The fundamental principles of weaving are, SHEDDING i.e. dividing the longitudinal threads called 'warp' into two sheets; PICKING i.e. insertion of transverse thread called 'weft' into the space created by the division of warp sheets and BEATING i.e. pulling the inserted wefts one after the other to form cloth. There is no change in these principles whether it is Handloom, Powerloom. Automatic Loom or Shuttleless Loom technology.
Shuttleless looms have been developed to overcome the inherent problems created by the dynamics of the picking mechanism on the conventional Fly Shuttle Looms and make use of entirely different methods of weft insertion. Air Jet, Water Jet, Rapier, Gripper (Projectile) and Multi-Phase are the various types of Shuttleless Weaving Machines named after the method employed for weft insertion.
Shuttleless Weaving Machines are generally of wider widths enabling the simultaneous weaving of two or more widths; upto 400/420 cms. in the case of Air Jet and Rapier and upto 540 cms. in case of Gripper. The weft insertion rates achieved are 1560, 1480, 2850 and 2565 Mtrs./Mt. for Gripper, Rapier, Air Jet and Water Jet Weaving Machines respectively.Shuttleless Weaving Machines are sviitably designed to match the requirements of high insertion rates, shedding, beating and other auxiliary motions. Let-off and take-up mechanisms and weft monitoring are invariably controlled through microprocessors. The machines are equipped with features like automatic pick finding & repairing and weft accumulators. There are FOUR different type of shuttleless looms .They are
o Rapier loom (single and double type);
o Gripper or projectile loom;
o Water jet
o Air jet loom
· Except the weft yarn is placed at the side of the loom, the weaving processes (primary and auxiliary motions) of shuttleless loom is similar to shuttle loom
· Insert weft yarn by means of projectile, rapier, air and water jet Weft yarn is placed outside the weaving loom. The speed is faster, quiet and better fabric quality
Advantages and disadvantages of each shuttleless loom
1. The problems of shuttle loom are the weft yarns are placed inside the shuttle. The shuttle is big and heavy and the machine speed is low and noisy to operate. In addition, a new pirn must be inserted to the empty shuttle for continue operation.
2. Shuttleless looms eliminate these problems by placing the cone of yarn at the side of theloom.
3. Once the yarn is bought across the loom, the yarn is cut, often leaving a little fringe of the edges of the fabric
4. . Shuttleless weave 2 to 4 times as much as conventional looms per unit time.
5. . The cost of pirn winding is eliminated.
6. Strain upon the warp threads is reduced due to smaller depth of shed
7. 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.
8. The physical and mental strain upon the weaver is reduced
9. There is no risk of shuttle fly out owing to the absence of conventional shuttle and packing being positive
10. Quality of the fabric gets enhanced because of a positive control over the weaving process.
11. The looms are easier to work and manipulate
12. . Efficiency of the shuttle weaving shed is comparatively higher
13. 10. 5% reduction in value loss for a Rs. 60/- Metre fabric would ensure an additional profit of Rs. 3/- meter
14. Higher production per loom.
15. Speed is not the only criterion for the selection of shuttleless looms. Efficiency is also an important criterion.Efficiency advantage of 10-15% due to shuttle changes, Un weaving of damages, reduced time for warp changes canbe obtained from shuttlelesslooms. 5% higher efficiency would provide an additional profit of Rs. 1/- per meter.
Rapier Loom
A rapier loom uses a rapier to pull the weft yarn across the loom.
· It can be a single rapier or double rapier.
· For a single rapier, a long rapier device is required to extend across the full width of warp.
For a double rapier loom, two rapiers enter the shed from opposite sides of the loom and transfer the weft from one rapier head to the other near the centre of the loom
· The advantage of two rapier system is only 50% of the rapier movement is utilized in the weft insertion of single rapier loom
Projectile loom (I)
· The picking action is accomplished by a small bullet like gripper which grips the weft yarn and carries it through the shed.
· This is a more positive way of inserting the weft yarn without restoring to the heavy shuttle.
· Because the mass of gripper is low, the forces needed to accelerate it are less and the picking mechanism can be lighter.
In addition, the running speed of the looms can be increased significantly compared with conventional shuttle loom. Small bullet like gripper is passed from one side to the other inside the shed
Projectile loom (II)
· Several grippers are normally used in the loom.
· While one is crossing the loom with weft yarn, the others are returning to the starting position.
· The dragging of the weft yarn across a loom creates strain on this yarn, so projectile looms are not suited for weaving with very weak yarn.
· However, it is excellent for use with heavy and bulky yarns, as well as regular size yarns.
· It is the most versatile of the shuttleless looms in regard to the range of fabric it can produce.
Air Jet (I)
· Jet looms take the weft yarn across the loom by using a high speed of either air or water.
· The force of air or water carriers the yarn from one side to the other.
· Jet looms are faster than projectile or rapier looms (picks per minute).
· However, they cannot produce as great a variety of fabrics (no heavy or bulky yarns), nor can they produce as a wide a fabric (jets have less yarn-carrying power).
· Jet looms also do less damage to the warp since there is no abrasion of this yarn by the jets of air or water, unlike the projectile or rapier.
Multiple air nozzles are used to insert the weft yarn into the shed.
Air jet (II)
With the air-jet looms, the initial propulsion force is provided by a main nozzle.The fabric width of air-jet loom is normally narrower than rapier or projectile loom
Water jet (I)
· With water jet looms, there is only a main nozzle to provided the propulsion of the weft yarn.
· The loom is very efficient, with only a small amount of water required and is the fastest type ofshuttleless loom.
· Water-jet looms are capable of producing 700 picks per min (ppm) for 75-inch fabrics compared to about 180 picks per min for shuttle looms with 44-inch fabric.
Water jet (II)
· Since wet fabric cannot be stored in a roll, water jet looms are equipped
with efficient drying units.
· The units use vacuum suction and heat to remove the water from the fabric.
· Water-jet looms are best suited for weaving filament yarns made of hydrophobic fibres (water-resistance fiber) like nylon, or polyester/cotton.
· Yarns made of fibres that lose strength when wet (e.g rayon) should not be used.
