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Zatarain M.,Ideko 4 Technological Center | Bediaga I.,Ideko 4 Technological Center | Munoa J.,Ideko 4 Technological Center | Insperger T.,Budapest University of Technology and Economics
International Journal of Advanced Manufacturing Technology | Year: 2010

The concept of directional factor for chatter stability analysis has been used from a long time ago. The analysis of its evolution for different feed directions in milling processes provides a good way of selecting the best cutting conditions. For very stable cutting directions, corresponding to very low directional factors, the single frequency analysis gives unacceptable results and multi-frequency, or alternative solutions as semi-discretisation must be used. It is found also that the period doubling lobes extend at both sides of the tooth pass frequency equivalent to twice the natural frequency. In these cases, helix angle has a very important effect on the stability. For end milling processes, where the mill axial pitch can be of the order of the stable limit depth of cut, a very stable situation is found except in those areas corresponding to period doubling, where instability islands are found. Besides, a graphical construction for accurate estimation of the stable limit depth of cut and starting rotational speed of the period doubling lobes is proposed. © Springer-Verlag London Limited 2009.

Munoa J.,Ideko 4 Technological Center | Dombovari Z.,Budapest University of Technology and Economics | Mancisidor I.,Ideko 4 Technological Center | Yang Y.,Beihang University | Zatarain M.,Ideko 4 Technological Center
Machining Science and Technology | Year: 2013

The productivity of many industrial cutting processes is limited by high amplitude chatter vibrations. An optimization technique based on the use of the stability lobes helps to increase the productivity of these processes, improving the life of machine elements and reducing the tool wear as well. The best-known lobes correspond to Hopf bifurcations. However, in case of interrupted cutting, additional lobes appear due to period doubling or flip bifurcation. When the system has more than one dominant vibration mode, important variations can appear in stability due to interaction between modes. The basic mathematics for the appearance of these new lobes are shown in this article. The frequency domain study shows that lobes related to flip bifurcation are a special case of the interaction between modes. The results of these interactions are verified by comparison with semi-discretization method and time domain simulations, respectively. Copyright © 2013 Taylor & Francis Group, LLC.

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