Analysis Of Thermal Characteristics And Core Cooling Of High Speed Motorized Spindle

The internal space of high-speed motorized spindle is limited.The rotor and stator of motor are placed inside the shell.The internal heat generation rate of motorized spindle is large and the air circulation is poor,resulting in a large amount of heat generated by the rotor flowing into the spindle shaft system.Therefore,the high temperature of the rotating shaft produces a large thermal elongation,which accumulates to the thermal error of the motorized spindle nose.At the same time,the temperature field will also have a non-negligible impact on the bearing,that is,the influence of life also changes the bearing preload,reduce the machining accuracy.In view of the above problems,this paper starts from the thermal analysis of the motorized spindle,through the simulation results to clarify the complex temperature changes in the motorized spindle,and proposes the cooling scheme and structure.A shaft core cooling structure is adopted to cool the shaft temperature and improve the cooling environment of the rotor indirectly.The main research contents of this paper include:Finite element method was used to analyze heat generation and heat transfer of motorized spindle,including simplified model,heat source heat generation calculation,surface heat transfer coefficient calculation and finite element simulation model.The steady-state thermal characteristics were analyzed,and the thermo-solid coupling simulation was established according to the temperature field data.It provides theoretical basis for testing thermal error prediction model of motorized spindle,and provides basic support for further cooling structure optimization strategy.Experimental verification was carried out according to thermal characteristics analysis results of the motorized spindle,including design verification experiments,and temperature and thermal errors under five groups of rotational speed conditions were collected.The error causes of simulation results and experimental results are analyzed to provide data support for the establishment of thermal error prediction model.Compensation system is an important step to improve machining accuracy,and the prediction model of thermal error is the basis to suppress the error.In this paper,the hybrid Gray Wolf Optimizer algorithm was used to search the support vector regression model parameters penalty factor and kernel width globally within the limited range,and the best parameters with the best fitness were selected to establish the SVR motorized spindle thermal error prediction model.The experimental data at a set of rotational speeds were used as training to predict the thermal error amount at different rotational speeds,and the feasibility of the model for thermal error prediction was verified.A comparative model was established to show the accuracy and robustness of the model.In order to further improve the internal temperature field of the spindle,aiming at the limited heat dissipation condition of the rotor of the motorized spindle running at high speed,the cooling channel is opened by the rotating shaft for cooling.And analyzed the cooling principle,based on the mass flow invariable principle of fluid simulation analysis,the flow field velocity,pressure and heat transfer coefficient distribution law.Then the thermal error and temperature field of spindle cooling structure are studied by thermal network method to verify the feasibility of spindle cooling structure.