Spinning
Spinning is the process that converts staple fibres into yarns. We briefly describe the processes involved in different spinning systems, but before that, for our understanding, let us first know what the processes involved in spinning would do.
The basic rule in any spinning system is to introduce twist into strands of staple fibres. Since fibrous mass is discontinuous, therefore, first and foremost, it is arranged mechanically to bring-in somewhat continuity in the mass before twist can be imparted by revolution. One revolution gives just one turn of twist.
In case of cotton fibres, the first process is to clean cotton, since cotton is grown in the fields so picks-up lot of foreign matters such as broken seeds, leaves, dirt and trash. Therefore, before spinning, cotton is got rid of these impurities. And wool, which picks up lot of grease during wool cropping from sheepskin, and dirt in the pastures, is first washed to remove grease and dirt.
Man-made fibres are normally clean from the beginning, as made in factories, therefore, do not require any cleaning operation. However, almost all type of fibres delivered to textile mills are packed compactly, wrapped in sacks, and fastened with straps. In textile mills, firstly, these bundles are broke opened and the compact mass of the fibrous material is loosened. After opening, loosening, and cleaning (in case of cotton), the fibres are straightened, converted into the form of sliver, than drawn out to make rove, than further drawn out and twisted to make usable yarn. As we see, the process of yarn making has several stages between the mass of fibres and yarn. Each type of fibrous mass is spun on a system that is appropriate to the characteristics of the fibre.
Principally, there are four yarn-making processes, as said earlier, better-known as, spinning systems.
1. Ring spinning
Ring spinning is a standard system, originally employed to spin cotton fibres, therefore, sometimes also described as cotton spinning system. Other than cotton, nowadays, this system is commonly used for any staple fibre, natural or man-made, usually with a staple length up to 45mm.
The principal processes involved are:
Fibres opening & blending in blow-room, followed by carding operation to form slivers, followed next by drawing, roving, and ring-spinning and winding in the form of cones. These stages are describes as follows:
Stage 1:
Blending, Opening and Cleaning:
Blending the raw fiber is put into blending feeders or blending machines to obtain uniformity of fiber quality.
After Blending ,Opening is done in openers to loosens hard fiber lumps and disentangle them.
Opening is followed by Cleaning in Mechanical Picker machines to remove thrash such as dirt, leaves and any remaining seeds.
The fibers come out from the picker in the form of a Lap which is a loosely entangled mass, about 1” thick and 4” wide.
Stage 2: Carding:
After Stage 1, the Lap is fed into Carding Machines in which carding takes place. Carding is the initial process of arranging the fibers in a parallel fashion. This process straightens the fibers and puts them into a somewhat parallel lengthwise alighnment. This is necessary for all staple fibers, otherwise it would be impossible to produce fine yarn from what is originally a tangled mass. In this process - the lap is fed into a beater section and drawn on a rapidly revolving cylinder covered with very fine hooks or wire brushes. As the cylinder rotates, the cotton is pulled by the cylinder through the small gaps under the brushes, which remove the remaining thrash disentangles the fibers and arranges them in a relatively parallel manner in the form of a thin web. This web is drawn through a funnel shaped device that moulds it into a round rope like mass called card-sliver. This is used for making carded yarns which are further used for making less expensive cotton fabrics.
Stage 3:Combing:
This process is followed after carding only if very fine yarns are required to make high quality fabrics of any kind .ie. cottons or worsteds. In case we do not require very high quality fine yarns then this process is eliminated and the card sliver straightaway goes to the drawing stage.
During combing, fine toothed combs continue straightening the fibers until they are arranged with such a high degree of parallelism that the very short fibers (called noils) are combed out and completely separated from the longer fibers. After this a comb sliver is formed which is made of the longest fibers. Which in turn produce smoother more even yarn. Combing is followed by drawing.
For coarser or less expensive yarns, the third stage ie the stage after carding is :
Drawing:
During this process, the combining of several slivers takes place to eliminate irregularities that would cause too much variations if the sliver were through singly. The Draw Frame has several pairs of rollers, each advanced set, which revolves at a progressively faster speed. As a result longer and thinner slivers are produced. This process is repeated several times till a uniform sliver is obtained. These uniform and thin slivers called slubbers are then coiled into roving cans.
Stage 4:Roving:
The slubbers are fed into roving frames in which several sets of rollers further draw and twist the slivers into even more thin form, almost as thin as the diameter of a pencil lead. Roving is the final product of several drawing operations and is a preparatory stage for the final insertion of twist. To this point only enough twist has been given to the stock to hold the fibers together. Roving has no tensile strength and it will break apart easily with any slight pull. The roving is wound on bobbins and sent for the final stage .ie. spinning.
Final Stage:Spinning:
The bobbins of the rove are placed in the spinning machine called Ring Spinning frame which completes the manufacturing of yarn :
1. by drawing out the roving ,
2. inserting twist,
3. and by winding the yarn on bobbins ---- all in one operation.
2. Worsted spinning
Worsted spinning is a system to spin long-staple fibres, though originally employed to spin wool and bast fibres like flax, however, these days is extensively used to make yarns even from long staple man-made fibres such as polyester and acrylic, and occasionally, for other longer staple natural fibres, such as mohair, and silk.
Processes involved are:
For wool fibres, the operations start from wool scouring, carding, followed by 3-passages of gilling, combing, roving, ring spinning, doubling, and winding. For fibres other than wool, the operations start either from carding, or gilling.
Scouring : a thorough washing of raw wools is done in an alkaline solution in scouring machines. The fibers after scouring are dried, so that they retain at least 12- 16 % of moisture which is suitable for further operations.
Oiling/ Blending / dyeing of fiber dyed wool is also done at this stage and is followed by Carding. Carding (as explained earlier) is followed by :
Gilling and combing:
The gilling (in three passages) process removes the shorter staples and straightens the fibers. This is followed by Combing which removes shorter fibers of 1” to 4” lengths. Combing places the longer fibers called tops as parallel as possible and further cleans the fibers Drawing them into thin and compact slubbers.
This is followed by Roving and then Spinning on ring frames or other types of spinning frames.
Nowadays, for spinning man-made fibres, the worsted processes may incorporate ‘tow-to-top’ operations, prior to 3-passages of gilling. ‘Tow’ is a grouping of many filaments together in the form of a rope. ‘Tow’ is produced in factories making man-made filaments or fibres. But, the ‘Tow-to-Top’ operations are carried out in worsted mills. This operation first cut the continuous filaments in shorter lengths while still keeping them together in the form of rope (now called top). The top is then processed through 3-passages of gilling and onwards.
Similarly, wool operations may be done in two separate factories: one doing operations up to combing, is known as combing mill, and second doing operations starting from 3-passages of gilling and onwards, is a worsted spinning mill.
Worsted spinning is normally used for longer fibres having staple length more than 55mm. Worsted spun yarns are of better quality compared with ring-spun yarns of similar fibres.
3. Woollen spinning
Woollen spinning is traditional and time-honoured spinning system, basically used for lambs wool, angora fibres, Shetland wool, and such short staple fibres including short wool and wool waste. The sequence of process is small as compared to other systems.
The process involves:
Scouring, Opening & blending of fibres, followed by passing the fibres through a long Carding machine where fiber are further opened up and forms a fibrous web. This fibrous web is broken in small ribbon and each ribbon is rolled to compress in round shape to form a rove by Roving, followed by twisting/ Spinning of the rove on the woollen ring-frames.
Yarns made with this system are fluffier as compared with yarns made from any other spinning system.
4. Open-end spinning (O-E Spinning)
Open-end spinning also known as rotor spinning is a non-conventional system, basically used for making yarns from short staple fibres. This system is also used for making yarns from staple wastes, although, normal staple length of fibres is also spun on this system. Mostly, this system is used for making coarse cotton yarns for denim fabric and terry-towels. The yarns made out of cotton waste are used for making coarse fabrics for variety of purposes.
The process sequence involves:
Opening, loosening and blending of fibres, followed by Carding, Drawing and spinning. After Carding, during drawing, the card sliver is fed past a number of rollers, thereby completely opening up the sliver so that the fibers can be virtually fed individually into the spinning operation on the open-end spinning machines. As the fiber is broken apart or opened, hence this spinning is called Open-End Spinning.
Quality differences
A cotton yarn made with open-end spinning system is different in characteristic than spun with ring spinning system. For example, cotton yarns spun with O.E. system are fluffier and more elastic than spun with ring spinning system. O.E. yarns can absorb more moisture than ring spun yarns.
Likewise, wool yarn spun on worsted system is distinctly different than wool yarn made on woollen spinning system.
For worsted spinning, longer lengths of fibres are used, so they make stronger yarns, whereas, in woollen system short fibres are used. However, the structure of the woollen spun yarns is such that make yarns to appear plump yet of lightweight, a character suitable to knitwear and tweeds. Similarly, a polyester/viscose-blended yarn made by ring spinning system is somewhat different in characteristics than worsted spun P/V blended yarns. For high grade suiting fabrics, worsted spun yarns are preferred, since they are with better uniformity and surface characteristics, and make durable fabrics with long lasting good visual appearance.
Yarn Packages: Cones & Hanks
The final package of yarn in a spinning mill or spinning department of a composite textile mill is cone, cheese or skein. Cones, having a conical-shaped core, produce a package of conical shape; cheeses are wound on tubes, with cylindrical-shaped cores, produce cylindrical packages. Skeins are coils of yarn wound with no supporting core. Skeins (or sometimes called hanks) are prepared on reeling machines.
Types of yarns
In addition to fundamental features such as fibre contents, twists and spinning system with which the yarn has been made, there are wide ranges of yarns, which have distinctive effect while woven in the fabrics and these yarns can be formed during main spinning process or with a supplementary process. Most of the yarns will fall under following heads.
Single yarns
Yarns are described as single or doubled types. Single yarns, as we know earlier in this chapter, are strands composed of fibres held together by twist either S-twist or Z-twist. It is the product of the first twisting operation that is performed by the ring-frames. These simple single yarns require no additional processing once the individual yarns have been formed. Single yarns are used in making most of the fabrics, mostly as weft in woven fabrics and as such for knitted fabrics.
Doubled or Ply yarns
Doubled, Ply, plied, or folded yarns, as you may articulate, is composed of two or more single yarns twisted together. Two-ply yarn, for example, is composed of two single strands; three-ply yarn is composed of three single strands and so on. Twist imparted in plied yarns may be in the same direction as in the single strands, say ‘Z’ twist, or may be in the opposite direction than the single strands, say ‘S’ twist. When both the single strands and the resultant ply yarns are twisted in the same direction, the yarn becomes firmer, producing harder texture and reducing flexibility. Ply yarns provide strength to heavy industrial fabrics and are also used for delicate-looking sheer fabrics.
Normally, two-ply yarns are made with balanced twist.
Balanced twist is a term used to describe a ply yarn when the forces due to twist of the ply are equal and opposite to those of the components of the single yarns. The most common method used to test a ply yarn for balance is to take approximately 1-yard length, hold one end in each hand, stretch a bit, and then bring the two ends together. If the yarn hangs freely in a loop, the twist is considered balanced; if the loop tends to twist in a kink, the twist is not balanced.
Piled Filament Yarns
Most of the man-made filament yarns are plied in multi-strands, known as multifilament. Thus a single strand of multifilament is a group of many individual filaments plied together with low twist. The reason for plying multifilament is to protect them against spraying or separating during weaving and knitting operations.
Cord or cable yarns
Twisting together two or more of ply yarns, each made of two or more strands of single yarns, produces cord or cable yarns. The final twist in the cord yarns is usually applied in the opposite direction to the twists in the individual strands. We may find cable yarns that follow ‘S-Z-S’ form, i.e. S-twisted singles plied with Z-twist, are further combined with an S-twist. Alternatively, cable yarns may follow ‘Z-S-Z’ form or ‘S-S-Z’ or ‘Z-Z-S’ pattern.
Cord yarns may be used as rope or twine, or may be made into very heavy industrial fabrics.
Textured yarns
As we know that man-made filaments possess smooth surface. Textured yarns are man-made continuous filaments, modified to impart special texture and appearance. The processes, which make modification to the filaments, are better known as texturising process. These processes were originally applied to reduce transparency, slipperiness, and the possibility of pilling (formation of small fibre tangles on a fabric surface), which are the typical character of filament yarns. Texturing processes make yarns more opaque, improves appearance and texture, and increase warmth and absorbency.
Core spun yarns
In most cases, combining filament yarns with fibres during the process of ring or worsted spinning makes the core spun yarns. These yarns are made on the ring frame machine with the help of a small attachment that feed the filament. The filament yarn remains in the centre (core) and the fibrous materials wrap around and cover the core. This is unique way of combining distinctiveness of filaments and fibers to make a resulting yarn having its own character. More often than not, the core filaments are elastromeric, i.e. possessing the property of stretchability, such as spandex. Cotton, wool or any man-made fibre may cover them. The other examples of core spun yarns are, Metallic yarns, and Tape yarns used so often by designers.
Processed yarns
Normally, yarns received from a spinning mills are greige (raw), having the colour that of the raw fibres, natural or man-made. These yarns can be further processed to give colour, or are bleached before being used in the fabric. Two yarns differently coloured may be twisted to get a special twist effect in the doubled yarns. Sometimes, yarns are spun from dyed fibres. A kind of mixture effect is obtained when two fibres differently coloured and blended to make yarns. Differently graded (light, medium, dark) gray coloured or any other colour yarns are produced by this technique. Yarns can also be printed in the hank form; spray printing is the example. These yarns produce special effect on the fabrics.
For special purposes, greige yarns are mercerized (a special treatment with NaoH chemical) and this process makes very brilliant yarns. The colours on mercerized yarns also look very bright. Sometimes the protruding hairs of the yarn structure are burnt down, thus making the yarn surface very smooth. This process is known as singeing. Thus singed yarns are very smooth yarns. Normally, sewing threads are processed yarns.
Fancy yarns
These are novelty yarns made by design to obtain special effects. For example, spinning technologists obtain special effects by intentionally inserting small fibrous lumps in the yarn structure, identified as slub yarns, or inserting small loops of fibres at regular or irregular distance on the surface of the yarn, identified as Boucle yarns. Similarly, there are many fancy effects that they create on the yarn surface with the help of special equipment attached to the spinning machinery or on stand-alone machine built specifically for the purpose. In some other way, natural fibres, including some linens, and wool to be woven into tweed, and the uneven filaments of some types of silk are allowed to retain their normal irregularities, attributing uneven surface that imparts a kind of fancy effect on the finished fabric. Fabric designers make use of these yarns in variety of ways.
Types of fancy yarns
There are two or more plies in the fancy yarns. One ply may be of one colour whereas the others of a different colour. Each components of the ply may be of differing thickness or count. A two-ply fancy yarn may have one spun ply combined with a filament ply. Frequently a fancy yarn in ply will have three basic parts:
The ground, or foundation or core
The effect or fancy
The binder
Boucle
In this type of yarns, the effect ply forms loops over the core yarn and the loops are projected from the body of the yarn at fairly regular intervals.
The effect yarn that produces the loops is wrapped around a core, or base yarn, and then the third ply, or binder, is wrapped over the effect ply to hold the loops in place. The individual plies may be filament or spun yarns. Their characteristics determine the ultimate design effect.
Chenille
True chenille yarns are produced from a woven leno fabric’s structure that is slit into narrow, warp wise strips to serve as yarn.
In effect, these are pile yarns; the pile length may be uniform throughout the length of the yarn, or it may vary in length to produce a yarn of irregular dimensions. These are used in furnishings and apparel.
Corkscrew
Twisting two plies that differ in size forms it. These two parts may be delivered to the twister at different rates of speed. These yarns are used in furnishings and apparel.
Gimp
The effect ply of the yarn is twisted in a somewhat spiral arrangement around the ground ply.
At intervals, a longer loop is thrown out, kinks back on itself, and is held in place by the binder. These yarns are used primarily furnishings.
Grindelle
These are fancy yarns made by twisting together two single yarns of contrasting colours. They are used to add colour effects and are found in suiting, coating, shirting and home furnishing fabrics.
Knot yarn
In this type of yarns, the effect ply is wrapped many times in the same place over the surface of a core ply to create a knot appearance. This action is repeated after some intervals. Two effect plies of different colours may be used and the knots arranged so that the coloured spots are alternated along the length of yarn. A binder is added during the twisting operation to hold the knots in place.
Loop
Loop yarn looks like boucle yarn. It has closed loops at regular intervals along the yarn.
These yarns are used in fabrics to create a looped pile that resembles caracul’s lambskin and is called astrakhan cloth. They are also used to give textured effects to other fabrics. Mohair, rayon and acetate are often used for the effect ply. These yarns are used in apparel and furnishings.
Nub
It is very similar to the knot yarn. Twisting the effect ply many times in same place makes it.
Two effect plies of different colors may be used and the knots arranged so the coloured spots alternate along the length of the yarns. A binder is added during the twisting operation. These yarns are used in apparel and furnishings.
Ratine yarn
In this type of yarns, the effect ply is twisted in a somewhat spiral arrangement around the ground ply. At intervals, the effect ply creates a longer loop, which kinks back on self, and is held in place by the binder
Slub
Most slub yarns are single yarns produced by twisting uneven yarn diameters. At intervals high diameter (thick) yarn with reduced twist is produced to make a soft bulky area called slub.
Slub yarns can be found in shantung, drapery, and upholstery fabrics as well as in hand knitting yarns and sweaters. Some of the rayon and polyester yarns make to resemble linen.
Snarl
Snarl yarns are made with effect ply twisted with the ground yarn but forms alternating snarled loops at intervals along both sides of the yarn. A binder is twisted along to hold the snarls in place.
Spiral yarn
The spiral yarns are produced from two piles. Each of which may vary in colour, count and twist. The core ply is with a hard twist and is wrapped with a coarse, soft twisted effect ply. No binder is used in this type of yarn.
Tweed
Coloured flecks of short fibers are twisted into the yarn. The specks create interesting spots. Tweed effects are often made of wool. It is found in apparel, upholstery and draperies.
Novelty yarns
Combination Yarns
Combination yarns are plied yarns twisted from single yarns of different fibres such as silk and rayon or rayon and acetate. Each ply in the yarn is composed of a different species fibre. These yarn types are widely used. Combination effect is also created in the fabric forms.
Mixture fabrics, or union fabrics are more common. These fabrics are composed of various yarns that differ from each in fibre composition. Usually, the lengthwise yarns of mixture fabrics are of one fibre composition and the crosswise yarns of another fibre composition. In another form of the mixture fabrics, yarns of different fibre composition are interlaced side by side.
Composite yarns
Composite yarns, or compound yarns, are structures consisting of at least two strands, one forming the centre axis, or core, of the yarn, and the other strand forms the covering or wrap.
One strand is usually composed of staple fibers and the other is of filaments. Composite yarns are even in diameter, relatively smooth, and available in the same size ranges as spun and filament yarns.
Stretch-Covered Yarn
These yarns were developed to make rubber threads more comfortable in foundation garments and surgical hose. These yarns consist of a central core of rubber or spandex covered with yarns. There are two kinds: single covered and double covered. Single-covered yarns have a single yarn wrapped around them. They are lighter, more resilient, and more economical than double covered yarns and can be used in satin, batiste, broadcloth, and suiting as well as for lightweight foundation garment. In double covered the second covering is usually twisted in the direction opposite from the first covering. Most ordinary elastic yarns are double-covered to give them balance and better coverage. Fabrics made with these yarns are heavier.
Yarns for fabric construction
More or less any yarn falling under any category described above can be used to manufacture fabrics, either woven or knitted types. In addition to category they belong, the yarns attain a classification according to the manner they are used for making fabrics. These nomenclatures are described as follows.
Hosiery yarns
For machine knitting, say, for making jersey fabrics, yarns with low twist, or as we may call, ‘soft twisted’ yarns are used because softness is desired in knit fabrics. The other reasons for using ‘soft yarns’ is that these yarns absorb more moisture and do not snarl thus making them trouble-free during knitting. Characteristically, these yarns are identified as ‘hosiery yarns’.
Warp & weft yarns
For weaving, two types of yarns are used:
Warp: yarns that run length-wise in the fabric, parallel to edges,
Weft: yarns that run across the width of the fabric, perpendicular to the edges.
Yarn faults
There can be many objectionable faults in the yarn. These objectionable faults get into the yarn during its formation stage. A good quality yarn is normally uniform in diameter and appearance through out its length. The extent of deviation, both on thicker and thinner side of the normal yarn structure, appearing on some sections of the running length of the yarn decides the severity of the fault. These faults could be thick sections, thin places or untwisted thick fibrous mass (slub), or a pinhead of fibrous mass (nep), or a clinging trash that could not be removed in the blow-room.
These faults if allowed to go into the final yarn package, and onto fabric formation stage, may lessen not only the efficiency of fabric production but also the finished fabric appearance. These faults are caused by basic deficiency in the fibrous mass, like short, immature, unopened cluster of fibres.
The other reasons for yarn faults are wrong settings of process parameters or damage in the processing machinery. Proper adjustments of atmospheric conditions within a spinning mill, i.e., temperature and humidity, are important to contain yarn faults.
The approach to the selection of fibres for making yarns of a particular yarn count and quality is one of the factors that may ultimately determine the amount of objectionable faults acceptable to us for marketing. However, one thing is clear, that the number of objectionable faults in the final package of yarn would decide its market price. A mill producing poor yarn quality loses its reputation and the product price.
The requirement of modern high speed weaving and knitting machines is fault free yarns. Even though, modern yarn spinning machines are self regulatory to contain most of the faults, yet many a times cost considerations take precedence to appropriate selection of fibres.
Eliminating yarn faults
Nowadays, many devices are being used on the spinning equipment to contain the yarn faults to the bare minimum; despite these efforts it is yet impossible to eliminate entirely the faults from the spun yarns. Devices such as auto-levellers on draw-frame machines, electronic yarn clearers and splicers on cone winding machines are now a regular feature of modern machines. These devices ensure that to some extent yarn faults are checked in the process.
Electronically cleared and spliced yarns
Most of the modern winding machines (cone package making equipment) are equipped with electronic yarn clearer and splicers. The electronic clearers check the faults through scanning electronically the running length of yarns and eliminate the faults during winding. The yarn broken during fault elimination are joined together by splicing, thankfully not by knotting, thus avoiding replacing a fault, i.e. thick, thin sections or a slub, by another fault, i.e., a knot.
Thus electronically cleared and spliced yarns are knot-free and with bare minimum faults, which may not be objectionable or could not diminish the appearance of the fabrics made from them. However, the cost of these yarns may be more than the normally wound yarns.
Faults in dyed yarns
A weaving mill purchases yarns, either in greige (raw) or dyed form, mostly in cone packages. Normally, for weaving designs in the fabric, such as checks, stripes or motifs, they use dyed yarns. Yarn making mills equipped with dyeing apparatus provide dyed yarns. These mills make shade cards, as a give away to their customers, enclosing small strips of dyed yarn shades, a sort of forecast of seasonal colours. There can be faults in the dyed yarns, other than the faults described above.
In certain cases, fibres are dyed first and then spun resulting into a coloured yarn. Coloured yarns made from pre-dyed fibres are better known as ‘top dyed’ yarns. These yarns if used both as warp and weft, straight off make coloured fabrics, requiring no further dyeing process in the form of fabric.
Yarns in skein form are also dyed, mostly if they require treatment like bulking as in high bulk acrylic yarns for knitting purpose. This is because bulking process is preferably done in the form of skein. In India, they dye skeins of cotton, silk and wool or for that matter any other fibre, for using in the handloom weaving process.
During dyeing process, some faults typical to this process gain entry into the yarn, like variations in shades, uneven dyeing in patches, non-fast colouring. Sometimes, faults like uneven dyeing or other unconventional faults appear only when yarn is actually woven as fabric. Some of these faults are often caused by non-compatible combination of dyestuff for a shade formation, or faulty process considerations, or operational faults in the equipment.
In addition to above, the inherent faults in the yarn, such as thick and thin places, uneven twists in patches, and variations in yarn count (thickness) beyond a certain limit can also be the cause of dyeing faults. Other than this, a fibre of different origin accidentally getting into the yarn structure during spinning stage could cause white speck or differently shaded streaks in the yarn. This is possible due to carelessness in the spinning section, since a spinning mill often handles fibres of different origins.
It is of common knowledge of dyeing technologists that when they apply dyes to the yarn they are using dyestuff intended for particular fibres (say cotton). Any other fibre, say acrylic, here and there if gets into the cotton yarn structure, will not pick up dyes meant for cotton and so remain un-dyed, thus creating a streak or a patch, a serious fault indeed.
But when we are blending two or more fibre types in definite proportion, we are taking a conscious decision, and accordingly we choose dyestuffs or the process parameters, to dye both fibres equitably, or leaving one fibre type un-dyed or dyed in different shade for an intended effect on the yarn, such as snarl yarns.
In case of man-made fibres, without going deep into the science of man-made fibre manufacturing,it suffices to say here that if fibres of different batch are supplied by different fibre manufacturers, even same fibre type, gets mixed up during spinning, are much prone to dyeing faults. So yarn spinning and dyeing is serious business and at best should be handled by professional dyers.
Yarn properties vs. cotton quality
1. YARN COUNT: longer, finer and stronger fibres can produce finer count of yarn.
2. TENSILE STRENGTH: This property of yarns is directly related to fibre strength. Longer length of fibre also helps to produce stronger yarns.
3. ELONGATION: This property of yam is beneficial for weaving efficiently. Yarn elongation can be co-related with fibre elongation.
4. HAIRINESS: Yarns manufactured with excessive short fibres in the cotton mixing will produce hairy yarn. Yarns also become hairy due to faster spinning speeds.
5. BRIGHTNESS: Yarn made with higher grade of cottons will give brighter appearance.
Fibre quality parameters
How it affects the yarns properties
Staple Length Spinning Potential, count decision.
Fiber Strength Yarn strength, less breakages during processing
Fineness Spinning potential, count decision
Maturity Yarn strength and even ness, dyeing quality
Non-Lint contents (Trash) Reduced waste, better yarn realisation
Uniformity Ratio Better productivity and yarn evenness
Elongation Less processing breakages
Friction Cohesiveness, degree of twist decision
Class Yarn appearance grade
Yellowness Yarn appearance
Neppiness Yarn neppiness and appearance
Moisture Content 8.5% moisture content optimum for spinning at 65% R.H.
Stapleclassification (Cotton) Fibre Length mm
Spinning Count that can be spun Short
Less than 24 Coarse Below 20s
Medium 24- 28
Medium Count 20s-34s Long
28 -34 Fine Count 34s - 60s
Extra Long 34- 40
Superfine Count 80s - 140s
Each yarn or threads have thickness. Some yarns are fine and the others coarse. Yarn number refers to the dimensions of yarn. For our purpose or in simple terms we can say that yarn number denote yarn thickness. Though, in real term, yarn number explains the relationship of length and weight. Therefore, a lean looking yarn may have same yarn number as a bulky looking yarn. This can happen because lean looking yarn may be constituted of fibres with high specific gravity, i.e. with fibres having heavier weight per unit length.
Primarily, there are two systems used in textile trade for describing yarn number,
Indirect System
Direct System
Indirect system
This system of measuring is basically based on length per unit weight. It means that if we take a fixed weight and weigh yarns lengths against this weight, we will see that yarns with longer length will be finer compared to yarns with lesser length. For example, if one pound is used as a standard weight unit against which different yarn lengths are measured, a fine yarn will be much longer than a coarser yarn to weigh a pound.
In ‘indirect system’ finer yarns are with higher numerical number than comparatively coarser yarns.
Cotton count
This count is indirect system of yarn numbering. This yarn number is named as ‘English cotton count’ or abbreviated as ‘count’ of the yarn and indicated by a suffix Ne or (‘s) after the yarn number, such as 30Ne or 30’s. When we say ‘count of yarn’, it would normally indicate yarn number in cotton count system, unless stated specifically a numbering system. The count of the yarn is an indication of the length of yarn (in hanks) that would weigh one pound.
In order to know the ‘count’ of the yarn, the length of yarns to be measured is reeled in the form of hanks, each hank containing 840 yards. The count of the yarn stands for ‘the number of hanks each of 840 yards that would weigh one pound’.
Thus, if the count of the yarn is 20’s, it suggests that 20 hanks, each of 840 yards (Total length=20 x 840=16800 yards) weigh one pound. A yarn of 40’s (Total length=40 x 840=33600 yards weighing one pound) will be finer than 20’s yarn.
So we see that higher counts indicate finer yarns. That is why this system is branded as indirect system.
Normally, 840 yards of yarn per hank are reeled for cotton and spun silk. In worsted spinning, in indirect yarn numbering system, length of 560 yards of yarns are reeled, and for yarns spun on woollen system, 256 yards are reeled per hank. However, the weight in each case against which the hanks are weighed is one pound. Worsted and woollen systems of denoting yarn numbers are rarely used these days.
Metric system
Metric system is also indirect numbering system, thus in this system also finer yarns will have higher number compared with coarser yarns. This system is based on ‘the number of hanks each of 1,000 metres (one kilometre) required to reach a weight of one kilogram’. This system is known as metric system and is usually used for staple spun yarns. The yarn number in this system is denoted by a suffix Nm, such as 20Nm. Now a days, yarn number of worsted spun yarns is indicated in metric system though this system can be used to denote yarn number of any type of yarns.
A simple formula below will convert the yarn number in cotton system to worsted, woollen or metric system.
Metric number = Cotton count x 1.69
(Nm = Ne x 1.69)
Ply yarn numbering
A ply yarn number, say 2 yarns of 30’s twisted together, will be denoted as 2/30’s and the yarn number of 3 strands of 40’s yarn plied together will be 3/40’s and so on. The resultant count in each case will be the count of single yarns divided by the number of plies.
For example, the resultant count of 2/30s ply yarn will be = 1/30 + 1/30 = 2 ÷ 30 = 1/15. The resultant yarn count will be written as 15s.
In case two plies of different counts have been twisted together, the resultant count will be calculated as follows.
Example,
Count of yarn ‘A’ = 20s
Count of yarn ‘B’ = 30s
Yarns ‘A’ and ‘B’ are twisted together to make a double ply yarn. In simple arithmetic terms, the resultant count is calculated as under.
Count of the ply yarn = 1/20 + 1/30 = (3 + 2) ÷ 60 = 5 ÷ 60 = 1/12. In this case the resultant yarn count is written as12s.
Similarly, resultant count of the 3 or 4 ply yarns is calculated. However, one thing should be noted that the resultant count calculated by simple arithmetic is only an indicative and an approximate. The actual count may be a bit coarser than calculated. For example, in above cases, on actual measurements, the resultant 15s count may be 14.85s or so, and the resultant ply count of 12s may be 11.75s or so. This is because two yarns on twisting also get contracted a bit and become bulkier than indicated by the calculated count. This phenomenon of yarn contraction is due to ‘twist contraction’ factor.
Direct system
Basically, this system of yarn number measurement is opposite to what we learnt for indirect system. For example, in this system, higher the yarn number coarser is the yarn. In this case, unlike count system, length of yarn is fixed, and how much this length would weigh will describe the yarn number. The well-known direct systems of yarn number are ‘denier’ and ‘tex’.
Denier
The denier number indicates the weight in grams of 9,000 metres of yarn. For example, if 9,000 metres of a yarn weigh 15 grams, it is a 15-denier yarn (written as 15d); if 9,000 metres of a yarn weigh 100 grams, it is a 100-denier yarn (or 100d). 100d yarn is much coarser than the 15d yarn. Thus a smaller number indicates a finer yarn. This system is normally used for man-made filament yarns.
Tex
The Tex system is a universal direct method developed for the measurement of staple fibre yarns as well as filament yarns. It is based on the weight in grams of one kilometre (1000 meters) of yarn.
Denier can be converted to Tex and vice versa. Similarly, direct yarn number can be converted to indirect yarn number and vice versa. The formulae for these conversions are given below.
Direct to direct system
Denier = Tex x 9
Tex = Denier/9
Direct to indirect system
Denier = 5310/Ne
Denier = 9000/Nm
Tex = 590/Ne
Tex = 1000/Nm
Indirect to direct system
Ne = 590/Tex
Ne = 5310/Denier
Nm = 1000/Tex
Nm = 9000/Denier
A detailed conversion chart from one system to another is given in annexure- of this book.
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