On-Line Monitoring of End Milling Forces Using a Thin Film Based Wireless Sensor Module

A sensor module that integrates a thin film PVDF piezoelectric strain sensor and a wireless data processing/transmitting platform has been designed and implemented for wireless monitoring of the feed force in the slot end milling process. The module, which is mounted on the tool shank, measures the dynamic strain produced in the tool and transmits data wirelessly to the receiver connected to a data acquisition computer. A first principles model based on the Euler-Bernoulli beam theory and constitutive equations of the piezoelectric sensor material is used to transform the wirelessly obtained data into the feed force acting on the tool in a slot milling operation. The wireless PVDF sensor signal is found to compare well with the expected (or theoretical) sensor signal computed from the measured feed force in slot milling experiments.