FreeCAD — Open Source 3D Parametric Modeler

Introduction

FreeCAD is a general-purpose parametric 3D CAD modeler. It is designed for mechanical engineering, product design, architecture, and other disciplines that require precise 3D modeling with constraint-based parametric geometry. The project is community-driven and extensible through Python scripting and custom workbenches.

What FreeCAD Does

• Creates parametric 3D models using constraint-based sketching and feature-based modeling
• Provides specialized workbenches for Part Design, Assembly, Architecture (BIM), FEM analysis, and CNC paths
• Imports and exports STEP, IGES, STL, OBJ, DXF, and other standard CAD formats
• Supports finite element analysis for structural and thermal simulations
• Generates technical drawings with dimensioning and annotations

Architecture Overview

FreeCAD is written in C++ with Python bindings using PyCXX and Qt for the GUI. The geometry kernel uses Open CASCADE Technology (OCCT) for B-Rep solid modeling. The application follows a workbench architecture where each module (Part Design, Sketcher, FEM, Path) provides its own tools and UI. A document-object model stores parametric features in a dependency graph that recomputes when parameters change.

Self-Hosting & Configuration

• Download binaries from freecad.org or install via system package managers
• Install additional workbenches through the Addon Manager (Tools > Addon Manager)
• Configure units, navigation style, and display settings in Edit > Preferences
• Set up macro paths for Python automation scripts
• Use the Start workbench to access recent files and tutorials

Key Features

• Parametric constraint-based sketcher for precise 2D profile creation
• Modular workbench system with Assembly, FEM, Path (CNC), and BIM modules
• Full Python scripting API for automation, macros, and custom workbench development
• Open CASCADE-based geometry kernel supporting advanced B-Rep operations
• Extensible through community add-ons including rendering, fasteners, and sheet metal

Comparison with Similar Tools

• Fusion 360 — cloud-based with integrated CAM, but proprietary and requires a subscription for commercial use
• SolidWorks — industry standard for mechanical design, but expensive and Windows-only
• OpenSCAD — code-based 3D modeling via CSG, but no interactive GUI modeling workflow
• Blender — powerful 3D modeling and rendering, but focused on artistic rather than engineering workflows
• Onshape — browser-based parametric CAD, but proprietary with limited free tier

FAQ

Q: Can FreeCAD handle assemblies? A: Yes. The Assembly workbench (integrated in FreeCAD 1.0+) supports multi-part assemblies with mates and constraints.

Q: Is FreeCAD suitable for 3D printing? A: Yes. FreeCAD exports STL and 3MF files and includes mesh repair tools for print preparation.

Q: Does FreeCAD support Python scripting? A: Yes. Nearly every feature is accessible through the Python console and scripting API, enabling full automation.

Q: What file formats does FreeCAD support? A: FreeCAD reads and writes STEP, IGES, STL, OBJ, DXF, SVG, and its native .FCStd format (a zipped XML document).

Sources

• https://github.com/FreeCAD/FreeCAD
• https://www.freecad.org/