Research And Application Of The Reliability Of CNC Turret Under Small Samples

CNC turret is one of the key functional components of the CNC machine tool,the level of its reliability restricts the reliability of CNC machine tools.At present,the market share of CNC turret is small,and the competitiveness of the company is small.There is a certain gap between the reliability and advanced level of the world.With the gradual improvement of the domestic CNC turret reliability,and the rapid product replacement,the short development cycle,and the small production batches,the failure data becomes scarce.And the traditional reliability research depended on large sample data is difficult to apply.In view of the above problems,this paper studies the reliability of CNC turret under small sample data.The specific research contents are as follows:(1)Bayesian theory was used to model the reliability of CNC turret under small sample data.The CNC turret of model AK36100 A and AK33100 D were defined as target and reference CNC turret.Collect failure data and determine extraction process based on experts judgment.The expert judgment results are converted into prior distribution,therefore the prior distribution of Weibull distribution parameters is established,and the posterior distribution of CNC turret reliability model parameters is calculated on WinBUGS software,thereby the reliability model of the CNC turret was established and the reliability index was evaluated,so that the mean time between failure of the CNC turret was calculated.(2)The reliability modeling method based on regression conversion method,and the reliability information and data of similar machine tool was used to expand small sample data.In order to verify the accuracy of the proposed method,the data that meets weibull distribution model was simulated with the Monte Carlo method,and compared with reliability modeling method based on the Bayes theory,then the applicability of the two methods is discussed.As the result,the applicability of the modeling method based on Bayes theory is stronger,but it relied on the current reliability technology level.And the calculation process of the regression convert method is more simpler.(3)In view of the complexity of CNC turret,the low frequency of failures,and the difficulty of quantitative analysis in the distribution process,a distribution method combined with AHP method,fuzzy comprehensive evaluation,and interval analysis was adopted.Considering many factors of the reliability distribution of CNC turret,the expert opinions are expressed in terms of interval numbers,which the accuracy of expert judgments was improved effectively,and ultimately resulted in the reliability distribution of the various subsystems of the CNC turret.It provides a reference for reliability design improvements.(4)Corresponding reliability measures are proposed for each stage of the life cycle of the CNC turret.At the design stage,preliminary reliability design criteria are established,and at the manufacturing stage,reliability checks are carried out in preparation for production,reliability assurance measures are established for key purchased parts,and reliability management for operations and maintenance is performed during the use phase.As the result,it contributes to reduce the downtime caused by human error and further increase the reliability of CNC turret.