How to Create URDF from CAD Software

Overview

This document explains how to create a URDF file from SolidWorks models by using:

1. SolidWorks to URDF Exporter

2. scikit-robot’s convert-urdf-mesh command

• SolidWorks to URDF Exporter This exporter helps convert SolidWorks assemblies into a format (3dxml) which is more easily processed to produce URDF-compatible mesh files.

• scikit-robot ``convert-urdf-mesh`` A tool within the scikit-robot library that can convert 3D model files (like .3dxml, .obj, .stl, etc.) into a URDF or mesh files (e.g., .dae) suitable for ROS.

Recommended: sw2robot (solidworks_urdf_exporter2)

If you are starting a new project, we recommend using sw2robot (solidworks_urdf_exporter2) together with scikit-robot. It is the modernized successor of the classic SolidWorks URDF Exporter and pairs well with convert-urdf-mesh.

Compared with the classic exporter, sw2robot:

• Infers the kinematic tree automatically by reading the assembly’s existing mates (constraints), instead of asking you to lay out the link hierarchy and set each joint origin/axis by hand inside SolidWorks.

• Ships a cross-platform browser editor so that the edit / build / export steps run natively on Windows, macOS, and Linux (only the extract step, which drives SolidWorks over COM, needs Windows + SolidWorks). You can re-root the tree, change joint types, edit frames, set materials/densities, and export a ROS / robot-compiler package.

• Works on any URDF, so you can also open a URDF produced by the classic add-in and clean it up in the editor.

Exports URDF + meshes directly (no ``convert-urdf-mesh`` step needed). sw2robot writes the URDF together with its mesh files for you, so with sw2robot you typically do not need to post-process the output with convert-urdf-mesh. In particular it can:

• Emit visual meshes directly as ``.glb`` (or ``.dae`` / ``.stl``), keeping per-part materials/colors — no separate 3dxml→dae conversion pass.

• Generate collision geometry for you instead of reusing the (heavy, concave) visual mesh. You can choose per export:

  • copy — reuse the visual mesh as-is,

  • hull — a single convex hull per link,

  • coacd — approximate convex decomposition into a set of convex parts (great for physics engines; balanced / fine quality presets),

  • primitive / box / cylinder / sphere — fit a native URDF primitive shape per link (no mesh file at all; primitive auto-picks the best-fitting shape).

Download from the release page. Prebuilt editors for Windows, macOS (Apple Silicon), and Linux (x64) are available on the releases page — no Python or SolidWorks required just to edit:

sw2robot releases (latest)

Click the binary matching your OS on that page to grab the latest prebuilt editor, then pick the visual mesh format (.glb recommended) and a collision mode (coacd or primitive for physics) right in the export dialog. See the project README for the full workflow.

Note

The convert-urdf-mesh workflow described below still applies when you are using the classic SolidWorks URDF Exporter (which produces .3dxml), or when you have existing meshes to reconvert. If you use sw2robot, prefer its built-in .glb + collision export instead.

Coordinate Systems

• .3dxml export: uses the overall assembly coordinate system from SolidWorks.

• .stl export: uses each part’s or link’s local coordinate system.

convert-urdf-mesh provides an option for adjusting coordinates:

• --force-zero-origin: Forces the origin to be the link’s local coordinate in the converted mesh files (e.g., .dae). - Useful when your source is in the assembly coordinate system (like .3dxml). - Highly recommended if you plan to use these meshes in MuJoCo.

Installation

1. Install scikit-robot

pip install scikit-robot

or clone directly from GitHub if you need the latest updates:

git clone https://github.com/iory/scikit-robot.git
cd scikit-robot
pip install -e .

2. Install a SolidWorks URDF Exporter

• Recommended: sw2robot (solidworks_urdf_exporter2). Download the prebuilt editor for your OS from the release page — no separate installation into SolidWorks is required to edit / build / export:

  sw2robot releases (latest)

• Classic exporter (alternative). Obtain the plugin from the following link:

  SolidWorks URDF Exporter Plugin

  Follow the official instructions to install it into your SolidWorks environment.

  Installation Instructions

Workflow

1. Export from SolidWorks

   • In SolidWorks, open your assembly.

   • Use the “SolidWorks to URDF Exporter” plugin to generate a .3dxml file.

2. Convert to DAE (or STL) and Generate URDF

   • Run the scikit-robot command to convert .3dxml (or other mesh formats) to .dae and generate a URDF automatically.

   • Example usage:

   convert-urdf-mesh <URDF_PATH> --output <OUTPUT_URDF_PATH>
   

   • This command outputs: - A set of mesh files (e.g., .dae) - A URDF file referencing those meshes

3. Verify URDF in ROS

   • Copy the generated URDF and mesh files into your ROS package.

   • Test in Rviz or another ROS-compatible viewer:

   roslaunch urdf_tutorial display.launch model:=path/to/generated.urdf
   

   • Confirm the model loads and displays properly.

4. Usage with MuJoCo

   • MuJoCo typically requires meshes to be centered at their local origin.

   • Therefore, always use the --force-zero-origin option when converting to ensure proper alignment.

   convert-urdf-mesh <URDF_PATH> --output <OUTPUT_URDF_PATH> --force-zero-origin