Yarn Manufacturing 1 4l3y6s

Yarn Manufacturing YM-2011

Yarn  A textile yarn is an assembly of substantial length

and relatively small cross-section of fibers and/or filaments with or without twist.  Yarn types   

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According to fiber length (staple, continuous filament) According to structure (single, plied, cabled) According to fiber type (fiber material like metal, glass, cellulose) According to twist (zero twist)

Staple Spun Fiber Yarn  These consist of staple fibers assembled and bound

together by various means to produce the required characteristics such as strength, handle, appearance etc.  Examples include, cotton, wool, jute yarn etc.

Continuous Filament Yarn  It is a produced by combining the required number

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of filaments and thickness of filaments simultaneously in one spinning operation. Examples include polyester filament yarn, silk filament yarn etc. The typical filament yarn is a collection of parallel filaments lying close together and virtually straight running the whole length of the yarn. Monofilament yarn (yarn with one filament) Multifilament (yarn with more than one filament)

Staple Fiber Yarn Production  Different techniques are used which depends upon

the factors as;    

Manufacturer’s preference of equipment Economic implications Fibers to be used Desired properties of the yarn

Staple Fiber Yarn Production  Techniques  Ring spinning  Open-end spinning  Friction spinning  Self twist spinning  Electrostatic spinning  Vortex spinning  Air-jet spinning  Twistless spinning

Ring Spinning  Widely used process

 Flexible process  Large count processing range  Easy process

 Basic manufacturing processes are;  Carding  Combing  Drafting  Twisting  Winding

Blending, Opening & Cleaning It is the first stage of staple fiber yarn formation process. Fibers are compressed in high density in bale form. Blending-uniform fiber quality Opening-loosen hard lumps of fiber Cleaning-remove trash like dirt, leaves, burrs etc Bale pickers are first machine of this line Number of openers or beaters are used depending upon the fiber quality.  When cotton is opened, trash falls through a series of grid bars.  Feeding to machine is done by lap or chute.  File       

Carding  It is used to arrange the fibers in parallel lengthwise direction.  In case of cotton, it also removes the rest of the trash during  

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opening. This process is carried on carding machine. It has a beater, which beats up the large wads of fiber proceeding by a rapidly revolving large cylinder covered with fine teeth/wire brushes. A moving belt of wire brushes slowly moves concentrically above the cylinder. Fiber es through this small gap between cylinder and belt when cylinder rotates causing teasing action which removes trash, disentangle the fibers and arranges them in parallel manner in form of thin web.

Examine it in full screen mode and consider the direction of rotation of all rollers here

Combing  It is used for fine and expensive yarn production.

 It is an additional fiber straightening process with

such a high degree of fiber parallelism that the short fibers are combed out and completely separated from longer fibers.  It uses fine toothed combs for process.  It produces a smoother and more even yarn.  It removes 25% of the original card sliver fibers.

Drawing  It eliminates irregularities that would cause too

much variation if slivers would put through singly.  Slivers are combined and drafted to achieve this process.  Drawframe has several pair of rollers, each advanced set of which revolves at progressively faster speed.  Drafting action pulls the staple lengthwise over each other, thereby producing longer and thinner slivers.

Roving  Sliver is placed on roving frame to further reduce its

weight/unit length.  It is the first stage of twist insertion to secure the fiber strand.  It is a preparatory stage for final twist insertion

Spinning  The roving on bobbins are placed on spinning frames

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to produce the yarn by reducing weight/unit length and insertion of twist along with winding on bobbin in a single stage. It also uses several sets of rollers running at successively higher rate of speed. Spinning frame are of two types: Ring frame (faster process, relatively coarse yarn) Mule frame (slow process, fine yarn such as worsted) Twist in ring

Open End Spinning Also called as break spinning Coarser yarn counts of up to about 40 Ne Use carded sliver Directly converts sliver into yarn Spiked rollers completely open/breaks the sliver Individual fiber form is fed to funnel shaped rotor A thin layer of fibers form in groove on the inner surface of rotor  Rotor rotates at very high speed  The centrifugal force of rotor builds up a multilayer of fibers which is peeled away from the collecting groove as it is simultaneously twisted by the rotation of the rotor and withdrawn continuously and being formed into a yarn.       

Open End Spinning

Ring & Open End Yarn Ring Spun Yarn

Open End Yarn

Spool is rotated to put twist in yarn

Spool does not need to rotate for twisting

Small Spools

Larger spools can be wound with knot free yarn

Labor intensive

Reduction in handling of spools

Low automation

Greater automation and hence better production economy

20-22 m/min production speed

3-5 times higher rate of production than ring spun

Good quality

Quality approx. equivalent to ring

High elongation, high hairiness and low evenness

Better evenness, less hairiness and low elongation

Yarn Structures

Limitations of Open End Spinning  Can’t spun 100% man made fibers due to fiber finish     

deposition in rotor groove and cause clogging Slivers should be free of foreign matter to prevent clogging Yarn have carded character and have rougher, sandier hand Counts generally lower than 40 Ne, and limit to coarser fabrics like denim, towel, interlinings etc 20% more twist than ring, they are 15-20% weaker due to their coarseness Yarn structures of ring and open end yarns are different so can’t be mixed in manufacture

Friction Spinning  Direct transformation of sliver into yarn  Fibers are opened by cylinder and transferred to       

spinning rollers Fibers are compressed by the action of nip of rollers Friction by same directional rotating rollers cause the fibers to twist around each other. Card sliver can also be used in DREF II system. Wide variety and quality of fibers can be processed Yarn may lack uniform distribution of twist through the cross section Bulky yarn with low tensile strength Count range is 6 to 18 Ne.

Friction Spinning System

Self Twist Spinning  Pairs of rovings are drawn out on a succession of    

drafting rollers Last set of rollers reciprocates axially, causing a rolling action of the strands as they emerge. This sideway movement of the drafting rollers cause the strands to wrap around each other. The resultant yarn have alternate lengths of right and left hand twist. To increase strength some additives may be used for cohesion or spun on conventional machine hereafter.

Self Twist Spinning

Electrostatic Spinning  Use to separate the fibers on behalf of their type and 

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length. For cotton, short fibers can be removed and increase in yarn strength and substantial improvement in yarn spinning efficiency. Careful control of humidity is essential for separation of short fibers in electrostatic field Carded sliver is drafted and are fed over rotating cylindrical electrodes of high field intensity which direct the long fiber to enter an air current for transport to the combed sliver stage. The short fibers, which move slowly, are carried by rotating electrodes of low field intensity to where they are moved to a receptacle.

Electrostatic Spinning

Air Vortex Spinning  Variation of open end spinning technique

 Rotor is replaced by a tangential air inlet that draws  

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fibers down a tube The free yarn end rotates in the air stream catches the fibers and twist them up by rotation of end The yarn is continuously drawn out of the tube keeping a standard length which rotates in the tube for further grasping of fibers It is a considerable cost saving process Yarn produced are weak and irregular.

Air Vortex Spinning

Air Jet Spinning  Sliver is drafted by rollers and ed into a cylindrical 

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pneumatic twisting chamber The walls of the chambers release compressed air from jets sets in the wall at predetermined angles to the central axis of the tube. Fibers whirled around each other With suction aid, strand is ed to second chamber and equal amount of twist in opposite direction in given. Yarn is stabilized and wound onto a takeup package. Yarn has uniform diameter and harsh hand.

Air Jet Spinning

Twistless Spinning