Abstract: An approach to automatically determine the parting line for molded parts is presented.Given a parting direction of molded part,we first classify the orientation of all faces with respect to the parting direction,their geometric characteristics and topological relationships into three groups;Then the largest contour of each face group is set up and two candidate parting lines are determined;The optimal one is finally chosen by a set of evaluation criteria.Test results show that the proposed approach is effective and efficient in automatically determining the parting line of a molded part.