Research On Key Technology Of Design And Manufacturing Reliability Of Ball Screw Pair

As a high speed and precision drive component,ball screw pair has the characteristics of high positioning precision,high transmission efficiency and good synchronization performance.It has a wide application in CNC machine tools.Its reliability directly affects the machining accuracy and reliability of CNC machine tools.With the steady development of China's basic manufacturing industry in recent years,the domestic ball screw production enterprises are steadily improving their own strength,and the production products are gradually closer to the international advanced level.But in the market competition,the domestic ball screw pair is still at a disadvantage.It is still the experience and technology of the quality and control of the domestic ball screw in the design,processing and assembly stage,which causes the low level of product reliability,and it is difficult to catch up with the international advanced level in the short term.Under this background,this paper is based on "the research and application of the reliability support technology of machine tool manufacturing process" belonged to the subject of "high-grade CNC machine tools and basic manufacturing equipment".Through the deep cooperation with the Nanjing Technical Equipment Manufacture Co.,Ltd.,the research work on the key technology of the reliability of the ball screw is carried out.The main contents include the following aspects:In the research and analysis of the key technology of reliability in the design stage of ball screw,the reliability modeling,evaluation,distribution of the product and the failure mode and influence analysis(FMEA)and fault tree analysis(FTA)are integrated to construct a framework for the reliability design of ball screw.In the FTA analysis,the trapezoid fuzzy number is used to express the occurrence probability of the basic events,to solve the probability of the occurrence of the top events,and to define the concept of the fuzzy critical importance,so as to make a comprehensive and accurate evaluation of the importance of the basic events.The reliability control technology of ball screw machining process is studied,mainly including two aspects: process stability and process heredity.In the study of process stability,process capability is used as a measurement index of process stability,and a complete process capability analysis process is established for enterprises.In the study of process heredity,the correlation relation of machining error between the front and back processis is analyzed by the partial relation number,so that the enterprise can adjust the tolerance of the preceding process and reduce the machining error,so as to reduce the adverse effect on the related working procedure and improve the process reliability and processing precision.According to the characteristics of the ball screw assembly process,the generalized stochastic Petri net(GSPN)technology is applied to the reliability modeling of ball screw assembly process.The GSPN model of assembly process is established,and the reliability of assembly is calculated.At the same time,the weak link of the assembly process is determined by the steady-state probability of the GSPN model.Then the influence factors of the reliability of assembly link are analyzed from six aspects: man,machine,material,method,environment and measurement,and the concrete measures to improve the reliability of the ball screw assembly process are formulated.The research results of this paper have important reference value for the manufacture of ball screw in China.