USTER
®
HVI SPECTRUM
Instruction Manual
Uster Technologies, Inc. Chapter 6
Configurations • Page 6-17
2.6 USTER® SCI Regression Coefficients
The USTER® Spinning Consistency Index (SCI) is a calculated value
based on multiple regression analyses that compare fiber properties to
yarn properties. Each equation takes into account the
HVI SPECTRUM
properties and calculates one value to be used on each test sample.
The standard equation for SCI is based on many samples that contain a
wide range of fiber properties such as yarn strength, appearance,
elongation, neppiness, and spinning potential yarn numbers. For
example:
Property Range
Length 15/16 - 1 3/8 inches (23.8 - 34.9 mm)
Strength 18 - 36 grams/tex
Micronaire 2.8 - 5.8
Table 6–1: Standard Equation for SCI - Example
These ranges of fiber properties represent more than 90% of the cottons
produced worldwide. This equation can be used on cottons produced
in any growth area in the world. Several research institutes have done
multiple regression analyses and have published results for their specific
varieties of cotton. Currently, the following equation is used for SCI:
Uniformity Index (where UHML and ML in inches are
used)
- 412.7 + 2.9 * Strength - 9.32 * Micronaire + 49.28 * Length
+ 4.80 * Uniformity + 0.65 * Rd
Table 6–2: SCI Equation
Inter-relationships exist among all cotton fiber properties. The SCI
equation uses these similarities to analyze the effect groups of bale
samples may have on yarn spinning consistency.
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