Failure Mode Analysis And Reliability Distribution Research On A Series Of Numerical Control Machining Center

The manufacture level of domestic Machining Center (MC) is low compared to overseas advanced manufacture level, mainly reflecting in low reliability and high failure frequency. Along with the market expansion of domestic MC, domestic factories must enhance the reliability of domestic MC when they compete with overseas brand. In addition, MC breaks down, directly affecting the production efficiency. So, it is important to improve their reliability and reduce the failure frequency for increasing the national prestige, enhancing competitive ability in the international market.The article analyzes a series of MC fault date. According to the actual situation of Machining Center, it will be divided into several subsystems:mechanical transmission system, electrical control system, cutter system, clamping systems, lathe bed the tailstock systems, hydraulic system, cooling system, lubrication system, CNC system and measuring system. Firstly, this paper analyzes the mechanical transmission system. Fitting probability density function and experience distribution function of time in failures. Proposing the hypothesis of obeying the Weibull distribution. Then making linear return analysis by least two multiplication method. Obtaining linear return equation. Again makes linear relevant examination by relevant coefficient method. The linear relevance is remarkable. Using the inspection method to carry on the Weibull distribution fitting supposition examination. Obtains time between failures of the mechanical transmission system to obey the Weibull distribution, and determinates probability density function and distribution function of time between failures. According to the steps of the mechanical transmission system reliability function, find out the reliability functions of other subsystems. Carrying on FMECA (Fault Mode, Effect and Criticality Analysis) analysis to failure datas of the Machining Centers and subsystems from failure mode, failure cause and failure criticality. Discovering the weak parts of the Machining Centers to improve the design.The paper introduces the purposes and rules of reliability distribution, the reliability target as the constraints, in meeting the target under the conditions of reliability, using the fuzzy distribution and calculating reliability target numeral which are assigned to each subsystems.