Piezo-Actuated Modulation-Assisted Drilling System With Integrated Force Sensing

Abstract

A new electromechanical modulation system designed with piezoelectric stacks for both linear actuation and force sensing functions is described. The system can be adapted for modulation-assisted machining (MAM) drilling processes where a low-frequency (<1000 Hz) sinusoidal oscillation is superimposed directly onto the drilling process, such that the feedrate is modulated. A series of drilling experiments were conducted in Ti6Al4V, 17-4 steel, and Al6061 with the system installed on a CNC machine. The drill displacement, thrust force, and chip morphology were characterized across a range of conventional and MAM drilling conditions. The mechanical response (stiffness) of the system agrees with the design specifications. The system offers new capabilities to control the modulation frequency and amplitude in MAM drilling, while simultaneously measuring the drilling thrust force in real time. The force sensing function enables detection of the intermittent separations between the drill tip and the workpiece surface (occurrence of discrete cutting), providing a method to prescribe and control the modulation conditions necessary for effective MAM drilling. Opportunities for force feedback control and process monitoring in MAM drilling processes are discussed. While the system described emphasizes MAM drilling, the capabilities can be extended to other machining processes.