Identification of bearing dynamics under operational conditions for chatter stability prediction in high speed machining operations
Özşahin, Orkun and Budak, Erhan and Özgüven, H. Nevzat (2015) Identification of bearing dynamics under operational conditions for chatter stability prediction in high speed machining operations. Precision Engineering, 42 . pp. 53-65. ISSN 0141-6359 (Print) 1873-2372 (Online)
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Official URL: http://dx.doi.org/10.1016/j.precisioneng.2015.03.010
Chatter is a major problem causing poor surface finish, low material removal rate, machine tool fail-ure, increased tool wear, excessive noise and thus increased cost for machining applications. Chattervibrations can be avoided using stability diagrams for which tool point frequency response function(FRF) must be determined accurately. During cutting operations, due to gyroscopic moments, centrifugalforces and thermal expansions bearing dynamics change resulting in tool point FRF variations. In addi-tion, gyroscopic moments on spindle–holder–tool assembly cause separation of modes in tool point FRFinto backward and forward modes which will lead to variations in tool point FRF. Therefore, for accuratestability predictions of machining operations, effects of operational conditions on machine tool dynamicsshould be considered in calculations. In this study, spindle bearing dynamics are identified for variousspindle rotational speeds and cutting forces. Then, for a real machining center, tool point FRFs underoperating conditions are determined using the identified speed dependent bearing dynamics and themathematical model proposed. Moreover, effects of gyroscopic moments and bearing dynamics varia-tions on tool point FRF are examined separately. Finally, computationally determined tool point FRFsusing revised bearing parameters are verified through chatter tests.
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