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Open AccessArticle

In-Process Monitoring of Changing Dynamics of a Thin-Walled Component During Milling Operation by Ball Shooter Excitation

1
MTA-BME Lendület Machine Tool Vibration Research Group, H-1111 Budapest, Hungary
2
Department of Applied Mechanics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
*
Author to whom correspondence should be addressed.
J. Manuf. Mater. Process. 2020, 4(3), 78; https://doi.org/10.3390/jmmp4030078
Received: 12 June 2020 / Revised: 24 July 2020 / Accepted: 27 July 2020 / Published: 3 August 2020
(This article belongs to the Special Issue Machine Tool Dynamics)
During the milling of thin-walled workpieces, the natural frequencies might change radically due to the material removal. To avoid resonant spindle speeds and chatter vibration, a precise knowledge of the instantaneous modal parameters is necessary. Many different numerical methods exist to predict the changes; however, small unmodelled effects can lead to unreliable results. The natural frequencies could be measured by human experts based on modal analysis for an often interrupted process; however, this method is not acceptable during production. We propose an online measurement method with an automatic ball shooter device which can excite a wide frequency range of the flexible workpiece. The method is presented for the case of blade profile machining. The change of the natural frequencies is predicted based on analytical models and finite element simulations. The measurement response for the impulse excitation of the ball shooter device is compared to the results of impulse modal tests performed with a micro hammer. It is shown that the ball shooter is capable of determining even the slight variation of the natural frequencies during the machining process and of distinguishing the slight change caused by different clamping methods. An improved FE model is proposed to include the contact stiffness of the fixture. View Full-Text
Keywords: ball shooter; natural frequencies; milling; thin-walled; in-process; online ball shooter; natural frequencies; milling; thin-walled; in-process; online
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Bachrathy, D.; Kiss, A.K.; Kossa, A.; Berezvai, S.; Hajdu, D.; Stepan, G. In-Process Monitoring of Changing Dynamics of a Thin-Walled Component During Milling Operation by Ball Shooter Excitation. J. Manuf. Mater. Process. 2020, 4, 78.

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