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EXPERIMENT NO 4 OBJECT: To study the weft insertion system of the rapier weaving machine. APPARATUS: Double Flexible Rapier Machine. THEORY: 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 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 reciprocating motion. The rapiers are made of coated steel or reinforced high performance man-made fibers like carbon. Double Rapier Machine Two rapiers are used for picking in this machine. One rapier takes the filling yarn from the accumulator on one side of the loom, brings it to the center, called GIVER or RAPIER. Other rapier takes the filling yarn from giver on the center of loom, transfers to the other end of loom, called TAKER or GRIPPER.

Rapier Weft

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Page 1: Rapier Weft

EXPERIMENT NO 4

OBJECT:

To study the weft insertion system of the rapier weaving machine.

APPARATUS:

Double Flexible Rapier Machine.

THEORY:

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 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 reciprocating motion. The rapiers are made of coated steel or reinforced

high performance man-made fibers like carbon.

Double Rapier Machine

Two rapiers are used for picking in this machine.

One rapier takes the filling yarn from the accumulator on one side of the loom, brings it

to the center, called GIVER or RAPIER.

Other rapier takes the filling yarn from giver on the center of loom, transfers to the other

end of loom, called TAKER or GRIPPER.

Types of Picking Mechanism:

The rapier weaving machine can be classified according to

Method of weft insertion

Types of rapiers

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Structure of Rapier Loom

Advantages of Rapier Loom:

A wide range of fabrics can be woven by this machine.

The range of the fabric they can be woven by this machine is 20-80 g/m2.

This machine is widely used for household as industrial fabrics.

By this machine not only the classic cotton, wool and man-made yarn, but also filament

yarns, finest silk and fancy yarns can be woven.

In this machine, minimum stresses are imparted on the yarn.

The gripper’s heads take a wide range of yarns counts ranging from 5-1000 Tex.

The speed of this machine is up to 600 rpm, but the modern machines having the speed

up to 1400 rpm.

Method of Weft Insertion:

1. Gabler system:

The weft is supplied from magazine cones weighing 3-4kg placed at the right hand side of the

machine. Weft is inserted by two flexible rapiers. The weft is laid in two pick weft insertion

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cycle with a hairpin shaped loop to form a smooth and uniform conventional selvedge at the right

hand side of the cloth and an unconventional leno selvedge at the left hand side.

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2. Dewas system:

In this system the supply packages are mounted in separate compartments of the magazine. Each

weft yarn passes forward through thread eye of its compartment and through a weft tension

device. The weft yarn then passes forward through an eye of one of the vertical selector needles.

A number of needles can be used depending upon weft color range. Downward movement of a

needle places the weft at the rapier level and a cam operated finger swings inwards towards the

temple to ensure that the selected weft is separated from the inoperative wefts. The weft selection

needles may be operated by a dobby or jacquard.

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Types of Rapiers:

Rigid Rapier:

They are guided through the shed from outside the working width. The disadvantages of rigid

rapier system is that it requires large floor space at least twice that of fabric width because the

rigid rapier must be pulled out completely from the warp shed before beat up. A useful feature of

rigid rapiers is that they can be simultaneously inserted in two sheds one above the other for

producing double plush and certain carpets.

Flexible Rapier:

They are guided through the track formed by ribs. The motion given to the track ribs is such that

they enter the shed through the bottom warp shed as the slay moves back and leaves by the same

route prior to beat up. The advantage of flexible type is that there is less space utilization.

WORKING:

Driving Mechanism:

The driving mechanism of rapier is as follows:

The crank which is mounted on the driving shaft carries an eccentrically mounted on the rotating

stud to give to and fro motion to and fro motion to a rack and pinion. The latter transfers its

oscillating motion through an intermediate wheel and oscillating arm to the tape wheel. The

rapier drive motions are lubricated by filtered oil supplied from a pump.

Shedding Mechanism:

The common shedding systems used for rapier machines are positive cam, electronically

controlled positive dobby and jacquard systems. The dobby permits weaving with up to 24

harnesses with a speed of 630 rpm. It is controlled by entering the fabric and machine specific

parameters. The shed operating angle is modified between 19-28o.

Main Shaft Bracket Crank Arm Rack

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Weft Insertion Mechanism:

Weft feeder draws the weft yarn off cross wound package and coils it onto accumulator drum at

a preset speed. The weft yarn is therefore always un-wound from the same drum diameter at weft

insertion and thus maintains a defined weft tension.

The double flexible rapier, the weft insertion is divided into three phases:

Phase A:

Weft finger places the pick in the ready position. Left hand rapier sizes the pick and clamps it,

and weft cutter cuts it off

Phase B:

The left hand rapier transfers the pick to right hand rapier.

Phase C:

The right hand rapier withdraws the pick and releases it. The reed beats up the inserted pick to

the cloth fell.

Page 7: Rapier Weft

EXPERIMENT NO. 5

OBJECT:

To study the weft insertion mechanism of Air jet loom.

THEORY:

Air jet is a type of shuttle less weaving system in which the air is used to insert the web in the

shed by action of the kinetic energy of the air. But the air should be free from moisture, dirt and

oil by the help of proper treatments. Because impure air will corrosion of metallic parts, stains on

fiber and may also result in choking and blocking of nozzles as the dirt particles will accumulate

in machine parts.

Construction:

Main Components:

Yarn feeders/ Weft accumulators

Main nozzle

Relay Nozzle

Profile Reed

1. Yarn Feeders or Weft Accumulators:

Yarn feeders draw filling yarn from the filling bobbin; ensure uniform winding

distribution on the drum, therefore automatically adjusting the winding speed according

to the loom requirement, which makes for general insertion. And allows smooth running

of yarn.

2. Main Nozzle:

It helps yarn to insert in the shed through air pressure. The filling yarn threaded into

nozzle tubes is accelerated by the concentrated air-jet and inserted into the shed. The

amount of air needed depends on the yarn structure and the yarn count. It is controlled by

means of pressure control valve. To keep the motionless pick tensioned, a weak air

stream is blown on to the yarn lying in the main nozzle. The air volume needed for this

purpose can be individually controlled.

To reduce the weft insertion time, a tandem nozzle is used, which is the equivalent of two

main nozzles positioned one behind the other. The tandem nozzle has the job of

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unwinding the weft yarn from the drum feeder. The winding resistance is thus

compensated for by the tandem nozzle. The pressure can be reduced at the main nozzle,

assuring very gentle yarn insertion.

3. Relay Nozzle:

It supports yarn throughout the width by applying pressure. So that yarn will run easily

from the start to the end of the fabric width.

Relay nozzles mounted on slay are connected in groups to electromagnetic valves. The

air-jet is started by the electromagnetic relay nozzle valve. The length of time the valve is

opened depends on the reed width and relay valve spacing as well as on the yarn. The

compressed air is distributed from compressed air tank via the valves to the nozzles.

If the stretching nozzle is not used, the last relay nozzles can be supplied from a separate

compressed air tank, thus keeping the weft yarn tensioned until the shed is closed. This

version is used in the spun fiber yarn sector.

4. Profile Reed:

Profile reed provides path for the flow of yarn.

WORKING:

Speed of air jet is 1500 m/min; yarn count which can be made on air jet is 70s to 80s.

Compressed air is passed through compressor, filter and junction then further distributed

to pipes J1; J2, S1; S2, C1; C2.For jet pressure sub nozzle pressure and cutting pressure

respectively.

Two pipes are used for two color yarns. For each color separate tank is also present.

Regulators are installed to adjust pressure.

There are three pressures which need to be controlled

Jet pressure

Sub nozzle pressure

Cutting Pressure

Jet pressure is used for the main nozzle, sub nozzles pressure is used to control pressure of relay

nozzles. Cutting pressure is used to support the yarn when cutter cuts it. Because when weft

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insertion is completed, cutter cuts the yarn, so cutting pressure is exerted to support the yarn,

otherwise yarn would come out.

Total 5 sets of sub nozzles are present, each set has 5 nozzles. And 5 solenoids are used for 5

valves of air pressure.1 valve provides pressure to 1 set of nozzles.

Air-Jet Loom Mechanism:

Air-Jet Weft Insertion:

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Air Being Used In Loom:

Compressed air of pressure 4 bars is being used. It should be free from moisture, dust and oil.

Air Requirements:

1. Moisture:

Moisture in liquid and in vaporized form must be eliminated. Moisture is removed from air by

process of cooling. Improper elimination of moisture will cause:

Corrosion of metallic parts

Adhesion of foreign particles on inner walls of piping thus creating obstruction towards

air flow.

Pinholes are produced on the wall of piping which causes eventual air leakage.

Degrading quality of fabrics.

2. Oil:

Aerosol form as well as vapor form must be eliminated by oil removers. Filters are used to

remove oil particulates. A 0.03 micron element is used to trap sub micron particles and improper

treatment will cause:

Corrosion of metal surface

Adhesion of foreign particles on inside surface of piping

Stain on fabric

Problems of environmental conditions as well as health

3. Dust:

Dust particles larger than 5 microns must be eliminated. This is done by air filters. Improper

treatment will cause chocking/blocking of nozzles, inaccurate valve action and serious hazards

when air mixed with oil and moisture.

Advantages of Air Jet Looms:

High productivity (bulk quantities of customized fabric styles.)

High filling insertion rates (on an average 2000-2500 meters/min and 1000 strokes/min).

Simple operation and reduced hazard because of few moving parts

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Low spare parts requirement reliability and minimum maintenance

Most productive in the manufacturing of light to medium weight fabrics, preferably made

of cotton and certain man-made.

Low noise level and vibration levels

It has anyway to be pointed out that technically positive results are obtained at present also with heavy weight fabrics (denims) and that some manufacturers produce also machine models for terry production.

The weaving widths range generally from 190 to 400 cm. As regards the multicolor weft

carrier, up to 8 different wefts can be fed.

Page 12: Rapier Weft

EXPERIMENT NO. 6

OBJECT:

To study the take up mechanism of an air jet looms and set its desired pick density.

THEORY:

The take up motion withdraws the cloth from the weaving machine at a constant rate so as to

give the desired pick spacing (picks/inch or picks/cm) and then winds it onto a cloth roller. There

are two types of take up motion, the negative and positive. The negative take up has very limited

use because the number of picks per unit distance cannot be precisely controlled.

Main Parts:

Yarn feelers Main nozzle

Relay nozzle Profile reed

Main shaft Timing pulley

Timing gear Timing belt

Gear box Standard gear

Changeable gear Straight gears

Embry roll Press roll

WORKING:

The main drive is given to the main shaft from where it is transmitted to the timing pulley which

transmits the motion to the timing gear with help of timing belt. The gear box is fixed inside

which is composed of 2 gears in different ratios. The standard gear has 150 teeth and changeable

gear has 68 teeth which can be adjusted according to required pick density. There are 4 small

gears placed above the changeable gear which keeps the speed constant. From here the motion is

transmitted to 2 straight gears. Ultimately the drive is given to 2 press roll and 1 embry roll.

Embry roll moves anti clockwise while the press rolls moves clockwise.

Page 13: Rapier Weft

EXPERIMENT NO.7

OBJECT:

To set mechanically and electronically the diameter of pre-winder drum in order to insert pick of

required length on an air jet loom.

THEORY:

Weft accumulator:

A weft yarn storage unit is present between a yarn supply package and a weft insertion device for

storing a weft yarn to be inserted in warp shed.

Functions of weft accumulator:

To provide smooth flow

To provide the required width of fabric it is done by the calculations. They can be varied

for different fabric width.

WORKING:

The thread is taken off from the cone by a thread guide 1.

The thread guide winds the threads on a drum 2, consisting of a series of fixed segments.

These segments move the coils forward along the surface, keeping them separated one

from another.

At the moment of the insertion the thread unwinds from the drum with a torsional

movement opposite to the winding movement.

It passes through the braking system 3 which has the task adjusting the thread tension and

controlling any variation.

CALCULATIONS:

Formula:

D = W____

3.14*T

Where,

D= Drum Diameter (mm)

T= turns/ picks

W = Reed Width = extra weft yarn for selvedge

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Procedure:

The turns/picks of different machines are different. In this case it is 3 and the width of fabrics

including selvedges can be measured with the help of measuring tape.

Values:

T= 3 turns/ picks

W= 70.5 inches = 70.5*25.4

= 1790.7 mm

D = 1790.7

3.14*3

D= 190.09 mm

RESULT:

The diameter of pre winder drum in air jet t insert pick of required length on air jet loom is found

to be 190.09 mm.