NC Modular Machine Tool Reliability Allocation Based On The Task Profile

The paper is based on the Jilin province science and technology development project----theNC modular machine tool reliability improvement technology for automobile manufacturing，which research on reliability allocation of the NC modular machine tool that mainly processautomobile fan clutch shell.The paper regards a task process that fan clutch shell processed by NC modular machinetool as the research object and the concept of “task” is introduced into the reliability allocation ofthe NC modular machine tool. According to principle of the mata-task group, the meta-task andthe execution unit,the processing task is divided into six aspects, respectively, the mata-task ofcontrolling system, fixture system,power system,auxiliary system,transport system and supportsystem.Then every meta-task is divided into the execution unit, namely modular machine toolsubsystems. Finally, we will establish multitasking profile level model of the fan clutch shellprocessing by the NC modular machine tool.The fuzzy uncertainty factors are quantified by three parameters interval argument and theintroduction of risk priority number. Then we get RPN value and the fault critically analysis ofthe NC modular machine tool. The mean rand order is used to modified the error order of failuredata caused by truncation data; the empirical distribution function is calculated by theapproximate middle rank method；the parameters are estimated via the least square method of Xand Y direction,the parameter estimation is preferred by the mean square error. Then we get thereliability functions in fan clutch shell processed by NC modular machine tool, what’s more, thereliability allocation objective is clear.Taking into the impact of frequent fault, fault hazard, maintainability and technical levelaccount for the task reliability allocation of the NC modular machine tool, we determine theinitial evaluation matrix on the basis of failure, repair information and the structure of machinetool. The paper uses entropy weight method and the least squares method of the right to getobjective and subjective weights of the factors, and then uses maximizing deviation principle todetermine the combination of these four factors’ weights. Then the weight of meta-task andexecution unit in each task will be calculated by a comprehensive evaluation of meta-task andexecution unit. The reliability of NC modular machine tool for task is allocated by proportionalmethod, along with multitasking profile level model of the fan clutch shell processing by the NCmodular machine tool and reliability function. The rationality of reliability allocation resultsconcerning the NC modular machine tool is explained by the comparison between reliabilityallocation and the exact solution of allocation.