The high-speed spindle unit mainly includes high-speed electric spindle, pneumatic spindle and hydraulic spindle. Among them, high-speed motorized spindle is the most common, high-speed motorized spindle unit is one of the most critical components in high-speed machining airport. At present, most of the electrospindle structures integrate the machining spindle and the motor shaft to achieve zero transmission. At the same time, the motor shell is equipped with a cooling system, and the high-speed motorized spindle is mainly composed of a shell with a cooling system, a stator, a rotor, a bearing and other parts. During operation, the speed can be increased or decreased by changing the frequency of the current. As the high-speed motorized spindle to achieve high-speed operation, the quality of the following parts directly affects the performance of the high-speed motorized spindle.
(1) The rotating shaft is the main rotating body of the high-speed electric spindle. His manufacturing accuracy directly affects the final accuracy of the motorized spindle. The form and position tolerance dimensional accuracy of the finished shaft is required to be very high. When the shaft is running at high speed, the vibration caused by the eccentric mass seriously affects its dynamic performance. Some parts installed on the shaft shall also be subject to dynamic balance test together with the shaft.
(2) The core supporting component of high-speed motorized spindle is high-speed precision bearing. Because the maximum speed of the electric spindle depends on the function, size, arrangement and lubrication method of the bearing, the bearing must have the advantages of high-speed performance, high dynamic load bearing capacity, good lubrication performance and small heat output. In recent years, the development of dynamic and static pressure bearings, ceramic bearings, magnetic bearings. Dynamic and static bearing has high stiffness and damping, which can greatly improve machining efficiency, machining quality, prolong tool life and reduce machining cost, and the life is semi infinite. High speed performance, high precision, easy to realize diagnosis and on-line monitoring. But this kind of spindle has not been widely used because of its complex electromagnetic measurement and control system, high price and long-term high. At present, ceramic bearings are widely used in the market. The inner and outer rings of angular contact ceramic bearings are steel rings, and the rolling element is ceramic material. Ceramic has the advantages of small density, good rigidity and small coefficient of thermal expansion. The results of theoretical calculation, contact fatigue test and crushing test show that the first failure of hybrid ceramic bearing is steel ring rather than ceramic ball. Because the theoretical life of the first three kinds of bearings is infinite, especially the magnetic bearing has the advantages of automatic adjustment of eccentricity. In the future market of ultra-high speed machine tools, with the development of technology, the magnetic bearing should be the development direction. In general high-speed machining machine tools, hybrid ceramic bearings or pure ceramic bearings will also have a wide range of applications.
(3) Good lubrication system has an important influence on the performance of high-speed motorized spindle. The typical lubrication method is oil mist lubrication or gas oil mixture lubrication. The former is mainly to atomize the lubricating oil to lubricate the bearing, the lubricating oil can not be recycled, and the air pollution is serious. The latter directly uses high-pressure air to blow the lubricating oil into the bearing, which plays the role of heat dissipation as well as lubrication.