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Introduction and types conventional and unconventional looms

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Introduction and types conventional and unconventional looms

  1. 1. Introduction and types conventional and unconventionallooms;working principle of rapier, waterjet,air jetand multiphaseweavingmachine with their figures HafeezullahMemon Zhejiang Sci-Tech University Hangzhou, China
  2. 2. Introduction and types conventional and unconventional looms: In the textile sector present time is the time of modern & new era. Man has invented a lot of modern loom using with modern weft insertion system. So the comparison of conventional loom & modern loom indicates how much the conventional loom is modified within the passing of time. Conventional Loom: It is still not certain when the weaving process was introduced to human society. It is clear from many historical records that weaving originated long before the time of Jesus Christ. In England the major shift from agriculture to woolen industry came in the 14th century. Earlier version of power loom was run by two men. After the steam engine and cast iron in early 1800, great attention was paid to increasing productivity of the machine. To help achieve the increase in productivity, William Radeliffe patented a dressing frame in 1803 for sizing and drying the warp threads prior to winding on to a weavers beam. Fig. Conventional loom
  3. 3. Features of Conventional 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. Unconventional Looms: Unconventional looms still weave by repeating in sequence the operations of shedding, picking, and beating in, but within that framework there has been considerable development during the 20th century. Several new types of loom have come into industrial use, whereas older types have been refined and their scope extended. Two main influences have been the rising cost of labour and the increasing use of man-made continuous- filament yarns. Unconventional looms may be divided as follows 1. Projectile looms 2. Rapier looms 3. Air jet looms 4. Water jet looms 5. Multiphase looms Projectile Loom: Sulzer brothers, Winterthur, Switzerland, Who are pioneer in the field of projectile method of weft insertion, have been able to convert a brilliant concept Roshman into a viable commercial weaving machine. It is introduced in the market in 1953.The main feature of this machine is weft insertion system. A bullet like shuttle 90 mm long & weighting about 40 g, technically named as gripper projectile is used here to insert the weft thread into the warp threads. Rapier Loom: Insertion of weft by rapier is a mechanically modern & refined version of the primitive method of fabric production in which the weft was secured in a slot of a stick. At present version of the gripper head which are attached to rapiers which are flexible tapes or rigid rods. Mr. John Gabler can be regarded as the father of modern rapier technology he has built a rapier device on a cotton weaving machine in 1922. Single rapier loom can insert weft only on alternate rapier traverse. In many cases this is modified to achieve a higher rapier velocity in the early and late parts of the movement and thus
  4. 4. a over maximum velocity halfway through the movement. Due to high rate of insertion the possibility of yarn breakages rate may increase. Additionally, it is necessary to control the weft by passing it trough an effective tension arrangement so that the weaving tension will be more uniform, this can also occurred weft break. Air Jet Loom: Weft insertion by means of air jet has made a major breakthrough in the early 70s and its importance is increasing further because of its ability to weave a wide range of fabrics at a very high speed weft insertion rate of about 2000 mpm. The first attempt to use a compressed air steam instead of shuttle is made by Brooks in 1914. It inserts the weft threads here used compressed air. It is not suitable for the coarser count or heavier fabric. The timing of jet activity should be controlled in such a way that the main nozzle is supplied with compressed air from the beginning of the weft insertion phase and the relay nozzles also receive compressed air. High maintenances is needed for it. Water Jet Loom: The first loom to make use of a water jet for insertion of weft was developed by Satyr.The loom was first shown at the Brussels textile Machinery Exhibition in 1995. For water jet looms, weft and warp yarn must be insensitive .i.e hydrophobic in nature, weaving of the water attractive fabric is not possible by the water jet loom, and thermoplastic yarns offer the advantages of severance of weft by a heated blade and the provision of a heat selvedge by fusing. It has required miniature pump to feed water under pressure to the nozzle. Multiphase Loom: The phase number of a loom is defined as the average number of shuttles or weft carriers inserting weft simultaneously. It is shown that existing multi-phase looms must have high phase numbers to compensate for their low shuttle velocity. The analysis suggests that looms with high-velocity flying shuttles would achieve equally high weft-insertion rates with moderate increases in the phase number. Such moderate increases in the phase number can be obtained by dividing the shedding and beat-up motions into a comparatively small number of sections. The suggested alternative would avoid many of the textile and engineering problems arising in existing multi-phase looms. A multi-phase loom with magnetic shuttle uses the spiral reed blade with shuttle path is used for beating-up. The linear motor is used for wefting, the heald wheel or electromagnetically excited heald needle is used for opening, and the weft opening with off-line multi-path asynchronous weft replenishing is used. Its advantages include high efficiency, high speed and low weaving cost. The multiphase loom can form many different sheds at different places, thereby enabling insertion of number of filling yarns, one behind the other.
  5. 5. Features of unconventional Loom:  Shuttleless weave 2 to 4 times as much as conventional looms per unit time.  The cost of pirn winding is eliminated  Strain upon the warp threads is reduced due to smaller depth of shed  Heavy cost of repairs and replenishment of worn out parts is reduced They can produce simpler tubes of fabrics on a large scale and provide opportunities for profitable exploitation in the long run.  The physical and mental strain upon the weaver is reduced  There is no risk of shuttle fly out owing to the absence of conventional shuttle and packing being positive  Quality of the fabric gets enhanced because of a positive control over the weaving process  The looms are easier to work and manipulate  Efficiency of the shuttle weaving shed is comparatively higher  Higher production per loom Working principle of rapier, water jet, air jet and multi phase weaving machine with their figures: Working principle of Rapier weaving loom: In some versions of the machine, two rapiers are used, each half the width of the fabric in size. One rapier carries the yarn to the center of the shed, where the opposing rapier picks up the yarn and carries it the remainder of the way across the shed. A disadvantage of both these techniques is the space required for the machine if a rigid rapier is used. The housing for the rapiers must take up as much space as the width of the machine. To overcome this problem, looms with flexible rapiers have been devised. The flexible rapier can be coiled as it is withdrawn and will therefore require less space. However, if the rapier is too stiff, it will not coil; if it is too flexible, it will buckle. The double rapier is used more frequently than the single rapier. Rigid and flexible rapier machines operate at speeds of up to 1,300 meters of weft per minute. These rapier looms are efficient. They operate at speeds ranging from about 200 to 260 ppm at about the noise level of projectile looms. They can produce a wide variety of fabrics ranging from muslin to drapery and upholstery materials.
  6. 6. Fig. Working principle of three rapier systems Newer rapier machines are built with two distinct weaving areas for two separate fabrics. On such machines, one rapier picks up the yarn from the center, between the two fabrics, and carries it across one weaving area; as it finishes laying that pick, the opposite end of the rapier picks up another yarn from the center, and the rapier moves in the other direction to lay a pick for the second weaving area, on the other half of the machine. The above figure shows the action on a single width of fabric for a single rigid rapier system, a double rigid rapier system, and a double flexible rapier system. Rapier machines weave more rapidly than most shuttle machines but more slowly than most projectile machines. An important advantage of rapier machines is their flexibility, which perm it’s the laying of picks of different colors. They also weave yarns of any type of fiber and can weave fabrics up to 110 inches in width without modification. Working principle of water-jet weaving loom: Water-jet weaving machines were first developed in Czechoslovakia in the 1950s and Subsequently refined by the Japanese in the1960s.Water-jet weaving machines are Not used as frequently as air jets, but they are preferred for some types of fabrics. The process is unsuitable for yarns of hydrophilic fibers because the fabric picks up too much moisture. Water-soluble warp sizings are used on most staple warp yarns. Therefore, the use of water-jet looms is
  7. 7. restricted to filament yarns of acetate, nylon, polyester, and glass; yarns that are non absorbent, and those that do not lose strength when wet. Furthermore, these fabrics come off the loom wet and must be dried. In this technique a water jet is shot under force and, with it, a weft yarn. The force of the water as it is propelled across the shed carries the yarn to the opposite side. This machine is economical in its operation. A water jet of only 0.1centimeter is sufficient to carry a yarn across a 48 inch shed. The amount of water required for each weft yarn is less than 2.0 cubic centimeters. Water-jet machines can reach speeds of 2,000 meters of picks per minute. The water-jet looms can produce superior high quality fabrics that have good appearance and feel. Both air and water jet weaving machines weave rapidly, provide for laying different colors in the weft direction, and produce uniform, high quality fabrics. They are less Noisy and require less space than most other types of weaving machines. They cause Minimal damage to warp yarns during the weaving operation, because the air or Water jets are less abrasive than moving metal parts. Fig. Water Jet loom The speeds of shuttle less weaving machines can be compared by measuring the Picks per minute(ppm)or the yards laid per minute (ypm) in weft insertion.In 1990, The top speed for a projectile weaving machine was 420 ppm with between 1000 and 1203 ypm weft insertion. Flexible rapier weaving machines operated at 524 ppm and rigid rapiers at 475ppm, laying weft at upto 1404 and 930ypm, respectively. Air jets could lay as many as 1200 ppm and water jets upto 1500 ppm, laying 2145 and 2360 ypm , respectively. If a fabric 60 inches wide is woven on each machine at a density of 50 pice per inch, Approximately 84 yards of weft yarn would be needed to produce an inch of fabric. In theory, the projectile would produce approximately 8.4 inches of fabric per minute; the flexible rapier,10.5 inches; the rigid rapier, 9.5 inches; the air jet, 24 inches; and the water jet, 30inches.The slowest of the new machines could produce a yard of fabric in 4.3 minutes, and the fastest would take just 1.2 minutes. Seldom do weaving machines operate at full capacity, but even at 50percent efficiency such machines could produce a yard offabricevery2.5 minutes.
  8. 8. Working principle of air jet loom: Air jet weaving machines were invented in Czechoslovakia and later refined by the Swiss, Dutch, and Japanese were designed to retain the tension less aspect of the picking action of the water jet while eliminating the problems caused by the use of water. The yarn is pulled from the supply package at a constant speed, which is regulated by the rollers, located with the measuring disk just in front of the yarn package. The measuring disk removes a length of yarn appropriate to the width of the fabric being woven. A clamp holds the yarn in an insertion storage area, where an auxiliary air nozzle forms it into the shape of a hairpin. Fig. Air Jet loom The main nozzle begins blowing air so that the yarn is set in motion as soon as clamp opens. The hairpin shape is stretched out as the yarn is blown into the guiding channel of the reed with the shed open. The yarn is carried through the shed by the air currents emitted by the relay nozzles along the channel. The initial propulsive force is provided by a main nozzle. Electronically controlled relay nozzles provide additional booster jets to carry the yarn across the shed. The maximum effective width for air-jet weaving machines is about 355 cm. At the end of the each insertion cycle the clamp closes; the yarn is beaten in, and then cut, after the shed is closed. Again some selvage-forming device is required to provide stability to the edges of the fabric. These weaving machines use a jet of air to propel the weft yarn through the shed at rates of up to 600 ppm. Date from manufacturers indicate that air-jet looms operate at speed up to 2200 meters of pick inserted per minute. They can weave multicolored yarns to make plaids and are available with both dobby and jacquard patterning mechanism. Air jet weaving is more popular because
  9. 9. the machines cost less to purchase, install, operate, and maintain than rapier or projectile weaving machines, and the air jet can be used on a broader variety of yarns than a water jet. Working principle of multiphase weaving loom: All the weaving techniques discussed thus far require that the shed be open all the way across the machine for the device carrying the filling yarns to pass through the shed. This imposes a limit on loom speed. The multiphase weaving machine overcomes this limitation by forming many different sheds at different places across the machine and forming these only as the weft yarn inserted. In this way, a number of weft yarns can be inserted, one behind the other. As a section of the shed opens, the weft passes, and the shed closes, opening again in the new pattern as the next weft yarn arrives. Speed is increased because of the number of yarns that can be inserted almost simultaneously one right after the other, but the actual speed of movement of the weft yarns is lower than in other types of machines. For this reason, weft yarns that are weaker can be used. Sultzer Ruti, the manufacturer of a multiphase machine, states that its loom will insert upto 5,400 meters of pick per minute. Fig. Multiphase weaving machine The process transforms weaving into a continuous process rather than a cycle of shedding, picking, and beating up. Multiphase loom continually inserts weft yarns from yarn carriers. Rotary beat-up devices press inserted yarn firmly against previously formed c1oth.If the pattern cbanges, small groups of yarns are changed into a new shedding position after each new yarn carrier has passed. The operation of multished weaving machines is based on a series of wave like motions across the weaving surface. In general, fabrics woven on these looms do not have a true 9O-degree
  10. 10. angle between warp and weft; the weft yarns are slightly slanted,or skewed. Multished weaving is limited to special types of fabrics, but it can be expected to gain acceptance in the years ahead. As many as 16 to 20 weft carriers insert the pre cut weft in a continuous process Instead of the intermittent process of single-shed weaving. Beating up and shedding arrangements are different. Ln this continuous weaving process, the number of picks Per minute is doubled. However, multiphase looms have never been extensively used in the industry.

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