Probably the most well-known design and 2D/3D modeling general purpose application is AutoCAD.. But if your specialty is mechanical engineering and you need a free solution to develop your projects, you will really like FreeCAD, very similar to programs like Catia, SolidWorks and Solid Edge.
The best free solution for 3D design and modelling.
It's an open source application focused on 3D modeling and on the design of products, based on parametric modeling. It's a perfect application for engineering and architecture students, as well as freelancers in this field.
- Complete application based on a GUI.
- Possibility to work from the command line.
- Possibility to import as a Python module.
- Application composed be means of modules.
- Possibility to solve the projects in a format based on ZIP, capable of storing different kinds of information.
- Option to use macros.