PVDF sensor-based monitoring of milling torque

A sensor module that incorporates a thin film polyvinylidene fluoride (PVDF) piezoelectric strain sensor rosette as well as data logging and wireless transmitting electronics has been designed and implemented for monitoring dynamic cutting torque in the end milling process—a material removal process widely used in the aerospace industry. The dynamic shear strain produced in the rotating tool during the cutting process is picked up by the PVDF sensor rosette attached to the tool shank and can be either logged into the onboard micro secure digital card or wirelessly transmitted to a nearby base station. The PVDF sensor rosette is largely insensitive to the pyroelectric effect of the PVDF sensor and the other strain components such as bending strain and thermal strain. A physics-based model is used to relate the measured PVDF sensor signal to the dynamic milling torque. The proposed method is experimentally validated using reference milling torque signals computed from cutting force signals measured using a platform-type piezoelectric force dynamometer.