Textile & Fashion World

A loom in which the weft yarn is propelled through the shed by means of a jet of air.
OR .
A shuttleless loom capable of very high speeds that uses an air jet to propel the filling yarn through the shed.
OR .
A loom using a jet of air to carry the yarn through the shed.

U.S. Pat. No. 4,606,152 illustrates a method and apparatus for grinding or buffing a metal reed of an air jet loom by manually moving a buffer along the tunnel while the reed is positioned on the loom.

U.S. Pat. No. 4,640,316 illustrates another apparatus for treating an air jet loom reed while on the loom wherein air measuring apparatus is manually moved in sliding motion along the top of the loom reed.

Heretofore there was no method or apparatus available which would uniformly and consistently permit measurements of air flow and at the same time provide a means to make indicated adjustments to the loom reed to meet requirements as to air flow performance. Accordingly, objects of this invention include analysis and regulation of air flow for different types of filling with reduction in air consumption of the loom.

Another object of the invention is to permit the correction of problems associated with filling insertion and to assist in speeding up the loom while providing higher quality of cloth with fewer loom stops.

It has been found that a method and apparatus may be provided for optimizing air flow characteristics of an air jet loom by removing the reed from the loom and positioning same in a frame where a carriage is provided for rolling contact according to a predetermined path for measuring the air flow characteristics and for altering the physical nature of the air tunnel to accommodate improved air flow.

FIG. 1 is a perspective view schematically illustrating a frame for positioning a loom reed in inverted position remote from the loom together with a driving apparatus for moving the carriage;

FIG. 2 is a transverse sectional elevation taken on the line 2--2 in FIG. 1 with a carriage illustrated as being positioned upon the loom reed;

FIG. 3 is a plan view of the carriage taken on the line 3--3 in FIG. 2; and 

FIG. 4 is a plan view illustrating an apparatus for positioning a buffer for altering the loom reed in accordance with the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

The drawings illustrate a method and apparatus for enhancing air flow characteristics in an air jet loom reed broadly designated at 10. The reed 10 has a tunnel 11 and a bottom channel 12. The air jet loom reed is first removed from an air jet loom (not shown). The air jet loom reed is then positioned in a mounting frame A in a fixed preferably inverted at least partially upright position. In inverted position the bottom channel 12 is at the top, with a top channel 13 on a lower guide rail 14 of the frame A. The rail 14 of the frame A is opposite an upper frame rail formed by a channel 15.

A carriage B driven by a pulley C is illustrated for driving a buffing device D and an air measuring device E at a predetermined speed along the reed. The carriage is illustrated as being suitably supported as by a wheel F which rolls on the bottom channel 12 of the loom reed. Thus, the path of the buffing device relative to the tunnel of the air jet loom reed is located with respect to an upper portion of the loom reed when fixed in the inverted position.

The frame A is carried by a tubular base support 16 and the lower guide rail 14 is supported by a bracket 17 while the channel 15 is carried by posts 18. A bar magnet 19 is provided to hold the reed 10 in position upon the frame A. Rolling contact of the carriage is maintained by the rollers G (FIG. 2) with the respective reed channels 12 and 13. A roller 15a is provided for positioning the carriage in respect to the channel 15.

Thus, FIGS. 1 and 2 illustrate a universal mounting frame A which can be used for all known air jet reeds of a tunnel variety of varying lengths, heights and locations of air jet tunnel relative to top or bottom channel of the reed. The reed is held in place in the frame by the lower guide or alignment rail 14 and the magnetic bar holder 19 together with the gravity effect of the weight of the reed.

The drive pulley C together with a nylon coated cable 20 provide uniform or other predetermined motion to the carriage along the reed. The pulley is driven by a motor 21. It is important to note in the drawings that the top channel 13 of the reed 10 (as mounted in the loom) is located along the bottom of the frame and the bottom channel 12 of the reed 10 (as mounted in the loom) is located exposed at the top of the frame (e.g. This is the reverse of the arrangement in the air jet loom).

This is important because it exposes the bottom of the reed channel for exact and uniform rolling motion of the carriage along any type of reed. All types of loom reeds have critical reed dimensions which are referenced from the bottom of the bottom channel and from the front of the bottom channel to the sides of the tunnel and to the bottom of the tunnel. Dimensions to and from the top channel of the reed are considerably less critical and in fact can vary from one reed to another within limits without effecting the function of the reed in the weaving process.

Universal adjustment of the air measuring device E, illustrated as a Pitot tube within the air jet tunnel 11, is provided by the mounting which also provides universal adjustment of the buffing or grinding wheel D in and around any and all sections of the air jet tunnel. Various types of buffing or grinding wheels designed for different buffing purposes may be utilized. Any such device or operation for altering the surface as configuration of the tunnel is referred to herein as a buffer or buffing. A universal mounting 23 (FIG. 3) for an air jet nozzle as illustrated at 24 is provided at any desired location relative to the tunnel and at a variable distance from the Pitot tube. The carriage B may be variable in width to permit extensive changes of the distance of the Pitot tube from the nozzle and also permit use of multiple nozzles if this is desirable. This feature is useful because at present the location of the nozzles on the loom relative to the tunnel are fixed. This is true in the case of each type of loom. This capability provides for a means to determine the optimum nozzle location for different types of filling materials depending on count, denier, twist, etc.

An air cylinder 25 and a potentiometer 26 are illustrated in FIG. 4 connected in relationship to the buffing mechanism universal mounting 22. The buffing mechanism having the wheel D is located by moving it in or out of the desired position. A desired pressure of the buffing wheel may be applied to any selected part of the tunnel. Further, by means of the potentionmeter the speed of the wheel D is regulated providing for a constant surface speed during its motion across the air jet reed and accommodating any wear in the buffing wheel. Since the Pitot tube E also has a universal mounting capability both up and down and in and around of the air jet reed tunnel air flow, i.e. pressure drop, measurements may be made in any locations in the profile of the air jet tunnel.

A nozzle 27 of vacuum system is located in the carriage. It is moved into position automatically when buffing is performed, and out of the way when measuring is performed. Its purpose is to clean the reed and constantly remove any particles created during the buffing process. Thus, apparatus has been provided for measuring air flow for all types of air jet reeds for all known air jet looms.

The measuring of air flow by pressure drop from a known pressure can be performed anywhere in the cross section of the tunnel and at any distance from the Pitot tube to the nozzle. A variety of nozzles can be used and the nozzle location is variable relative to the tunnel and the Pitot tube. The number of nozzles is also variable.

Air pressure to the nozzles can be set at variable pressures. Once air flow measurements are taken with potentially a variety of methods, the air flow can be recorded in any suitable way. Adjustments in air flow throughout the cross section of the air jet reed tunnel and over the full length of the air jet reed tunnel are possible. Variations in air flow can be produced in both cross sections and over the length of the air jet reed to accommodate optimum filling stop arrangements, different fillings, air consumption and resulting power conservation, loom speed as measured in picks per minute, and cloth quality. These adjustments are accomplished by removing or creating slight burrs on the metal profile dents, varying the surface finish of the metal profile dents, modifying the shape of the metal profile dent to increase or decrease air flow and to increase or decrease turbulence, varying nozzle location relative to air jet tunnel, and changing nozzle design.

While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

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Yarn Clearer 

Yarn clearer is the device which is used to remove the following faults of yarn in order to increase the yarn quality and weaving efficiency.

Faults of yarn are as follows

• Thick and thin places 
• Slab and neps 
• Loose fabric 
• Foreign materials

Types of Yarn Clearer

There are two types of yarn clearer

1. Mechanical Type

a. Conventional blunt type

b. Serrated blade type

2. Electronic type

a. Capacitance type

b. Photo electric type

Comprise between mechanical and electronic clearer

• Electronic clearer are more sensitive than mechanical clearers

• In case of mechanical clearers there is abrasion between yarn and clearer parts but in case of electronic clearers there is no such abrasion

• Mechanical clearers do not prevent soft slab from escaping through clearer where as electronic type does not allow passing of any types of faults

• Mechanical type does not break the thin places and the length of the fault is not considered

• Mechanical clearer are simple and easy to maintain while the electronic clearers are costly and requires high standard of maintenance.

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The primary distinction between different types of looms is the manner of filling insertion . The principal elements of any type of loom are the shedding, picking, and beating-up devices. In shedding, a path is formed for the filling by raising some warp threads while others are left down. Picking consists essentially of projecting the filling yarn from one side of the loom to the other. Beating-up forces the pick, that has just been left in the shed, up to the fell of the fabric. This is accomplished by the reed, which is brought forward with some force by the lay.

An apparatus for making fabric by weaving yarn or thread. A loom is a device used to weave cloth. The basic purpose of any loom is to hold the warp threads under tension to facilitate the interweaving of the weft threads. The precise shape of the loom and its mechanics may vary, but the basic function is the same.

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.

Classification of Modern Loom:

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.

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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 has 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.

Classification of Weaving Machines:
Weaving machines are classified according to their filling insertion mechanism. The classification is as follows:
 

1. Shuttle
2. Shuttle-less

• Projectile
• Rapier
• Air-Jet
• Water-Jet

Shuttle Weaving
In shuttle weaving, a shuttle that traverses back and forth across the loom width, inserts the filling. Shuttles can be made of wood or plastic. Filling yarn is wound on the quill and the quill is placed in the shuttle. As the shuttle move across the loom, the filling yarn is unwound from the pirn and lay in the shed.

Projectile Weaving
Projectile weaving machines use a projectile equipped with a gripper to insert the filling yarn across the machine. The gripper projectile draws the filling yarn into the shed. The Projectile glides through the shed in a rake- shaped guide. Braked in the receiving unit, the Projectile is then conveyed to its original position by a transport device installed under the shed.

Rapier Weaving
In Rapier weaving, a flexible or rigid solid element, called rapier, is used to insert the filling yarn across the shed. The rapier head picks up the filling yarn and carries it through the shed. After reaching the destination, the rapier head returns empty to pick up the next filling yarn, which completes the cycle. A rapier performs a reciprocating motion.

1. Single Rapier Machines: A single, rigid rapier is used in these machines. The rigid rapier is a metal or composite bar usually with a circular cross section. The rapier enters the shed from one side, picks up the tip of the filling yarn on the other side and passes it across the loom width while retracting. Therefore, a single rapier carries the yarn in one way only and half of the rapier movement is wasted. Also there is no yarn transfer since there is only one rapier. The single rapier’s length is equal to the width of the loom.

These machines are the ideal solution for those who want to produce bulk quantities of customized fabric styles. The weaving widths range generally from 190 to 400 cm. As regards the multicolor weft carrier, up to 8 different wefts can be fed. It has however to be considered that the air jet weaving machines require a high energy consumption to prepare the compressed air and that this consumption rises definitely with increasing loom width and running speed. The reduction in the energy consumption is in fact one of the main concerns of the manufacturers, and builds for the user an important selection criterion.

Water-Jet Weaving
A water-jet weaving machine inserts the filling yarn by highly pressurized water. The relative velocity between the filling yarn and the water jet provides the attractive force. If there is no velocity difference, then there would be no tension on the yarn results in curling and snarling of the yarn. Water-jet weaving machine can only be used for hydrophobic fibers.

 

Fig: Water-Jet Weaving

It cannot be performed with existing traditional methods and machines. It interlaces a multiple layer warp with multiple horizontal wefts and multiple vertical wefts producing directly shell, solid and tubular types of fully interlaced 3D fabrics with countless cross-sectional profiles.

First demonstrated in 1997, Dual-Directional (D-D) Shedding System is indispensable for performing 3D-weaving. This path breaking development has advanced the technology of weaving to a new dimension for the first time in its more than 27000 years of history.

Manufacturing Technology of 3D-Weaving
Special looms are required to operate the warp threads in 60o angle for weaving 3Dr-3 Directional fabrics. But the 3 Dimensional -3Dm- fabric can be woven by using ordinary loom with usual weaving principle-shedding, picking, beating - by having multi layers of warp and multi layers of weft. Even though the treble cloth with 3 series of warp and weft could be called 3Dm fabrics, in general, minimum 4 series of warp and weft are used in weaving to form several layers, one above the other to get the sufficient thickness resulting into 3 Dimensional fabric.
As per the principle of weft Tapestry fabric, to weave 3Dm fabrics, it is required to use one series of stitching warp and multi series of separating warp as per the number of layers to be formed. 

 As seen from the cross section, the stitching warp passes from top to bottom and bottom to top but all the separating warp lies almost straight and hence the stitching warp takes up more length than the separating warp. Therefore, the stitching warp is brought from a loose tension beam and the entire separating warp is brought from another normal tension beam.

The following points are to be understood from both the cross sections: -

The first layer weft (Face) - shown as "a" - lies between the stitching warp (shown as 1) and first separating warp series (shown as 3).
The second layer of weft (Middle) - shown as "b"- lies between the first and second separating warp series (shown as 3 and 4).

Application of 3D Weaving Fabric
A new method has been developed for the manufacture of bifurcated prosthesis used in medical applications and they are used to replace the defective blood vessels in patients so as to improve blood circulation.

The 3D fabrics have recently entered the medical field. Their specific area of application is in the weaving of vascular prosthesis. Vascular prosthesis are surgically implantable materials. They are used to replace the defective blood vessels in patients so as to improve blood circulation. Conventional types of prosthesis were made from air corps parachute cloth, vignon sailcloth, and other types of clothing materials.

Materials such as nylon, Teflon, orlon, stainless steel, glass, and Dacron polyester fibre have been found to be highly suitable for the manufacture of prosthesis. These materials were found to be significantly stable with regard to resistance to degradation, strength, and were not adversely affected by other factors. Dacron polyester, which has bio-compatibility and high tensile strength, is being used over a period of time as suture thread or artificial ligaments.

The main function of the heald shaft is as follows:

(i) It helps in shed formation
(ii) It is useful in identifying broken warp threads
(iii) It maintains the order or sequence of the warp threads
(iv) It determines the order of lifting or lowering the required number of healds for a pick. In other words it helps in forming the design or pattern in a fabric.
(v) It determines the warp thread density in a fabric, i.e. the numbers of heald wires per inch determine the warp thread density per inch.

2 .Sley or lay
It is made of wood and consists of the sley race or race board, reed cap and metal swords carried at either ends. The sley mechanism swings to and fro. It is responsible for pushing the last pick of weft to the fell of the cloth by means of the beat up motion. The sley moves faster when moving towards the fell of the cloth and moves slower when moving backwards. This unequal movement is known as ‘eccentricity of the sley’. It is needed in order to perform the beat up and also to give sufficient time for passage of shuttle to pass through the warp shed. The beat up of the lastly laid pick of weft is accomplished through a metal reed attached to the sley.

3 .Shuttle
It is basically a weft carrier and helps in interlacement of the weft with the warp threads to form cloth. The shuttle which is made of wood passes from one end of the loom to the other. It travels along the wooden sley race and passes between the top and bottom layers of the warp sheet. The shuttle enters a shuttle box fitted at either ends of the loom, after passing through the warp shed. A shuttle normally weighs about 0.45 kgs.

4 .Shuttle Box
It is the housing for the shuttle and is made of wood. It has a spindle and a picker. It may also accommodate the picker without spindle. The top and side of the box towards the sley race are open. The shuttle dwells inside the box for the intermediate period between two successive picks.

5 .Picker
The picker is a piece made either of leather or synthetic material. It may be placed on a spindle or grooves in the shuttle box. It is used to drive the shuttle from one box to another. It also sustains the force of the shuttle while entering the box.

6 .Reed
It is a metallic comb that is fixed to the sley with a reed cap. The reed is made of a number of wires and the gap between wires is known as dents. Each dent can accommodate one, two or more warp ends. The count of the reed is decided by the number of dents in two inches. The reed performs a number of functions which are enumerated as follows:

(i) It pushes the lastly laid pick of weft to the cloth fell
(ii) It helps to maintain the position of the warp threads
(iii) It acts as a guide to the shuttle which passes from one end of the loom to the other.
(iv) It determines the fineness of the cloth in conjunction with the healds.
(v) It determines the openness or closeness of the fabric. 

There are various types of reed such as ordinary reed, gauze reed, expanding reed, V reed etc.

7 .Warp Beam
This is also known as the weaver’s beam. It is fixed at the back of the loom. The warp sheet is wound on to this beam. The length of warp in the beam may be more than a thousand metres.

8 .Back Beam
This is also known as the back rest. It is placed above the weaver’s beam. It may be of the fixed or floating type. In the first case the back rest merely acts as a guide to the warp sheet coming from the weaver’s beam. In the second case it acts both as a guide and as a sensor for sensing the warp tension.

9 .Breast Beam
It is also known as the front rest. It is placed above the cloth roller at the front of the loom and acts as a guide for the cloth being wound on to the cloth roller. The front rest together with the back rest helps to keep the warp yarn and cloth in horizontal position and also maintain proper tension to facilitate weaving.

10 .Cloth Beam
It is also known as the cloth roller. The woven cloth is wound on to this roller. This roller is placed below the front rest. It is also known as the cloth roller. The woven cloth is wound on to this roller. This roller is placed below the front rest. 

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There are hundred types of name of fabric. As a textile engineering student, you should know some commercial name of fabric. Some commercial names of fabric are given below:

Bedford Cord 

A cord cotton-like fabric with raised ridges in the lengthwise direction. Since the fabric has a high strength and a high durability, it is often used for upholstery and work clothes.

Brushed Cotton 

A raised fabric produced by brushing, teazling or rubbing i.e. the fabric in open width is passed over roller covered in teazles(usually for wool) or fine wires to pull out the surface fibers to give the required effect.  Brushed jersey/fleece usually for sports use with a brushed back.

Cambric 

A light weight closely woven plain fabric usually stiffened. (74 g/m2)

Canvas 

A fabric made from cotton, hemp, flax, or jute, for 200 to 2000 g/m2. Covers cloths with a great variety of uses but salient features being strength and firmness.

Denim 

Traditionally a 3/1 warp-faced twill fabric made from yarn dyed warp and undyed weft typically 270 g/m2. True denim is a twill weave cotton-like fabric made with different colored yarns in the warp and the weft. Due to the twill construction, one color predominates on the fabric surface.

Double Cloth 

A fabric construction, in which two fabrics are woven on the loom at the same time, one on top of the other. In the weaving process, the two layers of woven fabric are held together using binder threads. The woven patterns in each layer of fabric can be similar or completely different.

Double Knit 

A weft knit fabric in which two layers of loops are formed that cannot be separated. A double knit machine, which has two complete sets of needles, is required for this construction.

Double Weave 

A woven fabric construction made by interlacing two or more sets of warp yarns with two or more sets of filling yarns. The most common double weave fabrics are made using a total of either four or five sets of yarns.

Duck 

A tightly woven, heavy, plain weave, bottom-weight fabric with a hard, durable finishes. The fabric is usually made of cotton, and is widely used in men's and women's slacks, and children's play clothes.

Flannel 

A medium-weight, plain or twill weave fabric that is typically made from cotton, a cotton blend, or wool. The fabric has a very soft hand, brushed on both sides to lift the fiber ends out of the base fabric and create a soft, fuzzy surface. End-uses include shirts and pajamas.

Gabardine 

A tightly woven, twilled, worsted fabric with a slight diagonal line on the right side. Wool gabardine is known as a year-round fabric for business suiting. Polyester, cotton, rayon, and various blends are also used in making gabardine.

Lace 

Fine openwork fabric with a ground of mesh or net made by looping twisting or knitting on which pattern may be worked - crocheting, tatting, embroidery, weaving or knitting.

Lawn 

A light, fine cloth made using carded or combed linen or cotton yarns. The fabric has a crease-resistant, crisp finish. Linen lawn is synonymous with handkerchief linen. Cotton lawn is a similar type of fabric, which can be white, solid colored, or printed.

Madras 

A lightweight plain weave cotton fabric with a striped, plaid, or checked pattern. True madras will bleed when washed. This type of fabric is usually imported from India. End-uses are men's and women's shirts and dresses.

Muslin 

An inexpensive, medium weight, plain weave, low count (less than 160 threads per square inch) cotton sheeting fabric. In its unfinished form, it is commonly used in fashion design to make trial garments for preliminary fit. A light weight plain open weave bleached and died (not exceeding 68 g/m2).

Net 

An open mesh fabric in which a firm structure formed by twisting interlocking or knitting.

Organdy 

A stiffened, sheer, lightweight plain weave fabric, with a medium to high yarn count. End-uses include blouses, dresses, and curtains/draperies.

Oxford 

A plain weave of good quality having two warp ends weaving as one often striped with fancy weave effects. A fine, soft, lightweight woven cotton or blended with manufactured fibers in a 2 x 1 basket weave variation of the plain weave construction. The fabric is used primarily in shirtings.

Pique (woven)

A fabric showing rounded cords in the weft direction with pronounced sunken lines between. Weave on the face of the cord plain with warp floats the width of the cords on the back. Wadding picks are used to accentuate the prominence of the cords.

Poplin 

A plain weave cotton type fabric with weft way ribs and high warp sett. The construction is characterized by having a slight ridge effect in one direction, usually the filling. Poplin used to be associated with casual clothing, but as the "world of work" has become more relaxed, this fabric has developed into a staple of men's wardrobes, being used frequently in casual trousers.

Sailcloth 

It is originally tightly woven cotton or linen canvas (now made from nylon or polyester for actual sails).

Sateen 

A weft faced fabric in which the binding places are arranged to produce a smooth fabric and avoid twills fabric. A fabric made from yarns with low luster, such as cotton or other staple length fibers. The fabric has a soft, smooth hand and a gentle, subtle luster. Sateen fabrics are often used for draperies and upholstery.

Satin 

A warp faced weave in which the binding places are arranged to produce a smooth fabric and avoid twills. Satin is a traditional fabric for evening and wedding garments. Typical examples of satin weave fabrics include: slipper satin, crepe-back satin, faille satin, bridal satin, moleskin, and antique satin.

Taffeta 

A lustrous, medium weight, plain weave fabric with a slight ribbed appearance in the filling (crosswise) direction. For formal wear, taffeta is a favorite choice. It provides a crisp hand, with lots of body.

Velvet 

A medium weight cut-pile constructed fabric in which the cut pile stands up very straight. It is woven using two sets of warp yarns; the extra set creates the pile. Velvet, a luxurious fabric, is commonly made with a filament fiber for high luster and smooth hand.

Yarn Tensioners are devices by the help of which tension is given to the yarn. This is an important device because it enables us to provide necessary tension to the yarn as it moves through the different parts of the mschine.

Types of tensioning device 

There are basically three types of method by which tension is applied to yarn. They are as follows

• Capstan method 
• Additive method 
• Combined method

Capstan Method

This is the simplest form of yarn tensioning device where the yarn is passed around posts where the tension on the yarn is provided from the friction between the posts and yarns.

This follows the classic law of

Output tension = Input tension x eµθ

Additive method

In this method the yarn is passed through the middle of two surfaces in contact. The force is applied from above to give suitable tension to the yarn.

Combined method

The combined system is a combination of capstan and additive method. This device is a complicated system which on allows the addition of tension. We cannot decrease the tension with this device. It is seldom used.

Important effects of tensioning device 

If the tension is too high then

• The yarn can be damaged 
• The rate of yarn breakage will be high 
• The elongation property of yarn will change

If the tension is too low then

• It can lead to unstable or loose package formation which will cause problems during unwinding

Variation in yarn in different parts of a wound package will cause undesirable effects

For man made filament yarn improper tension will cause

• Change in molecular structure 
• Variation in colour shades

For staple or spun yarn too high tension will cause

• Yarn breakage at thin places

Factors influencing the selection of Tensioners 

• The device must be reliable to control uniform tension 
• The device must be easily thread able 
• It must not introduce or magnify tension variation 
• It must not introduce variation in twist 
• It must not be affected by wear 
• It must be easily adjustable 
• It must not be affected by oil and dirt 
• It must not encourage dirt collection 
• It must be easily cleanable 
• The operating surface must be smooth 
• It must be cheap

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Weaving Resistance:
When warp and weft are interlaced in a fabric then they oppose to each other due to static electricity or other factors. This opposition or resistance is called weaving resistance. Weaving resistance or its counterpart, beat up force, is at the center of the relationship between pickspacing, yarn properties and loom settings. 


Factors Affecting Weaving Resistance:
In case of pick spacing requires a larger beat up force or, for a given spacing, a thicker weft requires a larger force. It is suggested that a discontinuous relationship between pick spacing and weaving resistance but that has not been confirmed by experiment - possibly because irregularities in yarn properties would smooth the discontinuities. Loom settings are also known to influence the relationship. 

Weaving resistance

 There are some factors which affecting weaving resistance are given below:

• The effect of warp tension
• The effect of shed balance
• The effect of shed timing
• The effect of cloth fell distance and beat-up force
• The effect of weave

The Effect of Warp Tension:
There seems to be general agreement that increasing warp tension increases weaving resistance. Theoretically increased tension increases inter yarn forces and hence the effect of friction. . However, the influence seems to be fairly small, both indicating a rise of about 10% in weaving resistance for a doubling of the basic or average tension.

The Effect of Shed Balance:
They show a very significant effect of tension ratio in the two warp sheets on weaving resistance. It had earlier been reported by Bramma21 and Snowden8 that an unbalanced shed was helpful in achieving high setts. Jederan22 considered the effect on weaving resistance and, according to the English abstract of his Hungarian paper, found that "contrary to what is generally accepted" no reduction resulted. Mallah20 had reported that peak warp tension was reduced when the shed was unbalanced and both Yehia11 and Leung in their limited experiments, from which the present study has evolved, showed a significant reduction in beat up force when the shed was unbalanced. Yehia's work suggested that the effect was influenced by shed timing. Leung used a crude method of unbalancing that avoided Ito's "kinematic" effect and was incidentally independent of shed timing; he inserted a heavy roller like a lease rod in the warp so that each of the slacker and tighter sheets was always composed of the same threads. With the more normal arrangement, using a raised back rail to unbalance the shed, each yarn is alternately in the slack and tight sheet of the open shed; but when the shed is closed, i. e. crossing, it is by definition also balanced.So it would be expected that the timing of the shed relative to beat up would affect the weaving resistance.

The Effect of Shed Timing:
In view of what has already been said, it is not surprising to find contradicting statements about shed timing. Greenwood said the effect was so small that its significance must be doubted. Badve found a difference but not all his results show the effect consistently. Yehia's results suggested a "normal" timing gave least resistance. to a small extent. Theoretical studies suggested that it was not so much the effect of timing (and hence shed angle at beat up) on the actual beating up that mattered, but its effect in opposing slipping back. In industry it seems generally to be accepted that an early timing enables picks. to be beaten more closely. So a confused picture emerges and it is clear that a more detailed and more precisely defined range of settings should be used than the "late", "normal" and "early" often adopted.

Cloth Fell Distance and Beat-up Force:
Although cloth fell distance is not a basic or independent parameter (except when it is set at the start of a period of weaving) it is a visible feature that forms an important link in the relationships between other variables and so has received some attention. Badve set out to measure c. f. d. in order to test Greenwood's equations and pointed out that in developing the beat up force it is not the fell displacement in absolute terms that is related to beat up force, but the displacement relative to that which would occur due to shedding, back rail movements, etc., in the absence of beat up. When he had developed a means of measuring that relative movement, the modified c. f. d. or, as he termed it, the "interference" between reed and fell, was still often greater than seemed necessary for the force, even when true load/extension curves were used instead of constant moduli in the relationship. These results led him to suggest slipping back of picks might be responsible, so that the cloth fell was not clearly defined but was rather a region that was neither warp nor cloth. Greenwood found some evidence that c. f. d. was influenced by loom speed being slightly increased when the speed was reduced. That might be explained in the elastic moduli being slightly lower for slower rates of strain but it could also be an effect of fell movement rather than displacement by the reed.
 

The Effect of Weave:
For given yarns it seems obvious that, just as maximum possible sett depends on the density of intersections in the weave, so weaving resistance would also depend on that density. Galuszinski, working on plain weave derivatives, claims to show a direct simple relationship between weaving resistance and setting formula. Chen Jui-lung had previously reported similar results but expressed in less precise terms.