Reliability-Based Sensitivity And Optimization Design Of Lathe Feed System

The feed system is the core of lathe. Its precision directly affects the quality of workpiece. At present, gear and screw guide accuracy of China have deeply been studied, but the reliability research of feed system. Therefore, the reliability sensitivity research of lathe feed system has highly engineering significance. The main contents of this paper are as follows:(1) Through the analysis of parameters about CA6140 lathe parts, including manufactured error and assembly error of gear, vice screw pitch error, straightness error and the error of tensional guide. Gear manufactured error includes the total cumulative pitch error and a gear tangential composite deviation. The assembly error of gear includes assembly eccentricity, shaft neck beating, bearing radial clearance. Vice screw pitch error is mainly caused by lead bar pitch tolerances. Straightness error is mainly caused by the guide rail straightness error in the horizontal plane. Finally the mathematical model of the lathe feed system precision is established.(2) According to the accuracy model of the lathe feed system, the accuracy state function of transmission chains are established. Use the theory of 3sigma to calculate the standard deviation of random variables. The perturbation method of reliability and sensitivity theory is used for calculating the reliability of precision and sensitivity of the lathe feed system. The reliability of the feeding system was simulated by MonteCarlo method. Finally, the effect of the reliability and sensitivity which caused by variation of random variables are studied.(3) In order to improve the reliability of the feed system, optimization design theory is used for optimizing the reliability. The negative reliability index of the transmission chain is considered as the objective function. According to the limit of tolerance and lathe thread precision, linear constraints are imposed on the random variables. The nonlinear optimization function is used for solving the minimum value of objective function. The maximum value of reliability index is got. The perturbation method of reliability and the Edgeworth series is used for calculating the reliability of precision and sensitivity of the lathe feed system again.By means of the optimizing of design parameters of the lathe feed system, its initial reliability has improved, and find out the factors that have great influence on the feed system. The basis for further improvement of its performance is provided.