Assignment:

Submitted by: Sajid Ali

Roll no. : 10-NTU-1124

Section : BBA (TMM)

Semester: 5th

Submitted To: Sir Rana Sarwar Sb.

Staple Yarn

Staple yarn formation involves multiple steps and can include :

Fiber cleaning and opening (as needed for natural fibers);

Fiber blending (to assure uniform mixing in natural fibers or in fiber blends);

Carding (to al ign fibers and to remove short fibers);

Combing (if highly aligned fibers are desired);

Drawing and spinning (to reduced the denier of the yarn, to provide twist and to give cohesion to the yarn); and

Doubling or plying and twisting of the yarns (as needed to provide greater uniformity).

The method used is depended upon factors such as:

Manufacturers preference of equipment

Economic implications

Fibers to be used

Desired properties of the yarn

Staple spinning Processes: Conventional ring spinning

Open end spinning or rotor spinning

Friction spinning

Self twist spinning

Electrostatic spinning

Vortex spinning

Air-jet spinning

Twist less spinning (Twilo)

Short Staple SpinningThe larger part of staple fiber, approx. 33 mio tons are processed in short staple spinning. This part of the spinning industry therefore is of great significance in the world of textile production. In this context the word “spinning” refers to the conversion of a large quantity of individual unordered fibers of relatively short length into a linear, ordered product of very great length by using suitable machines and devices. In processing natural fibers, the same basic operations are always involved.

Machines used in short-staple spinningOperation Machines

Opening Blowroom machines

Card

OE roto spinning machine

Cleaning Cleaning machines

Card

Comber

Drawframe (dust removal)

Rotor spinning machine

Blending Blowroom mahcines

Card (fiber blending)

Drawframe

Aligning Card

Comber

Drawframe

Roving frame

Final Spinning machines

Uniting Card

Comber

OE Rotor spinning machine

Operation Machines

Equalizing Card with leveller

Drawframe

OE Rotot spinning machine

Attenuating Card

Drawframe

Roving frame

Final Spinning machines

Imparting Strength

Final spinning machines

Winding Roving frame

Final spinning machine

Picking (Including Opening and Blending)

Picking includes the separation of the raw fibers from unwanted material: leaves, twigs, dirt, any remaining seeds, and other foreign items. The fibers are first blended with fibers from different lots or other sources to provide uniformity. (They also may be blended with different fibers to provide improved properties in the final fabric.) When cotton fibers are processed, the raw cotton is run through a cotton ginning operation and then undergoes a cleaning sequence before it is pressed into rectangular bales for shipment to the textile mill. There, the picking starts with a blending machine operation. Bales are opened and cotton from several lots is fed to the machine. The cotton then proceeds to an opening machine that opens tufts of cotton with spiked teeth that pull the fibers apart.

Blending and feeding cotton fibers — Cotton from bales (1), is dropped onto an apron conveyor (2), and moves to another apron conveyor (3), whose surface is covered with spikes. The spikes carry the cotton upward where some of it is knocked off by a ribbed roller (4). The cotton knocked back mixes with cotton carried by the spiked apron. Cotton that passes the knock-back roller is stripped off by another roll (5) and falls (6) to a conveyor that carries it to the next operation.

Opening cotton fibers — Cotton from the blending operation falls on an apron conveyor (1) and passes between feeder rolls (2) to a beater cylinder (3). The beater cylinder has rapidly rotating blades that take small tufts of cotton from the feeder rolls, loosen the bunches, remove trash, and move the cotton to the pair of screen rolls (4). The surfaces of these rolls are covered with a screen material. Air is drawn through the screens by a fan (5), pulling the cotton against the screens and forming a web. Small rolls (6), pull the cotton from the screen rolls and deposit it on another conveyor (7), that carries it to another beater (8), that removes more trash. The cotton then moves to the picker operation.

Picking cotton fibers — Cotton from the opening operation falls on an apron conveyor (1) which moves it to the first of a series of beaters (2), and screen rolls (3). The beaters and screen rolls in the series are all similar but are progressively more refined as the cotton moves through the equipment. Each beater removes more trash from the cotton. When it reaches the output section (4), the cotton is in the form of a web or lap that is wound into a lap roll (5) by winding rolls (6). The lap roll in then ready to be transported to the carding equipment.

CardingCarding is a process similar to combing and brushing. It disentangles bunches and locks of fibers and arranges them in a parallel direction. It also further eliminates burrs and other foreign materials and fibers that are too short. The operation is performed on cotton, wool, waste silk, and synthetic staple fibers by a carding machine that consists of a moving conveyor belt with fine wire brushes and a revolving cylinder, also with fine wire hooks or brushes. The fibers from the picking operation are called "picker lap", and are fed between the belt and the cylinder whose motions pull the fibers in the same direction to form a thin web. The web is fed into a funnel-like tube that forms it into a round rope-like body about 3/4 in (2 cm) in diameter. This is called a sliver or card sliver.

Carding cotton fibers—The lap (1) from the picking operation is unrolled and fed by the feed roll (2), to the lickerin roll (3), which has wire shaped like sawteeth. The lickerin roll moves the lap against cleaner bars (4), that remove trash, and

passes it to the large cylinder (5). The surface of the large cylinder holds the cotton with thousands of fine wires. The flats (6), with more fine wires, move in the direction opposite to that of the large cylinder. The cotton remains on the large cylinder until it reaches the doffer cylinder (7), which removes it from the large cylinder. A doffer comb (8), vibrates against the doffer cylinder and removes the cotton from it. The cotton, in a filmy web, passes through condenser rolls (9), and into a can through a coiler head (10). The subsequent operation is either combing or drawing.

CombingCombing is an additional fiber alignment operation performed on very fine yarns intended for finer fabrics. (Inexpensive and coarser fabrics are made from slivers processed without this further refining.) Fine-tooth combs are applied to the sliver from carding, separating out the shorter fibers, called noils, and aligning the longer fibers to a higher level of parallelism. The resulting strand is called a comb sliver. With its long fibers, the comb sliver provides a smoother, more even yarn.

Drawing (Drafting), (Re-Blending)

After carding and, if performed, combing, several slivers are combined into one strand that is drawn to be longer and thinner. Drawing frames have several pairs of rollers through which the slivers pass. Each successive pair of rollers runs at a higher speed than the preceding pair so that the sliver is pulled longer and thinner as it moves through the drawing frame. The operation is repeated through several stages. The drawing operations produce a product called roving which has less irregularities than the original sliver. Afterward, the finer sliver is given a slight twist and is wound on bobbins.

Drawing—Cans (1), filled with slivers from the carding operation, feed the slivers to the drawing frame. The slivers pass through spoons (2), that guide the slivers and stop the equipment if any should break. The rollers (3), turn successively faster as the slivers move through them, reducing the size of the slivers and increasing their length approximately sixfold. At this point, the slivers are combined into one which is deposited into a can (4), by a coiler head. The sliver fibers are much more parallel, and the combined sliver is much more uniform after the operation, which is usually repeated for further improvement of the cotton slivers.

Spinning (Twisting)

Further draws out and twists fibers to join them together in a continuous yarn or thread. The work is performed on a spinning frame after drawing. The twist is important in providing sufficient strength to the yarn because twisting causes the filaments to interlock further with one another. The roving passes first through another set of drafting rolls, resulting in lengthened yarn of the desired thickness.

There are three kinds of spinning frames: ring spinning, open-end (rotor) spinning, and air-jet spinning. With the common ring spinner, the lengthened yarn is fed onto a bobbin or spool on a rotating spindle. The winding is controlled by a traveler feed that moves on a ring around the spindle but at a slower speed than that of the spindle. The result is a twisting of the yarn. The yarn guide oscillates axially during winding to distribute the yarn neatly on the bobbin. The yarn can then be used to weave or knit textile fabrics or to make thread, cord or rope. Staple yarns, made from shorter fibers require more twist to provide a sufficiently strong yarn;

filaments have less need to be tightly twisted. For any fiber, yarns with a smaller amount of twist produce fabrics with a softer surface; yarn with considerable twist, hard-twisted yarns, provide a fabric with a more wear resistant surface and better resistance to wrinkles and dirt, but with a greater tendency to shrinkage. Hosiery and crepe fabrics are made from hard-twisted yarns.

Ring spinning. Spun sliver from the drawing operations, which is then called roving, and is wound on bobbins (1), and is fed through another series of drawing rollers (2), that further draw the strand to its final desired thickness. A larger bobbin (4) on a rotating spindle (3), turns at a constant speed. The speed of the final pair of drawing rollers is set a the speed that delivers the yarn so that it is twisted by the desired amount as it is wound on the bobbin. The yarn is guided by the traveler (5), which slides around the bobbin on the ring (6). Because of some drag on the traveler, the yarn winds on the bobbin at the same rate of speed as it is delivered by the final pair of rollers.

Ring Spinning

The ring spinning frame, commonly called the ring, is the conventional spinning system and it transforms the roving from the roving frame into spun yarn using the operations of Drawing, Twisting, Winding

Ring Frame Spinning

1. To draft the roving fed to the ring spinning frame 2. To insert the necessary amount of twist 3. To wind the twisted thread yarn on a cylindrical bobbin or tube.

Rotor spinning:

Open-end (also known as Rotor spinning or break spinning) spinning systems have come into wide use for spinning of short and medium staple fibers directly from sliver to yarn in one step without carding or roving. Sliver is fed into a breaking unit to separate the fibers from one another, and the fibers are then forced by air pressure into a hollow rotor rotating at high speed.

The fibers are deposited by centrifugal force on the sides of the hollow rotor, and the resulting yarn is removed continuously by a stationary tube mounted within the rotor. The rotating rotor provides twist to the yarn and produces a yarn with greater bulk and lower strength than ring spun yarns.

Air vortex spinning:

Air-vortex spinning is similar to open-end spinning but utilizes a stationary tube rather than a rotor. A high speed air vortex is created in the tube that deposits fibers within the tube and provides twist due to the vortex.

Friction spinning:

In this system, one or more slivers are fed onto a rapidly rotating card drum which opens the sliver to form single fiber. The separated single fibers are blown from the card drum onto the junction of two parallel drums turning in the same direction. The rotating drums under suction cause the fibers to be compressed and twist around one another to form a uniform yarn. The resultant yarns are bulky and have properties similar to woolen yarns.

Self-twist spinning:

In self-twist spinning, two parallel slivers are fed between two reciprocating rollers which form identical left hand or right hand twists in each of the slivers. The resulting false-twisted yarns are then brought together so that the right hand twist segment of one sliver is phased with the left hand twist of the other sliver. On relaxation, the slivers untwist over one another to form a stable yarn.

Twistless yarn:

in twistless systems liquid or powdered polymer adhesives are applied to sliver . The adhesive activated by heating or steam causes the individual fibers to adhere to one another. In some systems, after textile substrate formation from the twist1ess yarns the adhesive is removed to improve the aesthetics of the resulting textile. Adhesives used include polyvinyl acetate, polyvinyl alcohol. and starch.

Jet spinning:

In jet spinning long staple sliver without twist is introduced into a Iimited space and subjected to a jet imparting a false twist to the sliver. As the sliver exits the jet it rapidly untwists, and the outer fibers tend to break away from the sliver and wrap around the inner sliver to give a strong yarn consisting of mostly parallel fibers with some fibers tightly twisted around the outside.

Electrostatic spinning:

  Electrostatic spinning offers a fundamentally different approach to fiber production by introducing electrostatic forces to modify the fiber formation process. An electrostatic spinning system consisting of fiber-opening roll, electrostatic field for formation of yarn, yarn twister, and take-up roll developed by the authors is described. The opening roll covered with garnet wires opens the entangled fibers, and individual fibers are blown to the electrostatic field by the centrifuge of the roll. It was found that the opening-roll diameter should be increased with increasing fiber length to insure best performance and to prevent roll wraps. The electrostatic field is created by a pair of cone electrodes facing each other either in horizontal or vertical arrangement. In the horizontal type, the yarn formed is drawn out of the electrostatic field through a small hole at the tip of the cathode. In the vertical type, the cathode is placed above the anode, with the yarn drawn out of a small hole at the tip of the anode. The yarn twister resembles the false twister, and the take-up roll is driven by friction. The size and the shape of electrodes, the distance between the electrode pair, the geometry of fiber supply to the electrostatic field, and the air-conditioning, etc. were found to affect the fiber yield. Vertically-positioned electrodes were found to be better than horizontal ones with respect to the filer yield and compactness of the equipment. Revolving anode

and sharply-pointed cathode were found to be effective in straightening bent fibers, thereby obtaining uniform yarns.