Research Of Thermal Characteristic Of Spindle Bearing And Interrelated Thermal Error Modeling Of Spindle In Nc Machine Tools

The spindle system is the machine tool's key part. The heating quantity increases with the spindle's rotational speed. In the spindle system, the heat quantity generated by the spindle bearing's severe rubbing under high speed will distort the spindle itself, and the bearing's heat will cause an error on machining precision which cannot be ignored. In this dissertation, thermal dynamical models were built based on the spindle bearing system of dynamic pressure lubricating film in the NC machine tools, in order to study the spindle's thermal error modeling of the NC machine tools. The main research contents are as followings:Based on the finite difference and hydrodynamic lubrication theory, this paper gives a solution to Reynolds equation and viscosity- temperature equation, with the assumption that the temperature of every point in the film is equal to the average temperature of the entire film, and then put this temperature into the viscosity-temperature equation, in order to calculate viscosity changes after temperature rise of the bearing. The influence of viscosity variation on dynamic performance of lubricating oil in bearing is taken into account, to avoid the complex solution of three- dimensional energy equation.The pressure distribution was used to obtain the dynamic parameters with the numerical integration: the minimum film thickness, loaded capacity of the film, the quantity of leaked oil, the friction energy loss, and so on. Finally, this paper edits the interface of the program by VB, and calls Matlab through ActiveX technology, making use of the powerful numerical computing function of Matlab, and completed the development of the pressure and temperature analysis software of lubricating oil in spindle bearing.According to partial correlation theory, the correlations between different temperature groups and spindle thermal error were analyzed, to prove that spindle bearing temperature is the most critical factor to the spindle thermal error. A new thermal error modeling theory, the theory of the SVM is illustrated in detail, and an analysis and comparison are conducted about the parameter of the models'influence on prediction precision. Also, a research on the method of choosing parameters is conducted, and thus suitable parameters are chosen to complete the thermal modeling. The result of the modeling can be predicted by the experiment data, and it turned out that the predicting precision of the result has successfully met the need of error compensation, proving it to be a quick and effective thermal error modeling method.