Cotton Fiber Length Distribution Metrics and Carded Yarn Quality
AFIS short fiber content by weight in raw cotton must remain below 8.5 percent to prevent severe mass variance and tenacity drop in carded yarn spinning.
Fiber Span Length
Dimension Profile
The distance spanned by a specific percentage of fibers in a sample, as measured by a photo-electric instrument from a randomly aligned start line, represents the physical length distribution of a cotton batch. Spinning mills rely on fiber span length to set the distances between drafting rollers on drawframes and ring frames. This measurement does not evaluate the width of the fibers.
Roller Calibration
Drafting rollers must be spaced slightly further apart than the longest fibers to prevent fiber breakage during drafting. Measuring the fiber span length allows technicians to adjust these roller settings accurately. This optimization prevents yarn defects and machine stoppages.
Measurement Metrics
Two common metrics are the two and a half percent and fifty percent span lengths. The two and a half percent fiber span length indicates the length exceeded by the longest fibers in the sample, which corresponds closely to classer stapling. In contrast, the fifty percent value indicates the average length of the fiber population.
By analyzing both values, a spinner can calculate the uniformity ratio of the cotton.
Quality Assurance
Raw cotton purchase specifications include minimum span length values to ensure processability. Fibers that are too short will not be caught properly by both rollers, resulting in excessive drafting waves and yarn hairiness. High span length values ensure stronger yarns.