Analysis On Thermal Properties Of Hydrostatic Motorized Spindle System And Optimization

With the rapid development of high speed CNC machine tools, motorized spindletechnology has been developed. Built-in motor is used in hydrostatic motorizedspindle system, and the motor stator with a cooling water jacket is fitted to thehousing directly. Rotor and spindle assembly as a whole by interference fit makes themotorized spindle system the short transmission distance and compact structure. Thehigh temperature of motor and hydrostatic bearings and the large motor power haveaffected the development of hydrostatic spindle system. Therefore, it can provide areference for structural design to research the thermal characteristics of hydrostaticmotorized spindle. The main works of the dissertation are as follows:(1) Hydrostatic motorized spindle system structure, the heat resources and heattransferring mechanism were analyzed. The heat resources and heat tr ansferring wayshave been closely related with the components and the operating condition. Thehydrostatic bearings support the motorized spindle, T and the motor and spindle areintegrated as a whole. By analyzing the heat resources and heat transfer mechanism,heat transfer coefficient on the surface of the hydrostatic motorized spindle system,heat transfer coefficient of cooling water and heat transfer coefficient of lubricantswere calculated. The heat generated due to friction in the hydrostatic bearings wasanalyzed comparatively in theory and simulation. The theoretical result was close tothe simulation result.(2) The thermo-structure coupling of hydrostatic motorized spindle was analyzed.The finite element model of hydrostatic motorized spindle was established in ANSYSWorkbench. The temperature distribution was analyzed. And the results show that thehighest temperature is in the front sliding bearing and the highest temperature value.The thermal deformation at the radial and axial direction was calculated bythermal-structure coupling analysis on loading the temperature field and thedisplacement constraints. The result shows that the maximum deformation is in thefront of spindle. That the process parameters affect the radial deformation on the frontterminal face of spindle was analyzed. And the measures to improve the thermalproperties of hydrostatic motorized spindle system were proposed.(3) The structural parameters of hydrostatic bearing were optimized based on theanalysis of the thermal analysis of hydrostatic motorized spindle. The experimental design was established by optimal Latin hypercube design. The approximation modelwas constructed by regarding the bearing seal oil side length, length-to-diameter ratioand clearance as the design variables and regarding the bearing’s static stiffness andthe temperature as the optimization objectives. A Pareto optimal frontier predicted bythe approximations was identified by a multi-objective genetic algorithm. Thehydrostatic bearings produced the least heat quality, and the thermal deformation ofhydrostatic motorized spindle system was the minimum.In summary, the thermal characteristics of hydrostatic motorized spindle systemwere analyzed by theory and numerical simulation. Based on the thermal analysis ofhydrostatic motorized spindle system, the structural parameters of hydrostatic bearingwere optimized. The results provide a certain reference value for improving thethermal deformation of the hydrostatic motorized spindle system and the machiningaccuracy.