| High-speed motorized spindle as the main heat source and core component of high-speed machine tool,the power loss from the motor mounted in motorized spindle unit and the friction heat caused by baring rotation can't avoid,if the heat generated from the heat source failed to discharge,it could cause the thermal deformation of high-speed motorized spindle,if thermal deformation exceeded the permitted range,it will affect the running accuracy of motorized spindle.as a result,to analyze hot state characteristics of high speed motorized spindle is great significant to the structure design and optimization of the motorized spindle.In this paper,we chosen the GRP 135/110 RC type of four-head high speed motorized spindle as the research object,carried on the thorough analysis of its thermal state properties by using finite element software.The main contributions are as follows:(1)Analyzed the structural characteristics and working principle of four-head high speed motorized spindle,and studied the hot state characteristics of high-speed motorized spindle,mainly included the principle of the thermal deformation,heat source and the way to improve hot state characteristics of high-speed motorized spindle,emphatically analyzed the cooling way related thermal state performance of four-head high speed motorized spindle.(2)Calculated the heat production and heat generation rate from stator,rotor and spindle bearing of four-head high speed motorized spindle,determined the thermal load of the finite element analysis.The methodand process of heat transfer in motorized spindle system were studied,calculated the volume of cooling air required for heat dissipation of high speed motorized spindle shell,heat exchange coefficient between motor stator and cooling air,heat transfer coefficient between rotor end and ambient air,heat transfer coefficient between high speed motorized spindle and external air and heat transfer coefficient between bearing and cooling air,etc.So determined the boundary conditions of four-head high speed motorized spindle.(3)Introduced the related knowledge about ANSYS Workbench and the basic steps by using it for thermal analysis,built a geometric model of four-head high speed motorized spindle by solidworks,and respectively in the case of with and without cooling device,carried out the steady-state thermal analysis,transient thermal analysis and thermal structural coupling analysis of the motorized spindle,compared the two kinds of circumstances in the temperature field distribution,temperature rise law and thermal deformation differences,and puts forward the method to improve the running accuracy of motorized spindle.The results showed that larger temperature rising area of motorized spindle is mainly focused on near the main shaft bearing,due to the factors of 2.2 kW and 7.5 kW spindle unit have differences,sunch as configuration and pre-tightening methods,leading to different temperature field.The temperature of the motorized spindle increases with the extension of operation time,but the speed of temperature rise is gradually reduce,and ultimately tends to 0,the temperature reached steady state.The thermal deformation of 2.2 kW spindle unit front end is greater than the back-end,radial is greater than lateral,the deformation of bearing shaft parts is smaller than both ends,while the thermal deformation distribution of 7.5 kW motorized spindle unit is symmetrical,both ends is large,middle and bearing shaft parts is small,and the lateral deformation is greater than radial.When uing a forced air cooling device,the temperature rise and thermal deformation of rotation shaft in the two spindle unit is small,meeting the requirements of wood processing;When in the absence of forced air cooling device,the steady temperature and thermal deformation of 7.5 kW spindle unit is highest,in order to improve the running accuracy,we can preheat machine first on the premise of using forced air cooling device,and then processing. |
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