Abstract: Surface of a precision rotor, the typical helical surface, is too complicated to measure accurately with coordinate measuring machine(CMM). Aiming at this problem, a new proposal, based on geometric features and digital models, expressing complicated helical surface and its offset surface separately, is carried out to simplify contour measurement into parameter lead and transverse section profile measurement. Mathematical model of rotor and some methods for processing measurement data are explained, on this basis, continuous sampling mode of CMM is simulated to evaluate the uncertainty and select the optimal sampling strategy of measurement. After that, a method for measuring lead by rotary profile match is proposed to solve the problem existing in capturing spiral feature points; two solutions, one solves the problem of probe compensation by simulation re-measurement and the other avoids it directly, are also proposed to evaluate profile error. Simulation and actual measurement are carried out accordingly, and the comparison between measurement results and theoretical data provided by manufacturer proves that this proposal is advisable.

Key words: Digital model, Lead, Offset surface, Profile error, Rotor, Simulation re-measurement