A Piezo Tool Actuator for Precision Turning of Hardened Shafts

A piezo actuator based fast tool servo is presented for precision turning of cylindrical shafts. The monolithic actuator housing transmits motion to the tool assembly using solid flexures. The actuator has a stroke of 36 μm, 3200 Hz natural frequency, and 370 N/μm stiffness. Two sets of additional piezo actuators are placed in the transverse direction to clamp the tool for increased stiffness during hard turning operations. A sliding mode controller rejects cutting forces and compensates the piezo stack nonlinearities. The tool position is controlled to within 10 nm during finish hard turning on a conventional CNC lathe.