With the long run, "Mini Air Cooling Fan" within the bearing oil will evaporate and dry, the friction coefficient increases, fan operation affected may appear different sound, speed Pianman not even turn on. The ball bearing is replaced by rolling friction sliding friction, low coefficient of friction and to overcome the shortcomings of the friction coefficient is apt, therefore running stability, life is relatively much longer. "Mini Air Cooling Fan" use of oil-bearing copper-based sintered powder made by using lubricating oil bearings need to reduce the number of sliding friction, by lithium grease lubricating oil system Stuttgart modulation. With the long run, the oil inside the bearing will evaporate and dry, the friction coefficient increases, "Mini Air Cooling Fan" operation affected may appear different sound, speed Pianman not even turn on.