Online Tool Condition Monitoring of CNC Turnings based on Motor Current Signature Analysis

The modulation signal bispectrum (MSB) algorithm is used to analyze the current signal of machine tool spindle motor. Practical cases are analyzed to show that the MSB value can reveal information regarding tool condition. As appropriate descriptors, amplitude and phase of MSBs are introduced to automatically identify tool conditions. Experiments are conducted on a CNC turning center, and the results of the analysis provide evidence for this method. The results demonstrate that the tool wear state can be monitored in the turning process by identifying the amplitude and phase of MSB. An increase in MSB phase value has higher robustness to identify the wear of rough machining tools and can be applied practically.