Research On Reliability Growth And Reliability Evaluation Of CNC System

CNC system is the nerve center of CNC machine tools. Improving the reliability of CNC system is important to improve the reliability level of CNC machine tools. Effort to develop numerical control technology, which is the core of advanced manufacturing technology, has become an important way to accelerate economic development and enhance the comprehensive national strength. Thus increasing awareness of reliability, analyzing reliability status of CNC, developing and applying the efficient and practical technologies of reliability growth, have become the key to the development of CNC system.The thesis is one part of sub-project of major project on national science and technology "Research on Reliability Design and Reliability Growth of CNC". Through FMECA and FTA analysis, the weaknesses of CNC system are found, the reliability growth model is established, the reliability growth technology to enhance the reliability level of domestic CNC system is implemented, and the index evaluation of reliability of CNC system is evaluated.First, research on running CNC system, the failure data is obtained, the collection procedures and requirements is established, the criterions of the fault location, mode and cause are established, the software about the reliability information management is programmed.Through analysis of failure data, the frequent failure parts of CNC system, such as electrical systems, PLC unit and pre-processing module, the frequency of failure modes, such as the of damaged components, line or cable connection bad, the frequent failure cause, such as component damage,are found. Critical analysis about the subsystems of CNC system is done. The weaknesses are found and improving measures on reliability design are proposed. Based on the detailed analysis of failure data, the FTA framework about CNC system is established.The techniques about reliability growth are implemented. First, base on reliability design analysis of CNC system, the reliability design checklist and robust design of CNC system are proposed. Second, manufacturing technology on the power supply, components and circuit board are improved, while acceptance technology on purchased parts is improved. Third, eliminate early failures. Reliability growth test is designed and reliability growth model based on month failure rate of AMSAA is made.In this paper, based on the failure data, index evaluation of CNC system such as failure rates, MTBF, MTTFF, MTTR, and availability analysis are calculated, and reliability evaluation about domestic CNC system is made. A new index evaluation about CNC system, which is MFOP, is proposed. Some problems in reliability evaluation are pointed out and suggestions on the improvement are given.