Abstract: T he mechanical performance of the high -speed shafting of compound and greased molecular pump was analyzed, and thus the design optimization was carried out. In this paper, the CG-250/1600 pump was used as the prototype, and the bearing span and shaft stiffness were optimized and improved. The dynamic and static mechanical properties of the high -speed shaft were calculated before and after optimization design of the high -speed shafting. All the critical speed and mode formation of the rotor system were obtained, and two kinds of structures were tested and verified. The results show that the experimental results are basically the same as the theoretical analysis. After optimization, the critical speed of the rotor system varied slightly; the amplitude-frequency characteristic was basically unchanged; the start and stop process was more stable; the initial unbalance response decreased obviously, the hidden danger caused by the resonance was reduced, and the difficulty of the dynamic balancing debugging was reduced greatly.

Key words: compound molecular pump, high -speed shafting, supporting span, shafting stiffness, finite element method