Tool Wear Monitoring in CNC Milling Process Based on Vibration Signals from an On-Rotor Sensing Method

A three-axis vibration wireless on-rotor sensing (ORS) was developed for milling tool wear condition monitoring. It is designed with a novel inclination fixture allowing vibration in different directions: axial, transverse and rotation to be perceived by one sensor. The sensing system could be mounted on the cutter arbor and rotate in sync with the spindle. Due to this innovative design and mounting position, the vibration signal obtained by this ORS showed a higher SNR than that of commercial accelerometers fixed on the spindle holder and the workpiece. After analyses of the waveform in the time domain, six different characteristics viz. Absolute Mean, Root Mean Square, Standard Variance, Pulse Factor, Skewness, and Kurtosis were calculated and extracted for tool wear stages recognition. The comparison results proved that the vibration signal acquired from the ORS was more effective and sensitive. Finally, different tool wear progression stages could be best monitored and recognized by the sensor output of the combination between axial and transverse responses.