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Quality And Economic Aspects

Quality Aspects

  • Regularity tests shows open-end spun yarns to be more uniform than conventional yarns, but they still fall far short of perfection.
  • Detailed examination of open end spun yarns reveals various defects, which may be attributed to flaws in the fibres themselves, inclusions such as neps & trash, irregularities in preparation, or the operation of the rotor.
  •  Fibre defects stem from inherent fibre properties.
  •  For example, highly elastic fibres tend to contain poorly cut or over-length fibres, which may interfere with drafting or cause lapping of the carding roller, whereas brittle fibres, such as acrylic fibres, are susceptible to fibre damage, which results in an increase in short fibre & in accumulation of dust & fibre debris within rotor.
  • Fused fibre bundles cause disturbances inside the rotor & lead to end-breakages.
  •  Dyes & fibre finishes can form powdery or tacky deposits, which necessitate frequent cleaning of the rotors if end-breaks are to be avoided. The amount of crimp in man-made fibres can be important.
  •  In the early days, successful open-end spinning was only feasible if very high quality standards were maintained in the sliver fed
  • Partly owing to improvements in the machine & partly owing to a better understanding of the process, it has now been found possible to relax these requirements to some extent.
  •  Investa recommend that the sliver fed to the open-end spinner should conform to the following criteria :
    • It should contain no particles of trash individually weighing over 0.15mg;
    • The average weight of the particles of trash that may be extracted by hand should not exceed 0.10mg;
    • The average weight of the particles of trash that may be extracted by Shirley analyzer should not exceed 0.025mg; &.
    • The total weight of trash present should not exceed 0.4%, i.e., 4mg/g of sliver.
  • Unfortunately, few existing mills can meet such requirements with existing blowroom machinery & cards, so that it is often necessary in practice to accept rather lower standards of sliver excellence.
  •  In such an event, the main thing is to avoid hard impurities weighing more than 0.15mg each. Neps can not be broken down in the spinning unit & are normally extracted with the trash, but fortunately some neps do become buried in yarn during the formation of the ring by layering & are therefore not seen in the yarn.
  • In order to achieve satisfactory yarn regularity, it is recommended that second-passage drawframe sliver should be used & that the sliver should be regular according to uster standards, e.g., not more than 3 u% for a 3 ktex sliver.
  •  Defects that can be attributed directly to the rotor system & to general disorientation of the fibres.
  •  All the points mentioned above affect the end breakage rate & thus the cost of yarn manufacture.

Economic Aspects

  • Whereas ring spinning dominates in the range of ne 18-48 [13-33 tex] & for finer yarns, rotor spinning covers in the range ne 6-20 [30-100tex].

 



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