| High-speed electric spindle is a new "zero-drive" form of spindle unit,which is considered to be the most critical high technology in high-speed cutting.It is often used as the core functional component of high-speed machine tools.Accurate testing of the loading force and quantitative loading are prerequisites for the experimental study of the dynamic characteristics of high-speed electric spindles.The existing non-contact loading technology is relatively small.There is a lack of mature products.There is an urgent need to study non-contact loading methods for electric spindles,to develop non-contact loading devices,to study the testing methods for dynamic loading stiffness of electric spindles under high-speed rotation.Angular contact ball bearing is currently one of the most widely used support methods for high-speed electric spindles,which require different bearing preloads to match the different spindle speed bands.The main research works of this paper are as follows:(1)Based on the 6kW/60kr/min axial electromagnetic preload high-speed internal grinding electric spindle system developed by the group,a non-contact radial electromagnetic loading device is developed based on the radial external load analysis and electromagnetic force loading theory of the high-speed grinding electric spindle.The radial electromagnet structure is optimised to increase the number of turns of each pole coil to increase the output radial electromagnetic loading force of the loading device.(2)Based on the developed non-contact electromagnetic loading device,we analyze the high-speed electric spindle electromagnetic dynamic loading stiffness test method and realize the dynamic loading stiffness test of the spindle end under the high-speed rotation.The test methods include testing the radial displacement and radial electromagnetic loading force of the rotating spindle under radial electromagnetic loading.The ratio of the radial electromagnetic loading force to the radial displacement is used as the dynamic loading stiffness of the spindle shaft end.The radial displacement is measured by an eddy current displacement sensor.The radial electromagnetic loading force is obtained by solving for the drive current and the radial displacement.(3)Based on the developed non-contact electromagnetic loading device,the static and dynamic characteristics of the axial electromagnetic preload high-speed electric spindle system are improved.The dynamic characteristics of the electric spindle under radial dynamic loading are studied.The influence of bearing preload force,spindle speed and external load on the spindle stiffness is investigated.Based on the MADYN 2000 software,the dynamic characteristics of the high-speed electric spindle are analysed.The influence of the rotational speed and radial dynamic loading force on the dynamic support stiffness of the spindle is analysed.(4)An electromagnetic preload electromagnetic loading high-speed electric spindle test bench was built to test the spindle static stiffness,spindle inherent frequency,spindle bearing temperature rise and shaft end stiffness of the high-speed rotating spindle under non-contact electromagnetic loading.The correctness and practicality of the non-contact radial electromagnetic loading scheme,the axial controlled electromagnetic preload scheme and the radial dynamic stiffness test method of the electric spindle were verified by theoretical calculation results and comparative analysis of the experimental data.The research work in this paper can achieve non-contact radial electromagnetic loading,axial controlled electromagnetic preload and spindle end radial dynamic loading stiffness test in the spindle operating speed range,which provides an engineering reference for the practical application of non-contact electromagnetic loading technology and controlled preload technology. |
PDF Full Text Request