FreeCAD is a parametric 3D modeler. Parametric modeling + 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.
+FreeCAD is multiplatfom, and reads and writes many open + file formats such as STEP, IGES, STL and others.
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