FreeCAD is a general purpose feature-based, parametric 3D modeler for CAD , MCAD, CAx , CAE and PLM , aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties. It is 100% Open Source and extremely modular, allowing for very advanced extension and customization. FreeCAD is based on OpenCasCade , a powerful geometry kernel, features an Open Inventor -compliant 3D scene representation model provided by the Coin 3D library, and a broad Python API. The interface is built with Qt . FreeCAD runs exactly the same way on Windows, Mac OSX and Linux platforms. Learn more here...
Related: Free or Opensource Software