Abstract: Abstract: Aiming at the problems of low precision and easy omission of the matching hole’s radius difference and the axis coincidence ratio in the automobile sheet metal parts, the automatic inspection method of the radius difference and the axis coincidence degree of the matching holes in the sheet metal parts is proposed. Firstly, the obtained B-Rep three-dimensional model is topologically decomposed into the basic unit of the face by the method of the closing shell. Secondly, according to the characteristics of two semicircular arc lines and two straight lines on the cylindrical surface, the cylindrical surface is screened, and the circular holes and slots are extracted by using the cylindrical surface. Then the radius and axis of the circular hole and the slot are obtained respectively, and the point-to-point and point-to-line distance method is used to check and analyze the matching hole according to the hole matching principle. Finally, the hole pairs whose radius difference does not meet the requirements and the axes do not coincide is marked. The system design of related algorithms is carried out by using CAA development platform of CATIA, and the feasibility of the method was verified. The example inspection results show that the method can automatically and accurately check the radius difference and the axis coincidence ratio of the matching holes in the sheet metal parts.

Key words: Keywords: matching holes, B-Rep three-dimensional model, cylindrical surface, radius difference, axis coincidence ratio