Monday, March 2, 2015
Definition of fabric selvage or selvedges
In yard goods, the outer edges are constructed so they will not ravel. These finished edges are called the selvages (self-edges) and are often made with heavier and more closely spaced warp yarns than are used in the rest of the fabric by using more or stronger warp yarns or by using a stronger weave. Selvages (also called selvedges) provide strength to fabric for safe handling of the fabric. Selvage should not curl. The warp yarns always run parallel to the selvages. Proper use of the selvedges can also prevent the bowing and bias conditions that occur in some fabric. The weaving machines need mechanisms which through the formation of sufficiently strong selvedges bind the wefts together, thus imparting to the fabric a proper appearance and solidity and preventing the breaking up of the threads on the fabric edges during the subsequent operations.
In shuttle looms, there is no need for special selvedge; since the yarn is not cut after each weft insertion, the edges of the fabric are smooth and strong. On conventional shuttle looms, it is formed when the weft yarns turns to go back across the fabric. The conventional loom makes the same kind of selvedge on both sides of the fabric. At the present time this is the only advantage of shuttle loom over shuttleless loom. In shuttleless weaving, since the weft yarn is cut after every insertion, there are fringe selvedges on both sides of the fabric. In this case, special selvedges are needed to prevent slipping of outside warp yarns out of the fabric.
Types of selvedge designs
There are several types of selvedge designs that are used for this purpose with shuttleless looms. The kind of selvedge used depends upon economy of production and the expected use of the fabric.
These selvedges are constructed of the simple plain weave with the same size yarns as the rest of the fabric, but with the threads packed more closely together.
The tape selvedges are sometimes constructed with the plain weave but often are made of the basket or twill weaves, which makes a flatter edge. Tape selvedges are made of heavier yarns or ply yarns, which provide greater strength.
These are made by weaving a narrow width fabric twice its ordinary width with two selvedges in the centre. The fabric is then cut between the selvedges, and the cut edges are finished with a chain stitch or hemming. Split selvedges are used when items such as towels are woven side by side and cut apart after weaving.
These selvedges are made on fabrics of thermoplastic fibres, such as polypropylene, nylon, etc., by pressing a hot mechanical element on the edges of the fabric. The fibres melt and fuse together, sealing the edges.
The leno selvedges are obtained by binding the wefts with strong additional threads working in leno or gauze weave and by eliminating through cutting the protruding weft ends. Half cross leno weave fabrics have excellent shear resistance. They are made with special leno weaving harnesses. The leno selvedge is used on some shuttleless looms.
The tucked selvedge is a technique used on some shuttleless looms. A device is used to tuck and hold the cut ends into the fabric edge. In tucked-in selvedge, the fringed edges of the weft yarns are woven back into the body of the fabric using a special tuck-in mechanism. As a result, the weft density is doubled in the selvedge area. The tucked-in selvedge was being only used for projectile weaving machines in the past; however, it is now also applied to other shuttleless weaving machines.
Saturday, January 10, 2015
Weaving is the interlacing of two sets of yarn which inter-lace at right angles to each other. The length-wise threads are known as warps, individually they are called ends. The cross-wise threads are known as filling or weft; individually they are known as picks. Weaving is done on a loom which makes it possible to interlace the warp and filling threads according to a pre-arranged manner. The length-wise edges of the fabric are called selvages. Woven fabrics are produced by weaving.
Characteristics of Woven Fabrics
Count of cloth or thread count
The yarns of warp and yarns of filling are not incessantly of the same diameter. Also those utilized in one direction may be closer together than those of the other direction. Often there are more warp yarns than filling yarns to the inch since the strain on a fabric falls on the warp.
Some cloths like gingham are close woven while those like voile are loose woven. A closely woven fabric keeps its shape shrinks-less, slips-less at the seam and is more durable than a loosely woven cloth. The closeness or looseness of the weave is measured by the count of cloth. This is conditioned by the number of picks and ends to the square inch be changed by shrinkage during drying and finishing.
With the warp number thread count is written first, e.g. if there are 60 warps and 50 fillings to the inch then the count is 60 X 50. Thread count indicates the quality of a fabric. There are high count and low count clothes. The count is made with a thread counts. A small pocket magnifying glass, called a pick glass or linen tester is used for counting –
- Many warp yarns and many filling yarns are removed from the cloth.
- If the fabric is light in color, a cut of black material is put under it or vice versa.
- The tester is put on the raveled edge.
- Since the opening in the tester is ¼” square, the yarns are counted (first number of warps then of filling).
- Then number of yarns that run every way is multiplied by four to receive count per inch.
- A pin sometimes supports to separate the yarns.
Balance of cloth
The ratio of warp yarns to filling yarns is known as the balance of a cloth. If the number of warps and number of fillings to the inch are nearly the same (not more than 10 yarns difference) a cloth is said to have a good balance for instance if the count is 60 X 50, it would be a well. If the cloth has poor balance than the warp yarns have a tendency to slip over the filling yarns. Shirts, pillow slips and towels which have various washing must have a good balance.
A selvage is the self-edge of a fabric formed by filling yarn when it turns to go back across the fabric. They are made in many ways –
- Plain selvages: These are corresponding to the rest of the fabric. They do not shrink and can be used for seam edges in garments construction.
- Tape selvages: They are prepared of larger and for ply yarns to give strength. They are wider than the plain selvages.
- Split selvages: They are used when narrow items, such as towels are made by weaving two or more side by side cutting them apart after weaving. The cut edges are finished by a machine, chain-stitch or hem.
- Lased selvages: They are the heat sealed edges of ribbon generally utilized for synthetic fibres.
Monday, January 5, 2015
The centuries of silk cloth production have made certain weaves famous in the world markets by their names through which these silks are distinguished. Some of the widely known silk weaves are habutae, crepe, satin, faille, organdy, jacquard, pongee and shantung.
It is representative fabric with the oldest history in China and Japan. Habutae is a plain-weave fabric of unthrown silk yarn and in principle uses wet yarn for the weft. It has a wide variety of uses, including scarves, mufflers, blouses, men’s high quality underwear, lining for women’s wear and upholstery, ground material for chemical shoes and industrial material for the coating of electric wires. According to specifications there are 27 varieties of habutae; China is now producing most of the varieties of habutae fabrics.
Another variety is twill variety; like plain habutae it uses unthrown yarn for the warp and weft, and one of the features of the fabric is that its texture runs obliquely and its surface is smooth and slightly more lustrous than ordinary habutae. Twill habutae’s main uses include material for scarves, mufflers, dresses, blouses and neckties and lining for men and women’s quality wear.
It is a thrown yarn, thin and plain woven fabric; sheer crepe is akin to nylon and chiffon. This fabric resembles georgette crepe, but it has soft crinkles and one feels the difference in its soft feel due to its peculiar weaving of thrown yarn. It is used for scarves, blouses, dresses and linings for women’s quality wear.
There are two satin weaves; the one is raw silk satin and the other is just silk satin. The former is a satin woven fabric using raw silk for the warp and weft and later a satin-woven fabric using fully glossed organize for the warp and fully-glossed silk yarn for the weft. According to specifications, there are 13 varieties, and in addition, many fancy-woven items, including figured satin crepe. Satin have numerous end-uses – scarves, mufflers, dresses, neckties and lining.
It is a fabric of plain weave silk using raw degummed and dyed silk for warp and dyed dupion for the weft. The characteristics of this fabric is that is utilizes the slubs of dupion silk to run thick irregular lines in the weft which produces a sheer look of elegance. Shantung can also be made to appear gorgeous by proper treatment and designing.
It is high-class yarn-dyed fabric of plain weave that uses Tauri yarn for the warp. The demand for faille has increased after the world war-2. It was originally made of 24 momme or over but now varies are up to 20 momme through technical improvements and new weaving methods. There are a few fancy varieties including back satin faille and figured-faille, all of which are used for high-grade silk textiles. It is used for dresses and women’s quality wear.
This fabric is a plain-woven variety, woven thin with twisted yarn dyed silk, and is not scoured after weaving. The fabric itself is light weight but has a light finish different from habutae, satin or crepe. Organdy is originally an unthrown yarn fabric, but with the changes in its use and the increase in its demand, thrown yarn has come to be used in its manufacture. There are many fancy varieties of organdy such as figured and checked. Organdy’s end-uses range from dresses to lining, padding and even decorating material.
Once considered a top grade fabric, it adopts untwisted raw silk for warp and weft and its construction is rich in variety. There are two kinds of Jacquard silks; one is woven on a jacquard loom and the other on a dobby loom. Either loom weaves beautiful patterns by giving variety to the weft. Jacquard silk woven by a dobby loom is limited to simple patterns only and its construction is not so intricate. Jacquard silk is used for material for dresses and also for oriental kimonos and brocades.
The name is derived from the Chinese word for home weaving. Originally pongee fabrics were hand-woven tussah silk and tan or ecru in color. Indian tasar silk is also hand-spun and hand-woven and is similar to Chinese pongee silk. The pongee silk include all similar fabrics in modern textile usage and are much sought-after silk in the affluent world markets.
Friday, January 2, 2015
In recent years, consumption of apparel has grown rapidly along with income and this trend is expected to continue. Since the first pair of Jeans appeared in America about one and half century ago, denim wear has gained popularity all over the world. As a result, jeans wear is one of the most prominent apparel items in the world apparel market. Young people as well as older people have now great passion for the denim cloth. Trouser, skirt, jacket made of denim can be found in thousands stores and street markets in most countries. Millions of pairs of jeans are produced in America, Europe and Asian countries each year for local and international markets. Today jeans are available in many colors and designs. Young people like to mix and match colors and sizes to create different looks. Globally, denim designers are experimenting with fabric and garment in order to add value to their garments.
Definition of Denim and Jeans
- According to Textile Terms and Definition published by Textile Institute “Denim is traditionally a 3/1 warp faced twill fabric made from yarn dyed warp and undyed weft yarn and Jean is a 2/1 warp faced twill fabric used chiefly for overalls or casual wear”.
- According to Encyclopedia of Textile Finishing edited by Prof. Dr. Hans-Karl Rouette published by Springer “Denim is a firm 2/1 or 3/1 cotton twill-weave fabric (work wear twill) with a dyed blue warp and raw white weft. The warp is sometimes dyed during sizing”.
- “Jeans Originally an American term (now international) derived from Genes (cloth from Genoa). The term was coined in the USA to describe tight-fitting trousers made of cotton twill, usually woven with a dark blue dyed warp and undyed weft, stitched on seams and pockets and having copper rivets here and there. As a rule, blue jeans are dyed with indigo and thus have limited color fastness to rubbing and washing”.
- Traditionally, denim means sturdy, indigo-dyed cotton fabric woven with a dyed warp yarn and natural fill yarn available in various weights and qualities that is used to make pants, skirts, jackets, shirts and shorts etc. and jeans are pants made from denim.
World Denim market
The world market is likely to grow continuously for the next few years. However, supply is growing at a faster pace.
- World Jeans market – 51.6$ Billion in 2007
- Expected to become 70 billion by 2016
- Global demand growing at 5%, supply at 8%
- Global demin fabric production in 2006 was 2.7 billion metres
- Over 50% of this fabric production is based in Asia with Bangladesh, China, Pakistan, India and Turkey.
- 70% of the world jeans consumption is in EU, USA and China.
Denim Export to USA
USA is the most important market for denim jeans exporters around the world. Any change in demand in USA affects a number of exporters worldwide. With the recession having hit USA, the demand for most textile and related products had taken a hit. Luxury goods imports had been particularly hit. However, if we see the trend of this product imports over last 2-3 years, we find that it has been mostly positive and quite encouraging in the current economic scenario. The year 2010 has seen a marked increase of over 14% in imports of these items into the USA as compared to previous year with Men’s/Boys and Women/Girls jeans showing a vast increase in imports over the same period previous year.
Warp yarns for bottom weight jeans typically range in size from the Ne 4.0 to Ne 12.5/1. Finer yarns are used for lighter weight chambray shirting fabrics and lighter weight jeans, vests, dresses, and skirts. These yarns may range in count from Ne 12.5 to Ne 30.
Process flowchart of Denim manufacturing
Denim manufacturing is a more complex manufacturing process in compared to other fabrics. It has several routes to manufacture. The most distinguish feature of this manufacturing system is its dyeing which is a totally unique process and it is specialized for denim. Dyeing may be achieved in different forms like rope form, sheet form or perforated beam wound form. Each process requires separate preparation process specially the warping process. Moreover, sheet dyeing or slasher dyeing can be executed in different types dyeing machine e.g. continuous and combined sheet dyeing-sizing machine, loop dyeing machine. All these processes have both merits and demerits. Manufacturers should choice their production line considering these to get the optimum output.
Dyeing process in denim manufacturing is the most crucial in the production sequence. Once the dyeing in this manufacturing was only indigo dyes based due to its blue appearance. Up to 70’s most of the dyeing was indigo based. Then sulphur dyes specially the sulphur black were introduced. At present, sulphur dyes are used for pure black shade of denim or the different shade effect before or after indigo dyeing. Today the dyeing is not limited to blue and black rather it is now vastly diversified in different shades which are produced using reactive and other classes of dyes though their popularity and production are not comparable with blue and black shade based denim. Like the shades, the machineries of dyeing have different ranges. There are three general types of dyeing ranges.
- Rope dyeing range
- Open warp/Slasher dyeing range
- Loop dyeing range
Sizing is a process in which the threads of a warp are treated with a sizing assistance in order to increase the wear resistance. Sizing consists of impregnating the yarn with particular substances which form on the yarn surface a film with the aim of improving yarn smoothness and tenacity and elasticity, the yarn can stand without problems the tensions and the rubbing caused by weaving. There is not just one sizing recipe which is valid for all processes, on the contrary the sizing methods change depending on the type of weaving machine used, on the yarn type and count, on the technician’s experience and skill, but above all on the kind of material in progress.
Traditional denim fabrics are woven by interlacement of indigo dyed warp and grey weft. The sequence or order of interlacement of warp and weft may be varied in order to produce different weave designs. Although the traditional fabric is a 3/1 RHT warp faced fabrics, a variety of fabrics are made with different weave designs, such as 2/1 twill weave, broken twill, zig-zag twill, reverse twill etc. Today, denim fabrics are also manufactured with fancy design in order to meet the latest fashion. These fabrics normally made of weight range of 3.5 to 16.5 oz/yd2 though 21 oz/yd2 has recently developed by Japan.
The classical denim fabrics are made with open end rotor yarn in both warp and weft direction. However, ring yarn, ply yarn, filament yarn, lycra core yarn, slub yarn are extensively used to achieve some special effect, lusture, smoothness, and comfort in denim products.
The properties of this finished fabric largely depend upon the fabric construction. The warp and weft count influence several fabric properties such as weight, fabric tightness, cover, drape, hand, tensile strength, tear strength, and other fabric properties. All these parameters influence the durability and comfort of garments.
Traditionally, these fabrics are manufactured for a long time in rapier and projectile looms. But with the development of air-jet weaving technology, most of the fabrics are manufactured in air jet looms. The modern air jet looms are equipped with lot of computer controlled attachments which ensures faultless denim at high production rate. The robust and reinforced frame structure and perfect balancing of modern air jet looms allows high production speed and optimum denim quality with less vibration.
Denim finishing is basically very simple, usually consisting of pad applying a finish formula, drying and then sanforizing. However, control of denim finishing is more difficult since it is not normally desized, scoured or mercerized as other cotton fabrics typically are. These other fabric preparation steps serve to clean and stabilize the fabric. If denim was also pretreated by these steps, denim finishing would be much less demanding.
Monday, September 8, 2014
Multi component fabrics
A multi component fabric is one in which at least two layers of material or fabric have been combined to produce a new product with properties significantly different from those of its components parts. The components may be intimately joined to produce a material from which it is difficult to separate them, or it may be a loosely joined material in which the components retain their original forms. The major multi-component fabrics are bonded fabrics, laminated fabrics, foam-backed fabrics, and quilted fabrics.
|Multi component fbaric|
Friday, August 22, 2014
Main features of flocked fabrics
A surface effect that is similar to a nap or a pile may be created by flocking, a process in which short fibres are “glued” onto the surface of fabrics by an adhesive material. If the adhesive coats the entire surface of the fabric, the flocking will cover the entire surface of the fabric, but if the adhesive is printed onto the fabric in a pattern of some short, the flock will adhere only in the printed areas. All-over flocked fabrics may have suede like appearance.
Short lengths of fibre flocking can be made from any generic fibre type. Rayon is often used for flocking. Nylon may be selected for situations that require good abrasion resistance.
Fibres for flocking are made from bundle of tow fibre (continuous filament fibres without twist). The tow is fed through a finish removal bath and then onto a bank of cutters that cut flock of the desired length. The fibres maybe dyed before they are attached to the fabric, or the completed fabric may be dyed.
Application of flock to fabrics
The flock is applied to the fabric is one of two methods. The mechanical flocking process sifts loose flock onto the surface of the fabric to be coated. A series of beaters agitate the fabric, causing most of the fibres to be set in an upright position, with one end of each fibre “locked” into the adhesive.
The second method causes the fibres to be attached in an upright position by passing them through an electrostatic field. The fibres pick up the electric charge and align themselves vertically. One end penetrates into the adhesive, and the flok is formed. Electrostatic flocking ensures more complete vertical positioning, and the resultant fabrics are of better quality. It is a more costly process. When buying fabrics, a consumer cannot tell which process was used.
Durability of flocked fabrics
The durability of flocked fabrics depends largely on the adhesives that hold the flock firmly during either laundering or dry cleaning. In some cases, flock may be removed by dry-cleaning solvents. Permanent care labels should tell the consumers how to handle flocked fabrics. A second factor in the durability of flocked fabrics has to do with the fibre from which the flock has been made.
Saturday, August 16, 2014
Primary MotionsIn order to interlace warp and weft threads to produce fabric on any type of weaving machine, three operations are necessary:
Shedding: Separating the warp threads, which run down the fabric, into two layers to form a tunnel known as the shed;
Picking: Passing the weft thread, which traverses across the fabric, through the shed; and
Beating-up: Pushing the newly inserted length of weft, known as the pick, into the already woven fabric at a point known as the fell.
These three operations are often called the primary motions of weaving and must occur in a given sequence, but their precise timing in relation to one another is also of extreme importance and will be considered in detail later.
Two additional operations are essential if weaving is to be continuous:
Warp control (or let-off): this motion delivers warp to die weaving area at the required rate and at a suitable constant tension by unwinding if from a flanged tube known as the weaver's beam; and
Cloth control (or take-up): this motion withdraws fabrics from the weaving area at the constant rate that will give the required pick-spacing and then winds it onto a roller.
In addition to the five basic motions of a loom there are many other mechanisms on weaving machines to accomplish other functions. These include:
- A drop wire assembly, one wire for warp yarn, to stop the machine when a warp end is slack or broken
- A tension sensing and compensating whip roll assembly to maintain tension in warp sheet
- A mechanism to stop the machine when a filling yarn breaks
- Automatic pick finding device reduces machine downtimes in case of filling yarn breakages
- Filling feeders to control tension on each pick
- Pick mixers to blend alternate picks from two or more packages
- Filling selection mechanism for feeding multi-type filling patterns
- Filling selvage devices such as trimmers, tuckers, holders and special weave harnesses for selvage warp ends
- Filling replenishment system to provide un-interrupted filling insertion by switching from a depleted to a full package
- A temple assembly on each selvage to keep fabric width at the beat-up as near the width of the warp in the reed as possible
- Sensors to stop the machine in the event of mechanical failure
- A centralized lubrication control and dispensing system
- A reversing mechanism to avoid bad start ups after a machine stop
- A color coded light signal device to indicate the type of machine stop from a distance
- A production recording system
Friday, August 15, 2014
Weaving and woven fabric
In general terms, a textile fabric may be defined as an assembly of fibers, yarns or combinations of these. There are several ways to manufacture a fabric. Each manufacturing method is capable of producing a wide variety of fabric structures that depend on the raw materials used, equipment and machinery employed and the set up of control elements within the processes involved. Fabric selection for a given application depends on the performance requirements imposed by the end use and/or the desired aesthetic characteristics of the end over, with consideration for cost and price. Fabrics are used for many applications such as apparel, home furnishings, and industrial.
The most commonly used fabric forming methods are weaving, braiding, knitting, tufting, and non woven manufacturing.
Weaving is the interlacing of warp and filling yarns perpendicular to each other. There are practically an endless number of ways of interlacing warp and filling yarns. Each different way results in a different fabric structure.