Load cell for dynamic measurement of cutting forces generated during ultrasonic drilling and milling of hard materials

In this work, a novel design of load cell for the measurement of the dynamic forces generated during ultrasonic drilling and milling of hard materials is presented. The transducer, which allows for simultaneous sensing of three components of force, has been designed to minimize the influence of cross-coupling between the components acting in the three perpendicular directions and to measure low levels of force (typically a few tens of Newtons in magnitude) while retaining high mechanical stiffness. This is achieved by utilizing a membrane element for vertical measurement coupled with a multi-beam arrangement for the horizontal axes. The results from static and dynamic analyses of the proposed design conducted using analytical expressions for the membrane and finite element methods for the beam structures are presented. The paper also describes the associated instrumentation set-up, calibration and some example experimental results.