High speed machining technology more and more get the attention of people, it not only can obtain greater productivity, but also can obtain very high processing quality, and can reduce the production cost, and therefore is considered to be one of the most promising advanced manufacturing technology of the 21st century.In advanced industrial countries, the technology has been widely used in aviation, aerospace and die industries.In recent five years, the technology of our country has made great progress.
            High speed machine tool is the prerequisite to realize high speed cutting, high speed machine tools is the development trend of the machine tool.High speed machine tool and virtual axis machine tools are machine breakthrough.Both ordinary numerical control machine tool and virtual axis machine tool, the realization of high speed spindle unit is still the key components.High speed spindle used dn value (dn value refers to the main shaft bearing of average diameter (mm) and the limit of the spindle rotational speed (r/min) product), high-speed spindle often refers to the dn value above 1.0 x 106 spindle.With the development of the bearing, lubrication technology, spindle speed increase year by year.The data shows, in the 80 s, the main shaft bearing grease in the dn value under the condition of only 0.5 x 106, but when oil and gas lubrication device developed dn value rapidly increase to 1.0 x 106, after the angular contact ceramic ball bearings, main shaft bearing of dn value is further increased to 2.0 x 106.In the 90 s, using the new lubrication method, spray lubrication, make the main shaft of dn value reached 3.0 x 106.For speed spindle unit is more than 10000 r/min, is no longer appropriate, can be driven by belt or coupling is a reasonable way is to use the built-in motor direct drive, the rotor directly installed on the main shaft of the motor, stator installed in main shaft sleeve, made in the form of so-called motorized spindle.The motorized spindle has a compact structure, easy to balance, transmission rate is high, is the ideal of high-speed spindle structure.The performance of the motorized spindle besides greatly influenced by bearing and lubrication technology, also is affected by many factors, including the bearing pre-tightening force control, built-in heating and cooling of the motor, the spindle dynamic balance, connection shaft parts, etc.In addition, the spindle axis design is also high speed motorized spindle problem that nots allow to ignore.