Portable FreeCAD is a very useful 3D CAD modeler. FreeCAD will be a general purpose 3D CAD modeler. The development is completely Open Source (GPL & LGPL License). FreeCAD is aimed directly at mechanical engineering and product design but also fits in a wider range of uses around engineering, such as architecture or other engineering specialties.

FreeCAD features tools similar to Catia, SolidWorks or Solid Edge, and therefore also falls into the category of MCAD, PLM, CAx and CAE. It will be a feature based parametric modeler with a modular software architecture which makes it easy to provide additional functionality without modifying the core system.

Features:
1. A complete OpenCasCade-based geometry kernel allowing complex 3D operations on complex shape types, and supports natively concepts like brep, nurbs, booleans operations or fillets
2. A modular architecture that allow plugins (modules) to add functionality to the core application. Those extensions can be as complex as whole new applications or as simple as python scripts or self-recorded macros
3. A full parametric model allowing any type of parameter-driven custom objects, that can even be fully programmed in python
4. Complete access from python built-in interpreter, macros or external scripts to almost any part of FreeCAD, being geometry creation and transformation, the 2D or 3D representation of that geometry (scenegraph) or even the FreeCAD interface
5. Import/export to standard formats such as STEP, IGES, OBJ, DXF, SVG, U3D or STL

The license of this software is Free, you can free download and free use this cad software.