Analysis And Identification Technology Of System Errors Of Large Vertical Ultra-precision Machine Tool

Ultra-precision machining technology is the development foundation for high-tech industries. The semiconductor device supported by ultra-precision machining technology, laid the foundation for the development of electronics and information industry. The development of modern science and technology based on the test, almost all of the test equipment needs the support of ultra-precision machining technology. Now ultra-precision machining has entered the nano-scale, and become an indispensable key means of developing high-tech. Whether the military industry, or civilian industry, all need such advanced machining technology.The research on machining precision of a two-axis large ultra-precision machine tool, analyzing the errors of main components of machine tool by the transfer matrix method, finite element method and multi-body theory. In order to show the comprehensive characterization of workpiece, wavelet method, correlation analysis and power spectral density method are used to analyze the surface topography of workpiece, different from the traditional Fourier transfer method, wavelet method express the comprehensive characterization of the signal in time and frequency domain. Correlation analysis method can estimate the signal in two different processes. Power spectral density method can fully reflect the impact of small-scale waviness of surface morphology on the machined accuracy.For the hydrostatic bearings, the parameters equation of bearings was deduced by the knowledge of fluid mechanics, and the calculated results were compared with other calculations. The mathematical model of spindle system in equilibrium was established according to Newton's law, based on the model, the relationship between derivation angle and stiffness of bearing was deduced, and the stiffnesses in all directions are given. The forced vibration of spindle caused by unbalance during machining process was researched through dynamic model of spindle, dynamic frequency response was deduced according to the model of spindle. Thermal-mechanical model of spindle system was established, the calculation basis of the heat transfer in the spindle system was deuced, and thermal error was analyzed with heat transfer mechanism, the variation of bearing performance at the different conditions under the influence of thermal errors, and the impact on the machining accuracy was analyzed.The coupling error model of guideways of machine tool was established with multi-body system theory. For the complex structure of guideway and unloading slide, the pressure distribution of gas film of guideway with double row orifices by gas lubrication theory, and corresponding load capacity and gas stiffness was obtained. The movement frequency with gas film thickness of entire slide system during machining process was showed. The coupling dynamic model of motion and unloading slides was established through corresponding frequency, the dynamic response of slide with the variation of gas film thickness was deduced. Finally, the variation of moving frequency in the whole gas film thickness was obtained.Finally, the measured result of workpiece was processed by wavelet transfer. The rotation error model of spindle was proposed by Weierstrass function, and the correctness and feasibility of this model was verified by comparing with actual test results. The correlation between guideway, spindle system and measured result of workpiece was analyzed, thus the degree of influence of every error on the machining accuracy was deduced. Combained with wavelet method and power spectral density method, the errors of guideway and spindle systems was analyzed in frequency domain, the characteristics of vibration signal of machine tool in frequency domain was extracted, and various error that affect the machining accuracy were identified according to the spectral characteristics.