A Study of Magnetic Fluid Rotary Seals for Wafer Handling Robot

Magnetic fluid rotary seals have been shown to be effective in machinery operating in a vacuum chamber. Such seals have the advantages of simple design, zero leakage at almost any rotation speed and low friction. This paper presents the principle of magnetic fluid rotary seals technology. The seal differential pressure formulas of magnetic fluid rotary seals is deduced and obtained. The magnetic field distribution of the sealing gap flux densities is calculated by finite elements method through solving the magnetic vector potential with appropriate boundary conditions. Based on the magnetic field calculations, the influence of sealing gap and tooth parameters on seal pressure differential is analyzed. A coaxial twin-shaft magnetic fluid seal apparatus used for wafer handling robot is presented. It is shown that using the most advanced magnetic fluid technology and seal design technology, magnetic fluid rotary seals can provide satisfactory performance in this challenging new application.