OpenMagnetics Virtual Builder - JavaScript/Browser Version

Browser-compatible 3D magnetic component geometry generator using OpenCASCADE.js and Replicad.

Overview

This is a JavaScript port of the Python CadQuery-based geometry builder, enabling magnetic component visualization directly in web browsers.

Features

• Concentric turns for E-cores, PQ, RM, etc.
• Toroidal turns for toroidal cores
• Round and rectangular wire cross-sections
• Bobbin geometry generation
• STL and STEP export for 3D printing and CAD
• Three.js integration for real-time 3D visualization

Installation

npm install

Usage

Browser (with bundler)

import opencascade from 'replicad-opencascadejs';
import { setOC } from 'replicad';
import * as replicad from 'replicad';
import { 
  ReplicadBuilder, 
  WireDescription, 
  TurnDescription, 
  BobbinProcessedDescription,
  WireType, 
  ColumnShape 
} from 'open-magnetics-virtual-builder';

// Initialize OpenCASCADE (required once)
const oc = await opencascade();
setOC(oc);

// Create builder
const builder = new ReplicadBuilder(replicad);

// Create a turn
const turn = new TurnDescription({
  coordinates: [0.005, 0]  // [radial, height] in meters
});

const wire = new WireDescription({
  wireType: WireType.ROUND,
  outerDiameter: 0.0005  // 0.5mm
});

const bobbin = new BobbinProcessedDescription({
  columnDepth: 0.003,
  columnWidth: 0.003,
  columnShape: ColumnShape.RECTANGULAR
});

// Generate geometry
const shape = builder.getTurn(turn, wire, bobbin, false);

// Export to STL
const stlData = shape.exportSTL();

// Or get mesh for Three.js
const mesh = shape.mesh({ tolerance: 0.0001 });

Demo

Open index.html in a browser (requires a local server for ES modules):

npm run dev

API Reference

ReplicadBuilder

Main class for generating magnetic component geometry.

const builder = new ReplicadBuilder(replicad);

Methods

• getTurn(turnDescription, wireDescription, bobbinDescription, isToroidal) - Create a single turn
• getBobbin(bobbinDescription) - Create bobbin geometry
• getMagnetic(magneticData, projectName) - Build complete assembly

Types

WireType (Enum)

• ROUND - Round wire
• RECTANGULAR - Rectangular/flat wire
• LITZ - Litz wire (treated as round)
• FOIL - Foil winding
• PLANAR - PCB planar winding

ColumnShape (Enum)

• ROUND - Cylindrical column
• RECTANGULAR - Rectangular column

WireDescription

new WireDescription({
  wireType: WireType.ROUND,
  outerDiameter: 0.001,      // meters
  conductingDiameter: 0.0009, // meters (optional)
  outerWidth: 0.002,          // for rectangular
  outerHeight: 0.0005         // for rectangular
});

TurnDescription

new TurnDescription({
  coordinates: [0.005, 0.001],  // [radial, height] in meters
  rotation: 0,                   // degrees (for toroidal)
  dimensions: [0.001, 0.0005],   // [width, height] for rectangular wire
  additionalCoordinates: [[...]] // outer wire position for toroidal
});

BobbinProcessedDescription

new BobbinProcessedDescription({
  columnDepth: 0.003,           // half depth in meters
  columnWidth: 0.003,           // half width in meters
  columnThickness: 0.0005,      // wall thickness
  wallThickness: 0.001,         // top/bottom wall
  columnShape: ColumnShape.RECTANGULAR,
  windingWindowHeight: 0.01,
  windingWindowWidth: 0.005,
  windingWindowRadialHeight: 0.003,  // for toroidal
  windingWindowAngle: null           // for toroidal
});

Running Tests

Browser Tests (Recommended)

Start the development server and open the test pages:

npm run dev

Then open in browser:

• Simple API Tests: http://localhost:5175/simple_test.html

  • Tests basic Replicad functions (box, cylinder, torus, etc.)
  • Generates downloadable STL files

• Full Builder Tests: http://localhost:5175/test.html

  • Tests the ReplicadBuilder class
  • Tests concentric and toroidal turns
  • Tests bobbin generation

The tests will:

1. Load OpenCASCADE.js WASM (~10-20 seconds)
2. Run geometry generation tests
3. Show pass/fail results
4. Provide download links for generated STL files

Unit tests (Vitest)

npm test

Integration tests (Node.js - requires browser environment)

Note: The Node.js tests require browser-like environment for OpenCASCADE.js. Use the browser tests for full STL generation verification.

Coordinate System

Concentric Cores (E, PQ, RM, etc.)

• X axis: Core depth (perpendicular to winding window)
• Y axis: Core width (radial, distance from column)
• Z axis: Core height (vertical)

Toroidal Cores

• Y axis: Core axis (toroid revolves around Y)
• X axis: Radial direction (negative X = inside hole)
• Z axis: Tangential direction

File Structure

js/
├── src/
│   ├── index.js           # Main entry point
│   ├── types.js           # Type definitions
│   └── replicadBuilder.js # Geometry builder
├── tests/
│   ├── replicadBuilder.test.js  # Vitest unit tests
│   └── runTests.mjs       # Node.js integration tests
├── index.html             # Browser demo
├── package.json
├── vite.config.js
└── README.md

Browser Compatibility

Requires modern browsers with:

• ES2020+ support
• WebAssembly support
• Web Workers (for OpenCASCADE initialization)

Tested on:

• Chrome 90+
• Firefox 88+
• Safari 14+
• Edge 90+

Performance Notes

• OpenCASCADE.js WASM loading takes 2-5 seconds on first load
• Consider using Web Workers for heavy geometry operations
• Use lower tessellation quality for real-time preview

License

MIT