblies, and to reuse the same parts in multiple assemblies, multiple projects. The implementation of parts can change over time (e.g. optimize or migrate to CadQuery from STEP) without the need to update all of the consumers. Find more documentation here.

• Installation
• Browse models published to PartCAD
• Consume PartCAD models
• Publish PartCAD models
  • Parts
  • Assemblies
  • Packages
  • Troubleshooting
  • Render your project
  • Publishing
• Export PartCAD models
  • Images
  • Purchasing / Bill of materials
• Security
• Tools for mechanical engineering
• History

Installation

The recommended method to install PartCAD for most users is:

pip install partcad-cli

For contributors:

git clone https://github.com/openvmp/partcad.git
cd partcad
python3 -m pip install -e ./partcad
python3 -m pip install -e ./partcad-cli

PartCAD works best when conda is installed. Moreover, on Windows it is recommended to use PartCAD from within a conda environment.

Browse models published to PartCAD

To browse the public PartCAD repository from the command line:

$ pc init # to initialize new PartCAD package in the current folder
$ pc list # to list all available packages
$ pc list-parts -r # to list all parts in all available packages
$ pc list-assemblies -r # to list all assemblies in all available packages

The web UI to browse the public PartCAD repository is not yet published.

Consume PartCAD models

As PartCAD has no implicit dependencies built in, the current directory needs to be initialized as a PartCAD package and a dependency on the public PartCAD repository needs to be registered.

# Initialize new PartCAD package in the current folder
$ pc init

Alternatively, manually create partcad.yaml with the following content:

# partcad.yaml
import:
  # Public PartCAD repository (reference it explicitly if required)
  partcad-index:
    type: git
    url: https://github.com/openvmp/partcad-index.git

After this, all models in the public PartCAD repository are ready to be consumed. If you want to use these models in a CAD Design GUI (like FreeCAD or its paid alternatives), the best way to do it at the moment (before PartCAD plugins for these apps are available) is to export the models to STEP or 3MF files and, then, import them into the CAD Design GUI of your choice.

# Some "export to a file" examples:
$ pc render -p -t stl <part> [<package>]
$ pc render -p -t step -a <assembly> [<package>]

If you want to use these models in a CAD-as-code framework, find below the example how to do it in CadQuery. More examples are also available.

# Example: Consume PartCAD models in CadQuery
import cadquery as cq
import partcad as pc
...
part = pc.get_part(
     # Part name
     "fastener/screw-buttonhead",
     # Package name
     "standard-metric-cqwarehouse",
).get_cadquery()
...
show_object(part)

Publish PartCAD models

Each project that produces or consumes PartCAD models is a separate PartCAD package. Each package may export parts, assemblies and scenes. A package is defined by partcad.yaml.

Parts

PartCAD allows to define parts using any of the following methods:

Method	Example	Result
Python scripts: CadQuery, build123d	Place the following in "partcad.yaml": parts:     src/cylinder:         type: cadquery         # type: build123d Place the script in "src/cylinder.py".
CAD files: STEP, STL, 3MF	Place the following in "partcad.yaml": parts:     screw:         type: step         # type: stl         # type: 3mf Store the model in "screw.step", "screw.stl" or "screw.3mf" respectively.
CAD scripts: OpenSCAD	Place the following in "partcad.yaml": parts:     cube:         type: scad Store the model in "cube.scad".

Other methods to define parts are coming soon (e.g. SDF).

Assemblies

Assemblies are defined as parametrized instructions how to put parts and other assemblies together.

Currently, PartCAD allows to define parts only using ASSY (Assembly YAML):

Example	Result
# partcad.yaml assemblies: logo: type: assy # logo.assy links: - part: bone package: example_part_cadquery_logo location: [[0,0,0], [0,0,1], 0] - part: bone package: example_part_cadquery_logo location: [[0,0,-2.5], [0,0,1], -90] - part: head_half package: example_part_cadquery_logo name: head_half_1 location: [[0,0,27.5], [0,0,1], 0] - part: head_half package: example_part_cadquery_logo name: head_half_2 location: [[0,0,25], [0,0,1], -90] - part: bolt package: example_part_step location: [[0,0,7.5], [0,0,1], 0]

Packages

PartCAD packages may import parts, assemblies and scenes from its dependencies (other PartCAD packages). There are several methods to import other packages:

Method	Example
Local files (present in your own source code repository)	import:   other_directory     type: local     path: ../../other
GIT repository (HTTPS, SSH)	import:   other_directory     type: git     url: https://github.com/openvmp/partcad
Hosted tar ball (HTTPS)	import:   other_directory     type: tar     url: https://github.com/openv...090ca.tar.gz

The full syntax is below:

import:
    <package-name>:
        desc: <(optional) textual description>
        type: <git|tar|local>
        path: <(local only) relative path>
        url: <(git|tar only) url of the package>
        relPath: <(git|tar only) relative path within the repository>
        revision: <(git only) the exact revision to import>
        web: <(optional) package or maintainer's url>
        poc: <(optional) maintainer's email>
        pythonVersion: <(optional) python version for sandboxing if applicable>

Troubleshooting

At the moment, the best way to troubleshoot PartCAD is to use VS Code with OCP CAD Viewer. Any part or assembly can be displayed in OCP CAD Viewer by running pc show <part> [<package>] or pc show -a <assembly> [<package>] in a terminal view.

# Create a temporary folder
mkdir /tmp/test_show && cd /tmp/test_show

# Initialize a package with the default dependency on public PartCAD repository
pc init

# Show the part in 'OCP CAD Viewer'
pc show fastener/screw-buttonhead standard-metric-cqwarehouse

Render your project

Use pc render to render PartCAD parts and assemblies in the current package (the current directory).

git clone https://github.com/openvmp/partcad-cqwarehouse.git
cd partcad-cqwarehouse
pc render

See an example how to configure package's rendering settings.

Publishing

It's very simple to publish your package to the public PartCAD repository. First, publish your package (e.g. as a repo on GitHub). Then create a pull request in the public PartCAD repo to add a reference to your package.

Export PartCAD models

Images

Individual parts, assemblies and scenes can be rendered and exported into the following formats:

• SVG
• PNG
• STEP
• STL
• 3MF
• ThreeJS
• OBJ

# Some "export to a file" examples:
$ pc render -p -t stl <part> [<package>]
$ pc render -p -t step -a <assembly> [<package>]

Expect more image formats to be added to the list of supported export formats in the future.

Purchasing / Bill of materials

The bill of materials for each assembly can be produced using the following formats:

• CSV (not yet / in progress)
• Markdown (not yet / in progress)

Security

PartCAD is capable of rendering scripted parts (CadQuery and build123d use Python) in sandboxed environments.

While at the moment it is only useful from dependency management perspective, in the future PartCAD aims to achieve security isolation of the sandboxed environments. That will fundamentally change the security implications of using scripted models shared online.

Tools for mechanical engineering

Here is an overview of the open source tools to maintain mechanical projects. It shows where does this framework fit in the modern mechanical development workflows.

flowchart TB

subgraph repo["Your project's GIT repository"]
  subgraph custom_repo["Custom parts"]
    direction TB
    custom_part_internet["A STEP file\ndownloaded from Internet\nor the vendor site"]
    custom_part_cad["A part exported as a solid\nfrom a CAD tool not\nsuitable for collaboration"]
    custom_part_cq["An individual reusable part\nmaintained as a script\nunder a version control system"]
    custom_part_os["Another reusable part\nmaintained as a script\nunder a version control system"]
  end

  model["Your project's model defined\nas ASSY or Python code\nfor version control\nand collaboration"]

  subgraph scenes["Scenes"]
    test1["Capability 1\ntest scene"]
    test2["Capability 2\ntest scene"]
  end
end

subgraph external_repos["Third-party GIT repositories,\nCDN-hosted files or OCCI servers"]
  subgraph external_repo["Repository of standard\nor popular parts"]
  end
end

subgraph external_tools["External tools"]
  freecad["FreeCAD"]
  cadquery["CadQuery / build123d"]
  openscad["OpenSCAD"]
  gazebo["Gazebo"]

  partcad["PartCAD library"]
  style partcad fill:#c00
end

custom_part_cad <--- |Individual\ncontributor|freecad
custom_part_cq <--- |Part design\nworkflow| cadquery
custom_part_os <--- |Part design\nworkflow| openscad

external_repo ---> |Import| model
custom_repo ---> |Import| model
model -.-> |Import| test1
model -.-> |Import| test2

custom_repo <-. Maintained\nusing\nPartCAD\nconvention .- partcad
external_repo <-. Maintained\nusing\nPartCAD\nconvention .- partcad
model <--- partcad
test1 <--- partcad
test2 <--- partcad

test1 -.-> |Export| gazebo
test2 -.-> |Export| gazebo

Loading

History

PartCAD is the evolution of the modelling framework that was once used internally in OpenVMP. It is now being maintained separately as a generic tool.

The motivation behind this framework is to build a packaging and dependency tracking layer on top of both CadQuery/build123d and traditional CAD tools to enable version control and other features required for effective collaboration.

This framework currently uses build123d and, thus, OpenCASCADE under the hood. However this may change in the future, if the python C bindings for OpenCASCADE remain a blocker for unlocking multithreaded performance.