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Abstract:
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A method currently being used to define yarn evenness
is a Uniformity Index (also known as an Irregularity
Index). This can be defined as the ratio between the
actual, measured %CV of the yarn to the ideal %CV.
Past research has determined the Ideal CV to be
100/JN, N being the number of fibers possible of fitting
into a given cross-section. However the ideal CV formula
only considers denier as having an effect on yarn evenness,
not including any effect of staple length.
For this work eight specifications of fiber were spun;
two deniers and four staple lengths on an open-end, air-jet
and ring spinning frame. Once the yarn was spun,
statistical regression equations were generated to
determine how much of an effect staple length had on actual
yarn Uster %CV.
The regression equations relating changes in Uster %CV
to changes in denier and staple length showed a strong
indication that staple length does have an effect on yarn
evenness in two of the three spinning systems. As fiber
length was increased from 1.0" to 2.0", ring spun yarn became more even. A parabolic shaped curve best represents
the effect of length on open-end yarn evenness. Yarns spun
with 1.0" and 2.0" fibers are significantly less even than
yarns spun with 1.25" and 1.5" fiber lengths. Uster %CV of
air-jet spun yarns was not influenced by changes in fiber
length in this work.
Therefore, the Ideal %CV calculation of 100/jN may need
modification to include a factor of staple length that more
fairly represents the practical ideal yarn evenness
capability.
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