Ultrasonic assistance to reduce and monitor tool wear in deep drilling

In deep drilling, the large aspect ratio of hole depth to diameter causes problems in terms of chip formation and removal as well as tool vibrations. In addition, tool wear leads to a deterioration of process properties and decreasing process reliability. Therefore, scientific approaches aim to improve productivity and quality via a reduction of tool wear. Furthermore, methods for monitoring process conditions, specifically known as tool condition monitoring, contribute to an increase in performance. Superimposing ultrasonic vibrations to the conventional process is known as an approach with various potentials like reduced tool wear and burr formation or enhanced chip breaking behaviour. Aiming to realize in-process measurements to identify tool conditions, ultrasonic assistance enables the application of new monitoring techniques. In this context, the paper introduces a new approach to monitor tool wear using characteristic values of the resonant ultrasonic system coupled with the machining process. Experimental investigations considering deep drilling in steel 1.2311 show prove of the positive influence of ultrasonic assistance on the progress of tool wear. Furthermore, in-process measurements demonstrate that the new approach is able to monitor tool wear.