A novel variable-dimensional vibration-assisted actuator for drilling CFRP

Comparing to the conventional drilling (CD), vibration-assisted drilling (VAD) is a novel machining technique suitable for drilling in hard-to-machine materials such as carbon fiber-reinforced polymer (CFRP). However, the current VAD apparatuses are limit in the following vibration modes: one-dimensional longitude vibration and two-dimensional elliptic vibration, which both have the flaws for drilling in CFRP. In order to improve the VAD’s performance in the CFRP drilling, a novel variable-dimensional vibration-assisted drilling (VDVA) actuator is proposed, which can produce one-dimensional longitude vibration, two-dimensional elliptic vibration, and three-dimensional composite vibration, to adapt different machining phase in drilling FRP. One-dimensional longitude, three-dimensional composite, and two-dimensional elliptic vibration can be used in the entrance, middle, and export separately, which can improve drilling precision, chip capacity, and aperture accuracy and reduce the delamination and burr phenomena. Firstly, based on process requirements of drilling FRP, an actuator design method including piezoelectric transducer and horn design is proposed to establish the actuator model, which can be used to generate variable-dimensional vibration. Then, the system control for the proposed actuator is designed to output different vibration mode in actual drilling process. The resonant frequency and amplification ratios of the proposed actuator are analyzed by using FEA software. Based on the above analysis results, a prototype of the proposed actuator is fabricated, and then its vibration characteristics are evaluated by a micro-displacement sensor. With different phase sinusoidal driving voltages at different frequency of 20.7 and 5.8 kHz, the developed prototype achieved variable-dimensional vibration with one-dimensional longitude vibration of amplitude 11.0 μm, two-dimensional elliptic vibration of amplitudes 13.0 and 12.0 μm, and three-dimensional composite vibration of amplitudes 7.0, 10.8, and 12.1 μm. The experiments indicate that the performance of the developed actuator is satisfied, and the proposed actuator can be applied in composite material drilling process to improve the machining performance of composite material.