Research On Thermal Characteristic And Thermal Compensation Technology Of Spindle System Of CNC Machine Tool

With the development of CNC machine tool toward high-precision, high-speed and high flexibility, higher request for the precision of CNC machine tool and its reliability has been proposed. A lot of researches show that thermal error takes up to70%of the whole error, therefore research on thermal characteristic analysis and thermal compensation of CNC machine tool will become one central issue, which will effectively improve machining precision.The subject is from a sub-topic of National Science and Technology Projects (NO:2009ZX04001-053) and the project of research on key technology of rapid response and innovation design of CNC machine tool in Liaoning Province which mainly studies the thermal characteristic and methods of thermal compensation of the spindle system of one precision turning center. The main content of this paper is as follows:(1) The mathematical model of temperature field is established by theories of heat transfer and based on thermal deformation equation, elastic mechanics and finite element theory, the mathematical model of thermal deformation is built, which lay a foundation for research on thermal characteristic of spindle system.(2) The three-dimensional model of spindle system is constructed and it is meshed by ANSYS Workbench. The boundary condition and heat source of the spindle system is computed by relevant theory and the results are applied to the finite element model. By comparing results of FEM and experiment, adjust the boundary condition if necessary to make the analysis results similar to experimental results. Then the temperature field is used as a load to calculate thermal deformation.(3) Two ways of changing boundary condition of spindle system have been analyzed to find their influence on spindle thermal deformation, which are changing air flowing speed around headstock and setting up a cooling jacket at the front surface of the headstock respectively. By comparing them, it can be found that using a cooling jacket at the front surface of the headstock can reduce thermal deformation greatly(4) Based on gray system theory and regression method, the mathematical model of thermal compensation is established. All the temperature measuring points have been classified by gray correlation and the biggest value of each group is used to build linear regression equation. According to results of regression analysis of combination of the temperature measuring points, the measuring points used to determine thermal compensation mathematical model is confirmed and the regression equation is inspected by R, T and F method. Ultimately, the process of thermal compensation of the spindle system has been described.