Robust, parametric, fully-featured CAD/ CAM software provides the ability to create all complex geometry, allowing the models created to survive major changes to the design part, even late in the development cycle, thereby avoiding model reconstruction that would delay delivery of the tool.

However, not all systems that claim to be parametric are robust. Robust means the features created (i.e., rounds, drafts, chamfers, cuts, etc.) are able to survive major changes. Using the example from above, if the boss is changed from a cylindrical shape to a square shape, will the round still be able to attach itself correctly? In a robust CAD system, it will. Another example would be when modeling the parting surface. If the design model changes, what happens to the parting surface? In a robust CAD system, the parting surface will automatically update to the changes in the design part.