The document discusses different types of looms and their weft insertion mechanisms, including projectile looms, rapier looms, air jet looms, and multiphase looms. It describes the torsion bar picking mechanism of projectile looms and covers topics like weft insertion, selvedges, classifications of double rapier looms, air treatment systems for air jet looms, and calculations for fabric and yarn production.

1. Weaving Technology
Projectile Loom
In projectile loom the weft insertion is carried out by small projectiles, which number
depends on the weaving width and which with their grippers take out the weft yarn from big
cross-wound bobbins and insert it into the shed always in the same direction.
With projectile weft insertion virtually any yarn can be woven, e.g. cotton, wool, silk, mono- and
multi filaments and tapes,as well as hard fibres like jute and linen, and even metal.
Advantages for picking by projectile:
There is a torsion bar which is made of alloy metal and its spring like characteristics makes possible
to create a torsion angle of 11° without any hamper or degradation. It also reduces the loom sound.
Weft Insertion Mechanism of Projectile Loom:
i) Weft yarn is supplied from cone package through accumulator and feeder.
ii) At first the projectile lever moves backward, the projectile feeder remains closed.
iii) Feeder opens and projectile come in front of the projectile lever and grips the weft yarn.
iv) Weft brake releases the weft,tension lever moves upward and projectile lever beats the
projectile to perform a picking.
v) Projectile moves to other side of the loom and is caught by projectile brake.
vi) On the other side weft brake stops the yarn, tension lever moves downward.
vii) Weft end gripper on both side of the loom grips the yarn while projectile feeder is closed.
viii) Weft cutter come into action and cuts the weft while the projectile brake opens & releases
the projectile. This projectile falls below over a conveyor belt or chain & passed to the
other side. It is lifted by a pusher rod for further picking.
ix) The cut weft yarn is tucked inside the fabric by a tucking needle and also forms a tucked-in
selvedge.

2. Torsion bar picking mechanism:
i) The picking cam shaft 1 which rotates once every pick,
has a picking cam 2.
ii) As the cam 2 continues to turn, the roller 3 will lose
contact with the nose of the cam and turned the toggle
lever in a clockwise direction which is fulcrummed.
iii) In doing so, it has twisted the free end of the torsion rod 6
through the link 7 and the torsion lever 8, which is secured
to the torsion rod 6 near its free end.
iv) The picking lever 9 is attached to the free end of the
torsion rod 6 and carries the picker 10.
v) At this stage, the amount of twist at the free end of the
torsion rod is about 30°, and the picking lever has rotated
through a similar angle.
vi) The picker force the projectile to move forward.
1- Cam shaft
2- Picking cam
3- Roller
4- Toggle lever
5- Fulcrum
6- Torsion rod
7- Link
8- Torsion lever
9- Picking lever
10- Picker
11- Roller fixed on cam

3. 12- Curved contour
13- Oil brake
Rapier Loom
Insertion of weft by rapier is a mechanically modern and refined version of the primitive method of
fabric production. In the present version the gripper heads are attached to rapiers which are flexible
tapes or rigid rods. The rapiers are made of coated steelor reinforced high performance manmade
fibers like carbon.
Classification:
Sequence ofWeft Insertion:
i) Single-Rapier Loom:
It can insert weft only on alternate rapier traverses,and thus each rapier must be long
enough to extend across the full width of the loom. The mass of the reciprocating parts is
high.
ii) Dewas Double Rapier Loom:
It grips the weft outside one of the selvedges and carries it to the centre of the loom,
where the yarn is transferred to a gripping point in the other rapier head. This rapier then
pulls the weft across the loom to complete the traverse. Weft withdrawal from the supply
package thus occurs in two stages.
iii) Gabler Double Rapier Loom:
The weft is gripped outside the selvedge, and, as the rapier traverses the loom, a
hairpin of weft is formed. At the point of transfer,the yarn extends from the supply
package,round the rapier head, and back to the gripping point on the loom frame. When
the rapiers start to withdraw, the yarn is released from the gripping point and is
straightened out by the second rapier.

4. Disadvantages ofSingle Rapier:
i) Double time for both rigid and flexible.
ii) Double space for rigid but less space for flexible.
Adv. & Disadvantages ofDouble Rapier:
i) Less picking time for both rigid and flexible.
ii) More space for rigid but less space for flexible.
iii) In Gabler, weft yarn forms loop, half picking occurs and fabric become bulky, twist
opens.
Multi-Phase Loom:
Continuous weft insertion occurs in circular and multiphase looms. Multiphase looms are of 2 types:
i) Circular multiphase shuttle
ii) Flat circular airjet
Features:
 Heavy reciprocating parts & a precision system of shuttle propulsion is eliminated.
 In circular weaving machine, the advantages of complete rotary motion is in line with weft
knitting machine.
 In circular loom 8 shuttles may simultaneously be employed for weaving.
 Wave shed is produced & shed is vertical
 In circular loom metallic shuttle propulsion by magnetic block & pinion.
 In circular loom rotating spiked wheel is used for beating up
 Medium & coarse fabrics are produced.
 In circular loom multiple warp beams are simultaneously used.
 For plain weave- 32 harness is used
 Heald frames are horizontal
 Reed is fixed and it controls the warp spacing.
 Two shuttles per loom are frequently encountered especially in weaving hosepipes or small-
diameter sacking.

5. Air Jet Weaving:
The air jet weaving machines are supplied with compressed air from a centralcompressor in the
weave room or are equipped with individual built-in compressors. The weft yarn is inserted by means
of compressed air.
Air Quality:
If moisture, grease, oil,carbon and foreign particles are not removed from the compressed air:
a) The metallic parts of the loom and piping will corrode.
b) Nozzle efficiency will reduce and valve will not work
c) Particles will adhere in the compressed air pipe, passage resistance as wellas pressure loss
increases and pine holes made in the pipe wall result in air leakage.
d) The reed will soil and this will lead to inefficient weft insertion, malfunctioning of loom,
damage of reed and the impairment of fabric quality.
e) Operational environment will not be hygiene.
Typical Lay-out of Air Treatment Plant:
Notation Equipment Function
a. Compressor and Filter To collect raw air, separate large particles and compress the air.
b. Receiver Tank To store compressed air for preventing pressure pulsation, separate
moisture, grease and other impurities.
c. Air dryer A refrigerating air dryer is used to remove moisture.
d. Main line filter Removes 3-5 micron size foreign particles & scale compressed air.
e. Sub-micron filter Removes 0.3-1 micron size substances such as tar and carbon.
f Micro- mist Filter Removes 0.01 micron size particles (e.g. grease)
Weft Insertion Mechanism ofAir Jet Loom:
i) The weft yarn is drawn from the supply package at constant speed by rollers or drum
storage motion.
ii) The length of each pick is determined by the circumference and speed at the measuring
disc according to the fabric width.
iii) With the clamp closed the yarn is held ready for insertion in the tube storage motion in
the form of a hairpin by the air stream from an auxiliary nozzle.
iv) Immediately before the clamp opens, the main nozzle starts blowing, so that the yarn is
set in motion when the clamp opens.

6. v) The hairpin is stretched out.
vi) The yarn is blown into the guiding channel of the reed with the shed open.
vii) The yarn is then carried through the shed by the air currents of the relay nozzles along the
reed channel. At the end of each insertion cycle the clamp closes. The stretched yarn is
beaten up and cut after shed closure.
Disadvantage:
This fire hazard is probably the biggest disadvantage of an electrical warp stop-motion, and it makes it
totally unsuitable for use on looms that are intended for the weaving of soft-spun fibrous warp yarns.
Its quick action makes it ideal for looms weaving continuous-filament yarns and relatively fine
(probably combed) cotton and worsted yarns, which are generally used in quality fabrics.

7. Selvedge:
The finished edge of a fabric is called selvedge to keep fabric from unraveling or fraying apart.
Functions ofSelvedge:
 To prevent fraying apart of warp
 To maintain width
 To increase strength at the selvedges
 To prevent structural deformation
Types ofSelvedges:
i) Both end bounded selvedge ( on hand
loom & conventional loom)
ii) One end bounded selvedge ( on Gabler
Rapier)
iii)Fringed selvedge ( on air jet loom)
iv) Leno selvedge (Airjet, Rapier)
v) Tucked-in selvedge (projectile loom)
vi) Stitched selvedge
vii) Adhesive selvedge
viii) Fused selvedge
ix) Dummy selvedge
x) Twisted (Half & Full) selvedge
 Conventional selvedge:
- Produced on a conventional shuttle loom.
- Strength is necessary to counteract the pulling of the weft thread as the shuttle traverses the
loom, and this function must be performed by the outside ends of the fabric.
- The fabric surface must be absolutely uniform from one side of the cloth onto the other.
 Tucked-in Selvedge:
- The tucked selvedge is a technique used on some shuttleless
looms.
- A device is used to tuck and hold the cut ends into the fabric
edge using a special tuck-in mechanism
 Leno selvedge:
- The leno selvages are obtained by binding the wefts with strong additional
threads by eliminating through cutting the protruding weft ends.
- Half cross leno weave fabrics have excellent shear resistance.
- The leno gauze system is optimally suited for heavy fabrics, blankets, wall
coverings.

8. Twisted Selvedge:
Twisting the outside ends around each other is done by using a disc that carries
two bobbins (Fig. 5.8b). As the disc rotates, the threads from the bobbins are
made to twist around one another between picks.
 Fused Selvedge: These selvages are made on fabrics of thermoplastic
fibres, such as polypropylene, nylon, etc. by pressing a hot mechanical
element on the edges of the fabric. The fibres melt and fuse together,
sealing the edges. Electronically controlled thermal cutters are used to
cut and fuse selvedges of synthetic fabrics on weaving machines. The
temperature of the cutters is reduced when the machine is stopped. This
technique is sometimes used to split wide fabrics into narrower widths.
Production of loom:
PPM = 200, PPI = 50
Production per loom per minute =200/50 =4”
Production per loom per month = 4 x 60 x 24 x 30 inch
Production per loom per year at 70% efficiency = 4 x 60 x 24 x 30 x 12 x 0.7 inch
= (4 x 60 x 24 x 30 x 12 x 0.7) / 36 yds
= (4 x 60 x 24 x 30 x 12 x 0.7) / 39.37 m
= 36868.68 m (ANS)
Problem-2:
PPM = 350
PPI = 60
No. of loom = 45
Time = 7 days
Efficiency = 90%
Solution:
350 90 1
Production =…….. x (60 x 24 x 7) x 45 x …….. x ……….. m
60 100 39.37

9. 14288400000
= …………….. m
236220
= 60487.68 m (ANS)
Problem-3:
PPM = 650
PPI = 58
No. of loom = 10
Time = 35 days
Production = 110000 m
Solution:
650 x 60 x 24 x 35 x 10 x η
Production = …………………………………..
58 x 100 x 39.37
110000 x 58 x 100 x 39.37
=> η = ………………………………..
650 x 60 x 24 x 35 x 10
=> η = 76.77% (ANS)
Problem-4: Find out Wt. of yarn in fabric (warp & weft), from the following specification.
Warp count x Weft count
.………………………...... x Fabric width
EPI x PPI
or,
20 x 22
.………… x 56”
60 x 58
Solution:
In 5000m fabric, wt of weft warp,
60 x 56 x 5000 x 1.05
= ……………………………………… kg
0.914 x 840 x 20 x 2.2046
= 521.09 kg (ANS)
In 5000m fabric, wt of weft,
58 x 39.37 x 5000 x 56 x 1.05
= ……………………………………… Kg

10. 36 x 840 x 22 x 2.2046
= 457.73 kg (ANS)
Problem-5:
Find out the wt. of required warp & weft to produce 5000m fabric from the following
specification.
18 x 16
.…….. x 58”
66 x 62
Solution:
66 x 58 x 5000 x 1.05 x 1.1
Required warp = ………………………..…….. = 725.28 kg (ANS)
0.9144 x 840 x 18 x 2.0246
62 x 39.37 x 5000 x 58 x 1.05 x 1.1
Required weft = ………………………...................….. = 766.49 kg (ANS)
36 x 840 x 16 x 2.2046
Problem-6:
Calculate the yarn consumption of a loom per hour running at 180 PPM for producing from
the following specification.
40 x 60
…………. x 56” fabric
72 x 48
Solution:
180 1
Production/hour/loom = ……. X 60 x …… = 6.25 yd
48 36
72 x 56 x 6.25 x 1.05 x 1.1
Req. amount of warp = …………………………………= 0.393 Kg
840 x 40 x 2.004
48 x 36 x 6.25 x 56 x 1.05 x 1.1
Req. amount of weft = ……………………………….. = 0.175 Kg
36 x 840 x 60 x 2.024
4.67

11. Fabric Production Calculation
Loom Speed = Motor RPM * (Motor PullyDiametre)/(Loom PullyDiametre)
Loom Effeciency Percentage = (Actual Production/Calculated Production )* 100
Moisture Regain Percentage = {(Yarn Weight - Dried Yarn Weight)/Dried Yarn weight} *
100
Moistue Content Percentage = {(Yarn Weight - Dried Yarn Weight)/Yarn weight} * 100
Type of Yarn Moisture Regain % Moisture Content %
Cotton 8.50 7.83
Jute 13.75 12.10
Silk 11.00 9.91
Rayon, Viscose 11.00 9.91
Wool 17.00 14.50
Nylon 4.20 3.78
Warp Weight in Kg = (Total Ends * Tape Length in metres)/(1693.6 * Warp Count)
Weft Weight in Kg = (R.S in centimetres * cloth length in metres * PPI )/(4301.14 * weft
Count)
Cloth weight in GSM = {EPI/Warp Cout)+(PPI/Weft count)}* 25.6
oz (ounce ) per sq. yard = GSM(Grams per sq. metre)/34
Material Measurement
To calculate the length of any rolled fabrics, this formula gives the nearest accuracy.
L = {0.0655(D-d)(D+d)}/t
Where L = Length of material (Feet) t = Thickness of fabrics (inches)
D = Outside diameter (inches) d = Inside diameter (inches)
Weight of yarn in a cloth
The weight of cloth manufactured on looms depends upon the weight of yarns in thewarp and
weft: ends/inch, picks/inch and the weight of size on the warp. Therefore,
Cloth weight = Weight of warp + Weight of weft + Weight of size (All inlbs.)
Where as Weight of warp in lbs. = (Total No. of Ends * Tape Length in Yards)/(840 * warp
yarn count)