On-line tool wear monitoring during ultrasonic machining using tool resonance frequency

Ultrasonic machining is effective for materials of extreme hardness, although the tool also experiences wear, causing a reduction of machining efficiency. The present work proposes a new method of monitoring tool wear during ultrasonic machining. Theoretical analysis as well as experimental measurements are presented. Both results show a strong correlation between the tool length and the resonance frequency of the ultrasonic system, this observation leading to the concept of tool wear monitoring by resonance frequency. The resolution of monitoring is sufficiently high, viz. down to tens of micrometers in tool length. The machining process can be on-line monitored and stopped for tool change based on a pre-set tool-length limit.