Robust Design And Reliability Evaluation For High Speed Motorized Spindle Of Grinder

The dynamic and thermodynamic properties of high speed motorized spindle of grinder determine the machining accuracy and surface quality of work piece.In the present study,the motorized spindle is optimized by dynamic analysis,or from thermodynamic analysis.For the optimization of the comprehensive performance(dynamic and thermal properties)of the high speed motorized spindle,a robust design and reliability evaluation approach based on the hyperbolic response method is presented.The main achievements and innovations of this paper are as follows:1.The model of varied dynamic stiffness of high speed rolling bearing and shaft-rotor contacting stiffness-VDBT&SCT are proposed and constructed,thus improved the traditional finite element dynamic model of spindle system.A case study of electric spindle system of grinding wheel of Shanghai machine tool plant for comparison of two models through engineering experiments show that compared with the traditional model,the accuracy of the 1st and 2nd natural frequencies of improved model is 17% and 10% up respectively.2.A method of multi-objective robust design for the electric spindle system of high speed grinding wheel based on operating coupling dynamic and thermal performance and control of variable quantity-OCDTP&CVQ is proposed.This method takes the dynamic stiffness of spindle in working speed range,temperature rise of stator and bearing and the fluctuation of this performance as design objectives,takes the structure factors as variable.According to the result of coupled analysis,this paper sets up the function of the design variables and the optimization objective of the spindle based on the hyperbolic response method,uses the satisfaction function as combination function of multiple objectives and comprehensive performance evaluation to optimize the structure and design criteria of spindle system.It provides a new method to solve the problems cause by the traditional design method.3.A reliability evaluation method based on multi-factor sensitivity analysis is proposed.The maximum variation of the performance index of the manufacturing error of each design factor of the spindle system is calculated and evaluated.The failure mode and fatigue wear life of the spindle system were calculated and evaluated by using the life evaluation.Finally the advantages and disadvantages of the before and after optimization design spindle system in this various reliability evaluation indices are obtained.4.Taking the motorized spindle system of high speed grinding wheel of Shanghai machine tool as an example,the structure and layout of the spindle are optimized using this method.After optimization,the mass of the spindle system was decreased by 46%,and the length of the spindle system was decreased by 32%.In the working speed of 7200rpm(linear velocity 150m/s),the dynamic stiffness of the spindle system is improve by 12%,its maximum fluctuation is decreased by 10%;temperature rise of stator is decreased by 30%,its maximum fluctuation is decreased by 10% 70%;temperature rise of front bearing is decreased by 18%,its maximum fluctuation changes from the original 0.52?to 0.96?.