F. Kahleyss, K. Weinert, University of Dortmund, Dortmund, Germany; D. Biermann, Technische Universität Dortmund, Dortmund, Germany
Many modern production processes require the manufacturing of deep pockets or other complicated geometric forms which need to be machined with long overhanging tools. Typical examples for this are boring bars for internal longitudinal turning or milling with very long cutters. The tools tend to vibrate strongly at the cutting edge due to their slender and thus flexible shape in both cases. A conventional approach to dampen these vibrations would be either to integrate damping materials into the tool holder in order to absorb the existing vibrations or, to increase the stiffness of the machining system to increase its Eigen frequencies. The special properties of super-elastic and pseudo-plastic NiTi shape memory alloys allow combining these two approaches to improve the vibration properties of the tool-spindle-system at the same time. The stress-induced transformation of austenite to martensite and the distinctive hysteresis loop allow the NiTi to absorb vibration energy, while having considerable stiffness. This paper describes the damping properties of NiTi when exposed to high frequency vibrations. In a further step, this knowledge will be applied to a high speed milling process. Special damping elements were used to reduce the vibrations at the tool head and thus to increase the machining quality and to reduce the tool wear.
Summary: In machining processes long overhanging tools are subject to high vibration at the cutting edge due to their slender and thus flexible shape. In this work the effects of NiTi damping elements on an internal longitudinal turning process will be analysed.
