Nonlinear Thermal Characteristics And Experimental Study Of High Speed Motorized Spindle

With the rapid development of CNC machine tools,the requirements of the spindle speed and machining accuracy are also increasing.Thermal expansion deformation of high-speed motorized spindle is the main reason of thermal error of machine tool.Therefore,it is very important to study the thermal characteristics of motorized spindle reasonably to control temperature field of motorized spindle and reduce thermal deformation of spindle.In this thesis,the thermal characteristics of the spindle were analyzed theoretically,the thermal model of the spindle was established,and the thermal characteristics of the spindle was simulated and analyzed by using the finite element software.The thermal performance of the spindle was tested by the comprehensive performance testing platform.The main content is as follows:(1)The contact thermal resistance was proposed to influence the thermal characteristics of the spindle,and the relevant factors that influence the thermal contact resistance of the spindle were analyzed.The theoretical calculation formula of the contact thermal resistance of the spindle was deduced,and the contact resistance of common materials was given.(2)This thesis mainly analyzed the composition of the heat source of the spindle and calculated the heat of the high-speed spindle system.The heat transfer mode of the spindle system was studied,and the convection heat transfer coefficient was calculated in the interior of the spindle.(3)Based on the 100MD60Y4 spindle,comosol finite element software was used to establish a thermo-structural coupling model of the spindle.This thesis analyzed the temperature field and thermal deformation of the spindle at multiple speeds.The influence of the roughness and contact pressure on the thermal characteristics of the spindle was studied under the spindle speed of 16000r/min.The change rule of contact thermal resistance and the energy transfer rule of friction interface were analyzed under the condition of thermal spindle.(4)The motorized spindle comprehensive performance test platform was built.Under certain operating conditions,considering the cooling water temperature,cooling water flow rate,contact resistance and oil-gas lubrication,the thermal characteristics of high-speed spindle were tested.The influence of the thermal contact resistance between the spindle and the bearing,the bearing and the bearing support,the rotor and the spindle on the temperature field and the thermal deformation of the spindle were analyzed.The thermal diffusivity and thermal deformation of the spindle were studied to obtain the time-varying non-linearity of the spindle.The thermal characteristics of the spindle under consideration of the contact thermal resistance and the absence of contact thermal resistance were analyzed respectively and compared with the experimental results.The results showed that:? The spindle model established in this thesis can accurately predict the thermal characteristics of the spindle.The maximum temperature of the spindle simulation considering the contact thermal resistance is 1.9? higher than that of the spindle simulation without considering the contact thermal resistance,Thermal deformation in all three directions increased by 4.31%,7.92%and 5.6%respectively.?Through the simulation calculation,we can get the effect of the influence factors of contact thermal resistance on the temperature of interface.As the contact pressure increases,the internal temperature of the spindle decreases,of which the bearing inner ring is less affected,while the bearing outer ring and the rotor temperature drops significantly.With the increase of the roughness of the inner surface of the spindle,the temperature inside the spindle increases,and the inner ring and the outer ring of the bearing have little change in temperature while the temperature of the rotor increases greatly.