| "Industrial master machine",also known as CNC machine tool,is the backbone of cutting-edge manufacturing technology.There are more manufacturing operations in China than anywhere else in the world.Moreover,CNC machine tools have the largest market share in China.But at present,the demand for high-end CNC machine tools has long been reliant on imports,and China’s domestic CNC machine tool market is mainly concentrated in the low-end regions.The important reason for this phenomenon is that compared with foreign high-end CNC machine tools,domestic CNC machine tools have a higher failure rate and lower reliability.As you can see,the level of reliability has a direct impact on the market share of CNC machine tools.In order to make domestic CNC machines more competitive in the global market,it is therefore crucial to increase their level of reliability.An essential component of CNC machine tool reliability design is reliability allocation,which is the key technology to make CNC machines more dependable.However,the existing reliability allocation methods have the problem of not considering the subsystem fault correlation and the expert evaluation information is difficult to express accurately.Therefore,this paper takes a model of domestic CNC boring and milling machine tool as the research object,and conducts research on the CNC machine tool’s reliability allocation strategy taking into account the fault correlation and fuzzy evaluation of expert information.The following are the main research topics of this paper:(1)A fault correlation analysis method for CNC machine tool subsystem is proposed.A thorough analysis of the components and functions of the various subsystems of CNC machine tools is carried out to determine their structural composition.Combined with the failure situation of the same type of machine tools and expert experience,the Failure Mode,Effects and Criticality Analysis(FMECA)of CNC machine tools is carried out to clarify the possible failure modes of each subsystem and their effects and propose corresponding improvement and compensation measures.The severity level and probability level of each failure mode in FMECA are converted exponentially to make the evaluation result more reasonable.On the basis of FMECA of CNC machine tools,the failure modes that can make each subsystem interact with each other are clarified,the failure correlation is analyzed,and the failure correlation of subsystems is quantified by combining DEMATEL analysis.(2)For CNC machine tools,a reliability allocation technique that takes failure correlation into account is suggested.The corresponding weight value of each expert is determined according to the qualifications,work experience and domain familiarity of different experts.By incorporating linguistic intuitionistic fuzzy numbers to evaluate each subsystem of CNC machine tools and completing the initial reliability allocation,the evaluation method of the conventional TOPSIS reliability allocation method is enhanced.After this,based on the subsystem interaction fault chain and the subsystem comprehensive influence matrix,the initial reliability allocation result is corrected and the final reliability allocation result is obtained.(3)Creating a software for CNC machine tool reliability allocation.Using this paper’s approach to CNC machine tool reliability allocation,a general industrial software for reliability allocation of CNC machine tools considering fault correlation is developed using Python language and Py Qt framework.The main functions of the software include the analysis of CNC machine tool structure and function,FMECA of CNC machine tool,fault correlation analysis of CNC machine tool subsystem and reliability allocation of CNC machine tool considering fault correlation. |
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