FreeCAD is a multiplatform parametric 3D modeler which allows you to easily modify your design by going back into your model history and changing its parameters. FreeCAD is open source (LGPL license) and completely modular, allowing for very advanced extension and customization.
Install Freecad
sudo add-apt-repository ppa:freecad-maintainers/freecad-daily sudo apt-get update sudo apt-get upgrade sudo apt-get install freecad freecad-doc
