| As the most typical high-end manufacturing equipment in the manufacturing industry,the development level of NC machine directly determines the competitive position of national manufacturing industry in the world.At present,compared with other developed countries,there are still many deficiencies in the Chinese NC machines,such as low precision,poor reliability and backward core technology,etc.As the core measure of NC machine's performance,precision directly determine whether the NC machine can finish specified tasks,precision reliability embodies the machine's ability to finish the specified task,which is the guarantee of performance of the NC machine.Therefore,it is of great significance to carry out the precision reliability analysis of NC machines.Based on the transmission mechanism of a three-axis NC machine,this thesis develops three aspects of NC machine error modeling,precision reliability analysis and precision optimization.The specific contents are as follows:(1)Based on the multi-body system theory and the homogeneous coordinate transformation theory,a three-axis NC machine was used as an example,the comprehensive error modeling was established according to the relevant topological structure.(2)The geometric error model of transmission mechanism of NC machine was established,through mathematical calculation models,the manufacturing error of the ball screw pair,the force deformation error,the heat deformation error and the installation error,and the servo motor and deceleration mechanism were analyzed,the 21-item geometric error value of NC machine were determined.(3)Aiming at the coexistence of random error and interval error in the geometric error of the transmission mechanism of NC machine,a probability-interval mixed uncertain reliability analysis method based on the first order realibility method was applied to analyze the reliability of NC machine geometry error accuracy.(4)The sensitivity analysis of geometric error of transmission mechanism of NC machine using the partial derivative method was carried out.Based on the analysis results,a cost-tolerance model was established.Based on Matlab and Isight,the genetic algorithm(GA),two times sequence nonlinear optimization and error tracing method were applied to carry out the precision optimization design.Through the precision reliability analysis and optimization design of the transmission mechanism of NC machine,under the premise of satisfying the precision design requirements of NC machine,the precision reliability of the transmission mechanism of NC machine is improved and the manufacturing cost of the transmission mechanism is reduced,which provides the theoretical basis for the design and manufacture of the NC machine. |
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