Spinning Process 
                                                                                                        ~ Yong Kok Swee~        

1.3.1.6              Classification of Spinning Process: Depend on the nature of the fibre, the spinning processes can be classified as in the following:

1.        Short-staple spinning: The use of cotton spinning machinery to produce staple yarns from cotton fibres or any other type of fibres processing similar length and fineness characteristics.

2.        Jute-spun: Descriptive of staple yarn that has been prepared and spun on the machinery originally designed for spinning yarns from jute. The process of spinning of jute is essentially similar to those employed for heavy flax or hemp goods, the only difference being that a softening treatment must be given to the fibres before manufacturing and therefore this is the peculiarity of jute manufacturing.

3.        silk-spun: Yarn produced by dressing or combing processes from silk waste  that have been ‘boiled off’ to remove most of the gum. The spinning of silk-waste processes are: schapping – discharging – conditioning – beating – opening and filling – silk dressing （equivalent to combing in wool）-- noils – noils and and drafts.

4.        Woollen-spun: Woollen-spun is applied to staple yarn produced by carding, condensing, and spinning on machinery originally designed for the processing of wool into yarn. It is descriptive of processing technique and not the fibre content. Since the yarn may not contain any wool fibre, the alternative condenser spun is preferable.

5.        Worsted-spun: Yarn spun from staple fibre processed on worsted-spinning machinery by carding or preparing, combing, and drafting; or by converting a continuous-filament tow and drafting; or a combination of slivers or rovings from both systems. This definition is descriptive of processing technique and not fibre content.

6.        Core-spun yarn；Yarn consisting of a yarn surrounded by staple fibres. The yarn has the strength and/or elongation of the central thread whilst exhibiting most of the other characteristics of the surface staple. Example are: （ⅰ）a sewing thread consisting of a central synthetic continuous-filament yarn surrounded by cotton fires; （ⅱ）worsted yarn with bulked-nylon core, e.g. typically 1/24s worsted count （37 tex）with approximately 33% of nylon. These yarn are normally produced to give strength and elasticity to the fabric; （ⅲ）the spun yarn from either natural or manufactured fibres incorporating an elastomeric core filaments, these yarn are normally used in stretch fabrics.

7.        Bicomponent Yarns: Spun or filament yarns of two generic fibres or two variants of the same fibres.

1.3.2        Continuous-filament yarn

Continuous-filament yarn composed of one more filaments that run essentially the whole length of the yarn. Yarns of one or more filaments are usually referred as ‘monofilament’ or ‘multifilament’ yarn respectively. 

Raw silk are natural continuous filament or strands containing no twist, drawn off or reeled from silk cocoons produced by silk worms. The natural protein fibre is cover by sericin (silk gum), which is usually removed in processing. Pure silk in which there is no metallic or other weighting of any kind, except that which is an essential part for dyeing. Wild silk is the fibre that extruded by insect larvac other than Bombyx mori.

The manufacture of continuous filament yarn is a relatively simple matter of collecting the number of individual filaments necessary to produce the desired yarn size. As manufactured by the fibre producing companies, they are called “producer’ yarns”. They contain minimum twist, ranging from about zero to 2.5 turns per inch, which is just sufficient to maintain the yarn’s integrity.

Most producer’s yarn is delivered with a thin resinous finish, lubricant, or size which protects the filaments from damage due to abrasion and snagging. The finish, amounting usually to less than one percentage by weight, may or may not be water soluble. Such finishes should not be confused with water soluble sizes such as starch, gelatin, or synthetic resin, which may be applied in warp yarns at the mill to give additional protection during weaving. Sometimes, a light lubricant has also being applied to the yarn by the producer or the mill. This improves the running quality by reducing static and friction, and reduces abrasion of the yarn and wear on the textile machinery guides, rollers,etc.

Because of filament uniformity and the compete absence of protruding fibre ends, continuous filament yarns are particularly smooth and lustrous. Such properties are advantageous in the manufacture of many fabrics, but a degree of filament and yarn uniformity is necessary. Even minor irregularities will be observed as fabric defects due to change in luster, dye pick-up, irregular yarn twist or yarn spacing. Producers must always be on the alert to insure yarn uniformity, both within a package and among packages. Any differences in the amount that the yarn is drawn during manufacture will be manifested as differences in optical and physical properties, for example, dye absorption and residual rupture elongation. Excessive elongation at the beginning or end of the yarn package can result in fabric with visually obvious defects. Staple yarn being less uniform, can afford more irregularities, without the danger of the resulting fabrics being considered “defective”.    

1.3.2.1              Throwing and twisting of continuous filaments

There are so many different filament yarn constructions required by textile mills that it is quite impossible for the man-made fibre manufacturer to have all of them available, or make them on order. Instead the fibre producer sells several popular sizes, packaged usually on a standard spool. The textile mill must then arrange to have the producer’s yarn converted into the desired yarn of proper weight, twist and ply,, properly sized, lubricated, and packaged for subsequent mill operations. These procedures are collectively called “throwing”. Throwing may be carried out by the mill which will ultimately weave or otherwise use the yarn, or by a commission “throwster” The term usually applied to the preparation of relatively lightweight yarn, to contrast to “twisting” which pertains to the preparation of heavier yarn constructions. More recently, the term also applies to a company that specializes in texturing yarns.

It is usually impractical to make a heavy yarn by twisting many units or ends of producer’s yarn together in the same direction. Such a yarn would be soft, bulky, unstable, and might have low strength. Instead, plied yarns are constructed. Several turns of twist are inserted in one direction in single producer’s yarn, and then several of these are twisted together, usually in the opposite direction, to make the plied yarn. Several plied yarns can then be twisted together to form a cord. By properly designing the twist relationships among single, ply, and the cord, large size stable and balanced yarn, cords and ropes can be manufactured.

The two common methods for twisting are called “up-twisting” and “down-twisting”. Down-twisters operate on the ring traveller basis, the name being derived from the fact that the input yarns are placed above the twisting unit. They feed down to the twister bobbin where, via the ring and traveller, they may be twisted and wound up. The number of turns per inch inserted is a function of the traveller velocity and the feed roll speed. The up twister utilizes a vertical bobbin on a spindle which rotates at high speed. The yarn is drawn up over the end of the bobbin at a constant rate, and is wound upon a take-up bobbin. The ratio of spindle speed to windup speed determines the number of turns per inch inserted. 

1.3.2.2              Texturing of filament yarn

The process of crimping, imparting random loops, or otherwise modifying continuous filament yarn to increase cover, resilience, abrasion, resistance, warmth, insulation, and moisture absorption or to provide a different surface texture. Texturing methods can be placed roughly into six methods:

1.        Air Jet Method: in this method of texturing, yarn is led is led through the turbulent region of an air jet at a rate faster than it is drawn off on the far side of the jet. In the jet, the yarn structure is opened, loops are formed, and the structure is closed again. Some loops are locked inside and other are locked on the surface of the yarn. An example of this method is the Taslan process. Yarns texturing by this method are core-bulky yarn, and entangle yarn.

2.        False-twist method: This continuous method for producing textured yarns utilizes simultaneous twisting, heat setting, and untwisting. The yarn is taken from the supply package and fed at controlled tension through the heating unit, through a false-twist spindle or over a friction surface that is typically a stack of rotating disc called an aggregate, through a set of take-up rolls and onto a take-up package. The twist is set into the yarn by the action of the heater tube and subsequently is removed above the spindle or aggregate result into a group of filaments with the potential to form helical spring. Much higher speeds can be achieved with friction false twisting than with conventional spindle false twisting. Both stretch and bulky yarns can be produce by either process. Example of false-twist textured yarns are Superloft®, Flufflon®, and Helanca®.

3.        Edged Crimping Method: In this method of texturing, thermoplastic yarns in a heated and stretched condition are drawn over a crimping edge and cooled. Edged- crimping machines are used to make Agilon yarns, coil yarns.

4.        Gear Crimping Method: in this texturing method of texturing, yarn is fed through the meshing teeth of two gears. The yarn takes on the shape of the gear teeth. Gear crimping texturing used to produce crinkle yarn.

5.        Knit-de-Knit Method: in this method of texturing, the yarn is knit into a 2-inch diameter hoseleg, heat-set in an autoclave, and then unravelled and wound onto a final package this texturing method produces a crinkle yarn, e.g. crinkle yarn.

6.        Stuffer Box Method: The crimping unit consists of two feed rolls and a brass tube suffer box. By compressing the yarn into the heated stuffer box, the individual filaments are caused to fold or bend at a sharp angle, while being simultaneously set by a heating device.

1.3.2.3              Various types of Continuous Filament 

Depends on finished goods requirement, varies types of continuous yarns are used: 

1.        Reeled-silk filament: When cocoons have been gathered, the chrysalides are killed. All unreelable silk, caused by pierced cocoons or stained by premature death of crystalide or by other cause, are separated for spun silk manufacture. The uninjured cocoons are sorted for reeling operation. The object is to bring together the filaments from 2 or more cocoons and to form them into one continuous uniform and regular strand, which is the raw silk of commerce. To achieve this, the natural gum of the cocoons which holds the filaments together must be softened and ends of the filaments of the required number of cocoons caught so as to unwind and lay these filaments together to form a single rounded strand of raw silk.

2.        Multiple plied yarn; A yarn in which two or more single yarns are twisted together in one direction, e.g. two-fold yarn, three fold-yarn, etc. In some sections of textile industry, e.g. the marketing of hand knitting yarns, these yarn are referred to as two-ply, three-ply, etc.

3.        Cords, cable, and hawser: Several plied yarns may be further plied and twisted to form increasingly heavier yarn called cords, Depending upon the direction of twist in the singles and in the plies, the resulting cords are called cables or hawsers.

4.        crêpe yarn: A twisted and highly-lively yarn which may be used in the production of crêpe fabrics. The twist liveliness may be achieved through the insertion of very high twist or through the insertion of a moderate twist with an additional, thermally-set false twist. A balanced hand-knitting yarn with a plaited appearance produced by twisting together 3 or 4 two-fold yarns normally using Z, S and Z twists.

5.        Textured yarn: A continuous-filament yarn that has been processed to introduce durable crimps, coils, loops, or other fine distortions along the length of the filament. Most, but not all, texturing methods depend upon the thermoplastic properties of suitable manufactured fibres. The principal texturing procedures that are or have used are: air-jet, edge-crimping, false-twist, gear crimping, knit-de-knit and stuffer box method.

6.        Intermingled yarn（Interlaced yarn）: A multifilament yarn in which cohesion is imparted to the filament bundle by entwining the filament instead of or in addition to twisting. The effect is usually achieved by passing the yarn under light tension through the turbulent zone of an air-jet. Intermingled yarn has higher level of entanglement is achieved with the objective of producing texture or bulk. Intermingling should be distinguished from air- texturing. Some manufacturers describe the intermingled yarn as interlaced yarn.

7.        Bulk continuous filament, BCF yarn: A textured continuous-filament yarn, generally used either as a pile yarn in carpets or for upholstery fabrics. BCF yarn is usually made by hot-fluid jet texturing method.

8.        Coil-Bulked yarn: A bulky or textured yarn composed of two sets of filaments, one of which is straight to give dimensional stability and forms a core around and through which other set is coiled or looped to give bulk.

9.        Core, wrapped and combination spun-filament yarn: A continuous-filament yarn consisting of a number of component yarns, of which one or more are constrained to lie permanently at the central axis of the final thread, whilst the remaining yarns act as covering yarns. In case where a lofty or soft yarn of high breaking strength is required, a cored or wrapped yarn may be used. This usually consists of a high strength continuous filament core, about which is wrapped a soft low strength cover yarn. The cover may protect the core from abrasion, or give the wrapped yarn necessary bulk. Cotton wrapped glass or nylon core yarns are examples. Often wrapped yarns are made with a low cost core yarn, which does not show, and an expensive cover yarn. Another type is elastic yarn, where a cotton wrapped surrounds a rubber core. The helix of the cotton wrapped yarn permits the rubber to elongate under stress to a predetermined maximum. The rubber caused the combined structure to react when the stress is removed.

10.    Hot stretched and heat set yarns: Synthetic fibre yarns are usually thermally sensitive, in that they may shrink or become more plastic as temperature is increased. The fibre producer normally heat treats and mechanically draws the fibre to convert it from a weak, heavy amorphous filament into a strong, tough, textile filament. A heat treating and drawing procedure is selected which will permit the subsequent yarn or fabric manufacturer further to heat treat and tension his product to attain thermal stability.

11.    Modified stretch yarn: A stretch yarn that develops more bulk than usual but less than a bulky yarn in the finished fabric.

12.    Torque yarn: when a torque yarn is permitted to hang freely, it rotates or kinks to release the torque introduced into the yarn during texturing.

13.    Nontorque yarn: a yarn that does not rotate or kink when permitted to hang freely. A nontorque yarn may be the result of plying two equal but opposite torque yarns.

14.    Fancy yarn: A yarn that differs from the normal construction of single and folded yarns by way of deliberately produced irregularities in its construction. These irregularities relate to an increased input of one or more of its components, or to the inclusion of periodic effects, such as knots, loops, curls, slubs, or the like. Many types of fancy yarns can be made according to the requirements: e.g. boucle yarn, chenille yarn, cloud yarn, errentric yarn, fleck yarn, knickerbockers yarn（nepp yarn, knicker yarn）, knop yarn, loop yarn, mock-chenille yarn, slub yarn, snarl yarn, spiral yarn, spiral yarn（corkscrew yarn）, and stripe yarn, etc.

15.    Jaspé filament yarn: A yarn that has the appearance of, but is not, two differently coloured yarns folded together. It is made by texturing together of two continuous-filament yarns of which are in different chemical composition. e.g. nylon and polyester, and then dyeing only the of the two components.

16.    Bicomponent yarn: A yarn having two different staple-fibre and/or continuous components. Although normal usage excludes staple-fibre blends, it includes filament blends. In addition the term is sometimes used to describe yarns made from bicomponent-fibres for which the correct term is bicomponent-fibre yarns. The following may be regarded as bicomponent yarn:

(1)   Two fold staple yarn, when the singles components are different;

(2)   Two fold continuous-filament yarns, when the singles components are different;

(3)   Yarns in which a filament yarn is doubled or folded with a staple-fibre yarn;

(4)   Core-spun yarn, wrapped yarns, or other core-sheath configurations;

(5)   Filament blend yarns.

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