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Rotor Spinning for Speciality Yarns

 

Spinning of Core Spun Yarns

  • A simple method for the production of core spun yarns by the rotor spinning system is described by Neild & Ali .
  •  In this method, a feed tube positioned in the base of the rotor but in line with the axis of the doffing tube is used to feed the continuous-filamental core.
  • The filamental- core component must be fed with a suitable tension, in the absence of which it will fly to the collecting surface of the rotor instead of remaining taut along the axis of the rotor.
  • To start spinning, the staple fibre-yarn is pieced-up in the usual manner.
  • The doffing tube is then made to rotate in the direction opposite to that of the rotor, & the continuous - filament core.
     Any type of material, including metallic wires of high torsional rigidities, can be used as  cores to produce a core spun yarn .
     Thus the technique could be used for producing high insulation covered electrical flex.
  • The possible advantages listed for producing core-spun yarns on a rotor spinning spinning are :-.
    • The core-spun yarn is more likely to retain all the strength contributed by the core component & the full length of the core component, since the continuous filaments are not twisted during spinning & will therefore not suffer twist contraction;
    • Since the evenness of the rotor spun yarns is better than that of equivalent  ring spun structures, the evenness of rotor core spun yarns is expectedly better than that of equivalent ring core spun yarns;
    • The bulkiness of rotor core spun yarns should be greater than that of equivalent yarns spun on the conventional system ; thus a reduction in cloth set will be required to obtain the same cover from rotor core spun yarns;
    • The production rate of the rotor spinning machine , in terms of the yarn delivery rate, is higher than that of the ring spinning machine; Hence the production rates for rotor core spun yarns should also be greater than those for conventional systems; &.
    • The direct winding of the core spun yarn from the rotor onto cheeses or cones eliminates the rewinding process necessary for the conventional system & thus results in a significant cost reduction.
Spinning of Multicomponent Yarns
  • Multicomponent yarns consisting of two or more different yarns have been produced on modified rotor units , the aim being to spin a final yarn possessing all the desirable properties of the individual component yarns.
  •  Several problems have prevented the different techniques studied from progressing to at least the prototype stage.
  • The major & the most common difficulty is the high yarn breakage rate that occurs in the rotor. The frequency of yarn breaks is unacceptably high even when continuous-filament yarn is used as one component.
  • Not only is the yarn-breakage rate a problem, but the resultant yarn quality is also usually poor, since it is extremely difficult to achieve proper tension control of the yarn component yarns during spinning.
  • With rotor spinning system, the Multicomponent yarn has a construction in which the staple fibre component is positioned at the centre & a continuous filament yarn is wrapped around it.
  • The resulting yarn is claimed to possess the desirable properties of both spun yarn & continuous filament yarn.
  • It is reported to have a good handle , similar to that of spun staple fibre yarns, & also an excellent resistance to abrasion as a result of continuous-filament wrapper.
  •  The yarn is claimed to be suitable for use in fabrics intended to be made into outer garments.

Spinning of Fancy Slub Yarns

  • Fancy slub yarns can be produced on rotor spinning machines by varying the draft briefly in the sliver feed & opening roller system to give deliberately thick places in the yarn.
  • In an alternative method, patented by pittman, slubs or thick & thin places are produced through twist variations by changing the delivery speed of the yarn as it leaves the rotor.
  • The method produces a unique slub yarn, which has a portion of high twist adjacent to the slub in theyarn, which has lower yarn twist.
  • A second technique based on twist variations as shown in fig. 1.
  • The design of the system is such that the roving [12] is spun by rotor housed in [14]. The yarn leaves through doffing tube [18] & passes through rollers [21, 23] to be wound onto the bobbin [28].
  • A lever [20] with a roller at its end [19] swings randomly up & down to lengthen & shorten the yarn between the doff tube [18] & rollers [ 21, 23], which thereby speeds up & slows down the yarn leaving the doff tube.

 



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