Reliability Analysis Of Machining Center Based On Correlation And Parameter Degradation Model

As the fundamental equipment of modern production,machining center is the core of national industrial development.China has become the main competitive market for machine tool manufacturers in the world under the background that China is striding forward to become a powerful country of intelligent manufacturing industry.Compared with the CNC machine tool manufacturers in the world,Affected by the machining accuracy,processing speed and reliability,China’s high-tech machining center takes less share in the domestic market.The reliability analysis of correlation faults of machining centers provides basic guidance for reliability design,maintenance and fault diagnosis.This paper which benefits from the National Natural Science Foundation of China focuses on the correlation faults and parameter degradation of the machining center.The main contents are as follows:Firstly,the mathematical model of machining center is established by fault data which obtained on the spot.According to the reliability assessment scheme,107 fault data were collected,and the machining center was divided into 12 subsystems according to the structure,working principle and corresponding relationship of functional components.Furthermore,the reliability data are statistically analyzed,and the Weibull distribution reliability model is established by model optimization,parameter estimation and parameter goodness of fit test,and the reliability models of all subsystems are established.Secondly,improved fault criticality analysis and fault correlation analysis.According to the failure data,the Fault Mode and Effects Analysis(FMEA)of machining center are applied to analyze fault.The group decision-making method and the method of expert evaluation combined with entropy weight are introduced into the failure mode Criticality Analysis(CA)and subsystem Criticality Analysis,one is adopted to get the more suitable value of β and the other is adopted to solve the problem of the same weigh among three factors of α、β、λ.In order to make fault correlation analysis,the Decision Making Trial and Evaluation Laboratory(DEMATEL)is adopted to gain the fault correlation of machining center subsystem,and the influence degree、cause degree、influence degree and centrality degree are employed to express the correlation order and critical subsystem of subsystem faults.Combined with Interpretive Structural Modeling(ISM),the fault transmission process between system internal faults is defined,and the fault transmission process of machining center is divided into five levels,and the electrical system is determined to be the deepest influence system of the fifth level.Thirdly,the reliability influence degree of machining center subsystem is analyzed.In order to objectively and effectively analyze the influence degree of each subsystem on the machining center,the Data Envelopment Analysis(DEA)method is introduced to carry out the comprehensive impact ranking,On the basis of the relative effectiveness of data envelopment method,the weighted analysis is carried out with reference to the sorting index of subsystems,and the implicit weight of each subsystem index is effectively determined by the quantitative method.The principle of high score,high weight,low score and low weight is followed,and the effective information of each index is comprehensively used to analyze the influence degree of subsystem.Finally,the spindle system,hydraulic system and pneumatic system are the most significant subsystems.Finally,correlation degradation analysis of subsystem is obtained.The binary model is taken as an example,the correlation degradation of series system is analyzed by Gaussian copula、Clayton copula and frank Copula copula which describes the relationship between the elements and analyzes the reliability and probability density of the binary series model.Monte Carlo(MC)sampling are adopted to simulate the three Copula Functions and Inference Function for Margins(IFM)methods are adopted to estimate,and Akaike Information Criterion(AIC)is used to analyze the effectiveness of Copula functions,which determine the most appropriate degradation model and analyze its reliability changes.The reliability impact analysis of machining center subsystem determines that the hydraulic system is the key to pay attention to the subsystem,and the fault correlation analysis shows that the hydraulic system and the worktable have a high correlation degree.Therefore,taking the series system composed of the hydraulic system and the worktable of the machining center as the research object,the correlation degradation analysis is carried out,and Frank is determined Copula optimal description model,and its reliability is higher than that of independent assumption,which provides a reference for the formulation of system maintenance strategy and avoids excessive maintenance caused by enterprises.