Theory and calculation of cover factor

The figure shows projected views of two woven cloths of different construction. At A the warp and the weft threads cover the area of the cloth only partially, but at B the cloth area is covered completely with no spaces left between the adjacent warp yarns, and it will be seen that the relative closeness of yarns in a woven cloth is dependent upon the ratio of yarn diameter, d, to yarn spacing, p. This ratio known as relative cover, can be defined as the proportion of a projected view of a given area of cloth which is covered by threads, and will have a scale from 0 to 1, although it may also be expressed as percentage cover with a scale from 0 to 100 per cent.

d/p = relative cover,
(d x 100)/p = percentage cover

It is preferable to express warp and weft relative cover separately, as the cumulative value of cloth cover does not indicate the comparative importance of each set of yarns which is essential for the determination of certain cloth characteristics.

From the relationship shown above it will be obvious that if d= p. the value of relative cover is one, and this is regarded as the theoretical maximum cover. In practice, however, this value can be exceeded  considerably in any one direction, either through yarn distortion, or, by forcing the threads into different planes, especially if the relative cover of the opposite set of threads is reduced correspondingly.
The relative cover for one thread system can be calculated as follows by considering an area of 100 x 100mm:

Area per thread = 100 x d
Area covered by n threads of one system = n x 100 x d
Therefore, relative cover = (n x 100 x d)/(100 x 100) = (n x d)/100

Example: 

The cloth represented at A is specified as follows: Warp — 25 tex cotton, 267 ends/100 mm; weft—36 tex cotton, 334 picks/100 mm. Find the relative warp and weft cover. (Subscript 1 refers to warp, subscript 2 to weft.)

Warp relative cover = (n1 x d1)/100
= (267 x (25)/(26.7))/100
= 0.50

Weft relative cover = (n2 x d2)/100
= (334 x (36)/(26.7))/100
= 0.75

Fabric Construction and Weaving Operations

Fabric Construction:

Textiles are important for everyone. It is used for covering body, for warmth or coolness, personality enhancement and sometimes to display one’s status in the society. From the wholesale textile manufacturer and merchant to the retailer and the end- user, the customer, everyone consumes textile. Not only those who are in this direct trade are related to this product but there are certain industries which are indirectly associated with textile. Automobile industry is a good example of this type of industry which uses textile in various forms. Others who use textile in one or the other form may include designers, interior decorators, craftspersons, advertisers using hoardings and banners, painters etc.

Weaving- What is it?

Weaving is a major process of making fabric or cloth . In it, two distinct sets of yarns called the warp and the filling or weft are interlaced with each other to form a fabric. Yarn is a long continuous length of interlocked fibers. The lengthwise yarns which run from the back to the front of the loom are called the warp. The crosswise yarns are the filling or weft. A loom is a device for holding the warp threads in place while the filling threads are woven through them. Yarns made from natural fibers like cotton, silk, and wool and synthetic fibers such as nylon and Orlon are commonly used for weaving textile. But other fibers can also be used for weaving. Yarn intended for the warp goes through operations such as spooling, warping and slashing to prepare them to withstand the strain of the weaving process.

Weaving operations:

Four major operations are involved in weaving- Shedding, Picking, Beating up (Battening) and Taking up and letting off.

Shedding:

Each alternate warp yarn is raised to insert the filling yarn into the warp to form a shed.

Picking:

As the warp is raised, the filling yarn is inserted through the shed by a carrier device. Different types of looms are used for carrying the filling yarn through the shed- Shuttle loom, shuttle less looms, circular looms etc.

Beating up (Battening):

With each picking operation, the reed pushes or beats each filling yarn against the portion of the fabric that has already been formed. Reed is a comb like structure attached to the looms. It gives the fabric a firm, compact construction.

Taking up and letting off:

With each shedding,Picking, Battening operation, the new fabric must be wound on the cloth beam which is called ‘taking up’. At the same time, the warp yarns must be released from the warp beam which is called l ‘letting off’.

As the shuttle moves back and forth across the width of the shed, a self edge is woven which is called selvage or selvedge. The selvage prevents the fabric from muddling. It is usually more compact and strong than the rest of the fabric. There are different kinds of selvages depending upon the expected use of the fabric- Plain Selvages, Tape Selvages, Split Selvages, Fused Selvages, Leno Selvages and Tucked Selvages.

Knitting:

After weaving, the most prevalent method of fabric construction is knitting. Its popularity has grown tremendously over the recent years . Today, knitting is a very big industry which has two main divisions.

One division manufactures knitted goods for apparel production, sewing centers, consumers and others. The other division manufactures finished apparel such as hosiery, sweaters and underwear.

The knitted fabric has the advantage of stretchability which provides fit and comfort. It also gives warmth. At the same time, they are porous and provide breathing comfort. It is light in weight and wrinkle- resistant. However, certain specialized techniques like Pak- nit or Permasized have to be used so that it may not shrink too much. Also, care should be taken so that not a single loop breaks. If even one loop breaks, a hole is made and it starts running. This disadvantage can be eliminated by variation in the stitch that protects the fabric from raveling.

The kind and quality of the needle also affect the quality of the knitted fabric. Different kinds of needles are used in knitting latch needle, spring- beard needle, compound needle etc.

Weft and warp knitting:

There are two major varieties of knitting: weft knitting and warp knitting. In weft knitting, one continuous yarn forms courses across the fabric. In warp knitting, a series of yarns form wales in the lengthwise direction of the fabric.

The knitting machine also called knitting frame, knitting loom, or hand knitting machine, is used to manufacture knit fabrics. These fabrics are produced on a fixed bed of hooked needles. The Knitting machines can be hand driven or motor powered.

The machines come in domestic and industrial models, with either flat or circular beds that produce rectangular or tubular fabrics. The fabric produced by a knitting machine has a more fine texture than hand-knitted fabric.

Basic Weaving Operations With Warps & Wefts Weaving Preparing

Weaving:

Weaving is the most basic process in which two different sets of yarns or threads are interlaced with each other to form a fabric or cloth. One of these sets is called warp which is the lengthwise yarn running from the back to the front of the loom. The other set of crosswise yarns are the filling which are called the weft or the woof.

Preparing Warps and Wefts for Weaving:
The warps form the basic structure of fabrics. As such, they are made to pass through many operations before actual weaving is done. These 
operations include spooling, warping and slashing. In spooling, the yarn is wound on larger spools, or cones, that are placed on a rack known as creel. From the creel, the yarns are wound on a warp beam, which looks like a huge spool. These lengths of hundreds of warped yarns lie parallel to one another. These yarns are unwound for slashing, or sizing. The yarn is coated with sizing with the help of slasher machine. Slashing prevents chafing or breaking of yarns during weaving process. Sizing is either starch based or a synthetic like polyvinyl alcohol or a water soluble acrylic polymers. The sized yarns are then wound on a final warp beam and are ready for the loom.

The filling yarns experience less strain during the weaving process. Their preparation includes spinning them to the required size and giving them just the right amount of twist desired for the kind of fabric they will be used.

Basic Weaving Operations:
No matter what type of weaving is being done, four major operations are performed in sequence and are continuously repeated.

Shedding:
In shedding, alternate warp yarns are raised to insert the filling yarn into the warp to form a shed. Shedding is automatically performed by the harness on the modern weaving looms. Harness is a rectangular frame to which a series of wires, called heddles, are attached. As each warp yarn comes from the warp beam, it passes through an opening in the heddle. The operation of drawing each warp yarn through its appropriate heddle eye is known as drawing in.

Picking:
As the warp yarns are raised through shedding, the weft yarn is inserted through the shed by a carrier device. A single crossing of the filling from one side of the loom to the other is called a pick. Different methods are used for carrying the filling yarn through the shed in different kinds of looms. There are many types of looms including shuttle loom, shuttle less loom, and circular loom.

Beating Up:
This weaving operation is also called battening. In it, all warp yarns pass through the heddle eyelets and through openings in another frame that looks like a comb and is known as reed. With each picking operation, the reed pushes or beats each weft yarn against the portion of the fabric that has already been formed. It results in a firm and compact fabric construction.

Taking Up and Letting Off:
As the shedding, picking and battening processes are being operated, the new fabric is wound on the cloth beam. This is known as ‘taking up’. At the same time, the warp yarns are released from the warp beam which is known as ‘letting off’.

The pattern of the weave depends on the manner in which groups of warped yarns are raised by the harnesses to allow the insertion of the weft yarn. These differences are responsible for producing different types of fabric weaves. Weave patterns can create various degrees of durability in fabrics apart from their utility and looks.

Shuttle Loom: 

The shuttle loom is the oldest type of weaving loom which uses a shuttle which contains a bobbin of filling yarn that appears through a hole situated in the side. The shuttle is batted across the loom and during this process, it leaves a trail of the filling at the rate of about 110 to 225 picks per minute (ppm). Although very effective and versatile, the shuttle looms are slow and noisy. Also the shuttle sometimes leads to abrasion on the warp yarns and at other times causes thread breaks. As a result the machine has to be stopped for tying the broken yarns.

Shuttle less loom: 

Many kinds of shuttle less looms are used for weaving such as Projectile Looms; Rapier Looms; Water Jet Looms; and Air Jet Looms.

Projectile Loom:

 It is sometimes called missile loom as the picking action is done by a series of small bullet like projectiles which hold the weft yarn and carry it through the shed and then return empty. All the filling yarns are inserted from the same side of the loom. A special tucking device holds the ends of the wefts in place at the edge of the cloth to form the selvage. This loom needs smooth, uniform yarn which is properly sized in order to reduce friction. Projectile loom can produce up to 300 ppm and is less noisier then the shuttle loom.

Rapier Loom: 

Rapier loom comes in many types. Early models of it use one long rapier device that travels along the width of the loom to carry the weft from one side to the other. Another type of rapier loom has two rapiers, one on each side of the loom. They may be rigid, flexible or telescopic. One rapier feeds the weft halfway through the sheds of warp yarns to the arm on the other side, which reaches in and carries it across the rest of the way. Rapier looms are very efficient and their speed ranges from 200 to 260 ppm. These looms can manufacture a variety of fabrics ranging from muslin fabric to drapery fabrics and even upholstery fabrics.

Water Jet Loom: 

In it, a pre measured length of weft yarn is carried across the loom by a jet of water. These looms are very fast with speeds up to 600 ppm and very low noise. Also they don’t place much tension on the filling yarn. As the pick is tension less, very high quality of warp yarns are needed for efficient operation. Also, only yarns that are not readily absorbent can be used to make fabrics on water jet looms such as filament yarn of acetate, nylon, polyester, and glass. However, it can produce very high quality fabrics having great appearance and feel.

Air Jet Looms: 

In the air jet weaving looms, a jet of air is used to propel the weft yarn through the shed at speeds of up to 600 ppm. Uniform weft yarns are needed to make fabrics on this loom. Also heavier yarns are suitable for air jet looms as the lighter fabrics are very difficult to control through shed. However, too heavy yarns also can’t be carried across the loom by air jet. In spite of these limitations, air jet loom can produce a wide variety of fabrics.

Circular Looms: 

These looms are particularly used for making tubular fabrics rather than flat fabrics. A shuttle device in it circulates the weft in a shed formed around the machine. A circular loom is primarily used for bagging material.

Principle of Winding Machine

There are two widely used types of winding machine:

1.) drum winders (used to wind staple-spun yarns into random-wound packages)

2.)precision winders (for winding filament yarns into precision-wound packages).

1.) drum winders:

They are also called as “Random Winders”. Drum-winding machines rotate the forming package through surface contact with a cylindrical drum, and the yarn is traversed either by an independent traverse, typically a wing cam, or by grooves in the drum. Figure  1   illustrates the two types of traverse systems

Fig 1: Winding traverse motion

• Wing Cam:

There are several different independent traverse systems, but the simplicity of the wing cam makes it a useful example to describe. As shown, the end, A, of a yarn guide bar moves the yarn while the other, B, is made to move around the periphery of the cam, traveling one circuit of the periphery per revolution of the camshaft. As B makes one circuit of the cam, A reciprocates, moving the yarn through a return traverse (i.e., double traverse) along the length of the bobbin. The reciprocating yarn guide limits the winding speed because of the inertia on reversals. A very high rate of traverse is impeded by the mechanics of the guide system, since forces of 16 to 64 times the weight of the yarn guide can be present during the reciprocating action. The reciprocating guide can be replaced by a spirally grooved traverse roller, which moves the yarn along the traverse length. In this case, only the yarn undergoes reversal as it is held in the traversing groove of the rotating roller, and speeds in excess of 1500 m/min can be achieved. A further advantage of the grooved traverse roller is that, as a result of tension, the yarn being wound enters the groove without the need for threading up as is required with the independent traverse system.

• Grooved Drum:

With the grooved drum system, the surface speed of the drum, and the traverse speed are kept constant. A continuous helical groove (i.e., interconnected clockwise and counter clockwise helical grooves) around the drum circumference guides the yarn along the traverse length as the yarn is wound onto the bobbin. A continuous helix has points of crossover of the clockwise and counter clockwise helices. To retain the yarn in the correct groove during its traverse, particularly at the intersections, one groove is made deeper than the other, and the shallower groove is slightly angled.

2.)precision winders:

They are also known as Spindle driven Winders. the Principle of precision winder is as shown in figure.

With precision winders, the package is mounted onto a drive spindle, and a reciprocating yarn guide, driven by a cylindrical cam coupled to the spindle drive, is used to move the yarn along the traverse length. The reciprocating yarn guide limits the winding speed because of the inertia on reversals.

The term precision refers to the control of positioning each layer of yarn as it is wound onto the bobbin. There is a precise ratio of spindle to traverse speed. Therefore, as the package diameter increases, the wind and TR are kept constant.

Preparation of weaving machines

To obtain satisfactory weaving performance, it is essential to have not only a correct yarn preparation, but also an efficient organization which permits to have warps available at the right moment, thus avoiding any dead time with style or beam change. All these prerequisites aim at ensuring to the weaving mills a sufficient flexibility and at permitting them to cope promptly with a variable market demand.

Currently several weaving mills have installed weaving machines which enable to perform the quick style change (QSC), leading to a considerable reduction of the waiting time of the machine.

The following chart presents the possible alternatives for the preparation of the weaving machine:

Changing style means producing a new fabric style, weaver’s beam changing means going on weaving the same fabric style just replacing the empty beam with a full beam of same type. Drawing-in consists of threading the warp yarns through the drop wires, the healds and the reed (fig.1). Depending on the styles of the produced fabrics and on the company’s size, this operation can be carried out manually, by drawing-in female workers operating in pairs (a time consuming activity which requires also skill and care), or by using automatic drawing-in machines.

Fig. 1− Drawing-in:

Fig. 2 shows one of the most established heald drawing-in machines. The drawing-in begins by placing the weaver’s beam, the harness and the row of healds on the proper anchor brackets, then the drawing-in program is typed in on the computer and the machine is started. A sort of long needle picks up in sequence the threads and inserts them with only one movement into the drop wires, the healds and the reed dents, which are selected each time and lined up to that purpose. The computer controls the different functions and supervises them electronically, ensuring the exact execution of the operation and interrupting it in case of defects. The machine can be used with the usual types of healds, drop wires and reeds and can process a wide range of yarn types and counts, from silk yarns to coarse glass fibre yarns. The drawing-in speed can in optimum conditions exceed 6,000 threads/hour.

Fig 2.: Heddle drawing-in machine:

Fig. 30 presents another automatic drawing-in machine which carries out same functions as previous machine, however without needing the weaver’s beam. In fact it is fed by a common cotton twine which it inserts among the various elements of the warp stop motion, of the harness and of the reed according to the program set up on the computer and under its control and supervision. At the end of the drawing-in, the drawn-in devices are moved on the frame of a knotting station in which an automatic warp tying-in machine joins the drawing-in threads together with the threads of the beam. This operation can be made also on board the loom.

Fig 3:- Automatic drawing-in machine (Staubli KK / Korea Branch):

This machine offers the advantage of working always under optimum operating conditions (use of same yarn), independently of the quality of the warp to be prepared and in advance in respect to warping, therefore with higher flexibility. The drawing-in rate can reach 3600 threads/hour. Fig.4  shows a harness and a reed with already drawn-in threads, ready to be brought to the knotting station.

Fig. 4:-  A harness and a reed with drawn-in threads ready to be moved to the knotting station:

The piecing-up of the warp yarns (Fig. 5) permits to the weaving mills which are in a position to use it (not many mills at the moment) to simplify and speed up considerably the loom starting operations in case of warps which were drawn-in or tied-up outside the weaving machine. The warp threads are laid into a uniform layer by the brush roller of the piecing-up machine and successively pieced-up between two plastic sheets respectively about 5 cm and 140 cm wide, both covering the whole warp width.

The plastic sheet can be inserted into the weaving machine simply and quickly, avoiding to group the threads together into bundles; the threads are then pieced-up on the tying cloth of the take-up roller.

Fig. 5 − Piecing-up:

If a new drawing-in operation is not necessary (this expensive operation is avoided whenever possible) because no style change is needed, the warp is taken from the beam store and brought directly to the weaving room, where it is knotted on board the loom to the warp prepared with the knotting machine.

As an alternative to the usual knotting on board the loom, the knotting outside the loom or stationary knotting of a new warp with an already drawn-in warp can be carried out in the preparation department. The devices bearing the threads of the old warps are taken from the weaving machine and the knotting can be started in the preparation room under better conditions, leaving the weaving machine free for rapid cleaning and maintenance operations.

The stationary knotting, in particular, takes place in following stages:

• Taking out of the loom the prepared beam with the harness
• Transport of the beam into the weaving preparation department
• Fastening of the heald frames and of the reed on the proper frame
• Knotting
• Passing of the knots by proper drawing
• Warp piecing-up
• Temporary maintenance of the new warp with the harness
• Transport of the new warp inclusive of harness with proper carriage
• Loading of the weaving machine and start of the weaving process using plastic sheet (fig.7)
• Weaving

Fig. 6 − A knotting machine in operation on a warp with colour sequence, tensioned on the proper frame:

Fig. 7 − Harness loading in the weaving machine:

The automatic knotting machines can process a wide range of yarn types and counts at highly reliable and rapid operating conditions (up to 600 knots/minute), with mechanical or electronic control on double knots and on the sequence of warp patterns in case of multi-coloured warps. Fig. 6 shows a knotting machine in operation on a warp with colour  equence, tensioned on the proper frame.

Weaving Technology

A fabric can be defined as an manufactured assembly of fibres or yarns which has substantial area relation to its thickness and sufficient mechanical strength to give assembly in-heart cohesion.

Fabric can be manufactured by any one of the following methods:1. Weaving technology
2. Knitting technology
3. Braiding technology
4. Nonwoven technology

The process of producing fabrics by interlacement of warp and weft is known as weaving. Yarns are placed in length wise direction while weft yarns are placed in width wise direction in fabric.

During weaving process the warp yarns are wound on a weavers beam in sheet form. Weft yarn may be wound on pirns and ring frame bobbins (in modern machines direct cross wound packages are supplied). If the weft is supplied in form of pirns it is termed as “rewound weft” and if supplied in form of ring frame bobbin than it is termed as “direct weft”. For better quality of fabric rewound weft is preferred.

Individual warp yarns are also known as “ends” and individual warp yarns are known as “picks” it’s also known as “filling yarns”.
Warp and weft are interlaced on a machine known as “loom”. So, loom is a machine to produce fabric from yarn. The loom may be power driven or hand driven. Power driven looms are known as “power looms” were as hand driven looms are known as “hand looms”.

Power looms can be further classified as follows:1. Non-automatic looms
2. Automatic looms
3. Shuttle less looms

A power loom without any attachment produce fancy fabric is known as plain power looms.

•  Time line of power looms:

Edmund Cartwright built and patented a power loom in 1785, and it was this that was adopted by the nascent cotton industry in England. A silk loom was made by Jacques Vaucanson in 1745, which used the same ideas but it wasn’t developed further. The invention of the flying shuttle by John Kay had been critical to the development of a commercially successful power loom. Cartwright’s loom was impractical but the ideas were developed by numerous inventors in the Manchester area in England, where by 1818 there were 32 factories containing 5732 looms.

Horrocks loom was viable but it was the Roberts Loom in 1830 that marked the turning point. Before this time hand looms had outnumbered power looms. Incremental changes to the three motions continued to be made. The problems of sizing, stop-motions, consistent take-up and a temple to maintain the width remained. In 1841, Kenworthy and Bullough produced the Lancashire Loom which was self-acting or semi-automatic. This enables a 15-year-old spinner to run six looms at the same time. Incrementally, the Dickinson Loom, and then the Keighley born inventor Northrop working for Draper in Lowell produced the fully automatic Northrop Loom which recharged the shuttle when the pirn was empty. The Draper E and X model became the leading products from 1909 until they were challenged by the different characteristics of synthetic fibers such as rayon.

From 1942 the faster and more efficient shuttleless Sulzer Looms and the rapier looms were introduced. Modern industrial looms can weave at 2000 weft insertions per minute. Today, advances in technology have produced a variety of looms designed to maximize production for specific types of material. The most common of these are air-jet looms and water-jet looms.

Basic Weaves

The great variety of weaves found in the textiles of to-day are modifications of a few fundamental weaves invented in the earliest times.

The chief fundamental weaves are:

(1) Plain weave.
(2) Twills.
(3) Sateen.

To which may be added the derivatives—
(4) Rib weave.
(5) Basket weave.

DIAGRAM OF FANCY KNIT GOODS

These do not include the many fancy weaves, too numerous to classify, and the open work weaves, made in the Leno loom, in which some of the threads are crossed. Knit goods are made by the interloping of a single thread, by hand or on circular knitting machines and lace by an analogous process, using several systems of threads. Felt is made up of matted fibers of fur and wool and has no thread structure.

WEAVE DIAGRAMS

• Plain Weave:

The plain weave is the most common, nearly all light weight goods being thus woven. In plain weaving, each thread of both warp and filling passes alternately over and under the threads at right angles. This makes a comparatively open cloth, requiring the smallest amount of yarn for the surface covered. This weave is used in nearly all cotton goods, as in muslins, sheetings, calicoes, ginghams, and thin woolen goods. Even in the plain weave variety is obtained by having some of the threads larger than others, either in warp or filling or both, thus producing stripes and checked effects.

SECTIONS OF WEAVES
a—Plain weave; b—Prunella twill; c—Cassimere twill; d—Swansdown twill.

• Twills:

After the plain weave the twill is the most common, being much used for dress goods, suitings, etc., as well as some of the thicker cottons. In this weave the intersections of the threads produce characteristic lines diagonally across the fabric, most often at an angle of 45°. The twill may be hardly visible or very pronounced. The simplest twills are the so-called “doeskin” and “prunella.” In the doeskin the filling threads pass over one and under two of the warp threads and in the prunella twill over two and under one. The most common twill is the cassimere twill in which both the warp and filling run over two and under two of the threads at right angles.

DIAGRAM OF RIB AND BASKET WEAVE AND DOUBLE CLOTH

• Uneven Twills:

A twill made by running both warp and filling under one and over three threads is called a swansdown twill and the reverse is known as the crow weave. In these the diagonal twilled effect is much more marked. Various twills are often combined with each other and with plain weave, making a great variety of texture. Numerous uneven twills are made, two over and three under, etc.

• Sateen Weave:

In the sateen weave, nearly all of either the warp or the filling threads are on the surface, the object being to produce a smooth surface fabric like sateen. With this weave it is possible to use a cotton warp and silk filling, having most of the silk appear on the surface of the fabric.

TEXTILE DESIGN
A—On cross-section paper; B—Graphic diagram.

• Rib and Basket Weaves:

The rib and basket weaves are derivatives of the plain weave, two or more threads replacing the single strand. In the rib weave, either the warp or the filling threads run double or more, thus making a corded effect. In the basket weave, both warp and filling are run double or treble, giving a coarse texture. This weave is sometimes called the panama weave.

• Double Cloth:

In the thicker fabrics like men’s suitings and overcoatings, there may be a double series of warp threads, only one series appearing on the face of the goods, and in the still thicker fabrics, there may be a double set of both warp and filling threads, making double cloth, the two sides of which may be entirely different in color and design.

• Velvet:

In weaving plush, velvet and velveteen, loops are made in the filling or warp threads which are afterwards cut, producing the pile.

The hazards in the textile industry

Every environment in which a working activity is performed, presents higher or lower accident hazards. The textile industry is characterized by the presence of a wide typology of machines and equipment, with automatic or manual transport systems connecting the various machines and departments, with dwell and storing areas; therefore the maximum attention must be paid by the operator, who has to comply scrupulously with the procedures and the active and passive safety systems with which modern machines are largely equipped. Often the distraction or the excess of ″confidence″ with the machines are the occasions for accident hazards. The hazards can also be increased by the environmental conditions of certain departments, by the kind of organization and by the existing work paces.

The risks of damages and diseases for the human organism in the textile industry can have following causes:

1) unhealthy microclimate: this is the case in particularly of the dye-houses, the environment of which is characterized by a high humidity level and by the presence of more or less harmful or irritant fumes, which are often associated with high temperatures and with an insufficient change of air. Also in certain spinning departments the necessary humidity rate, often combined with a certain presence of dust in the air, can result in breathing problems. The fibre dust which is emitted mostly when processing vegetal fibres can cause, in the more sensible subjects, an irritation of the bronchus, associated with a continuous production of mucus, and originate with the time chronic diseases as pharyngitis, tracheitis and bronchitis;

2) noise: noise represents in various departments and above all in weaving mills a problem of primary importance, especially if there is not enough room available and no  dequate
soundproofing intervention on the machine and on the rooms have been carried out. In such cases the alternative is the use of individual safety devices. A high noise level can  entail a reduction in the functions and other secondary collateral effects;

3) illumination, working position, precision, rhythm, repetitiveness, turnover system: various tasks require a considerable stress on the sight, or need body postures which have to be maintained long time, or require much attention, rapidity of execution, repetitiveness at very short intervals, temporary adaptations which can be the source of various pathologies both at physical and at psychical level.

Noise in the weaving rooms:

In the textile industry, the noise problem in the various working departments is a cause of serious concern. The highest noise levels are to be found in the weaving rooms, where the operators are exposed to levels of 94 to 100 dBa. The needs of having the possibility to control fabric quality prevent any casing or partial shielding of the weaving machines, it is however possibile to correct the acoustics of the working room. The mostly used materials are:
1. glass wool baffles put in a glass fabric envelope and hang up on the ceiling;
2. glass fibre panels with an interspace between panel and adjoining wall;

These measures, unfortunately, are not very effective, so that the personnel is anyway compelled to use the devices for individual protection. In fact these measures reduce the noise level only by 1 to 1,5 dBa between the weaving machines and by 2 to 3 dBa between the beams and in the department passageways. The above mentioned modest results, typical of the weaving rooms, are due to the preponderance of the direct waves (coming from the noise sources) over the waves which are reflected by other bodies and to the distance of the sound absorbent material from the noise sources. The devices for individual protection which the workers have to use against noise are of various types and give different results with the variation of the frequency. There are devices which protect better at high frequency values (1000-8000 Hz) and others which are more efficient at low to medium frequency 125-1000 Hz).

Noise origin and problems in weaving machines:

Noise is caused by the vibration of the mechanical parts of the machine. These parts can be either in motion (various kinematic motions) or standing (structural parts, boxes, casings). The moving parts are the main origin of vibrations, which are then transmitted to the other parts of the machine. The vibrations are the higher, the more intense are the load variations to which the moving elements are submitted: sley, heald frames, weft inserting elements.

These movements are alternative motions and have rather high operation frequency levels; as such motions generate the maximum load variation values on the involved  mechanical elements, it is easily understandable that the resulting vibrations and the pertaining noise, can attain very high values.The noise of a machine depends therefore to a very large extent on the operating speed but also on the machine equipment viz. on its composition, as this entails a different quantity and typology of the mechanical units, each with different vibration mode. For this reason the weaving machine manufacturers are following two well known basic lines in their production:

1. noise reduction already at the designing stage;
2. reduction of the noise reaching the operator by means of physical barriers between the noise sources and the subject (casings).

A further possibility could be, as previously indicated, the modification of the mill acoustics. In fact, although a great deal of progress has been accomplished to reduce noise in the weaving rooms, there is still a long way to go.

We need only to consider that the noise emitted by a modern rapier machine is about 90 dBa (maximum level of acoustic pressure in 8 hours per day for a single person at 1 meter distance from the machine surface) when the machine turns at 500 strokes per minute without screenings, viz. the same noise level emitted by an old shuttle loom running at 180-200 strokes/minute. Thanks to the technological development, the weaving speed in the last 20 years has more than doubled, however without increasing the level of acoustic pressure. The attention which most of the industrial countries give today to the issue of environment pollution is more than justified. The noise is not only annoying, but can be harmful to health and at the end increase the social costs.

The EEC guideline Machines 89/392 draws the attention to this problem and invites the manufacturers to design machines in such a way, that the risks due to noise emission are reduced to a minimum, in consideration of the technical progress and of the technical means available to reduce the emissions at their source. This guideline obliges the manufacturers to declare the noise levels emitted by their machines. The noise evaluation of a single weaving machine is anyway not sufficient; in the textile mills dozens, not to say hundreds, work simultaneously in one and the same weaving room and the sound level increases in proportion to the number of looms, even exceeding the threshold of 90 dBa indicated by the present Italian legislation.

The graphics here below show the noise increase in relation to the variation in the intensity of the sound produced by a certain number of sources positioned side by side. You can note that, with 8 noise sources at 89 dBa, the noise level on a central measurement point is equal to 89 dBa; in the case for instance of two noise sources, by increasing the noise level of each source by 5 dBa, we get a variation in the central point of 2 dBa.In the third graphic, if we bring the same noise sources to 90 dBa, we get a central point at a level of 94 dBa. This variation in the value of the central detection point in relation to the change of the sound level of the two noise sources follows a logarithmic trend.

Fabric defects and problems of machine regulation

The finished fabrics can show various kind of faults which can be ascribed to the operations which follow one another till the realization of the finished fabric. The most common defects which appear in more or less extended areas of the fabric are:

• knot;
• crease, mark;
• abrasion or hole;
• tear;
• stain;
• dirt, contamination;
• moirè = presence of vawy areas in periodical sequence, reflecting the light and due to a different compression of weft or also of warp.
• grain = presence of designs with streaked and sinuous lines.

The most common fabric defects due to warp are:- Faulty thread = a thread or pieces of thread which are coarse, fine, irregular owing to higher or lower twist or to other twist direction, of different colour, with two or three ends;
- missing thread = a thread or pieces of ground or effect threads which are missing in the fabric weave;
- tight/slack thread = a thread or pieces of thread which are tighter or slacker than the other pieces/threads;
- incorrectly woven yarn = a thread which in some parts only of the fabric is not interlaced in the standard way
- broken warp = small pieces of cut or missing warp thread
- reversed thread = crossed, exchanged threads or thread pieces;
- warp stripes = one or more faulty threads giving rise to zones of different aspect; it can be due to scraping or rubbing from members of production machines or to inaccurate reeding;

The most common fabric defects due to weft are:• Faulty weft = a weft or pieces of weft which are coarse, fine, irregular (slubs, etc.), twisted, reversed, with different twist, of different colour, double weft;
• missing weft = weft or pieces of weft missing in the fabric weave;
• tight/slack weft = a weft or pieces of weft which are tighter or slacker than the other pieces/wefts;
• incorrectly woven weft = a weft which in some parts only of the fabric is not interlaced in the standard way;
• cut wefts = short pieces of cut wefts;
• weft bars (starting marks) = visual light/dark effect in weft direction due to higher or lower weft density caused by the weaving machine.

The quality control on the fabrics is carried out on a special inspecting machine, equipped with special lamps which facilitate the defect detection by the operator, marks them with labels of different colours according to the fault type and importance.

Depending on the number of faults and on their importance, the fabric pieces can be classified as standard (in respect to quality specifications) or can be subjected to a more or less serious degrading with consequent compensations to the customers or with the sale of the fabric at a reduced price.

Various defects can arise during the stages of weaving preparation (warping, sizing, threading-in into the heddles and into the reed) as well as during weaving itself. It is therefore important to regulate accurately the various devices of the weaving machine and to understand how to act in case of anomalous operating situations which create defects and/or reduce weaving efficiency.Let us see in the following which practical effects some of the most common regulations might have.

Warp tension:

The warp must be under tension to permit weft insertion and fabric construction. The increase in the tension avoids stressing heavily the yarns during the reed beat-up, reduces their sticking together during shedding especially when weaving yarns with poor elasticity and with low airiness, facilitates the separation of the interlaced or glued yarns and the passage of the knots through the reed. The tension might however increase the tensile stress on the warp threads and consequently lead to a higher number of broken ends. On the other hand the reduction in the tension results into a lower yarn breakage rate and also into a lower friction of the threads against the heald frames. In certain cases it could cause however difficulties in obtaining the desired weft density owing to the less effective stroke.

Position of the back rest roller:• horizontal regulation: it is suggested to move the back rest roller away from the harness to reduce the elongation of the single threads, particularly when using yarn with low elastic recovery or when weaving with a high number of heald frames. The back rest roller can be however brought near to the harness when you want to increase the elongation of the single yarns with the purpose of reducing the sticking of the threads together; at the same time an adequate distance from the warp stop motion should be maintained in order to favour the lining up of the threads with the respective drop wires and to facilitate the repair operations;

• vertical regulation: with back rest roller positioned in the centre to get a symmetric shed and thus to reduce the stress on the threads during shed opening (normal condition); with back rest roller moved upwards to loosen the threads of the upper shed and to favour the insertion of the wefts in very dense fabrics; with back rest roller moved downwards to reduce the stress on there lease springs of the heald frames in the Jacquard machines or when weaving with the warp effect of greatly unbalanced weaves turned upside down;

• locking position: the locking of the back rest roller is carried out when stiff warp yarns are used in order to reduce the oscillations, or when snarls arise owing to the twist of the beam threads;
• free rotation: the back rest roller rotates when delicate warps, elastic warps or warps with high elongation are used or when only few heald frames are in motion (limited oscillations).

Warp stop motion:The selection of the type of drop wire, of the weight and density of each contact rail must be made with great care on basis of the yarn count and composition, following the indication of the manufacturers. The responsiveness of the warp stop motion can be increased by reducing the drop height of the drop wires towards the contact rail, in case of threads which are prone to getentangled or which show very difference counts or twists. This responsiveness can be reduced in case of loose threads or false stops.

Shedding:The centring of the shed towards the weft insertion tool used plays an important role, to avoid abrasion risks, weave defects, thread cutting, selvedge trimming and other faults. An increase in the shed dimension reduces the possibility of mistakes and thread breakage caused by their sticking together, whereas a decrease in the shed dimension reduces the stress on the threads.Sometimes it can be necessary to offset the heald frames to favour the separation of the threads or to avoid placing threads with too different tension close to each other.

Timing of the dobby:It might be convenient to advance the shed closing time of the dobby when using very dense and hairy warps, to improve the clearness of the shed; this way the possibility of producing loose wefts after the opening of the pulling rapier is reduced and the possibility of blocking the wefts during the stroke is increased. The closing of the shed is on the contrary delayed to obtain a better extension of the weft and to facilitate its insertion.

Take-up coatings:The take-up coating plays an important role to prevent fabric gliding during its taking-down,which would cause unavoidably streakiness. In general the friction coefficient should grow with the increasing of the warp tension. The maximum adhesion of the fabric is obtained using emery cloth coatings, but sometimes this kind of coating can result in abrasion spots on delicate fabrics.In these cases surfaces coated with rough or smooth rubber, or with resin are used.

Anti-streakiness cycles:The modern machines equipped with electrically connected electronic warp let-off and cloth takeup motions which are managed by the microprocessor system of the controller permit to carry out maintenance cycles aimed at avoiding the formation of stripes (continuous stripes and loom starting marks) after machine stops, while taking into account, at loom re-starting, the different reed beat-up speed in respect to the running speed, the plastic deformations of the threads and of the fabric, as well as possible displacements of the fabric formation edge during the stop. To avoid different initial beat-up conditions, it is also possible to carry out idle strokes.

Other interventions:Many other regulations are possible: on weft feeding and braking mechanisms, on selvedge formation devices, on temples, on weft cutting, on insertion mechanisms used. The fact of being in a position to produce the best suited regulations and corrections contributes in a decisive way to he improvement of the fabric quality and of the weaving efficiency.

Staubli Jacquards

Jacquard weaving solutions:

The world of Stäubli jacquard machines is a fascinating one, in the entire world; countless weaving mills produce innovative high-quality fabrics with these reliable and multipurpose machines. The variety of ranges from the finest silks to the most complex technical textiles and original decorative fabrics. Stäubli electronic control is high-performance machines, benefiting from many years of technical experience. They are distinguished by their high Performance characteristics, the quality of the materials used and their impressive service life. Stäubli Jacquard machines represent a complete range of formats, ranging from 32 to 24576 hooks for producing all types of fabric. know-how to all weaving mills, at the international level .

Exacting requirements and high-performance:

Shedding machines guarantee optimal performance and portability. They perfectly fulfill weaving machine and shed forming requirements, geometries, openings and adjustments are almost unlimited. Weave medications are extremely flexible and can be changed rapidly.With a cam motion, a dobby or Jacquard machine, Stäubli systems allow you to get the most out of weaving machines owing to transmission systems, quick frame connects or through a custom made harness or carbon fibre frames. Stäubli attaches major importance to the reliability and user friendliness of its shed forming machines

Basic construction features of Stäubli Jacquard:

TRANSMISSION:

The DX 100 and DX 110 are delivered with the adaptation elements required for each type of weaving machine pre-installed . The transmission is based on a cardan drive with bevel gears, whose position is determined according to the weaving machine to optimize the cardan shaft angle . For wide microprocesred spaces, the optional addition of a modulator accelerates shed opening . The compact structure of DX 100 and DX 110 machines enables them to be used on standard frames and in low ceiling weaving rooms.

CONTROL BOX:

Each machine has its own electrical power supply and is equipped with an electronic controller and is equipped with a JC6 electronic controller with touch screen. This user-friendly interface between the user and the DX features the latest generation of microprocessor. A flash disk advantageously replaces hard drive technology and patterns can be transferred either via USB key, external drive or the network. The latter offers multiple possibilities and facilitates weaving room management or several remote sites.

T H E M6 MODULE:

The patented M6 module ensures the connection between the lifting mechanism and the harness. Compact, and engineered from composite materials, the M6 module is sealed and wear resistant and consumes very little energy.

If required, depending on the loads and speeds in use, M6 module can be equipped with two journal bearings (version A), one journal bearing at the bottom and a ball bearing (C) on the top or with two ball bearings (B) . Module replacement is easy and quick .

The rollers built into the module make hooking and unhooking the harness cords easy – the system is also available with QUICK LINK.

 

SELECTING HOOKS IN A MODULE:

The double roller enables the upper and lower shed position of the harness cords in double lift.

Low shed position:

The electromagnet (f) is activated. The retaining hook (c) does not retain the mobile hook (a) which follows the lowering knife (e).

Upper shed position:

The electromagnet (f) is notactivated. The retaining hook (c)retains the mobile hook (a).

Low shed Upper shed

SIMPLIFIED KINEMATICS:

 The kinematics of Stäubli Jacquard machines is characterised by:

· Controlled by a single cam housing running in an oil bath

· An extremely simplified transmission via a coaxial shaft system

· Perfect mass balance of the moving parts for optimally smooth running

· Simple and fast adjustment of lift and inclined shed

QUICK LINK:

The QUICK LINK connection system was developed for speedy hooking and unhooking of the harness cord.

   

Quick link connection Harness BLOBAR automatic blowing

HARNESSES:

Developed thanks to Stäubli’s know-how, our harnesses are designed for all applications: labels, silk goods, lining, clothing, upholstery fabrics, table and bed linen, automotive seats, airbags, bedspreads, terry cloth and pile fabric . Our harness specialists have developed a line of harness cords, heddles and springs depending on the article, the characteristics of the warp yarn and the weaving conditions.

The comber boards are made and drilled to customer specifications. The links between the harness cords and the heddles, the heddles and the springs are designed to meet all your needs.

BLOBAR BLOWING SYSTEM:

Designed to facilitate the cleaning of harness springs, Stäubli developed the BLOBAR automatic blowing system, at the back of the down pull frame. The pneumatic blowing device limits fl y deposit and facilitates manual cleaning.

The Formation of Woven Velour by Jacquard:

Velour – “From the Latin vellosus, meaning hairy. The material is a thick bodied, close napped, soft type of cloth. Generally speaking, a velour is a cloth that runs from 10 to 20 ounces per yard, and is given a face finish”

Where we found Velour fabrics?

Woven velvets and velours can be found in every textile market: Apparel, Automotive, Home Furnishing, Contract Upholstery, Transportation and Industrial/Specialty Fabrics. Each use is represented by a uniquely constructed product depending upon the cost, aesthetics, and performance expectations of the customers. The two largest markets for this product are Automotives and Home Furnishings.

How to form?

Although there are other ways of forming a velour fabric such as the wire method, primary focus will be on the production of current transportation velour. The method of choice for producing velour today is to use a double insertion rapier machine.

The shedding motion is usually controlled either by jacquard head. The pile warp yarn is either pulled (jacquard) into the fell of the fabric.

The sandwich structure is made by the interlacing of the pile warp yarns between the picks of the top and bottom pieces of fabric.

Woven Construction Sandwich:

•  So the basic requirement of a lifting system which will form multi shade

Basic Motions (Mechanisms) of Weaving

1.1 Introduction:

The process of producing a fabric by interlacing warp and weft threads is known as weaving. The machine used for weaving is known as weaving machine or loom. Weaving is an art that has been practiced for thousands of years. The earliest application of weaving dates back to the Egyptian civilization. Over the years, both the process as well as the machine have undergone phenomenal changes. As of today, there is a wide range of looms being used, right from the simplest handloom to the most sophisticated loom. In this rang, the most widely prevalent loom, especially with reference to India, is the ubiquitous “plain power loom”. In this and in the chapters that follow, the various mechanisms associated with the plain power loom are discussed in elaborate detail.

1.2 Basic Mechanisms in a Plain Power Loom:

In order to interlace wrap and weft threads to produce a fabric, the following mechanisms are necessary on any type of loom: 1. Primary mechanisms 2. Secondary mechanisms 3. Auxillary mechanisms

1.2.1 Primary Mechanisms:

These are fundamental or essential mechanisms. Without these mechanisms, it is practically impossible to produce a fabric. It is for this reason that these mechanisms are called ‘primary’ mechanisms. The primary mechanisms are three in number. a. Shedding mechanism b. Picking mechanism c. Beat-up mechanism

Primary Motions

a. Shedding mechanism:

The shedding mechanism separates the warp threads into two layers or divisions to form a tunnel known as ‘shed’

b. Picking mechanism:

The picking mechanism passes weft thread from one selvedge of the fabric to the other through the shed by means of a shuttle, a projectile, a rapier, a needle, an air-jet or a water-jet. The inserted weft thread is known as “pick”.

c. Beat-up mechanism:

The beat-up mechanism beats or pushes the newly inserted length of weft thread (pick) into the already woven fabric at a point known as “fell of the cloth”. These three mechanisms namely shedding, picking and then beat-up are done in sequence.

1.2.2 Secondary Mechanisms:

These mechanisms are next in importance to the primary mechanisms. If weaving is to be continuous, these mechanisms are essential. So they are called the ‘secondary’ mechanisms. They are: a. Take-up motion b. Let-off motion

a. Take-up motion:

The take-up motion withdraws the cloth from the weaving area at a constant rate so as to give the required pick-spacing (in picks/inch or picks/cm) and then winds it on to a cloth roller.

b. Let-off motion:

The let-off motion delivers the warp to the weaving area at the required rate and at constant tension by unwinding it from the weaver’s beam. The secondary motions are carried out simultaneously.

1.2.3 Auxillary Mechanisms:

To get high productivity and good quality of fabric, additional mechanisms, called auxillary mechanisms, are added to a plain power loom. The auxillary mechanisms are useful but not absolutely essential. This is why they are called the ‘auxillary’ mechanisms. These are listed below. a. Warp protector mechanism b. Weft stop motion c. Temples d. Brake e. Warp stop motion (Predominantly found in automatic looms)

a. Warp protector mechanism:

The warp protector mechanism will stop the loom if the shuttle gets trapped between the top and bottom layers of the shed. It thus prevents excessive damage to the warp threads, reed wires and shuttle.

b. Weft stop motion:

The object of the weft stop motion is to stop the loom when a weft thread breaks or gets exhausted. This motion helps to avoid cracks in a fabric.

c. Temples:

The function of the temples is to grip the cloth and hold it at the same width as the warp in the reed, before it is taken up.

d. Brake:

The brake stops the loom immediately whenever required. The weaver uses it to stop the loom to repair broken ends and picks.

e. Warp stop motion:

The object of the warp stop motion is to stop the loom immediately when a warp thread breaks during the weaving process.

Splicing

The process of piecing (joining) two yarn ends—resulting from yarn breaks, removal of a yarn defect, or due to the end of the supply package—has received considerable attention in the past two decades. An ideal yarn piecing would be one which can withstand the subsequent processes without interruption and which does not lead to any deterioration in the quality of the finished product. The yarn joining or piecing technique should be suitable for all fiber types irrespective of yarn structure and linear density. Earlier attempts in this area were directed to tying two ends by a weaver’s knot or fisherman’s knot such that the ends do not slip apart. However, the size of the knot, which depends on the type of knotter and the linear density of the yarns, would normally be two to three times the diameter of the single yarn, leading to a characteristic objectionable fault in the finished product. Knots have a detrimental effect on quality; they are obstructive because of their prominence and so frequently cause breaks due to catching in thread guides or even being sheared off. This leads to time-wasting stoppages of the machinery during warping, sizing, and weaving. Due to the above-mentioned drawbacks of knotted yarns, knotless

yarn joining methods have received considerable attention by researchers.

Methods for Producing Knot-Free Yarns:

The development of methods for producing knotless yarns began during the early 1970s. Various methods have been used for producing knot-free yarn piecing, including.

1. Wrapping
2. Gluing
3. Welding or fusing
4. Splicing
   a. Mechanical splicing
   b. Electrostatic splicing
   c. Pneumatic splicing

Fig1;-Different methods for producing knot-free yarn.

In the wrapping method, two yarn ends are overlapped, and an auxiliary yarn is wrapped around them to produce a joint of high strength, as shown in Fig. 1a. This method produces a thick and rigid joint, and the mechanism involved is very complicated. The auxiliary thread often causes problems during subsequent processing. In the gluing method, two overlapped ends of yarns are glued by a special adhesive, as shown in Fig.1 b. This technique produces a thick joint and rigid structure because of the rigidity of the glue (adhesive) used. Also, drying of the adhesive takes a long time, resulting in lower productivity of the process. In the welding technique two yarn ends are welded together by a melting process, as shown in Fig. 1c. Although this technique produces a short but high strength joint, it can be applied only for thermoplastic fibers (e.g., nylon), and the welded portion has a different structure due to the melting process. The first three methods listed above are no longer used in practice because the pieced portion (joint) is thicker and more rigid and also in one case contains an extraneous material, namely, the adhesive.

Splicing:

In splicing, the joint is more or less like the yarn itself and produces sufficiently strong piecing without adversely affecting the appearance of the final fabric, and consequently it is more widely used in modern winders. The concept of splicing is similar to the method of joining rope (or cable) ends together. For the purpose of joining, the two ends of a rope are untwisted and then intermingled by some mechanical means. The methods of yarn splicing involve mechanical, electrostatic, and pneumatic systems.

Mechanical Splicing:

In mechanical splicing the yarn ends are untwisted to open the fibers. Two ends are overlapped and then twisted together again to essentially the same twist level as in the basic yarn, as shown in Fig. 1d. The fibers at the end of the yarn are used to bind the splice joint resulting in a corkscrew-like appearance. The disadvantages of this system are

(1) it is difficult to open up the yarn ends consistently due to irregular twist distribution;

(2) it is possible to achieve proper separation of fibers at yarn ends only for short staple fibers—for long staple yarn it is somewhat difficult to separate fibers at the yarn ends, which has a negative effect on binding of fibers;

(3) different twisting wheels are required for opening and twisting of yarns of different twist levels and made from different staple length fibers, involving costly adjustments;

(4) in this splicing technique it is not possible to splice plied yarns as opening by untwisting is not possible; and

(5) mechanical splicers require more frequent maintenance and servicing due to the entry of dust and fly.

Fig1;-Different methods for producing knot-free yarn.

Electrostatic Splicing:

The yarn ends are separated and untwisted in the opening zone. The opened-up yarn ends are then spread out evenly in an electrostatic field, after which they are intermingled and bound again by a pole change, while simultaneously twist is inserted corresponding to the twist in the basic yarn, as shown in Fig. 1e. Theoretically, this method of splicing
is very suitable as it provides ideal blending of fibers in the splice zone, but it suffers from some practical drawbacks; these include

1. Required opening and separation of fiber ends for effective spread-out in the electronic field is not always achieved satisfactorily. This is due to irregular twist distribution in the base yarn.
2. For a yarn containing a large number of fibers in the cross section the intermingling of prepared fibers at the yarn ends is a problem as fibers obstruct one another.

3. Plied yarns cannot be spliced due to difficulty in opening fibers at the yarn ends by mechanically untwisting.

4. The time taken to splice the yarn is quite long, thus decreasing the efficiency of the winding process. Also, high voltage is required to achieve the desired charge. The climatic condition of the winding room has an obvious effect on the electrostatic field.

Pneumatic Splicing:

In this method, the yarn ends are inserted into a splicing chamber and then overlapped to join them together by means of a strong current of compressed air, as shown in Fig. 1f. The splicing time and air pressure are determined according to fiber type and yarn characteristics. The splicing operation consists of the vertical application of air to the fibers and a simultaneous rotational movement of the air to twist/untwist the yarn. This type of air movement is achieved by the position of the blower apertures and the design of the shape of the splicing chamber. Pneumatically spliced yarn produces a joint that can meet all the requirements in subsequent processing, both in terms of strength and appearance. The time taken to carry out efficient pneumatic splicing is relatively short, thus winding efficiency is not severely limited. Moreover, pneumatic splicing can be applied to a wide range of fiber and yarn types without requiring precise adjustments or settings,
thus facilitating efficient winding.

Double Splicing:

This splicing technique has attained considerable importance in the synthetic fiber manufacturing industry because knots have a detrimental effect on quality. Anew splicing technique called ‘‘double splice’’, based on the principle of pneumatic splicing, is normally used in joining continuous filament yarns and tire cords. In this technique, yarn filaments are intermingled by using an air splicer, leaving virtually no protruding ends.