Balancing of Turbomolecular Pumps: Modal Balancing Approach and Experimental Results

摘要

Customer requests in terms of noise and vibration are becoming very challenging in most high-speed rotor applications. In turbomolecular pumps the main source of noise is the vibration due to rotor unbalance that is transmitted to the pump's body through the bearings. Additionally, turbomolecular pumps may present several critical speeds that amplify the unbalance response and the generated acoustic noise. Therefore, a very accurate balancing process is required for the entire speed range of the pump. The goal of the present paper is to present and test a method for the identification of balancing mass sets for high speed rotors that allows to selectively balance one critical speed at a time while having minimum impact on the remainder of the unbalance response in the speed range of interest. The proposed method is used to obtain sets of balancing masses calculated to minimize the amplitude of critical speeds and the acoustic noise generated by the pump. Finally, the calculated mass sets are used to balance a group of turbomolecular pump prototypes. The results of the new balancing process are compared to the standard balancing process in terms of performance and process time showing relevant improvement in both parameters.