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Rotor Spinning for Man-made Fibres and Blends

  • The doubling effect in the rotor after the complete separation down to individual fibres is well known to result in a homogenous fibre distribution in the yarn cross section. This situation is ideal for blending .
  • Therefore it provides an opportunity, by correct use of the rotor spinning process , to produce polyester-fibre-cotton blended-fibre yarns not only more economically but also with improved yarn quality.
  •  However some of the properties of man-made fibres can impose limitations on the use of the rotor spinning process.
  •  In the first place , the dielectric properties of the fibres themselves may cause a build up of static charges on the fibres during processing.
  •  Secondly, the surface of the fibres, especially that of dull or matt fibres , may become an aggressive agent , damaging the machine parts that are liable to come into contact with fibres  during spinning.
  • In addition, it is not only a low fibre strength but also fibre brittleness that is partly responsible for fibre damage, shortening , & the consequent rotor dust accumulation.

  • The following conditions have to be taken care :-.

  • Staple length:-.

More the staple length more will be the fibre friction & more difficulty for opening roller to separate fibres.

This will lead to fibre shortening & then rotor fauling.

 Hence comparitively ( comparing with ring  spinning) shoter staple lengths are used[ for polyester fibres 32mm.].

  • Fibre fineness:-.

 The advantage of finer fibres is that, while maintaining the minimum number of fibres in the cross section, one can raise the fine-yarn count limit for rotor spun yarn considerably.

 Further advantages are the ability to reduce yarn twist & increase breaking tenacity.

 But use of extremly fine fibres may lead to fibre damages during preparation especially during carding.[Ideal linear density =1.5 denier].

  • Fibre crimp:-.

Highly crimped fibres have greater resistance to extraction from the sliver by opening roller,which leads to fibre damage & rotor fauling.

 Also they do not flow smoothly in the duct between the opening roller & the rotor; Furthermore they do not lie in a compact mass in the `v` of the rotor groove.

While the fibres with low crimp levels give higher yarn strength, fewer yarn defects & a reduced number of ends down.

 But the fibres with too low crimp level or performance will have poor card-web cohesion & result in a poorly drawn sliver.

  • Tenacity :-.
 

High tenacity fibres are reported to perform  better than lower-strength versions because they minimize the strength loss of open end spun yarns, suffer less breakage & therefore produce fewer rotor deposits.

  • Relative humidity & temperature:-.
Relative humidity should be between 50-55% & temperature should not be lower than 23 deg. Celsius.
  • Sliver preparation :-.

  • Rotor spinning parameters :-.

  • Combed sliver do not much improve the yarn quality as compared to the carded sliver.
  •  Blending can be done by flock-blending & draft sliver blending methods.
  • However, with draft-sliver blending, even after the second passage of drawing, the sliver is still basically in a stripe form.

  •  If the sliver blending is used, autolevelling should be therefore carried out at the card with two or three drawframe passages prior to spinning.

  • 1] opening roller parameters :-

    • .Inclination of teeth of clothing = 90 degrees, the tooth height = 1.2 mm. , THE DISTANCE BETWEEN THE TEETH = 4 mm. , Density of teethes =14 teethes per  square centimeter. , Opening roller speed= 6000-7000rpm.

  •  2] rotor parameters :-.

    • Twist factors = 120 - 140;

    • Spinning tension must not exceed 60 % of the yarn strength ;

    • Ratio of rotor diameter to fibre length should not be less than 1;

    • Smaller rotor diameters require higher rotor twist;

    • Higher rotor speeds leads to a steep rise in yarn tension, & resulting yarn friction against the doffing tube may cause localized melting of synthetic fibres.

  •  3] Doffing tube parameters :-.

    • Smooth doffing tubes are recommended in preference to the notched type in order to keep stresses on the yarn within acceptable limits

 



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