Kinematic analysis and process stability of ultrasonic-assisted drilling

Regarding drilling, ultrasonic-assistance enables various potentials such as less tool wear, enhanced chip breaking and burr reduction. Although there are many technological studies verifying these advantages, no theory for process behaviour, design and parameter evaluation is available. Thus, this paper presents a kinematic analysis of the interaction between tool and workpiece to contribute to overall process understanding. Specific process scenarios are classified and characteristic parameters for the evaluation and design of ultrasonic-assisted drilling are determined. In addition, experimental investigations based on the developed process model are carried out analysing chip shape, bore surface and process stability acquired by acoustic measurements. The kinematic analysis shows the classification of ultrasonic-assisted drilling according to continuous and intermitted cutting conditions. In addition, the superposition of ultrasonic vibrations causes a modulation of uncut chip thickness related to the ratio of ultrasonic frequency and spindle speed. In general, experimental results show that ultrasonic-assisted drilling is leading to shorter chips. While using parameters for intermitted cutting conditions needle chips occur. At the same time, intermitted cutting conditions induce process instabilities identified using the acoustic measurement approach.