F. Kahleyss, T. Surmann, C. Machai, Technische Universitaet Dortmund, Dortmund, Germany; R. Lima de Miranda, C. Zamponi, E. Quandt, University of Kiel, Kiel, Germany; D. Biermann, Technische Universität Dortmund, Dortmund, Germany
Nowadays, many manufacturing processes require the machining of complex forms with a high aspect ratio or cavities. Tools with a long overhang length are a common method to meet these requirements. Typical examples for this are boring bars for bore-turning and the milling with very long cutters. These tools tend to vibrate strongly due to their slender shape. The stress-induced transformation of austenite to martensite and the distinctive hysteresis loop allow the NiTi shape memory alloys (SMA) to absorb vibration energy. This paper describes the innovative approach to dampen process vibrations by coating the tool shafts of cutting tools with long overhang with NiTi thin films. It explores how these thin films can be applied on polished tungsten carbide shafts and how their modal parameters are modified by these coatings. In a further step, this knowledge is used to calculate stability charts of corresponding machining processes. The work reported in this paper identified the stabilizing effects of coatings with a thickness of 2-4 µm on milling processes. The minimum stability limit was increased by up to 200 %.
Summary: This paper describes the innovative approach to dampen process vibrations in machining processes by coating the tool shafts of cutting tools with long overhang with NiTi thin films. A modal analysis of the tool shafts enables the simulation of stability charts. These show an improved process stability of coated tools.
