YARN AND YARN MANUFACTURING-Doubling and Drawing:-4.8.1

Doubling and Drawing:

In preparing the fibre tufts for spinning, doubling and drawing represent two essentialoperations and their combined effect permits a sliver with a more regular section to beobtained(through doubling) equipped with parallel fibres (through drawing) as well as thecount requested by the spinning plan. The drawing operation done with the machine called the draw frame, permits a homogeneousblend both with fibers of the same nature as well as fibers with a different nature; the doublingsteps are usually between four and eight.
On a par with fiber characteristics such as length and fineness, a sliver with parallel fibrespermits a yarn with better regularity and resistance. The drawing depends on some factors suchas the number of doublings carried out and the value of the count of the entry sliver anddelivery sliver. With drawing, curls, crimps and hooks are also eliminated, meaning the fibresfolded in on themselves, present in the carded sliver.Drawing is a process in which the sliver is elongated by passing it through a series of pair of rollers, each pair moving faster than the previous. This permits combination of several slivers and drawing and elongating them to straighten and create greater uniformity to form a regular sliver of smaller diameter. This action pulls the staple lengthwise over each other, therebyproducing longer and thinner slivers. Finally the sliver is taken to the sliver can.
  The main objects of the Draw-Frame are below: • Crimped, curled and hooked fibres are straightened;
• Parallelisation of fibres;
• Reduction of sliver weight per unit length;
• Reduce irregularities of fibres by doubling and drafting;
• Remove remaining dust from sliver;
• Blending of fibre to provide compensation of raw material variation.• Parallelisation of fibres;• Reduction of sliver weight per unit length;• Reduce irregularities of fibres by doubling and drafting;• Remove remaining dust from sliver;• Blending of fibre to provide compensation of raw material variation. There are two passages of drawing are uses-• Breaker drawing and• Finisher drawing The main difference between them, like on the card, there are also autolevelers on the finisherdrawframes, whose job it is to correct the draft in function of variations in the fibrous mass, tomaintain the section of sliver as even as possible and therefore reduce the frequency ofbreaking threads in spinning and in successive operations.        

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