Reliability Allocation Of CNC Lathe And Comprehensive Failure Analysis Based On The Failure Information

At present,there still exists a big gap between the domestic CNC lathes and the foreign advanced machine tools when comes to the comprehensive performance and reliability level of CNC lathe.Thus,improving the high reliability turns into the priority of domestic CNC research team and Lathe manufacturing enterprises.As an equipment of complex mechanical and electrical system,the CNC lathe is generally made up by the basic system.The reliability of the lathe machine depends on the reliability of each subsystem,and the reliability of the subsystem level is determined by the assigned reliability index,so the scientific and rational reliability allocation for subsystems' reliability index is particularly important.On the basis of failure information,this paper put forward a set of fuzzy reliability allocation method based on failure information and the supporting software,and the failure mode and causes were analyzed in detail.This paper introduced the reliability database building process and reliability modeling theory.According to the E type CNC lathe failure information,the reliability database was established.Two kinds of modeling method based on the failure information were put forward including a modeling method based on Maximum Likelihood Estimation method and a modeling method based on the Edgeworth series method.It was easy to complete the E type CNC lathe machine and its subsystem's reliability function modeling using the first method.On the basis of the reliability of CNC lathe model,four kinds of influence factors were considered on the basis of the use of entropy method,respectively including failure number,failure stopping time,complexity of subsystem and reliability of the effect.Then,based on the fuzzy mathematics theory and Allns allocation method,a new kind of reliability allocation considering various factors was put forward whose reliability index was more scientific and reasonable.In addition,a software for CNC lathe reliability allocation based on GUI function was developed which was based on the failure information rather then relying on subjective factors such as expert evaluation,making the allocation process simpler and more objective relatively.Through a quick sort of the E type CNC lathe failure database,the machine failure positions,failure modes and failure causes were statisticaly analyzed separately.Through frequency graph,the high frequency of failure positions,failure modes and failure causes can be found out easily.To the higher frequency of failure subsystem,the mode and causes of the failure were further analyzed.At last,several reasonable suggestions and measures was put forward in view of the frequent failures.