Research On Reliability Test Technology Of Horizontal Machining Centers

With the rapid development of science and the rising of domestic industrialstructure, the demand of NC machine tools in China turned to high-endproducts.Horizontal Machining Tool Center is the biggest concern with highesttechnical content. Due to the big disparity in terms of reliability between domestic andforeign products, a large number of imported machining centers are needed inChina,and this restricts the development of manufacturing industry and national defenseindustry in China. It is the priority to improve the reliability of machining tool center tothe develope the equipment manufacturing industry.This paper is supported by the National Major Scientific and Technological SpecialProject for “High-grade CNC and Basic Manufacturing Equipment”(No.2012ZX04011-031). This paper studied on a certain series domestic horizontalmachining tool center,and several basic theories and key technologies of reliability testare studied. It provides theoretical support and technical preparation for theestablishment of reliability test specification of machining centers and enriched thecontent of reliability test technology.The main work and contribution of this paper is as follow:①The Analysis the Failure Mechanisms of Horizontal Machining Tool Center.Through the collection and analyses of filed failure data of domestic machiningtool centers, the fault spectrum of the whole machine were obtained.Through the studyof the structure of subsystem with high failure rate, the environment stresses of eachfunction group were known,and then the detection of failure mechanism of somecommon failure of NC rotary table was performed qualitatively.At last,the quantitativeanalysis of the bolt looseness and hydraulic cylinder leakage fault were carried out,andthe mathematical models were obtained.It was a thought to do the failure mechanismanalysis of machining center broadly and in-depth.②Comprehensive Evaluation and Value Analysis of Objects of ReliabilityGrowth Test of Horizontal Machining Tool Center.At first the evaluation of defects, considering the interrelations between failures,was obtained, using the House of reliability method, which is a combine of FMECA andQFD.Then the evaluation scores,probability of failure,and ratio of improvement ofdefects were used to calculate the function ratio of the reliability growth testing of machining centers.At last,the costs and worth analysis of each reliability growth testwere represented following Tanaka’s approach.③Research on Method to Select Accelerated Stresses in Accelerated ReliabilityGrowth Test of Horizontal Machining Tool CenterThe concept of failure characteristic attribute was given and used to present a faultto find the relationship between failures and failure stresses without knowledge offailure mechanism.Fuzzy comprehensive evaluation method was used to get thejudgment of failure stresses and then the problem of selection of accelerated stressessolved.④Reliability Evaluation of Horizontal Machining Tool Center Based onCompeting Weibull model.To evaluate the reliability of machining centers using competing weibull model,theconcept of failure information sequence was given and the fuzzy clustering algorithmwas used to get the classification of the failure data according to different failuremechanism.Bootstrap and improved Bootstrap based on gray prediction algorithm wereused to get the parameter estimations of weibull model. The using of competing weibullmodel and the classification of failure data were kind of trying in reliability testassessment of machining centers.