Normal consistent arithmetic of surface based on topology of grid edge

The algorithm of automatically reversing normal which is based on topology after surface mesh repairing is presented. This algorithm of automatically reversing normal comes from the concept of coedge during ACIS's surface healing and topology repairing is proposed. This algorithm can rapidly and accurately achieve the consistency of surface element normals by adjusting nodes of common edges of neighboring elements to make the two coedges belonging to the same common edge have the opposite directions. This algorithm has good adaptability by effectively dealing with faults such as crack between elements, isolated element (s) and element group (s), overlap element (s). This algorithm can accurately achieve consistency mesh normal of punch tools and provide necessary precondition for the follow contact algorithm before numerical simulation technology of sheet forming process. The validity is confirmed by results which the complex automobile panels normal are automatically reversed.