STL to STEP Converter

A modular Node.js web application for converting STL files to STEP format with automatic file cleanup and Redis-based job tracking.

Features

• ✅ Upload STL files via drag-and-drop or file picker
• ✅ Convert STL to STEP format
• ✅ Track conversion jobs with unique IDs
• ✅ Redis-based job management with TTL
• ✅ Automatic file cleanup scheduler
• ✅ Download converted STEP files
• ✅ Expiration tracking and display
• ✅ Modular architecture

Project Structure

stl-to-step-converter/
├── src/
│   ├── config/
│   │   └── index.js              # Configuration
│   ├── services/
│   │   ├── redis.service.js      # Redis operations
│   │   ├── converter.service.js  # STL to STEP conversion
│   │   ├── file.service.js       # File management
│   │   └── cleanup.service.js    # Scheduled cleanup
│   ├── routes/
│   │   └── conversion.routes.js  # API endpoints
│   └── server.js                 # Main application
├── public/
│   ├── index.html                # Frontend UI
│   └── app.js                    # Frontend logic
├── uploads/                      # Uploaded STL files
├── converted/                    # Converted STEP files
└── package.json

Prerequisites

• Node.js 14+
• Redis server
• FreeCAD (with freecadcmd CLI tool)

Installation

1. Install FreeCAD:

   • Ubuntu/Debian: sudo apt-get install freecad
   • macOS: brew install freecad
   • Windows: Download from FreeCAD website

2. Install Node.js dependencies:

npm install

3. Start Redis (if not running):

redis-server

4. Start the application:

npm start

For development with auto-reload:

npm run dev

4. Open browser to http://localhost:3000

Configuration

Edit src/config/index.js to customize:

• Port: Server port (default: 3000)
• Redis: Connection settings
• Upload: Max file size and directory
• Jobs: TTL (time-to-live) and cleanup schedule
• Cleanup Cron: Default runs every 15 minutes

API Endpoints

POST /api/convert

Upload and convert STL file

• Body: multipart/form-data with stlFile field
• Returns: { success, jobId, message }

GET /api/job/:jobId

Get job status and expiration info

• Returns: Job details including expiresIn (seconds)

GET /api/download/:jobId

Download converted STEP file

• Returns: File download

Environment Variables

PORT=3000
REDIS_HOST=localhost
REDIS_PORT=6379

How It Works

1. Upload: User uploads STL file via web interface
2. Job Creation: System creates job in Redis with TTL
3. Conversion: STL file is converted to STEP format
4. Storage: Both files stored temporarily
5. Download: User downloads converted file
6. Cleanup: Scheduled job removes expired files and Redis entries

Cleanup Process

• Runs every 15 minutes (configurable)
• Removes Redis jobs past TTL
• Deletes associated files
• Cleans up orphaned files

Conversion Process

The application uses FreeCAD's command-line interface (freecadcmd) to convert STL files to STEP format:

1. Mesh Import: STL file is imported using FreeCAD's Mesh module
2. Shape Creation: Mesh topology is converted to a Part shape with 0.01 tolerance
3. Document Creation: Temporary FreeCAD document is created for the conversion
4. Export: Shape is exported to STEP format using FreeCAD's Import module
5. Cleanup: Temporary document is closed to free memory

The conversion command:

freecadcmd -c "import Part; import Mesh; import FreeCAD; import Import; mesh = Mesh.read('input.stl'); shape = Part.Shape(); shape.makeShapeFromMesh(mesh.Topology, 0.01); doc = FreeCAD.newDocument('STLImport'); obj = doc.addObject('Part::Feature', 'MeshShape'); obj.Shape = shape; Import.export([obj], 'output.step'); FreeCAD.closeDocument('STLImport')"

Note: FreeCAD must be installed and the freecadcmd command must be available in your system PATH.

Security Considerations

• File type validation (STL only)
• File size limits (50MB default)
• Automatic cleanup prevents disk filling
• Redis TTL prevents memory leaks
• Input sanitization on all endpoints

License

MIT