Nonlinear characteristic and chip breaking mechanism for an axial low-frequency self-excited vibration drilling robot

Abstract

Drilling is one of the essential material removal methods in the aerospace field. This study proposes a flexible variable-stiffness axial low-frequency self-excited vibration drilling scheme for automatic manufacturing platforms. Firstly, an elastic zone active conversion mechanism of the drilling actuator is established, which could realize robot stiffness control in different directions and the directional tool vibration excitation. Then, the nonlinear characteristic of self-excited vibration excitation and vibration waveform is analyzed under various inherent characteristics and drilling parameters. An interface separation chip breaking condition of dual-frequency self-excited vibration drilling is proposed based on the dynamic equivalent undamped state. Finally, the self-excited vibration drilling state, tool trajectory, chip breaking performance, chip morphology, and action mechanism of parameters coupling characteristics are investigated based on experiment and simulation results. This drilling system could produce stable self-excited vibration and smooth chip breaking without a vibration excitation device.