Air-Drill With Accelerometer And Microphone For Composite Drilling Application
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Date
2022-07-15
Authors
Koh, Wei Tong
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Impaired dimensional accuracy and assembly tolerance due to tool wear could leads to
serious problem such as part dismissals in substantial amount on the structure of
aircraft. To make sure that drilled holes in composite materials are of good quality
from various aspects, current practice in the industries was the disposal of the drill bits
after it is being used for a predetermined number of cycles. However, this leads to
wastage of some of the expensive drill bit which can still produce holes without
delamination even though it has been used for predetermined number of cycles. To
monitor the tools condition, researchers have conduct various experiment to correlate
tool wear with process variables such as cutting force, thrust force, vibrations, spindle
current, acoustic emission etc. In this research, the effect of sharpness of drill bits on
vibrations of air drill, sound produced during drilling and quality of holes produced
will be studied. In this experiment, 3 accelerometers have been attached on locations
near the spindle, at the middle and near the handle of air drill to measure the
vibrations of the air drill. Microphone was placed about 1 meter away from the jig and
the sounds produced during drilling process were collected. The vibrations of air drill
and sound produced during drilling with different conditions of drill bit are analysed
and compared. The result shows that vibrations measured by accelerometer placed
nearest to the spindle are most sensitive to change in condition of drill bit. For CFRP
plate, maximum amplitude of air drill vibration increases with condition of air drill in
order: sharp, no drill bit, blunt, and chipped off. For GFRP plate, maximum amplitude
of air drill vibration increases with condition of air drill in order: no drill bit, blunt,
chipped off and sharp. Other than that, the fast Fourier Transform of the vibration
signals from this accelerometer shows that there was a unique set of frequencies with
significant peaks with different conditions of drill bits.