WEAVING

Fabric Manufturing

II

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.

CHRONOLOGICAL/ HISTORICAL DEVELOPMENT OF LOOM

1. Vertical loom: Damask, Tapestry.

2. Pit loom.

3. Frame loom.

4. Chittarangan/ Semi-automatic loom:Take up automatic but let off manually.

5. Hattersley loom.

6. Natural Source/ Ordinary power loom: a) Water wheel was until 195b) Steam engine

c) Diesel engine

7. Electric power loom: 1st power loom 17841st weaving mill with power loom 1789

a) Large single motorb) Large group motor c) Individual motor with 1930

8. Modern loom:a) Projectile b) Rapierc) Air Jetd) Water Jete) Multiphase

PRIMITIVE OR VERTICAL LOOM:

PIT LOOM:

Weaving has a long tradition in Egypt going back as far as 6,000BC during which time methods have changed enormously. This simple pit loom is the kind that is frequently found in farms and villages operated by men and women who make carpets, chair covers, shawls, blankets and bed covers

The weaver sits with his or her legs in the pit where there are two pedals which open the warp threads allowing the weft shuttle to pass through freely. This type of loom leaves the weavers' hands free to pass the weft shuttle through from side to side and to compress the weaving as they go.

PIT LOOM

FRAME LOOM

Simple and effective- wonderful introduction to weaving- very quick to warp and weave- strong- compact

Create wall hangings, cushions, tablemats and coasters. The loom is ideal for students or any weaver wanting a simple way to be creative. Made from solid Silver Beech hard wood the frames are strong and robust for a variety of warps and tensions. Small and compact, the weaving frame is ideal for taking on holiday. The finished piece can be left in the frame and hung on the wall

FRAME LOOM

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-offTertiary 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.

POWER DEVELOPMENT OF LOOM DRIVE

1. Hand loom: Human power drive

2. Power loom:1. Water wheel

2. Steam wheel

3. Diesel Wheel

4. Electric wheel

3. Large common motor (200loom/ motor)

4. Group motor ( 200 loom/ motor)

5. Individual motor invented at 19301. Direct drive

2. Indirect drive

6. Multiple motor : for each modern loom

GROUP MOTOR

Disadvantage: Absenteeism of warker

Shortage of raw materials

Shortage of worker

Style change

Shortage of spare parts

Natural calamities

Political issue

Power loss

Advantages:

Less man power required

Minimum cable required

Less initial cost

Less electric complexity

INDIVIDUAL MOTOR Advantage:

Randomly power supply

Power saving

Simple driving system

Least amount of production loss

Disadvantage: Higher initial cost

More cable required

More possibility of fire hazard

Maximum electric personnel required

Distribution and sub distribution board required

High manpower

METHODS OF POWER DRIVE IN WEAVING LOOM:

Direct drive

Loom driven directly by on-off system of motor

High initial torque is required

Saves energy

No side way thrust is required

High initial cost

Used in jute loom

No use of clutch

Indirect drive

Clutch declutch system

Low initial torque

Apply undesirable side way thrust

Low initial cost

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

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

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

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 directionE Arrow showing the half distance

of a shed in a downward direction

A

B

C

D

E A

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

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

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

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

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

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

BASIC SHEDDING MECHANISMS:

1. Paddle/ treadle loom: hand loom

2. Tappet shedding mechanism

3. Dobby shedding mechanism

4. Jacquard shedding mechanism

5. Combined shedding

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

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.

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 healdshaft 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.

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.

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

DEFECTS 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