There are various commonly used popular Yarn Formation Systems .Some of them are Cotton woollen or worsted,staple,Filament yarn formation systems. Also some of the common types of yarns like mercerdised ,dyed,grindle or twisted,yarns are discussed in this page.
For making the stripes and jacquard design fabrics, the dyed yarns are used. Yarns are dyed by manually and by sophisticated machines. In manual yarn dyeing, we can not expect the consistency of shades, yarn strength and better quality. Hence it is always advised to dye the yarns with the latest machines only.
For yarn dyeing, only combed yarns are used. Also the yarn should have more yarn strength. It is called Count Strength Product (CSP).
Popular Yarn Formation Systems
Cotton Yarn Formation
On removing the cotton from the bales, the cotton is opened up, blended and mixed with cotton from other bales. Finally the fibers are formed into a thin partially oriented continuous web of intertwined fibers called a picker lap. The picker lap in turn undergoes carding to remove short fibers and remaining trash and to provide additional orientation to the fibers.
The cotton sliver from carded machines are combed before feeding to drawing in order to further straighten and orient the fibers and to remove additional short tangled fibers. The drawing portion of the operation is referred to as the drafting process.
Subsequent drawing and high speed twisting is carried out by ring spinning in which the drafted, lightly twi sted sliver (roving) is fed from the drafting unit onto a high speed spindle via a traveller holding the spun yarn to a ring surrounding the reciprocating spindle.
Woolen and Worsted Yarn Formation
The wool is washed in successive baths of detergent solution to remove the impurities. The process is called scouring, and the weight of the raw wool can be reduced by as much as 50% by the scouring process.
Vegetable matter remaining in the wool can be removed by passing the wool through concentrated sulfuric acid to chemically destroy the cellulosic matter, a process called carborization.
After washing and drying, the cleaned wool is blended and carded to form a sliver. The sl iver must undergo additional straightening, orientation, and removal of short fibers to be used in the worsted system. The process involves several successive steps including gilling (a form of pin orientation) and combing to give wool top. The wool top is drawn and slightly twisted in several stages to form a roving which is finally spun into a highly twisted worsted yarn.
Other Staple Yarn Formation
Cut staple manmade fibers arrive in boxes at the mill and are ready for carding and processing into yarn. When two or more different staple fibers are mixed, it is critical to provide extensive blending before carding and repeated doubl ing of the sl iver to assure intimate blending prior to roving and spinning.
Filament Yarn Formation
Filament spinning systems are much less complex because the fibers are continuous and do not need to be highly twisted to give a cohesive strong yarn. Filament yarn spinning usually involves man-made fibers and only the portion of the ring spinning system that involves twisting and winding onto spindles is used.
These yarns are also called ‘Twisted Yarns’. Two yarns of same counts but in different colours are twisted together. Among these 2 colours, one colour will be in lighter shade and the other will be in darker shade. After the twisting, the yarn will be in a different mixing shade. We must be sure of these yarns are in same counts and have same yarn strength. Also when they are being twisted together, the number of twists per inch (usually 14) should be even for the full length of yarn. If the twisting is not done properly, then we will face problems during knitting.
After combing and twisting, the yarn will be singed (gassed). By this process, the yarn will pass rapidly through flames and the superficial hair around the yarn would be eliminated. Due to more heat, the hairy particles of the yarn will be burnt out. (Now this is called Gassed Yarn).
Then the yarn is treated with caustic soda under perfectly controlled tension. This process is called Mercerising. Mercerising is done to strengthen the yarn and to improve luster of yarn. After mercerising, the yarn will have great strength and greater brightness. Also the yarn will capture 20% more humidity without getting wet. Further, this mercerising process increases the resistance of yarn and reduces its becoming dirty. (Now the yarn is called Gassed Mercerised Yarn).