Study On Technlogy For Reliability Allocation Of CNC Lathe Based On Correlation

Numerical control technology and equipment is the enabling technology and basic equipment to the development of new high-tech industry and advanced industrial. The reliability level reflects the strategic position and overall national strength. The reliability allocation is an important part in the stage of reliability design as well as the powerful security of inherent reliability of products. The high level and complexity of CNC equipment decide the necessity and urgency to realize the reliability allocation reasonably and effectively.This paper researches a certain series of CNC lathe. First, Collect field failure information and identify subsystems of CNC lathe according to characteristics and working process. Then introduce the relevant theory into the reliability allocation area, including structure correlation, fault correlation and maintainability index correlation. Carry on reliability allocation of CNC lathe through reliability modeling, reliability influence index calculation, and failure analysis and maintenance evaluation.This paper establishes the criteria of reliability allocation including the reliability influence between subsystem and system, the influence among subsystems, maintenance, complexity, manufacturing technology, working conditions and the cost. Conduct reliability allocation from these seven aspects. First, establish the reliability functions of system and subsystems by Minitab, then propose reliability influence theory and establish reliability static influence, reliability dynamic influence and reliability dynamic core influence based on the structure correlation between the subsystem and system to quantify the reliability influence of subsystems. And calculate the weight of each reliability influence index by Entropy method, afterwards calculate the comprehensive influences of reliability of subsystems. Second, analyze failure mechanism of CNC lathe to identity relevant failure, then to establish matrix and combine failure frequency information of subsystems to build the influence model among subsystems. Besides, rank the influence among subsystems in the case of relevant failure. Third, analyze maintainability of subsystems. Determine the maintainability index and analyze the correlation among these indexes and formulate maintenance index factors'quantitative criteria. Then adopt the causal graph theory to build maintenance evaluation model based on correlation. Through the maintenance correlation matrix and Permanent function to calculate each subsystem's maintenance comprehensive index. Fourth, analyze other impact factors to reliability allocation, including complexity, manufacturing technology, working conditions and cost. Then calculate the latter three factors with the experts' knowledge and experience in this research area. Afterwards, using TOPSIS method to rank these subsystems, and calculate the weight of each index through Entropy. Take the results as the foundation of reliability allocation. Besides, introduce Copula function to establish reliability allocation model of CNC lathe. Then use Matlab to achieve the reliability range and MTBF range of each subsystem to realize the reliability allocation task of CNC lathe.