Study On Condition Monitoring And Fault Diagnosis Based On Vibration Diagnosis Technology For NC Machine Tools

Equipment fault diagnosis technology has played a key role in protecting the safe operation of equipment, preventing accidents, achieving equipment status maintenance, improving equipment service life, and achieved remarkable economic and social benefits. Vibration diagnosis technology is the most effective and most common means applied in mechanical equipment condition monitoring and fault diagnosis This paper aimed at studying the vibration diagnosis technology in the NC machine tool condition monitoring and fault diagnosis applications. Major research work are as follows:The structural characteristics of NC machine tools are analyzed, the object for monitoring and diagnosis are identified; The determining methods of monitoring parameters, measuring point and direction, test condition and monitoring cycle are researched in the monitoring condition; The vibration criterion of NC machine tools is established based on the regular monitoring; And the state identification and trend analysis of NC machine tools are researched.Commonly vibration signal processing and analysis method is summaried. The vibration signal pre-processing methods include filtering, time-domain synchronous averaging and envelope demodulation method. The vibration signal analysis methods include time domain analysis and frequency domain analysis of two categories: the time-domain analysis includes probabilistic analysis, and extracting the time-domain characteristics of waveform parameters and the non-dimensional dynamic indicators, correlation function analysis; the frequency domain analysis includes spectral analysis, cepstrum analysis, envelope analysis.It is focused on the study of failures of bearings and gears mostly occurred in NC machine tools. It is focused on the study of shock pulse vibration mechanism caused by failure for rolling bearing, the calculation method of rolling bearing fault characteristic frequency, the typical fault vibration time-domain and frequency domain characteristics of roller bearing and for different fault types using different diagnostic methods,And to demonstrate that the envelope demodulation method is the most effective diagnostic method through actual diagnosis of rolling bearing. The vibration fault mechanism of gear is described, by make use of dynamic model, based on analyzing the cyclical changes in gear mesh stiffness; The gear fault characteristics is analyzed the from signal modulation, and the time-domain frequency domain characteristics of vibration of typical faults is specially analyzed; The frequency-domain analysis method is proved to be useful for gear fault diagnosis by the actual diagnosis The typical faults of other studies and examples of successful diagnosis are also introduced, including the main shaft coupling misalignment, mechanical loose and electrical faults.