Analysis Of Thermal Characteristics Of Motorized Spindle System Based On Fractal Theory

Motorized spindle system has been widely used because of its advantages such as good machining accuracy and quality,it has been the core components of the high-grade CNC machining center.The machining accuracy of the high-grade CNC machining center is directly determined by the dynamic and thermodynamic characteristics of the motorized spindle system and the thermal characteristics of the motorized spindle system is determined directly by the microtopography of the contact surfaces in the motorized spindle system.Therefore,the application of fractal theory to the thermal contact conductance(TCC)between the circular-arc contact surfaces and its influence on the thermal characteristics of the motorized spindle system is of great significance.In this paper,the ES series motorized spindle system of a company is taken as the research object.The contact mechanical model of the joints between the circular-arc contact surface is established and the TCC characteristics is analyzed.At the same time,based on the fractal theory,the thermal resistance network model of the motorized spindle system is established and the thermal characteristics is explored.The influencing factors of the TCC between the circular-arc contact surfaces is analyzed from the experimental point of view.The influence of the fractal parameters on the thermal distribution characteristics of the motorized spindle system is analyzed.The main research contents of this paper include:(1)Analysis of fractal characteristics of joints between circular-arc contact surfaces.Based on the fractal theory and the determination method of fractal dimensions,the influencing factors of the surface morphology characterization of the joints is analyzed.Based on the W-M function,the calculation method of multi-phase values is derived.In order to extract fractal parameters,the influence of material and contact surface roughness on fractal characteristics are explored.The topography measurement experiment of the joint between circular-arc contact surfaces is carried out to verify the accuracy of theoretical results.(2)Research on the solution method for TCC between circular-arc contact surfaces based on fractal theory.The contact mechanical model of the joint is established considering three deformation states of elastic,elastic-plastic and plastic.The influence of contact azimuth angle on contact pressure is analyzed and the accuracy of the theoretical method is verified through comparing with the classical contact model and experiment.The TCC model between circular-arc contact surfaces is established and the influence of fractal parameters on TCC is analyzed.(3)Research on thermal distribution characteristics of motorized spindle system based on fractal theory.The main heat source and heat generation in the motorized spindle system is analyzed,and the heat transfer of the motorized spindle system is calculated.The axial heat-conduction resistance and thermal-convection resistance are calculated.The heat resistance network model of the motorized spindle system is established based on the fractal theory and the temperature-rise state of each key node of the motorized spindle system is analyzed by solving the heat balance equation.The influence of the fractal parameters on the temperature change of the motorized spindle system node is analyzed.(4)Experimental method and result analysis.The heat-conduction experiment is carried out and the experimental calculation principle of TCC is analyzed.The experimental results are compared with the simulation methods to verify the influencing factors of TCC between circular-arc contact surfaces.The temperaturerise experiment of the motorized spindle system is carried out to analyze the influence of the spindle speed on the transient and steady temperature of the key components of the motorized spindle system.The thermal distribution characteristics of the motorized spindle is explored.In summary,the heat conduction state of the circular-arc contact surfaces at the micro scale is analyzed in this paper based on the fractal theory,and the TCC between the circulararc contact surfaces can be predicted effectively.At the macro scale,the thermal distribution characteristics of the motorized spindle system can be effectively predicted by analyzing the law of heat generation and heat transfer among the key components of the motorized spindle system.The correctness of the analytical solution of TCC and the temperature value of the nodes of the motorized spindle system are verified by the experimental results.