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

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...

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Bibliographic Details
Published in:Journal of Manufacturing and Materials Processing 2020-09, Vol.4 (3), p.78
Main Authors: Bachrathy, Daniel, Kiss, Adam K., Kossa, Attila, Berezvai, Szabolcs, Hajdu, David, Stepan, Gabor
Format: Article
Language:English
Subjects:
ball shooter
Chatter
Computer simulation
Excitation
Finite element method
Frequency ranges
Geometry
in-process
Investigations
Mathematical models
Methods
milling
Milling (machining)
Milling (Metals)
Modal analysis
natural frequencies
Numerical methods
online
Productivity
Resonant frequencies
Stiffness
thin-walled
Vibration
Vibration control
Workpieces
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Summary: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.
ISSN:2504-4494
2504-4494
DOI:10.3390/jmmp4030078