Vibration Reduction Technology for High-Speed Centrifuges Commonly Used in Laboratories

　　Laboratory high-speed centrifuges typically employ two types of shafts: One type has a slender, elongated shaft that inherently exhibits significant flexibility, enabling it to automatically self-align. The other type features a thicker, shorter shaft with minimal inherent bending deflection; however, layered vibration dampers ensure that the system’s operating speed remains above the critical speed, thus maintaining the system’s flexible nature. Although both are flexible systems, the key difference in operation between the slender flexible shaft and the relatively rigid shaft lies in how they achieve automatic alignment: In the case of the slender flexible shaft, automatic centering is primarily accomplished through the shaft’s bending, allowing the rotor to rotate around its center of mass. By contrast, on the more rigid shaft, automatic centering is achieved via relative flexural displacements among the various components within the entire rotating system.
　　Meanwhile, Lu Xiangyi centrifuge believes that longer, thinner shafts are best made from spring steel, while shorter, thicker shafts are more appropriately made from quenched and tempered alloy steel.
　　Long-term production experiments, as well as the many factors that cause vibration in high-speed centrifuges encountered during Lu Xiangyi’s centrifuge after-sales service, have revealed a wide variety of causes. Centrifuge vibration is one of the key indicators for assessing the performance quality of a centrifuge. Generally speaking, vibration reduction can be achieved through two main approaches: active vibration reduction and passive vibration reduction. Active vibration reduction involves designing the centrifuge in such a way that its operating speed is kept far away from the critical speed of the rotating system (in laboratory high-speed centrifuges, the critical speed is typically designed to be significantly lower than the operating speed). Additionally, dynamic balancing must be performed during rotor manufacturing. Passive vibration reduction, on the other hand, involves using various types of vibration dampers to isolate potential vibrations from the machine frame and foundation.
　　Rubber vibration dampers generally meet the vibration-damping requirements of high-speed centrifuges. Given a fixed damper structure, the higher the rubber hardness, the higher the system's critical rotational speed will be. If the hardness of the damper is too low, its strength will fail to meet the requirements and it will easily become damaged.
　　In centrifuge design, active and passive vibration reduction are typically applied simultaneously. For high-speed centrifuges, vibration reduction is generally considered in three distinct areas:
　　(1) Design the spindle bearing housing in a flexible vibration-damping configuration;
　　(2) The entire drive system is flexibly connected to the frame.
　　(3) The spindle is connected to the motor via a flexible coupling;
　　In addition to the flexible vibration-damping design adopted for the three aforementioned components, an elastic coupling can also be used between the rotor and the spindle. For instance, in the high-speed centrifuge model RC-z manufactured by the U.S. company Sorvall, a layer of silicone rubber is interposed between the spindle and the rotor, which further helps absorb vibrations. Beyond their vibration-isolation function, these various vibration-damping measures also lower the critical rotational speed of the rotating system, ensuring that the operating speed remains well away from the critical speed. This is precisely why the spindles of some high-speed centrifuges are relatively thick yet not excessively long—yet the entire system still operates above its critical rotational speed.