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  • Measurement of neps and short fibres

    Chapter 2 - Cotton value addition - Neps and short fibres 


    There are several ‘yarn evenness’ instruments widely used by the global textile industry to measure neps on yarns. These instruments typically use electro-optical sensors to detect yarn neps and to measure yarn evenness, thick and thin places, and hairiness. The incidence of short fibres cannot be directly measured using the yarn.

    Modern yarn spinning mills are increasingly trying to monitor both neps and short fibres. For example, yarn quality at each spinning position is monitored by ‘yarn clearers’. Also, some carding machines may be equipped with an instrument that monitors neps in the card web.

    Note that while advances in online monitoring of quality are useful, the best solution to nep and short fibre problems is prevention: that is, finding ways to reduce the occurrence of these problems in the raw fibres delivered to textile mills.

    The AFIS® instrument

    The only commercial instrument in global use for measuring neps and short fibres in raw cotton is the Advanced Fiber Information System (AFIS®), made by Uster Technologies. It also measures other fibre properties, such as fineness, maturity, trash and dust. Since AFIS® obtains measurements on individual fibres, it can provide quantitative data on the distributional behavior of the cotton (see figure 2.19, for instance). As previously suggested, information on the distribution of fibre properties is much more useful than information just on the average of these properties.

    While AFIS® is being successfully used within textile plants, it is neither high-volume enough nor repeatable enough for use in the cotton marketing system. However, great care with protocols for sampling and measuring make it a useful tool in:

    • Breeding and biotechnology programmes aimed at developing fibres that are less susceptible to nep formation and short fibres; and
    • Harvesting and ginning evaluations to reduce nep formation and fibre breakage in such processes.
    • While it is obvious how AFIS® may be used to evaluate the mechanical processes of harvesting and ginning, it may not be clear how it could facilitate the development of improved fibres. One way it could help is by identifying varieties that have a tendency to fibre breakage. Another way is by identifying varieties that have a higher percentage of fibres that elongate but do not mature fully. Still another possibility for use of AFIS® is to identify cotton varieties that have a genetic tendency to a higher percentage of fibres that do not elongate like the others.

    Other instruments for raw cotton

    The measurement of neps by image analysis of a cotton web is part of the design of the Lintronics Fiberlab®. Measurement of the fibre length distribution by image analysis is part of the design of the STI IsoTester®. Widespread testing of these instruments has not yet been done; therefore, their usefulness is not yet established.

    Besides the AFIS, the measurement of the length distribution and nep content is also possible with instruments from other manufacturers, as e.g.

    • The aQura, manufactured by Premier Evolvics, based on an automatic separation and detection of neps, and on the length measurement of beards, which are end-aligned automatically;
    • The Lintronics Fiberlab® for the neps measurement by image analysis of a cotton web;
    • The STI Iso Tester® for the length distribution measurement by image analysis.