Abstract: Abstract: In the development process of the automatic programming system for computer numerical control (CNC) machining of aircraft structural parts, the process defects of the part feature, especially the shortest distance between the inner surfaces of the pockets being too small, was likely to complicate the processing of parts, incur high cost, or even render the processing impossible. At present, this model problem was mainly inspected manually, which was inefficient and error-prone. For the pockets of aircraft structural parts with complex shapes and such complex features as open and closed angles and indentations, it was difficult to determine the shortest distance between side walls. Based on the extraction of feature geometric parameters, the calculation of the shortest distance between side walls was converted to the computation of the shortest distance between lines. The validity rules of the distance calculation between lines were presented to simplify the calculation according to geometric features of the pocket’s characteristics, and the shortest distance between inner wall surfaces of pocket features was obtained. Finally, an aircraft structure model is taken as an example to verify the feasibility and effectiveness of the algorithm.

Key words: Keywords: shortest distance, processing property, computer numerical control machining automatic programming, aircraft structure, pocket