Machining of high-performance materials with ultrasonically modulated cutting speed

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In order to meet the constantly increasing requirements with regard to lightweight design and energy efficiency, difficult-to-machine materials such as hard metals, ceramics and fiber-reinforced plastics are gaining in importance. Considering conventional machining processes, these materials can only be machined with high tool wear. Ultrasonic-assisted machining has proved to be suitable to successfully address this issue.In the case of ultrasonically assisted machining, an additional high-frequency oscillation is superimposed on the kinematics of the conventional machining process. This generates oscillations on the tool cutting edge in the region of a few micrometers, thereby causing a high-frequency change in the cutting speed or the feed. Consequently, a reduction in cutting forces, an increase in the tool life as well as an improvement in workpiece quality can be achieved. In milling and grinding it has been shown that these effects are already partially present in the case of a vibration excitation in the axial direction relative to the workpiece, that is perpendicular to the cutting direction. Further improvements of the process results can be achieved by superimposing a vibration in the cutting direction and thus modifying the cutting speed at high frequency.Therefore, the aim of the research project is to provide a basis for vibration-assisted milling and grinding with ultrasonically modulated cutting speed. For this purpose, an ultrasonic actuator is constructed, with which both the milling and the grinding tool can be superimposed with a longitudinal-torsional-ultrasonic vibration. Subsequently, fundamental investigations are carried out for vibration-assisted milling and grinding.During milling, the hard-to-machine titanium Ti-6Al-4V alloy will be machined. The influence of conventional process parameters (speed, feed rate, cutting depth and tool geometry) and oscillation parameters (frequency and amplitude) are evaluated. In doing so, the occurring effects are analyzed aiming at minimizing tool wear and increasing the workpiece quality. At the same time, basic investigations are carried out for the grinding of hard-brittle materials with an ultrasonically modulated cutting speed, in which the interactions between conventional and vibration parameters (amplitude and frequency) are also studied.The milling experiments are carried out on an Ultrasonic linear 40 machine tool, which was provided by the DFG for fundamental studies particularly on vibration-assisted machining.