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Abstract:
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Defects which exist in card sliver have been shown to
result in yarn defects which are costly to yarn and fabric
producers. Currently, monitoring card sliver for defects
is a labor intensive process which interferes with product
flow and provides information only on a small percentage o f
actual card production. An on-line method of
monitoring sliver quality would provide opportunities to
improve yarn quality and the effective management of the
carding process.
Recent advancements in computer and sensor technology
have made the development of an on-line test method for the
detection of sliver defects possible. The Qualteq Acoustic
Sensor is a newly developed sensor which determines sliver
weight by measuring the noise created as sliver passes
through the trumpet at carding and drawing. Information
provided from this sensor is currently being used to
determine sliver weight, weight variability, detect periodic
defects, and calculate machine efficiency at the carding and
drawing processes.
The Acoustic Sensor has several advantages over sensors
currently being used to measure sliver weight on-line.
These advantages include the lack of moving parts,
the ability to withstand harsh production environments, and the passive which it employs to measure sliver weight. It
is also easily retrofitted to production equipment. It
produces an signal which is extremely sensitive to changes
in sliver weight and easily converted into usable
information.
It was the purpose of this thesis to determine if the
Qualteq Acoustic Sensor could also be used to detect u l trashort
term defects in card sliver on a real-time basis . The
defects under investigation included slub type defects which
are usually under 2 centimeters in length and coarse trash .
Both of these defects have been shown to adversely effect
yarn quality.
Sliver defects are abrupt increases in sliver density
which exist in sliver. Most sliver slubs originate at the
carding processes as a result of improper operating
conditions. The Acoustic Sensor was capable of detecting
slub type defects in card sliver which were greater then
115% of normal sliver weight. The sensor was also capable
of providing information on both the density and length of
the defect. A direct correlation existed between slub
levels recognized by the ITT SLiver Analyzer and the
Acoustic Sensor. Results from the coarse trash trial have shown the
Acoustic Sensor to be an excellent tool in determining trash
levels in card sliver, which is an indication of a
mechanical condition. The ability to monitor trash levels
exiting individual cards twenty-four hours a day, seven days
a week, will provide valuable insight into the wear patterns
of card wire and other vital card components.
Cards which were determined to be high in sliver
defects by the Acoustic Sensor produced yarns which were of
inferior quality to yarn produced exclusively of quality
sliver. The major effects on both ring spun and open-end
spun yarn were on breaking strength and Classimat defect
levels.
Once fully developed this application of the Acoustic
Sensor will provide yarn manufacturers with vital quality
assurance information on every inch of card sliver produced.
Thus allowing for the isolation of individual cards
producing off-quality sliver which adversely affects yarn
and fabric properties.
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