A feature-based automatic broken surfaces fitting method for complex aircraft skin parts

Because of product design and digital model conversion between different computer-aided design (CAD) systems and computer-aided manufacturing (CAM) systems, a lot of broken surfaces are introduced in the digital models of aircraft skin parts, which have a great negative impact on numerical control (NC) programming efficiency. Broken surfaces fitting is an effective means to solve the above issues. The difficulties of broken surfaces fitting contain two aspects: (1) how to determine which ones of all the broken surfaces should be combined together automatically according to process requirements, and (2) how to obtain complete surface boundaries which could satisfy process requirements. In order to address the above difficulties, a feature-based automatic broken surfaces fitting method for complex aircraft skin parts is proposed in this paper. In contrast to traditional feature definition where broken surfaces and boundaries are restrained, while a novel feature definition method is introduced, where broken surfaces and boundaries are taken into account by considering adjacent relationship between surfaces. The broken surfaces which need to be fitted into one surface according to process requirements can be grouped automatically from all the broken surfaces by taking advantage of features definition and recognition. The broken surfaces fitting results show that the size, shape, and boundary of the fitted surfaces have good consistency with original surfaces, which could be directly used for NC programming, and it is expected to improve NC programming efficiency of skin parts dramatically.