Abstract
This study is focused on the dynamic characteristics of a vertical turbo molecular pump rotor-bearing system. The research methods can be divided into two parts, which are numerical analysis and experimental measurements. In numerical analysis, we use the finite element analysis software ANSYS and DyRoBeS to construct a two-dimensional and three-dimensional model of the rotor-bearing system. In the analysis process, by constantly changing the pump system assembly methods we can correct and verify the rotor-bearing system finite element model under different boundary conditions. Next, we calculate the Campbell diagram to understand the dynamic characteristics of the rotor-bearing system, and to compare with the experimental results to verify the model. Finally, we found the relationship between the rotor critical speed and the bearing stiffness in order to provide the design of the molecular pump rotor and the bearing system. Experimental measurements were divided into two parts: static percussion tests and dynamic measurements. Static test can provide the natural frequencies of the rotor-bearing system. Waterfall diagram of the dynamic test can measure the pump system’s critical speed from zero speed up to the working speed crossing, and to insure that the pump working speed is far from the critical speed of 10% in the safe range. In summary, the results of the experimental measurements and numerical analysis can be the basis for the design of the turbo molecular vacuum pump rotor-bearing system analysis techniques in order to identify and prevent pump vibrations.