Open Source 3D Parametric CAD Modeler

Getting Started with FreeCAD

FreeCAD is available as precompiled installers for Windows, macOS, and Linux on the latest releases page. On Linux, it's often available via your distribution's package manager or software center. For developers and advanced users, building from source is supported using CMake. The official Developers Handbook provides detailed build instructions. Once installed, launch FreeCAD and explore the workbenches via the toolbar. The Python console and macro system enable automation and customization. For learning resources, visit the Getting Started guide on the FreeCAD wiki.

# Ubuntu/Debian
sudo apt install freecad

# macOS (Homebrew)
brew install --cask freecad

# Windows: Download from https://github.com/FreeCAD/FreeCAD/releases/latest

Parametric 3D Modeling with Python API

FreeCAD's parametric modeling engine allows users to define objects with editable parameters, enabling design iterations by simply adjusting values. The Python API exposes the entire modeling stack, letting developers create complex geometries programmatically. Using the Part and PartDesign workbenches, you can generate primitives, perform Boolean operations, add fillets/chamfers, and create features like pads, pockets, and revolutions—all via Python. This capability is essential for generative design, topology optimization, and integrating CAD with simulation or manufacturing workflows. The API supports both object-oriented and functional approaches, making it suitable for scripting, macros, and full-featured plugins. With access to the underlying OpenCASCADE kernel, FreeCAD delivers professional-grade geometric operations while maintaining ease of use for beginners.

import FreeCAD as App
import Part

# Create document and object
doc = App.newDocument()
cube = doc.addObject("Part::Box", "Cube")
cube.Length = 10
cube.Width = 20
cube.Height = 30
App.ActiveDocument.recompute()

# Modify dimensions later
cube.Length = 15
App.ActiveDocument.recompute()

2D Sketching & Drafting Workbench

FreeCAD includes a robust 2D sketching environment integrated with the 3D modeling pipeline. The Sketcher workbench allows users to draw geometry-constrained 2D profiles using lines, arcs, circles, and splines. Constraints such as horizontal, vertical, parallel, perpendicular, and dimensional constraints ensure precise control over the sketch geometry. Once complete, these sketches serve as the foundation for 3D features like extrusions, revolutions, and lofts. Additionally, the Draft workbench provides tools for creating 2D vector drawings without constraints, ideal for architectural floor plans or technical illustrations. The Drawing workbench enables the generation of orthographic projections, section views, and annotated drawings from 3D models, supporting ISO-compliant technical documentation with dimensioning, tolerancing, and bill-of-materials features.

import FreeCAD as App
import Sketcher
import PartDesign

doc = App.newDocument()
Part = doc.addObject("PartDesign::Body")
Sketch = doc.addObject("Sketcher::SketchObject", "Sketch")
Sketch.Placement = App.Placement(App.Vector(0,0,0), App.Rotation(App.Vector(0,0,1),0))

# Add geometry
Sketch.addGeometry(Part.LineSegment(App.Vector(-10,0,0),App.Vector(10,0,0)),False)
Sketch.addGeometry(Part.LineSegment(App.Vector(10,0,0),App.Vector(10,10,0)),False)
Sketch.addGeometry(Part.LineSegment(App.Vector(10,10,0),App.Vector(-10,10,0)),False)
Sketch.addGeometry(Part.LineSegment(App.Vector(-10,10,0),App.Vector(-10,0,0)),False)

# Add constraints
Sketch.addConstraint(Sketcher.Constraint('Coincident',0,2,1,1))
Sketch.addConstraint(Sketcher.Constraint('Coincident',1,2,2,1))
Sketch.addConstraint(Sketcher.Constraint('Coincident',2,2,3,1))
Sketch.addConstraint(Sketcher.Constraint('Coincident',3,2,0,1))
Sketch.addConstraint(Sketcher.Constraint('Horizontal',0))
Sketch.addConstraint(Sketcher.Constraint('Vertical',1))

# Extrude
Pad = doc.addObject("PartDesign::Pad", "Pad")
Pad.Profile = Sketch
Pad.Length = 5
doc.recompute()

Assembly Design & Constraint Solving

FreeCAD supports complex assembly modeling through the Assembly4 and Assembly3 workbenches, enabling users to combine multiple parts into functional mechanisms. Assemblies are built using constraints such as coincident, parallel, perpendicular, tangent, and distance to define relative positions and movements between components. The solver automatically updates the assembly when any part or constraint is modified, ensuring design integrity. This capability is vital for mechanical engineering tasks like gear trains, linkages, and housing designs. Assemblies can be exported as STEP files for collaboration with other CAD systems, and motion simulation is possible through integration with external tools like Yade or custom Python scripts. The parametric nature of FreeCAD ensures that changes to individual parts propagate automatically to the assembly, reducing manual updates and minimizing errors.

import FreeCAD as App
import Assembly4

doc = App.newDocument("Assembly")
# Add parts
Part1 = doc.addObject("Part::Box", "Block1")
Part1.Length, Part1.Width, Part1.Height = 10, 10, 10
Part2 = doc.addObject("Part::Cylinder", "Cylinder1")
Part2.Radius, Part2.Height = 3, 15

# Create assembly
asm = doc.addObject("App::Part", "Assembly")
asm.Type = "Assembly"
asm.addObject(Part1)
asm.addObject(Part2)

# Apply constraint (simplified)
# In practice, use Assembly4's Constraint class for full functionality
App.ActiveDocument.recompute()

BIM & Architectural Modeling Tools

FreeCAD includes specialized tools for Building Information Modeling (BIM) and architectural design through the Arch workbench. Users can create walls, floors, roofs, windows, doors, and structural elements using intuitive parametric objects. These objects automatically update when their parameters change, supporting iterative design and compliance with building codes. The workbench supports IFC (Industry Foundation Classes) import/export, enabling interoperability with industry-standard BIM software like Revit and Archicad. Features like site planning, energy analysis setup, and material take-offs make FreeCAD suitable for early-stage architectural design and documentation. Additionally, the Draft and Sketcher workbenches integrate seamlessly for creating precise floor plans and elevations, while the Drawing workbench generates construction documents with annotations, dimensions, and schedules.

import FreeCAD as App
import Arch

doc = App.newDocument("Building")
# Create wall
Wall = Arch.makeWall(length=5000, width=200, height=3000)
Wall.Base = Arch.makeSketch([0,0,0], [5000,0,0], [5000,200,0], [0,200,0])

# Create window
Window = Arch.makeWindow(1200, 1500)
Window.Base = Arch.makeSketch([1000,100,0], [2200,100,0], [2200,1600,0], [1000,1600,0])
Window.Host = Wall

App.ActiveDocument.recompute()