Control of deviations and prediction of surface roughness from micro machining of THz waveguides using acoustic emission signals

James M. Griffin, F. Diaz, E. Geerling, M. Clasing, V. Ponce, C. Taylor, S. Turner, E. A. Michael, F. P. Mena, L. Bronfman

    Research output: Contribution to journalArticlepeer-review

    30 Citations (Scopus)
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    Abstract

    By using acoustic emission (AE) it is possible to control deviations and surface quality during micro milling operations. The method of micro milling is used to manufacture a submillimetre waveguide where micro machining is employed to achieve the required superior finish and geometrical tolerances. Submillimetre waveguide technology is used in deep space signal retrieval where highest detection efficiencies are needed and therefore every possible signal loss in the receiver has to be avoided and stringent tolerances achieved. With a sub-standard surface finish the signals travelling along the waveguides dissipate away faster than with perfect surfaces where the residual roughness becomes comparable with the electromagnetic skin depth. Therefore, the higher the radio frequency the more critical this becomes. The method of time-frequency analysis (STFT) is used to transfer raw AE into more meaningful salient signal features (SF). This information was then correlated against the measured geometrical deviations and, the onset of catastrophic tool wear. Such deviations can be offset from different AE signals (different deviations from subsequent tests) and feedback for a final spring cut ensuring the geometrical accuracies are met. Geometrical differences can impact on the required transfer of AE signals (change in cut off frequencies and diminished SNR at the interface) and therefore errors have to be minimised to within 1 µm. Rules based on both Classification and Regression Trees (CART) and Neural Networks (NN) were used to implement a simulation displaying how such a control regime could be used as a real time controller, be it corrective measures (via spring cuts) over several initial machining passes or, with a micron cut introducing a level plain measure for allowing setup corrective measures (similar to a spirit level).
    Original languageEnglish
    Pages (from-to)1020-1034
    Number of pages14
    JournalMechanical Systems and Signal Processing
    Volume85
    Early online date3 Nov 2016
    DOIs
    Publication statusPublished - 15 Feb 2017

    Bibliographical note

    NOTICE: this is the author’s version of a work that was accepted for publication in Mechanical Systems and Signal Processing. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Mechanical Systems and Signal Processing, [85, (2017)] DOI: 10.1016/j.ymssp.2016.09.016

    © 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

    Keywords

    • Acoustic emission
    • Precision manufacturing
    • Surface finish
    • Precision control
    • Submillimetre waveguide manufacturing
    • CART
    • Neural networks and simulations

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