Performance of an ultrasonic-assisted drilling module

The ultrasonic-assisted drilling (UAD) process is a technology which applies high frequency vibrations (> 20 kHz) at amplitudes of 2-20 mu m in the feed direction to the drill tip in order to improve machining conditions and productivity. Past work in this field is reviewed, noting the valuable foundation provided by laboratory-based research systems. This work is aimed at the development of a robust UAD module, fully compatible with computer numerical control (CNC) systems, and able to function in a production environment, describing results of drilling tests on 4340 steel. The UAD module, designed using FEA methods, with a 16-mm carbide drill, attached by shrink fit, is used to study the effects of ultrasonics on thrust force, torque, surface quality, hole size, and the microstructure of drilled 4340 steel. In order to provide a better understanding of the performance of this module, two different test scenarios were designed and the results for each were compared with the results obtained from baseline settings for conventional drilling. The results show that ultrasonic vibrations not only can reduce the average values of thrust force and torque but also can improve the surface quality of the hole. It is also found that a major increase in productivity could be achieved by using ultrasonic vibrations. Finally, the effects of ultrasonic vibrations on hardness and microstructure of the drilled hole is assessed and the results show that high frequency vibrations do not have significant effect on dimensional accuracy or on the microstructure of the drilled holes.