Models often contain surfaces that are distorted, sometimes folded or twisted. CADfix deals with many of these surface problems automatically in the flavoring process but this example demonstrates how they could be dealt manually if required.
Folded surface is more of an application-specific issue that may or may not need to be addressed. When scanning your model, CADfix detects Folded surfaces and classifies them as a less serious problem. Several fix methods are available. Most of the time, the only solution will be to refit surfaces. But this method can transform your model. Make sure to set an appropriate Max surface change threshold. It will reject replacement if the change is too big. Simplifying NURBS is the best option, but not always possible. In addition, make sure your CAD system supports analytic surfaces. Problematic NURBS will be transformed to analytic surfaces (Sphere, plane, cylinder, torus, ...) and the problem will be solved.