Actuator and Process Development for Vibration Assisted Turning of Steel

The continuous tool engagement means that turning processes tend to produce long chips when machining ductile materials. These chip forms have a negative impact on the process performance and productivity. A solution approach to improve chip breakage is the aimed superposition of the turning process with vibrations in the feed direction, which leads to a cyclical change in undeformed chip thickness. In this way, predetermined breaking points are implemented in the evolving chip, which improve chip breaking. In a joint industrial project with Schaeffler Technologies AG&Co.KG, the Fraunhofer IWU developed an oscillating actuator for internal turning that converts a rotational movement of a drive motor into a translational movement via an eccentric gear with connecting rod. Therefor the tool shank is supported in solid joint packages, which have a low stiffness in the oscillation direction and a high stiffness perpendicular to it. With this prototypical system a cyclic movement of the tool in feed direction can be realized. The typical operation parameters of the actuator are low-frequency range from 1-100 Hz with adjustable oscillation amplitudes up to 0.6 mm peak-peak. For this purpose, technological process models were developed and verified by means of practical machining tests. A significant improvement in chip breakage during the machining of different steel materials could be shown in the experiment.