CalcSX Bobbin Exporter for Fusion 360

Exports groove channel geometry from a Fusion 360 bobbin model into a .bobsx file that CalcSX can import directly. Each selected groove face becomes an individual channel with exact centerline coordinates and surface normals sampled from Fusion's CAD kernel.

Install

Option A — One-click installer (recommended)

1. Download the latest release zip from the Releases page.
2. Unzip it.
3. Run the installer for your OS:
   • macOS: double-click install-macos.command (If macOS blocks it, right-click → Open, then confirm.)
   • Windows: double-click install-windows.bat
4. Restart Fusion 360 if it was running.

The installer copies the script into Fusion's API/Scripts directory automatically.

Option B — Manual install

1. Download or clone this repository.
2. Copy the calcsx_exporter/ folder into Fusion 360's Scripts directory:
   • macOS: ~/Library/Application Support/Autodesk/Autodesk Fusion 360/API/Scripts/
   • Windows: %APPDATA%\Autodesk\Autodesk Fusion 360\API\Scripts\
3. Restart Fusion 360.

Either install path makes the script appear under UTILITIES → Scripts and Add-Ins → My Scripts → calcsx_exporter.

Usage

1. Open your bobbin model in Fusion 360.
2. Go to UTILITIES → Scripts and Add-Ins → My Scripts → calcsx_exporter → Run.
3. A command dialog appears — select all groove floor faces:
   • Click a groove face to select it.
   • Hold Ctrl (Windows) or Cmd (Mac) to select additional faces.
   • Each face becomes one channel in the output.
4. Set Points per channel (default 500 — higher = smoother centerline).
5. Click OK.
6. Choose a save location — the file is saved as .bobsx.

In CalcSX

1. Click Import Bobbin (⬡) in the SIMULATION ribbon.
2. Select your .bobsx file.
3. Each channel appears as a separate coil that can be:
   • Shown/hidden via the eye toggle in the browser panel.
   • Deleted individually.
   • Analyzed independently or as part of a multi-coil superposition.

What Gets Exported

• Channels: one per selected face. Each contains 3D centerline points with exact surface normals evaluated from the parametric CAD surface (not the tessellation mesh).
• Bobbin mesh (optional): a triangulated display mesh of the bobbin body for visual context in CalcSX. Not used for physics calculations.

File Format

The .bobsx file is JSON:

{
  "version": 1,
  "unit": "cm",
  "channels": [
    {
      "name": "groove_1",
      "points": [
        {"x": 1.0, "y": 2.0, "z": 3.0, "nx": 0.0, "ny": 0.0, "nz": 1.0}
      ]
    }
  ],
  "bobbin_mesh": {
    "vertices": [[x, y, z], ...],
    "faces": [[i, j, k], ...]
  }
}

Coordinates are in centimeters (Fusion's internal unit). CalcSX converts to metres on import.

Repository Layout

calcsx_exporter/         Fusion 360 script package (drop into API/Scripts/)
  calcsx_exporter.py     Main script
  calcsx_exporter.manifest
install/                 Per-OS installers shipped in the release zip
  install-macos.command
  install-windows.bat
  INSTALL.txt
.github/workflows/       Release automation

Cutting a Release

Push a v* tag and the release workflow builds and publishes the installer zip:

git tag v1.0.0
git push origin v1.0.0

A version-agnostic calcsx_exporter.zip is attached to the release. CalcSX's "Download Fusion 360 exporter" link should point at:

https://github.com/<owner>/<repo>/releases/latest/download/calcsx_exporter.zip

Because the asset filename does not change between releases, that URL always serves the newest installer with no code change in CalcSX. The version is preserved inside the zip — extracting it produces a calcsx_exporter-vX.Y.Z/ folder so users can tell which release they have locally.

Requirements

• Fusion 360 (any recent version).
• No additional Python packages — the script uses only Fusion's built-in API.