Weaving Department about loom mechanism _unit_2 prepared by: ROHIT SINGH

1. WEAVINGWEAVING
UNIT - IIUNIT - II
Prepared byPrepared by
ROHIT SINGHROHIT SINGH
nitragzb20152019@gmail.comnitragzb20152019@gmail.com
94503169279450316927
NITRA TECHNICAL CAMPUSNITRA TECHNICAL CAMPUS
GHAZIABADGHAZIABAD

2. Loom:
• Loom is machine or device which is used to
produce woven fabric. It is the central point
of whole process of cloth production.
It 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.

3. • Loom motions: There are three types of loom
motions:-
1. Primary
2. Secondary.
3. Tertiary.
Primary motions are: a) Shedding b) Picking c) Beating.
Secondary motions are: a) Take-up b) Let-off
Tertiary motions are: a) Warp stop b) Weft stop c) Reed
stop.
Drafting: The process of passing yarn through the drop wire
is called drafting.
Drawing: The process of passing yarn through the heald eye
is called drawing.
Denting: The process of passing yarn through the reed is
called denting.

5. SHEDDINGSHEDDING

6. Shedding:
• Dividation of warp threads into two parts for
insertion of weft threads is called shed and
mechanism of shed is called shedding.it is the first
primary motion of weaving.
Types of shed:
• Bottom close shed
• Centre close shed
• Semi open shed
• Open shed

7. Bottom close shed
• This type of
shedding is produced
by giving motion
only to threads that
are to form the upper
line.under this condition,
the warp is level in the
bottom line. Hence in A→ Bottom line of warp
order to form a top shed B→ Rising and falling line
it is necessary to move C→ An arrow showing the space
some threads through a passed through
space equal to twice the
depth of a shed.
A
B
C

8. Advantage:
• Used in hand loom
• Alternate tightening and slacking the warp threads
produce a covered cloth
DISADVANTAGE:
• More stress or tension on top warp line
• Different tension on the warp threads
• Low speed
• Not possible to produce compact fabric
• Poor quality fabric
• More chance of breakage on top warp line
• More power consumption

9. Centre close shed
• This type of shed is produced by imparting an upward movement
to those threads which are to form the top line and a downward
movement to the threads which are to form the bottom line.
Then after inserting pick both trhe lines meet at the centre
between the highest and lowest lines of a divided warp
• A→ Closed warp line
• B, C→ Upper and lower lines of
a divided warp
• D→ Arrow showing the half distance
of a shed in an upward direction
E→ Arrow showing the half distance
of a shed in a downward direction
A
B
C
D
E A

10. Advantage:
• Equal tension on top and bottom warp line
• Less time required, so high production
• Less wear of the machine
• Less power consumption
• Less tear of the threads
DISADVANTAGE:
• Beat up takes place in the closed shed
• Compact fabric can not be produced
• Chance of weft being moved backward

11. Semi open shed
• In this shed, the stationary bottom is retained but threads
for the top line either passes to bottom at one movement
and again carried to the top mid way and again carried to
top. In this shed close and open shed occurred
simultaneously. In it the stationary bottom line is retained,
but threads for the top line either pass to the bottom at
one movement, or are arrested midway and again carried
to the top. Such a shed can be formed as expeditiously as
an open shed, for the upward movement begins and ends
with the downward through movement, and the arrested
downward movement is converted into an upward
movement immediately the falling threads are in the same
plane as the rising ones. They all reach the top together but
the strain upon them is not equally distribut

12. Semi-open shed:
A→ Stationary bottom line
B→ Top point
C→ The point where downward movement ceases in threads
D, E→ Showing the movement of through healds
F→ Arrow showing the threads which are to lift for the next pick
C
A
D
B
F
E

13. Semi-open shed:
ADVANTAGE:
• Equal tension on the top and bottom warp line
• Beat up takes place in the close shed
• Speed faster
• For fency fabric
• Less power need
• Less tear of threads
• Possible to produce compact fabric
Disadvantage:
unusual movement

14. Open shed:
• In open shed, the warp threads form two stationary lines, the
top line and the bottom line and changes are made by
carrying the threads from one fixed line to the other without
any interval.
• A, B→ Stationary warp line
C, D→ Arrows which show the movement of rising and falling
warp to equal the distance between A & B
C
A
D
B

15. Open shed
ADVANTAGE:
• Beat up takes place in cross shed condition
• Equal tension top and bottom warp threads
• Faster speed
• Extensively used in tappet shedding mechanism
• Basic fabric (twill, sateen, plain) can be produced
• Less power consumption
• Less wear of loom
DISADVANTAGE:
• High breakage rate
• If higher no of heald shafts are used then warp in back
healds are more stained than the front ones

16. Basic shedding mechanisms:
1. Paddle/ treadle loom: hand loom
2. Tappet shedding mechanism
3. Dobby shedding mechanism
4. Jacquard shedding mechanism
5. Combined shedding

17. Tappet shedding
• A type of cam which transforms a rotary motion into a
reciprocating motion in rods and levers by sliding
contact is tappet.
When the receives a series of lifts, with intervals of rest
and thus forms a shed called tappet
Scope of tappet shedding:
• Maximum capacity 14 heald shafts
• Normally produce square design
• Only the basic weave and small design are produced

18. Construction of tappet shedding:
• The figure shows a negative tappet shedding mechanism. A pair of
tappets A and B are fixed to the bottom shaft C at 180 degrees to each
other. Two treadle levers D and E are connected to the loom back-rail by a
bracket F.
The bracket acts as a fulcrum for the levers. The two treadles have teeth
to carry the lamb rods G and H respectively. Two heald shafts J and K are
connected to the lamb rods. A top reversing roller shaft Q carries two
rollers of different diameters. The roller of small diameter N is connected
to a leather strap L to which the front heald shaft J is connected. The
roller P of large diameter is connected to a leather strap M to which the
back heald shaft K is connected. The tappets A and B touch the anti-
friction bowls or followers R and S respectively, which are fixed to the
treadle levers. The heald shafts have heald eyes T and U through which
the war p threads pass X is the war p sheet and Y is the cloth. The odd
ends are passed through one heald shaft while the even ends are passed
through the other heald shaft.

20. Working principle of tappet:
• When the bottom shaft is rotate as shown in the figure, the tappets
also rotate. The tappet will depress the anti-friction bowl and the
treadle. Being fulcrumed at one end, the front portion of the treadle
moves down. This action is transferred to the lamb rod, the heald shaft
and the leather strap. So one heald shaft is lowered and the threads
connected to this heald shaft are lowered and form the bottom layer of
the shed.
• The leather straps attached to the reversing rollers are connected in
opposite directions, i.e. when leather strap is pulled down, it is
unwound from its roller. The shaft therefore rotates in the clockwise
direction and the other leather strap is wound on to its roller. The heald
shaft is raised and therefore the lamb rod and treadle lever are also
raised. The threads connected to the heald shaft are also raised and
form the top layer of the shed.
• For the next shed, the other tappet works with the other set of bowl,
treadle, lamb rod, heald shaft, strap and roller and the other heald
shaft is lowered.

21. Types of tappet:
• Negative tappet: in a tappet shedding mechanism
if the tappet controls only one movement either
an upward or downward movement of heald
shaft, then the shedding is known as negative
tappet shedding.
• Positive tappet: : in a tappet shedding
mechanism if the tappet controls both the
upward and downward movement of heald
shaft,then the shedding is known as positive
tappet shedding.

23. Advantages of tappet shedding:
• Simplest
• Cheapest
• If properly used, it gives the best results within its
capasity
• Action is certain
• It is capable of lifting heavy weights with less
wear and tear than other shedding mechanisms
• Less wear and tear
• Consumes less power and give greater output

24. Disadvantages of tappet shedding:
• Over shedding strains and breaks the warp
threads
• Under shedding does not permit the space to
pass the shuttle through the shed.
• Sometimes unequal shedding by lifting one end
of the shaft more than the other
• Missed shedding
• May impart jerky motion
• Capacity is only 14 heald shaft

25. PICKINGPICKING

26. Advancement in weft insertion
system
Projectile weaving machine
Rapier weaving machine
Air-jet weaving machine
Water-jet weaving machine
Multiphase weaving machine
26

27. Projectile Weaving Machine
• The Projectile weaving machine introduced into
market in 1952 by Sulzer as the first successful
shuttle less weaving machine.
• Projectile machine uses a projectile equipped with a
gripper to insert the filling yarn across the machine.
• The unique principle of this machine is that we can
practically insert the any kind of yarn like cotton
,wool, filament yarn, poly propylene or even jute as
well, this is because all the finer or coarser yarns are
securely grip by a gripper and inserted by the
projectile
27

28. Projectile motion
Fig: Hitting of Projectile with torsion rod and picking lever
28

29. The principle operation
The projectile draws the filing yarn into the shed.
Energy requires for picking is build up by twisting a
torsion rod.
On release the rod immediately returns to initial
position smoothly accelerating the projectile by means
of a picking lever.
The projectile slides through the shed in rake shape
guide and braked into the receiving unit.
Projectile is then conveyed into the original position by
a transport device (belt) installed under the shed .
29

30. Advantages of projectile weaving machine
Low power consumption
Reduced waste of filling insertion due to unique
clean ,tucked in selvages
Quick warp and change style
Easy operation ,maintenance and low spare parts
requirements
More than one width of fabric woven at a time due
to large machine width such as 33-540cms
Energy saving
Different designs and color sequences can be
woven.
30

31. Rapier weaving machineRapier weaving machine
• In this type of 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 a cycle.
• A rapier performs a reciprocating motion. 31

32. Single Rapier Double Rapier
TYPES OF RAPIER WEAVING MACHINES
Flexible RapierRigid Rapier
Dewas system Gabler System
32

33. Single rapier weaving 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 weaving machine
while retracting.
33

34. Fig: Single rapier transfers the yarn in one way34

35. • A single rapier carries the yarn in one way only and
half of the rapier movement is wasted.
• The single rapier’s length is equal to the width of
the weaving machine; this requires relatively high
mass and rigidity of the rapier to ensure straight
movement of the rapier head.
• For these reasons, single rapier machines are not
popular. However, since there is no yarn transfer
from rapier to rapier, they are suitable for filling
yarns that are difficult to control.
35

36. Double rapier weaving machines
• Two rapiers are used in these machines one rapier,
is called the giver, takes the filling yarn from the
yarn accumulator on one side of the weaving
machine, brings it to the centre of the machine and
transfers it to the second rapier which is called the
taker.
• The taker withdraws and brings the filling yarn to
the other side.
• Similar to the single rapier machines, only half of
the rapier movements is used for filling insertion.
36

37. • Double rapier machines can be
rigid or flexible.
• Double rigid rapiers are further
classified into two types: Dewas
system and Gabler system.
• In Dewas system the giver grip
the tip of the yarn, brings it to
the centre and transfers it to the
taker which retracts and carries
the yarn to the other side of the
weaving machine.
37

38. In the Gabler system, the yarn is
not gripped. The giver extends
the yarn in the form of “U”
shape to the centre of the
weaving machine.
The yarn is then transferred to
the taker, which extends the
yarn to the other side of the
weaving machine by
straightening it.
since both rapiers extend to the
out side of the weaving machine,
the space requirement of the
double rigid rapier machines is
high.
38

39. • In flexible rapier machines the rapier has
tape-like structure that can be wound on a
drum.
• This saves space and allows narrower
machine widths compared to the double rigid
machines.
• The yarn is gripped both by giver and taker.
• Double flexible rapier machines are more
common than the rigid rapier machines.
39

40. Water jet weaving machine
• The water-jet weaving machines inserts the filling yarn by
highly pressurized water.
• The tractive force (pulling force) is provided by the relative
velocity between the filling yarn and water jet.
• if there is no velocity difference between the water and
yarn then there would be no tension on the yarn which
would be result in curling and snarling of the yarn.
• The tractive force is affected by the viscosity of the water
and roughness and length of the filling yarn; higher
viscosities cause higher retractive forces.
• The viscosity of water depends on the temperature.
40

41. Water jet weaving machine
• Water jet weaving machines have the same basic
functions of any other type of weaving machines.
• the principle of weft insertion with a water jet is
similar to the filling insertion with an air jet: they
both use a fluid to carry the yarn.
• however there are some differences has affect the
performance and acceptance of water jet weaving
machines.
• For example, the yarn must be wettable in order to
develop enough tractive force. 41

42. Water jet weaving machine
The flow of water has three phases:
1. Acceleration inside the pump prior to injection into the nozzle.
2. Jet out let from the nozzle
3. Flow inside the shed.
The water flow inside the shape has conical shape with three
regions;
Compact, split and atomized. Compact and split portions are
better for yarn insertion. due to water weight the jets axis forms
a parabola which necessitates adjusting the axis of the nozzle
upward by some angle. the flow of water then flows the motion
of angular projection.
• 42

43. Water jet weaving machine
• The width of the water-jet weaving machine
depends on the water pressure and diameter of the
Jet.
• Since water is not compressible it is relatively easy
to give enough pressure to water-jet for insertion.
• The diameter of Jet is around 0.1 cm and the
amount of water used for one pick is less than 2 cc.
• Double pump system, with two nozzle at will filling
insertion, is suitable for weaving fabrics with two
different fillings.
43

44. Air- Jet weaving machine
• A cutter is used to cut the yarn when the insertion is
completed.
• The air-jet weaving machine combines high performance
with low manufacturing requirements.
• It has an extremely high insertion rate, due to its
exceptional performance.
• Air-jet weaving machines are used primarily for the
economical production of standard fabrics, covering a wide
range of styles.
• Meanwhile, more and more special fabric segments are
covered: heavy cotton fabrics such as denim, terry fabrics,
glass fabrics, tire cord, etc. 44

45. Principle operation of air jet weft insertion system
Profiled reed 45

46. Multi-phase weaving
• Further increases the production rates of woven
fabrics(woven area/machine hour) require new technologies
such as multi-phase weaving machine is one in which several
phases of the working cycle take place at any instant such
that several filling yarns can be inserted simultaneously.
• In these machines more than one shed is formed at a time,
there fore they are also called Multi-shed weaving machines.
• This concept is drastically different than single shed weaving
machines in which each of the five functions takes place
subsequently.
• Therefore it is appropriate to consider the multi-phase
weaving machines as the third generation of weaving
machines.
46

47. 47

48. DEVELOPMENTS IN WEAVING MACHINESDEVELOPMENTS IN WEAVING MACHINES

49. DEVELOPMENTS IN PROJECTILE MACHINES
1) COLOUR SELECTION
 1 X 1, 2, 4 and 6 colors can be used in weft direction.
 The system is freely programmable and operated by servo controller.
 No limitations on feeder position shifting.
2) ELECTRONIC WEFT BRAKER
 This device keeps a uniform tension on weft.
 The braking force and the braking duration are programmable.
 Program can be given for each pick.
 The device is driven by stepper motor.
3) Pre-acceleration to weft yarn is given by compressed air, which
relieves extra tension in weft while inserting.
4) K3 Synthetic projectile can be used for weaving of delicate yarns.
49

50. 5)The no. of heald shafts operable by cam motion is
extended to 14.
6)Speed has been increased upto 470 rpm due to
improvement in many related mechanisms.
7)LED display at signal pole for machine speed,
projectile arrival time, angle of machine stop, etc.
which helps in monitoring of process.
8)Automatic weft brake repair motion enables shifting
of feed package to a reserved one in the event of
weft break between package and accumulator, no
stopping of machine which increases the machine
efficiency.
50

51. DEVELOPMENTS IN AIR JET WEAVING
Modification In Weft Insertion System
The multi nozzles are divided into two zones and connected directly
with separate tanks.The weft yarn requires higher pressure at later part
of its flight, and this separation has helped greatly in optimization of
pressure in duration of Jet opening.
The weft insertion, based on a precise electronic control
that includes ATC (automatic timing control), also uses
newly developed nozzles, which guarantees optimum
weft insertion conditions.
Independent pressure tanks make it possible to set weft
insertion pressures at optimal levels, this makes a
significant contribution to energy conservation.
 All settings regarding picking is done by microprocessor
keyboard, which reduces machine down time.
51

52. Tandem Nozzles: -
In tandem nozzles, the two main nozzles are arranged in
series so called tandem nozzles.
Advantages: -
 It reduces the nozzle pressure
Saving in energy
Also use of wider weft count range.
Low pressure weft insertion to occur, making effective
for super high-speed operation accommodating yarns
with low breaking strength.
52

53. Tapered Sub-Nozzles: -
It consists of a tapered hole to prevent air dispersion.
Advantages: -
 It enables stable weft insertion with lower air volumes.
 It stabilizes air injection angles during weft insertion.
 The weft insertion is more stable and requires less air.
Tapered Tunnel Reed: -
A tapered shape has also been applied to the tunnel selection of reed
blade.
Advantages: -
 It helps in preventing air dispersion.
 The weft insertion is more stable and requires less air.
Electronic Braking System: -
One of the serious drawback of Air-jet picking was tension peak
in weft when brake is applied. The electronic braking system can
precisely control braking time and brake stroke, which significantly
reduces tension pick, thereby reduction in weft breaks.
53

54. Take-up motionTake-up motion
Take-up motion –
The system has the following controls:-
Tension control—The servomotor controls the warp yarn
tension and slack according to the signa collected by the
tension sensor. This process ensures that the warp yarn’s
tension is controlled properly during opening, warp loosening,
and warp let-off.
Manual warp yarn loosening and tightening—When the
machine is not operating, the user can manually tighten or
loosen the warp by controlling the servomotor’s forward and
reverse rotator.
Fabric take-up control—This function pulls the finished cloth
away from the opening in time as required by the weft
density so that the position of the opening does not vary with
the new weft- yarn, ensuring successful production.

55. Take-up motionTake-up motion
A→ ETU GEAR BOX
B→GEAR
C→ FRICTION GEAR
D→ COMPOUND GEAR
E→ SPUR GEAR
F→ DRIVE GEAR
G→ PRESS ROLL
To pull the cloth forward after the
beat-up of weft, maintaining the
same pick density and spacing
throughout weaving of a cloth
and throughout winding the
woven cloth onto a roller.

56. Let-off
• Let-off. - To allow the warp to unwind from
the warp beam during weaving and also to
maintain an average constant tension of warp
as it weaves down.

57. Auxiliary motion
In order to produce a good quality of cloth and to prevent damages it is
necessary to have some stop motion provided on the loom. They can be
termed as auxiliary motions.
Warp protector. - To protect the warp thread by stopping the loom when the
weft fails to reach, and box properly into either the winder during picking.
Warp stop.- To stop the loom when a warp thread breaks or excessively
loose.
The operating system is the following .:-
Each warp thread is passed into the bottom slit of a metallic drop wire 2,
• Which this way is supported by the thread under tension. Through the top
slit of the drop wire passes the contact rail 3 composed of an u-shaped
outside coating in stainless steel, of a strip of insulating material and of a flat
conductive inside blade in nickel-plated copper, Provided on the upper part
with a toothing.
• The contact rail 3 is part of a low voltage electric circuit, of which the drop
wire 2 acts as circuit Breaker.

58. Warp stop motionWarp stop motion

59. Weft stop motionWeft stop motion
• In the case of air jet machines for staple yarn weaving,
an optoelectronic weft stops motion in twin
arrangement can be delivered. While the first of the
two weft stop motions serves as support for the
machine control, the second one records the weft
threads broken in the shed or expelled.
• When the first one gets the weft, which means the
weft thread has travelled the predetermined distance,
the loom remains running. And in case of the second
one gets the weft, which means the weft thread has
broken and travelled excess than the predetermined
distance, it knocks-off the loom instantly.

60. Weft stop motionWeft stop motion

61. THE ENDTHE END
SESSION ISESSION I