Study On Structure And Performance Optimization Of Motor Built In And Liquid Suspension Electric Spindles For Ultra-high Speed Grinding

Ultra-high speed grinding is a challenging high-efficiency precision machiningtechnology in advanced manufacturing field. The ultra-high speed CNC grindingmachine is equipment foundation to realize ultra-high speed grinding. Liquidsuspension electric spindles are the core function component of the ultra-high speedCNC grinding machine. Motor arranged-back liquid suspension electric spindles havebig rotor inertia, slow dynamic response and are difficult to meet the need ofultra-high speed grinding. Motor built-in liquid suspension electric spindles canovercome the above weaknesses. However, sealing difficulty, high temperature riseare caused due to high-speed and integrated structure. Furthermore, the damage tospindle is caused with the decrease of oil film viscosity and thickness due to hightemperature rise. Therefore, it is urgent need to study structure and performanceoptimization of motor built-in liquid suspension electric spindles for ultra-high speedgrinding.Motor built-in liquid suspension electric spindles are developed, and theirengineering applications are achieved. The forced circulation cooling solution is usedto cool motor. The rotor dynamic analysis is performed. The dynamic balancing isalso calculated.The numerical calculation model of bearing oil film flow field based on CFD isestablished. The discrete method of oil film mesh for radial and thrust bearings, andthe selection method of boundary conditions and calculation parameters are discussed.The structure grid is used to achieve the oil film three-dimensional discrete meshdivision.The forced mesh size function is adopted to ensure the coordination of thegrid, and achieve integrated optimization of computational efficiency and accuracy.The established model and CFD method are adopted to study oil film flow fielddistribution, stiffness, flow rate and temperature rise with different structureparameters and working parameters.Experimental study is done on the basis of the developed prototype electricspindle. The stiffness, flow rate and temperature of bearings with different workingparameters are obtained on the test bed. The running condiction and the performanceof the electric spindle are good. The value of the calculated film stiffness and one ofthe measured film stiffness are in good agreement. It is confirmed that the structure, cooling, seal and first critical speed design, and rotor dynamic balancing of theelectric spindle are successful. The numerical calculation method of radial and thrustbearings oil film flow field based on CFD is feasible and effective.The engineering reference is provided to achieve the reasonable design of liquidsuspension electric spindles and optimization of hybrid bearing structure parametersand working parameters.