Mechanical Fault Root Cause Tracing Of CNC Lathe Based On Information Transmission

Under the background of "intelligent manufacturing",CNC machine tools are the main equipment for manufacturing and its reliability affects the development of modern production in China.The structure coupling relationship of CNC machine tools create conditions for fault propagation,and also increase the difficulty of fault identification and tracking.At present,although the mechanical structure of modern CNC machine tools has been simplified,the effect of the stress leads to the multi-layer propagation of fault in the actual process of processing.The manpower,material resources and financial resources spent on the location of fault source cannot be ignored.Therefore,it is of great significance for improving the reliability of CNC machine tools,enhancing the core competitiveness of domestic CNC machine tools and realizing intelligent manufacturing to monitor the machining status of CNC machine tools in real time and find,track and repair the faults in time.Firstly,the CNC lathe is simplified and separated by analyzing kinematic correlation of the mechanical components and the action fault mechanism.Considering the propagation of mechanical fault,the mechanical fault graph model of CNC lathe was established based on graph theory method to simplify and clarify the subsequent fault tracking process.Secondly,according to the performance and parameters,the sensors whose precision meet the measurement requirements are selected to collect the machining information of the CNC lathe's mechanical unit.In order to reduce the interference of Gaussian white noise,the optimal wavelet base and the number of decomposed layers are determined by simulation and comparison.The signal noise of CNC lathe is reduced based on wavelet transform.In order to reduce the dynamic noise and improve the operational efficiency,the multi-objective optimization method based on Shannon entropy is used to determine the optimal symbol number.Finally,based on the first-order Markov process hypothesis,the improved C-C method is applied to determine the predicted time delay.Based on the symbolized processing signal of CNC lathe,the symbolic transfer entropy is calculated between variables to quantitatively describe the intensity and direction of information transfer.Combining with mechanical fault graph model of the CNC lathe established,the weighted-directed graph of CNC lathe's mechanical fault propagation is established.Considering the function of feedback mechanism,the upper and lower limits of control interval are determined based on the sliding window method.The key paths of fault propagation are monitored to identify the fault in time.Based on the weighted-directed graph model of feedback mechanism,the root cause of mechanical fault of CNC lathe is traced and identified.The feasibility and credibility of the method are verified by fault excitation experiments on CNC lathe.