Woven Fabric -I Teaching Materials

Teaching Material

On

Woven Fabric Manufacture-I

By: Alhayat Getu

(Lecturer, Wollo University Institute of Technology, Department of Textile Engineering)

(This material is used for teaching only not for sale)

August 27/2012

Woven Fabric Manufactring –I Teaching Material, Wollo University

I By: Alhayat Getu 2012

TABLE OF CONTENTS………………………………………………………………………...I

LIST OF FIGURES……………………………………………………………………………..V

LIST OF TABLES…………………………………………………………………………….VIII

LIST OF SYMBOLS…………………………………………………………………………….IX

ACKNOWLEDGEMENT ............................................................................................................. X

CHAPTERONE: INTRODUCTION TO WEAVING PREPARATORY ..................................... 1

1.1. Technical preface of weaving .......................................................................................... 4

1.2 Sequence of machines in weaving mill ................................................................................. 4

UNIT TWO: WINDING ................................................................................................................. 6

2.1. Introduction .......................................................................................................................... 6

2.2. Objectives of warp winding ................................................................................................. 7

2.3. Technical Requirements of Winding Process .................................................................... 12

2.4 Basic Mechanisms of Warp Winding Process .................................................................... 12

2.4.1. Unwinding ................................................................................................................... 13

2.4.2. Tensioning ................................................................................................................... 13

2.4.3. Yarn Clearing .............................................................................................................. 15

2.4.4. Package Formation ...................................................................................................... 16

2.4.5. Yarn Lubrication .......................................................................................................... 18

2.5 WARP WINDING MACHINES ........................................................................................ 18

2.6. Weft Winding Mechanisms and Machines ........................................................................ 19

2.6.1 Weft yarn preparation ................................................................................................... 19

2.6.2 Weft or Pirn winding process ....................................................................................... 19

2.7 Automatic pirn winding machines and Mechanisms .......................................................... 20

2.8 Pirn Stripping Machines ...................................................................................................... 22

2.9. Moistening and Emulsifying of Weft yarn ......................................................................... 22

2.10. Calculations Of Machines Productivity ........................................................................... 23

2.10.1. Production of Warp Winding Machines .................................................................... 23

2.10.2 Yarn speed and productivity in weft winding machines ............................................ 24

2.11. Winding Defects and Wastes ........................................................................................... 25


II By: Alhayat Getu 2012

2.11.1 Warp winding faults and wastes ................................................................................. 25

2.11.2 Faults and wastes in Weft Winding ............................................................................ 26

Exercise on winding ...................................................................................................................... 27

UNITE THREE: WARPING ........................................................................................................ 41

3.1 objectives ............................................................................................................................. 41

3.2 Technical Requirements of the Process .............................................................................. 42

3.3. Warping Machines and Mechanisms ................................................................................. 42

3.4 Warping Systems................................................................................................................. 43

3.4.1 Direct System preparatory beam warping or beam warping ........................................ 43

3.4.2. Package driving mechanisms....................................................................................... 48

3.4.3. Adjustable reed ............................................................................................................ 49

3.4.4. Measuring motion ........................................................................................................ 50

3.4.5.Braking mechanism ...................................................................................................... 50

3.5. Automatic stop motion of yarn........................................................................................... 50

3.6. Indirect System, sectional warping (conical drum or dresser warping) ............................. 51

3.7. Warping Machines Productivity......................................................................................... 54

3.8 Warping Defects and Wastes .............................................................................................. 56

Solved exercise on warping .......................................................................................................... 56

UNIT FOUR: SIZING .................................................................................................................. 65

4.1. Functions of the sizing operation ....................................................................................... 66

4.2 Technical Requirements of Sizing Process ......................................................................... 67

4.3. Influence of sizing on yarn properties ................................................................................ 67

4.4. The chemistry of sizing compounds................................................................................... 68

4.5 properties of size materials .................................................................................................. 69

4.5.1. STARCH ..................................................................................................................... 71

4.5.2. Chemical agents ........................................................................................................... 71

4.5.3. Softners ........................................................................................................................ 71

4.5.4. Deliquescent ................................................................................................................ 72

4.5.5. Wetting and Antifoaming agent .................................................................................. 72

4.5.6. Preservatives ................................................................................................................ 72

4.5.6. Water ........................................................................................................................... 72

4.6. Sizing Parameters ............................................................................................................... 72


III By: Alhayat Getu 2012

4.7. Sizing–Weaving Curve ...................................................................................................... 73

4.8. Sizing Machines ................................................................................................................. 74

4.8.1. Creels—Unwinding Zone ............................................................................................ 75

4.8.2. Size Boxes—Sizing Zone ............................................................................................ 78

4.8.3. Drying Cylinders—Drying Zone ................................................................................. 81

4.8. 4.Lease Rods—Splitting Zone ........................................................................................ 84

4.8.5. Head Stock ................................................................................................................... 84

4.9. Controls and Instrumentation ............................................................................................. 87

4.10. Effect of Sizing Machine Parameters ............................................................................... 88

4.10.1Creel Zone ................................................................................................................... 89

4.10.2. Size Box ..................................................................................................................... 89

4.11. SINGLE-END SIZING SYSTEMS ................................................................................. 96

4.12.Sizing Machine Productivity ............................................................................................. 98

4.13. Sizing Defect and Wastes ................................................................................................. 98

Solved problem on sizing.............................................................................................................. 99

UNIT FIVE LOOMING ............................................................................................................. 115

5.1. Objective .......................................................................................................................... 115

5.2. Drawing-in ....................................................................................................................... 115

5.3. Tying-in (Knotting) .......................................................................................................... 118

5.4 faults and wastes in drawing in and tying in processes. .................................................... 120

UNIT SIX WEAVING MACHINES.......................................................................................... 122

6.1.General remarks ................................................................................................................ 122

6.2. Classification of looms ..................................................................................................... 123

6.3. Classification of loom motions ........................................................................................ 123

6.4 Sheding .............................................................................................................................. 124

6.4.1. Negative Tappet Shedding Mechanism: .................................................................... 127

6.4.2 Positive tappet shedding motion: ................................................................................ 128

6.5. Dobby shedding: .............................................................................................................. 129

6.5.1 Classification of dobbies: ........................................................................................... 130

6.6 Jacquard Shedding............................................................................................................. 130

6.6.1 Single Lift Single Cylinder Jacquard: ........................................................................ 132

6.6.2 Double lift double cylinder jacquard: ......................................................................... 133


IV By: Alhayat Getu 2012

6.7 Picking:.............................................................................................................................. 133

6.7.1 Cone Over-pick Mechanism: ...................................................................................... 134

6.7.2 Lever Under-pick Motion: .......................................................................................... 136

6.7.3 Cone Under-pick Mechanism: .................................................................................... 136

6.8. Beat-Up Mechanism:........................................................................................................ 138

6.8.1 Eccentricity of Sley‘s motion: .................................................................................... 139

6.9 Take-up motion ................................................................................................................. 141

6.9.1 Objectives of take-up motion: .................................................................................... 141

6.9.2 Types of take-up motions: .......................................................................................... 141

6.10 Let-Off Motion ................................................................................................................ 144

6.10.1 Negative let-off ......................................................................................................... 145

6.10.2 Negative let-off motion ............................................................................................ 145

Exercise: ...................................................................................................................................... 146

Reference: ................................................................................................................................... 147


V By: Alhayat Getu 2012

LIST OF FIGURE

Fig. 1.1 Interlacements in plain-weave fabric…………………………………………………..2

Fig 1.2 flow chart of preparatory……………………………………………………………......3

Fig. 2.1(a) Schematics showing typical yarn faults…………………………………………….7

Fig. 2.1 (b) Schematic showing the principle of mechanical slub and thick place removal during

winding…………………………………………………………………………………………..7

Fig. 2.2 Cross-wound package…………………………………………………………………..8

Fig. 2.3 Random winding………………………………………………………………………..9

Fig. 2.4 Digicone winding………………………………………………………………………10

Fig. 2.5 Relationship between winding ratio and package diameter for digicone and precision

winding…………………………………………………………………………………………..11

Fig 2.6 sketch of winding processes…………………………………………………………….12

Fig 2.7 the relationship between tension and unwinding………………………………………..13

Fig 2.8 Multiplicative type tensioner…………………………………………………………….14

Fig 2.9 Additive type tensioner…………………………………………………………………..14

Fig 2.10 Disc type tensioner……………………………………………………………………..14

Fig 2.11 Gate type tensioner……………………………………………………………………..15

Fig 2.12 sketch of Yarn Clearing………………………………………………………………...15

Fig 2.13 types of knot and splice………………………………………………………………..16

Fig 2.14 cam operation…………………………………………………………………………..16

Fig 2.15 Rotary or drum traverse (2-crossing drum)…………………………………………….17

Fig 2.16 Propeller or fun traverse………………………………………………………………..17

Fig 2.17 weft winding machine………………………………………………………………….21

Fig 2.18. Yarn moistening unit…………………………………………………………………..23

Fig. 3.1 Warping systems………………………………………………………………………..43

Fig. 3.2 Direct warping system…………………………………………………………………..44


VI By: Alhayat Getu 2012

Fig 3.3. Continuous chain type (reversible) creel…………………………………………….45

Fig 3.4. Truck or mobile creel………………………………………………………………..46

Fig 3.5. Magazine creel………………………………………………………………………47

Fig 3.6. duplicate creels……………………………………………………………………….47

Fig 3.7. Swiveling creel……………………………………………………………………….48

Fig 3.8 Automatic creel……………………………………………………………………….48

Fig 3.9. Adjustable reed………………………………………………………………………49

Fig 3.10 Automatic stop motion………………………………………………………………51

Fig. 3.11 Schematics of section warping……………………………………………………..52

Fig. 4.1 Fiber–size binding in a yarn………………………………………………………….66

Fig. 4.2 Schematics showing size distribution………………………………………………..68

Fig. 4.3 A typical sizing–weaving curve……………………………………………………...73

Fig. 4.4 Schematic of sizing operation………………………………………………………..75

Fig. 4.5 Over/under creel………………………………………………………………….......76

Fig. 4.6 Over/under creel for two size boxes………………………………………………….76

Fig. 4.7 Equitension creel……………………………………………………………………..77

Fig. 4.8 Inclined creel…………………………………………………………………………77

Fig. 4.9 Vertical creel…………………………………………………………………………77

Fig. 4.10 Rope or belt braking system………………………………………………………..78

Fig. 4.11 Schematics of size box……………………………………………………………..79

Fig. 4.12 Schematics showing nip deformation in high pressure squeezing…………………80

Fig. 4.13 Schematic of double squeeze rollers……………………………………………….81

Fig. 4.14 Equisqueeze size box………………………………………………………………81

Fig. 4.15 Schematic of convection dryer…………………………………………………......83

Fig. 4.16 Schematics of splitting zone………………………………………………………..84

Fig. 4.17 Head end of a sizing machine………………………………………………………85

Fig. 4.18 Side view of a typical head stock…………………………………………………..86

Fig. 4.19 Sensors and controls on a typical two–size box slasher…………………………...87

Fig. 4.20 cylinder drying in sizing……………………………………………………………93

Fig. 4.21 Single-end sizing systems………………………………………………………….96

Fig. 4.22 Beam-to-beam sizing machine……………………………………………………..98

Fig. 5.1 Drawing-in………………………………………………………………………….116


VII By: Alhayat Getu 2012

Fig. 5.2 Heddle drawing-in machine………………………………………………………….116

Fig. 5.3 Automatic drawing-in machine……………………………………………………….117

Fig. 5.4 A harness and a reed with drawn-in threads ready to be moved to the knotting

station…………………………………………………………………………………………..117

Fig. 5.5. Piecing-up…………………………………………………………………………….119

Fig. 5.6. A knotting machine in operation on a warp with colour sequence, tensioned on the

proper frame…………………………………………………………………………………….120

Fig. 5.7.Harness loading in the weaving machine……………………………………………..120

Fig. 6.1.General scheme of a weaving machine……………………………………………….122

Fig 6.2. Negative tappet shedding mechanism…………………………………………………127

Fig.6.3. Positive Tappet Shedding Mechanism………………………………………………...128

Fig. 6.4. Single lift single cylinder jacquard……………………………………………………132

Fig.6.5 Double lift double cylinder jacquard…………………………………………………..133

Fig.6.6 Cone Over Pick Mechanism……………………………………………………………135

Fig.6.7 Lever Under-Pick Mechanism………………………………………………………….136

Fig.6.8 Cone Under-pick Mechanism………………………………………………………….137

Fig. 6.9 Beat-up Mechanism…………………………………………………………………..139

Fig.6.10 Eccentricity of sley……………………………………………………………………140

Fig. 6.11 Negative Take Up……………………………………………………………………141

Fig. 6.12 Negative Take Up……………………………………………………………………142

Fig. 6.13-Wheel Take-Up Motion………………………………………………………….......143

Fig. 6.14 Negative Let-Off Mechanism………………………………………………………..145


VIII By: Alhayat Getu 2012

LIST OF TABLE

Table 1.1 Characteristics of a Good Warp for Efficient Weaving……………………………...2

Table 4.1 Properties of a Good Sizing Material………………………………………………..70

Table 6.1. Types of Sheds………………………………………………………………………124

Table 6.2. Comparison of shedding systems…………………………………………………...126


IX By: Alhayat Getu 2012

SYMBOLS

yds………………………………………………………………………....yards(=0.914meter)

lb…………………………………………………………………………...pound

min…………………………………………………………………………minute

r.p.m/R.P.M……………………………………………………………….revolution per minute

wt…………………………………………………………………………..weight

reqd…………………………………………………………………………required

dia…………………………………………………………………………..diameter


X By: Alhayat Getu 2012

ACKNOWLEDGEMENT

I warmly thank Mr. Sajid A.Qureshi, Lecturers in Wollo University, KITO for his valuable

advice and friendly help. His extensive discussions around my work and interesting explorations

in operations have been very helpful for this work. Finally I would like to thanks my staff

colleagues for their valuable advice and cooperation.


1 By: Alhayat Getu 2012

CHAPTERONE: INTRODUCTION TO WEAVING PREPARATORY

A plain woven fabric is produced by interlacing two sets of threads, commonly known as warp

and weft (or filling). Warp usually runs along the length of the fabric and the weft or filling

essentially at a right angle to warp across the width of the fabric, as shown in Fig. 1.1a. The

process of interlacement (Fig. 1.1b), commonly known as weaving, transforms the individual

yarns into a woven fabric. Although there is a large variety of different ways to interlace two sets

of threads to produce different types of fabric structures, a plain weave is the most widely used.

A fabric usually consists of several thousand warp yarns across the whole width. It is in no way

practically feasible to weave a fabric by placing several thousand warp yarn packages side by

side at the back of a weaving machine, i.e., the loom, for numerous reasons. The weaving

process, therefore, requires the preparation of a weaver‘s beam which is placed at the back of the

loom. The weaver‘s beam contains the exact number of warp yarns (ends) required to produce a

fabric of the given specifications. To assemble the weaver‘s beam containing several thousand

warp yarns and to make it sufficiently strong to withstand mechanical stresses and abrasion

during weaving, the warp yarns generally need to be sized with chemicals by the process known

as sizing or slashing. It is also not practically feasible to place several thousand warp yarns at the

back of the sizing machine. So a number of flange beams, called warper‘s beams, containing

several hundred warp yarns are placed at the back of the sizing machine. A single warper‘s beam

is assembled by placing in the creel as many packages as required by the number of yarns in it.

The packages placed in the creel of the warping machine are large wound packages in the case of

ring-spun yarn or direct packages from modern spinning systems such as open end, friction, and

air jet. Therefore, in a nutshell the process of weaving requires certain preparatory steps to

transfer the spun yarns from the spinner‘s package to a weaver‘s beam ready for weaving. The

processes involved are

1. Winding

2. Warping

3. Sizing

4. Drawing-in and tying

The success of the weaving operation is considerably influenced by the quality of yarn and the

care taken during the preparatory weaving processes, such as winding, warping, and sizing. Also,



careful consideration of the sizing ingredients, size add-on levels, process of slashing, and

slasher-related parameters are a few of the several variables that must be controlled precisely for

the success of an efficient weaving operation. The yarn supplied from the spinning machines

should be sufficiently strong, uniform, smooth, knot-free, and slub-free to withstand the cyclic

stresses and abrasion the yarns are subjected to during the process of weaving. Table 4.1

summarizes the characteristics of a good warp yarn for efficient weaving. A poor quality yarn

will cause excessive breakages during weaving no matter how carefully the warp has been

assembled during the preparatory weaving processes[1,2,4].

Table 1.1 Characteristics of a Good Warp for Efficient Weaving

Strong

Uniform

Smooth

Knot-free

Slub-free

Withstands abrasion of moving loom parts

Withstands cyclic strains and stresses of loom

Fig. 1.1 Interlacements in plain-weave fabric[1].



A fabric is a flat structure consisting of fibrous products, either natural or ″man made″.Nowadays

there are various technologies suitable to create textiles, which all of them go by the name of

fabrics. We shall deal here exclusively with the technology producing orthogonal fabrics by

interlacing together two elements: warp and weft. The first element is represented by the threads

placed lengthwise in the fabric, while the second is represented by the threads placed in width

direction. The yarn is marketed wound on various types of packages, which generally depend on

the technology of the spinning process from which the yarn originates; the most common

packages are cones (either cones or bicones, or tubes, or tricones), spools or bobbins, flanged

bobbins, hanks and cheeses. Owing to the specialization trend of modern technology, the

weaving industry is supplied today only with ″hard″ packages, with yarn wound on rigid tubes

which consequently can be used as such in the weaving process. this type of package not be

appropriate, then the first operation to carry out would be rewinding (cone winding), a

processing phase which can be considered as the last integration of the spinning process. Starting

from the storehouse, the yarn is subjected to following working sequence until the weaving

stage[1,2]:

Fig 1.2 flow chart of preparatory[1]



1.1. Technical preface of weaving

Woven fabric is obtained from yarns by weaving. Weaving is the interlacing of two systems of

yarns, which interlaced at right angle to each other. The lengthwise threads are called warp while

the crosswise threads are called weft. In order to interlace warp and weft threads to produce

fabric on any type of weaving machine, three operations are necessary[1]:

(a) Shedding: separating the warp threads, which run down the fabric, into two layers to form a

space for the passage of weft threads

(b) Picking: passing the weft thread, which traverses across the fabric, through the shed; and

(c) Beating-up: pushing the newly inserted length of weft into the already woven fabric at a

point known as the fabric fell.

These three operations must occur in a given sequence, but their precise timing in relation to one

another is also of extreme importance .in addition to the above three necessary operation two

additional operations are essential if weaving is to be continuous:

(d) Warp control (or let-off): delivers warp to the weaving area at the required rate and at a

suitable constant tension by unwinding it from a the weaver's beam; and

(e) Cloth control (or take-up): withdraws fabric from the weaving area at the constant rate that

will give the required pick[1,2].

1.2 Sequence of machines in weaving mill

Spinning mills deliver yarn to weaving mills in packages of different build and size, mostly in

cops and bobbins, sometimes in hanks and cones. For weaving on looms, it is necessary to have

packages of a certain build and size. And hence, Warp yarns and weft yarns should be

preliminarily wound on suitable packages (see fig 1.2).

Preparation of warp yarn for weaving is essential not only because weaving requires packages of

certain build and size, but also because the warp yarn must be able to withstand destructive

forces to which it is subjected during the weaving process. Moreover, the warp yarn must be

sufficiently and regular in order to pass without breaking through the drop wire eyelets, the

healds and between reed dents[1].



During winding, yarn is cleared from spinning defects- slubs, thin and thick places…

During warping, a certain number of ends of a given length are wound in warpers in to a

package known as warping beam.

During sizing process, the yarn is impregnated with a special glueing composition and

hence the warp yarn becomes stronger, smoother, and wears resistance.

Moistening and emulsifying of weft threads reduces the number of weft loops,

corkscrews, slough-offs as well as the weft yarn breakage rate during weaving and

ensures the production of higher quality fabric.

All rooms where yarn is prepared for weaving as whole are known as preparation department.

The room in which weaving takes place e is named as the weaving room or shed. In general, yarn

preparation is done to furnish the fabric making unit with a fault free yarn, wound on to the most

suitable and effective supply package[1,2,3].

Factors that must be considered during yarn preparation

Package shape.

Package density and weight.

Yarn length on the package.

Package identification.

Yarn fault.

Frictional characteristics of the yarn

There are two types of yarn preparation equipments: Single end winders, which produce

packages such as cones, and multi-end winders, which produce packages such as beams.



UNIT TWO WINDING

2.1. Introduction

Unevenness in traditionally spun staple yarns is a natural phenomenon usually induced by the

process of manufacturing (spinning). Although with modern process controls and machines

many imperfections in the spun yarns can be controlled, some still remain in the final yarns.

Most common of all imperfections are thin or weak places, thick places, slubs, neps, and wild

fibers, as shown schematically in Fig. 2.1. During the subsequent processes of winding, warping,

and slashing, not all but some of these imperfections create obstacles to steady and smooth

working. Therefore, it is important to classify, quantify, and remove those imperfections which

may cause the interruption of the operation[1].

In other words, only ‗‗objectionable‘‘ faults need to be removed for trouble-free processing of

the yarns. The ring-spinning operation produces a ring bobbin containing just a few grams of

yarn which is unsuitable for the efficiency of further processing, such as warping, twisting, and

quilling. This necessitates the preparation of a dense and uniform yarn package of sufficiently

large size which can unwind in the subsequent operations without interruptions. The packages

prepared for warping are normally cross-wound, containing several kilograms of yarns[1,2].

This implies that a number of knots or splices are introduced within each final package. Bear in

mind, each knot or splice itself is an artificially introduced imperfection; therefore, the size of

this knot or splice must be precisely controlled to avoid an unacceptable fault in the final fabric.

In modern winding machines, knots and splices are tested photoelectrically for size, and only

acceptable knots and splices are allowed to pass on to the winding package. In modern spinning

processes, such as open end, friction and air jet, the spinning process itself produces a large

cross-wound package, thus eliminating the winding operation. Nowadays splices are used on all

the spinning systems including ring, open end, and air jet for repairing ends down during

spinning. In the absence of winding, it is pertinent to note that the yarn spun on such modern

spinning systems must have no or only a small number of objectionable imperfections. In most

modern spinning machines, the manufacturers have incorporated devices that continuously

monitor the quality of the yarn being spun, thus assuring fault-free spun yarns[1].



Fig. 2.1 (a) Schematics showing typical yarn faults[1].

Fig. (2.1) (b)Schematic showing the principle of mechanical slub and thick place removal during

winding[1,2].

2.2. Objectives of warp winding

The Objectives of warp winding process are

Formation of suitable package for warping.

Checking and clearing the yarn from spinning defects

A. Formation of suitable package for warping: Making larger package is an essential function

of winding, especially for staple yarn spun on a ring-spinning system. Smaller ring bobbins

containing relatively short lengths of yarn are cross-wound onto a larger wound package, usually

a cone or parallel wound or flanged cylindrical package. These wound packages, as shown in

Fig. 2.2, are made up of several ring bobbins by joining the ends. Such increased lengths of yarns

will ensure continuous operation in subsequent mass production processes such as warping,

twisting, quilling, and weaving. The type and quality of package prepared during winding



depend upon the winding systems employed. There are three principal types of winding that are

commonly used on modern winding machines, namely[2,3,4]]:

1. Random or open winding

2. Precision winding

3. Digicone winding

Fig. 2.2 Cross-wound package[1]

In random or open winding the package is surface driven by its frictional contact with the driving

cylinder or drum, as shown in Fig. 2.3. In the case where a plain driving cylinder is used for

driving the package, the yarn guide is driven by belts or gears to impart one full traverse along

the length of the package. However, in most modern winders the driving drum is grooved so as

to guide the yarn for a full traverse across the length of the package. More often, the drum is

driven by a shaft, running at a constant speed, across the whole length of the winder or by an

individual motor attached to each drum. In this type of winding, the ratio between the package

revolutions per minute and the double traverse, known as winding ratio, changes constantly

during the entire process of winding. For a bigger package, this winding ratio is small and vice

versa. The helix angle—half of the crossing angle—does not change throughout the build of the

package. As the double traverse remains constant, the increase in the package diameter has to be

compensated with a constant decrease of revolutions per double traverse, this results in gradually

decreasing winding ratios. When this winding ratio becomes a whole number, such as 1:1, 2:1,

3:1, and so on, the yarn is laid over the yarn wound in the previous traverse, resulting in the

formation of a ‗‗ribbon‘‘. This ribbon zone has a higher winding density and poor unwinding



behavior caused by ‗‗sluff-off‘‘ of the yarn. Prevention of ribbon formation is achieved by

several methods, namely, (1) modulating the yarn guide frequency, (2) creating slippage between

the package and grooved drum, and (3) lifting the package away from the driving drum at fixed

time intervals. All these methods momentarily alter the winding ratio, thereby avoiding ribbon

formation[1,2,5,8].

In precision winding, the package itself is driven by a train of gears, and the yarn guide is

directly connected as shown in Fig. 2.4. The ratio between the package revolutions and the

double traverse—the winding ratio—remains constant, whereas the helix angle changes

constantly throughout the package build, higher (open) at the smaller package diameter and

lower (close) at the higher package diameter. Because the package itself is driven, the rotational

speed (rpm) of the package has to be decreased constantly with the increase in the package

diameter so as to maintain constant winding speed. The major advantage of this type of winding

is that there is no ribbon formation because the winding ratio remains constant throughout the

package. However, the major drawback of this type of winding is constantly increasing density

of the package as the package grows larger because of the constantly decreasing helix angle.

A more recent development of winding type is ‗‗Digicone‘‘ winding, where the control systems,

consisting of digital microprocessor, produce wellbuilt packages of uniform density. A schematic

of Digicone winding is shown in Fig. 2.5 The control system consists of two sensors, n1 and n2,

to register the revolutions of the package and variable drive, P. The microprocessor calculates

and analyzes the signals provided by the sensors, placed near the package holder and the traverse

mechanism. These values are in turn compared with the programmed values (in EPROM), and

the drive system is activated as necessary[8,9,10,11,12],.

Fig. 2.3 Random winding[1]



On the Digicone winder the most appropriate helix angle for a particular end-use application can

be ascertained. For difficult-to-dye yarn, a crossing angle of 180is proved to be best. On the other

hand for accommodating longer lengths of yarn on the package the crossing angle may be

decreased to as low as 100. On the Digicone system, any crossing angle between these two

extreme limits (10 to 180) can be easily set by changing the appropriate pulley on the shaft of the

driving drum, D. The crossing angle remains constant because the drive to drum and the yarn

guide are connected through the variable drive and belts, as shown in Fig.2.3. The mechanism

allows the process to achieve correct winding speed and traverse of the yarn guide to maintain

constant crossing angle[2,12].

In Digicone winding, the mechanism begins with a precision winding operation such that a

crossing angle of α1 is set initially. As the winding progresses (the package diameter increases),

the crossing angle decreases until a programmed crossing angle of α2 is reached. At this stage,

the microprocessor will reset the drive to change the crossing angle back to the same level as in

the beginning, i.e., α1. Again the precision winding is continued until a preprogrammed crossing

angle of α2 is reached, and so on until the final package diameter is reached. Figure 4.8

graphically displays this process of package building. The difference between α1 and α2 is set to

such a small value that no appreciable density difference occurs. This results in stable, uniform,

and well-built packages, leading to optimal performance during weaving, knitting, and dyeing

operations [12].

Fig. 2.4 Digicone winding[1,2].



Fig. 2.5 Relationship between winding ratio and package diameter for digicone and precision

winding[12].

B. Checking and clearing the yarn from spinning defects: Clearing is a process of removing

imperfections from the spun yarn. The clearing operation must be carried out during the winding

process only because the cost of the winding/clearing operation is usually far lower than that of

the subsequent operations, such as warping, slashing, and weaving. Moreover, attempting to

clear faults at a later stage (e.g., in warping) will be inefficient as a number of good warp yarns

will become inoperative. For example, a break of a single warp yarn on the loom brings the

entire loom to a stop, thus reducing the efficiency of the loom. The imperfections or faults which

occur in spun yarns include slubs or thick places, weak or thin places, neps, and wild fibers, as

shown in Fig. 2.1.

Thin places in the yarn are usually weak spots, making the yarn susceptible to breakage during

subsequent preparatory and weaving operations. Therefore, such thin places which are weak

should be replaced with a strong knot or splice. Some of these thin places which are not

unacceptably weak can be covered by the application of size during the slashing operation. The

thin places are usually removed by applying tension to the yarn during the winding process. The

level of tension applied determines the number of thin places (weak spots) removed. Thin places

having a breaking strength lower than the tension applied are usually broken during the winding

operation. Thick places and slubs are the places in the yarn having a diameter significantly

greater than the normal diameter of the yarn. Such faults are removed either electronically (using

optical or capacitance sensors) or mechanically. In the latter case, the yarn is passed through a

small slit, usually twice or more the size of the diameter of the yarn during its travel from the

ring tubes to the winding package, as shown in Fig. 2.3. Those slubs and thick places larger than

the opening of the slit are cut and replaced by a knot or an end-to-end splice. Otherwise, in



modern winding machines thick places and slubs are measured by a photoelectrical device which

continuously senses the diameter of the yarn being wound and compares the cross section of the

yarn with that of such faults[1].

2.3. Technical Requirements of Winding Process

The physical and mechanical properties of the yarn should not be impaired.

Package should be built to ensure easy running off during warping at high speed

The package should contain maximum length of yarn

The yarn ends should be tied with strong knots of correct structure easily passing at subsequent

processing

The process should remove the objectionable fault

Yarn wastes must be as small as possible

The yarn tension should be regular and ensure constant winding condition

2.4 Basic Mechanisms of Warp Winding Process

The Basic mechanisms of warp winding process are:

Unwinding

Tensioning

Yarn clearing

Package built

Lubrication

Fig 2.6 sketch of winding processes[1,12]



2.4.1. Unwinding

Factors affecting yarn tension by Grishin:

𝑇 = 𝑚𝑣2[2 + 𝑘𝑠𝑖𝑛ℬ 𝑕

𝑟 2

Where:

m – mass/unit length h – Balloon height

β - Wind angle r – Package radius

v – Linear velocity of yarn K – Twist

Therefore,

Coarser yarn have higher tension

High yarn velocity causes more tension on yarn which leads to more breakage

Tension is higher at nose as compared to shoulder

Tension increases with the increase in balloon height

Fig 2.7 the relationship between tension and unwinding[1]

When 75% of the package unwinds from the spinning cop, tension of yarn will be increased

considerably. And hence the last layer of the yarn not able to form balloon since it licks around

the package that results more yarn breakage at the bottom of the bobbin. Therefore, unwinding

accelerator (anti-balloon device) should be used. The anti-balloon device decreases the tension

by having more number of loops. So we can go for high unwinding speed[1,2,6,7,12].

2.4.2. Tensioning

The needs for tensioning are:

It gives required winding density

It gives suitable tension to the yarn



It facilitates winding

It aids to remove weak yarns

Tension devises can be classified in to four groups

(I) Multiplicative type (Post type or Capstan)

Fig 2.8 Multiplicative type tensioner

Where, Ti =initial tension of yarn.

To = out put tension of yarn.

ϴ= angle of curvature

= coefficient of friction between yarn and guide

(II) Additive type

Fig 2.9 Additive type tensioner

𝑇𝑜 = 𝑇𝑖 + 2𝑁

Where: N = Weight of the Washer

μ = Coefficient of friction between the yarn and steel guide

(III) Disc type (Combination of additive & multiplicative type)

Fig 2.10 Disc type tensioner

𝑇𝑜 = 𝑇𝑖𝑒𝛳 + 2N

(III) Compensation type (Gate type)



One movable comb held by weight and the other is fixed. If the tension of yarn is high, then the

comb will move inside to decrease the angle of wrap and vise-versa[1].

Fig 2.11 Gate type tensioner

2.4.3. Yarn Clearing

Yarn clearer is a device which detects and removes yarn faults.Yarn clearer can be grouped in to

i. Mechanical clearer

ii. Electromechanical clearer

iii. Electronic clearer

Capacitance type

Photoelectric type

Fig 2.12 sketch of Yarn Clearing [1]

When thick places of yarn pass through the measuring device, the change in capacitance caused

by the change in yarn thickness is converted in voltage oscillation which is amplified and

actuates the cutting mechanism. So every yarn break should be replaced with either knot or

splice.

Knots – fastening made by tying a pieces of yarn



Splice – joint of yarn ends by means of pneumatic or mechanical i.e pre-opening or

untwisting followed by intermingling and twisting[2,5,7,8].

Fig 2.13 types of knot and splice

2.4.4. Package Formation

During winding the yarn undergoes two motions. It is wound around the package by the package

drive and it is given a lateral motion to cover the package by the traverse mechanism.

There are two ways to drive the yarn take up package.

i. Drum winder (by surface contact)

ii. Spindle winder (by direct drive to the package spindle)

There three ways commonly in use to traverse the yarn to build-up the package.

i. Cam operation

ii. Rotary or Drum traverse

iii. Propeller or fun traverse

(A) Cam operation

The guide eye of the traverse motion oscillates from side to side along the traverse and laying the

yarn in helix pattern on the package. Speed is limited due to acceleration, sudden stop and

instantaneous change in direction[1,2,9,10].

Fig 2.14 cam operation



(B) Rotary or Grooved drum traverse

It becomes more popular due to the lack of speed limitation. The yarn is guided along the

traverse and back by a groove in the driving drum, which is helical (only the yarn has to change

direction). The drum is denoted as a 2- crossing drum, 2.5-crossing drum, or 3-crossing drum etc.

Fig 2.15 Rotary or drum traverse (2-crossing drum)

(C) Propeller or fun traverse

The two blades are rotating in opposite direction to lay the yarn on the package. The mechanism

works independently from the package drive. There is no mechanical speed limitation. It is used

for filament and delicate yarns[1].

Fig 2.16 Propeller or fun traverse

Package Build:Wind is coils of yarn of yarn laid on the package surface per single traverse. and

wind per double traverse (Traverse Ratio) is the number of coils laid on the package during a

double traverse, during the time it takes the yarn to go from one side of the package and return to

the same side.

𝑇𝑟𝑎𝑣𝑒𝑟𝑠𝑒 𝑟𝑎𝑡𝑖𝑜 = 2 ∗ 𝑤𝑖𝑛𝑑 = (𝑝𝑎𝑐𝑘𝑎𝑔𝑒 𝑟𝑒𝑣/min)/(𝑑𝑜𝑢𝑏𝑙𝑒 𝑡𝑟𝑎𝑣𝑒𝑟𝑠𝑒/𝑚𝑖𝑛)

Consider a cylindrical package to determine the angle of wind and coil angle.



𝑡𝑎𝑛𝛳 = 𝑉𝑡/𝑉𝑠

Where:

θ = angle of wind

β = 90 - θ = Coil angle

Vs = Surface speed

Vt = Traverse speed

2.4.5. Yarn Lubrication

Lubricants are used for reduction of friction. A lubricant (wax) is applied for knitting yarn

because the level of twist is low. In winding of warp yarn, lubricants are not used[2,3,5,6,7].

2.5 WARP WINDING MACHINES

Based on the transfer of skill from the operator to the machine and the equipment flexibility,

winding machines can be classified as

(i) Non automatic winder

(ii) Automatic winder

(1) Non automatic winder:They are commonly used for specialist applications such as filament

yarns (7.7 dtex – 2222 dtex) at a speed of 900 m/min to 1000 m/min, 44 dtex hosiery, polyester

and industrial yarn. Eg. SSM precision cone winder model PS.However, for a great majority of

winding applications fully automatic winders substitute the non-automatic winder[2,12].

(2) Automatic winder:The features for development of automatic winders are

(i) Design

(ii) Configuration and the number of winding positions to be serviced by one knotter

(iii) Degree of automation Automation based on configuration and the number of winding

positions to be serviced by one knotter can be:

Rectilinear with stationary winding positions and traveling knotter. Eg. Schalafhorst

Autoconer

Circular with traveling spindle positions and stationary knotter, Eg. Schweiter CA 11

One knotter per spindle ,Eg. Murata No. 7-II Machconer, Savio RAS.



2.6. Weft Winding Mechanisms and Machines

2.6.1 Weft yarn preparation

The whole process of weft yarn preparation for weaving consists of two operations

(i) Weft yarn rewinding

(ii) Humidification or Emulsifying

The objectives of weft preparation process is to supply the weft yarn packages with adequate

shape, size and moisture for weaving besides improving the yarn properties by cleaning it from

trashes and partially eliminating spinning faults[1].

2.6.2 Weft or Pirn winding process

It is a rewinding process which aids to supply a suitable package for shuttle loom. A pirn is a

yarn package that is fitted to a shuttle in order to supply the weft at loom.

A small sized pirn accommodate longer length by using short conical traverse we can

accommodate maximum possible length and minimize unwinding problems as in the case of

cross winding and slough-off as in the case of parallel winding[1,2,6].

PIRN BUILD

The three basic types of empty pirn are

(i) Plain taper

It can be used for most yarn type, but sometimes the finer yarns do not run off easily when the

pirn is nearly exhausted.

(ii) Pirn with a half-built-up base



It can be used for finner yarns to overcome the 'sloughing' or slipping off when only a few layers

of yarn are left on the pirn[1].

(iii) Pirn with a fully-built-up base

It can be used for relatively coarse and fibrous (hairy) yarns, since an even run-off being ensured

and the hairiness of the yarns preventing sloughing[2,11,12].

2.7 Automatic pirn winding machines and Mechanisms

The principle function of the automatic pirn winding machine is to transfer cleared yam from a

secondary package such as a cone to a weft pirn, of a size and construction so that it can be

Accommodated in the loom shuttle, and be capable of withstanding the checking forces. The

fundamental difference between weft winding and warp winding is that in the former the feeding

package is very much larger than the delivered package and in the latter the reverse

applies. In automatic cone winders, the feeder package should be automated, whereas in the pirn-

winder the delivered package must be automated.

The main requirements of the pirn winding machine and they affect the basic machine design

are:

i. Pirn density and cohesion

ii. Consistency of pirn

iii. Bunch building- The bunch must be adjustable for yarn length to satisfy the different looms

with different reed space. The normal range is 5-15m.

iv. Yarn tails and backwind - The yarn tails must be cut and tucked, and the backwind minimized

and not buried in the pirn rings and made inaccessible.



v. Spindle speeds-Speeds of 12,000rpm are now considered normal, but it must be recognized

that the speed is related to 'wind'.

vi. Direction of rotation

vii. Degree of automation

Automatic pirn winders are classified based on

the method of pirn securing

the number of pirns wound simultaneously

the type of yarn guide used

In weft rewinding for obtaining a pirn, three kinds of motions are performed

(i) Rotary movement for winding the yarn on the tube

(ii) Reciprocation motion for spreading the coil

(iii) Translatory movement for shifting the yarn layers

The three movements are performed by two devices namely the winding devices (spindle) and

the spreading devices (traverse)[2,12].

Fig 2.17 weft winding machine

Key:

1- Bobbin

2- Anti-balloon device

3- Disc tension arrangement

4- Automatic stop motion

5- Yarn guide (loop)

6- Eyelet of traverse

7- Rotating pirn

Basic Operations that can be carried out in automatic pirn winding machines:



i. Stoppage of the leading gripper and pirn

ii. Retreat the traverse in to the initial position

iii. Release of the pirn at the retreat of the supporting gripper.

iv. Installation of a new pirn in the grippers

v. Clamping of yarn by the pirn head

vi. Yarn trimming

vii. Engagement of the leading gripper

viii. Winding of the reserve bunch

ix. Traverse engagement for normal spreading of yarn coils

on the pirn

2.8 Pirn Stripping Machines

When fabrics are produced on automatic looms, the reserve winding or bunch remains on the

pirns. Since, manual pirn stripping is a very tiresome and time consuming process; weaving mills

use special pirn strippers.

The pirns must be of the same diameter if not the deviation should not exceed 1 mm since

the blades will damage the pirn surface or leave some rests of the reserve bunch on the

pirn.

The capacity of the pirn stripper is up to 4000 pirns per hour[1].

2.9. Moistening and Emulsifying of Weft yarn

Weft yarn being hygroscopic enough rapidly changes its moisture content when environment

changes.

Insufficient moisture on weft yarn results more breakages and slough-offs in weaving.

With an increased moisture of weft, the cohesion between separate coils in the package

increases and the yarn stiffness decreases. Moreover, the friction factor increases. As a

result, curling and sloughing are reduced. Thus, if the moisture is insufficient, prior to use

on looms, the weft yarn must be artificially moistened[1,2].

Methods of yarn moistening

keeping the yarn in chambers with relatively high air humidity

Steaming the yarn in special kettles or apparatuses

Application of special emulsions.



Fig 2.18. Yarn moistening unit[1,2]

Key

1- Feeding lattice

2- Conveyor

3- Water spraying nozzles

4- Perforated pipes for steam

5- Thermometer

6- Box for moistened yarn

2.10. Calculations Of Machines Productivity

2.10.1. Production of Warp Winding Machines

The production of winding machine is determined by the weight of the yarn wound in a certain

period of time. Types of productivity calculations:

Theoretical production

Actual production

The theoretical production (Pth) of one spindle (winding head) can be:

𝑃𝑡𝑕 = 𝑉 ∗ 𝑡 ∗ 𝑇 ∗ 10−6 [𝐾𝑔/𝑕𝑟]

Where: V= Average winding speed (m/min)

t = Rated working time (min)

T = Linear density of yarn (tex)



The actual production (Pa) of one spindle or winding head:

𝑃𝑎 = 𝑃𝑡𝑕 ∗ 𝜖 = 𝑉 ∗ 𝑡 ∗ 𝑇 ∗ 𝜖 ∗ 10−6 [𝐾𝑔/𝑕𝑟]

Where: ε =Machine efficiency

𝑃 = 𝑃𝑎 ∗ 𝑛 = 𝑉 ∗ 𝑡 ∗ 𝑇 ∗ 𝑛 ∗ 𝜖 ∗ 10−6 [𝐾𝑔/𝑕𝑟]

Where: n = The number of spindles or winding Hence, the production of winding machine will

be heads on the machine.

2.10.2 Yarn speed and productivity in weft winding machines

Yarn speed (V) can be calculated in terms of

𝑉 = 𝑉12 + 𝑉22

= 𝜋𝑑𝑛1 2 + 2𝑕𝑛2 2 [𝑚/𝑚𝑖𝑛]

Where:

V1= Pirn circumferential speed (m/min)

V2= Conveying speed (m/min)

d = Average yarn winding diameter of pirn (m)

h = Axial displacement of the spindle (m)

n1= Rotational speed of the gripper (rev/min) but,

𝑑 = 𝑑1 + 𝑑2 + 2𝑑/4

Where,

d1= Pirn diameter at winding base (m)

d2= Pirn diameter at winding apex (m)

D = Diameter of cylindrical part of the pirn (m)

Hence, productivity of weft winding machines can be calculated as:

𝑃 = 𝑉 ∗ 𝑡 ∗ 𝑇 ∗ 𝑛 ∗ 𝜖 ∗ 10−6 [𝐾𝑔/𝑕𝑟]

Where:

V = Average weft winding speed (m/min)

t = Machine operation time (min)

T = Linear density of yarn (tex)



n = Number of spindles on the machine

ε = Machine efficiency

2.11. Winding Defects and Wastes

2.11.1 Warp winding faults and wastes

The most common defects which can occur in warp winding process are:

(1) Cob webbing (stitch):If the coil angle is too large, the coils on the package tend to slip out

ward. Also if the yarn is not tensioned, it may cause slippage of coils and cause cob webbing.

(2) Hard edges: Ideally, only a small amount of yarn should be laid on the edges of package but

a yarn cannot stop instantaneously and change its direction. Hence, there will be a small delay in

the traverse motion which causes the yarn to be laid at the reversal point.The difference in the

package density from the edges to center would lead to uneven flow dye liquor.

(3) Slough off: During unwinding more than one coil get unwound, which is severe problem in

the case of warping. So, we can use 2.5 or 3.0 crossing drum instead of 2.0 crossing drum.

(4) Patterning: Patterning occurs when the coils on adjacent layers are superimposed on each

other and seen as ridges on the package. Patterning occurs when the traverse ratio is exactly an

integer. It causes shed variation during package dyeing and slough-off in warping.

Solution for patterning

To remove patterning or ridges, the second coil has to slightly



displace from the first. This displacement is know as Gain (g)

Gain can be linear gain (gl) and revolution gain (gr).

The linear gain (gl) can be calculated as

𝑔1 = 𝑑/𝑠𝑖𝑛𝛳

Where: d = yarn diameter

θ = angle of wind

gl = linear gain

And hence, the revolution gain (gr) can be:

𝑔𝑟 = 𝑙𝑖𝑛𝑒𝑎𝑟𝑔𝑎𝑖𝑛

𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑎𝑛𝑐𝑒 𝑜𝑓 𝑡𝑕𝑒 𝑝𝑎𝑐𝑘𝑔𝑒=

𝑔1

𝜋𝑑′

Where: d’ = Package diameter

(5) Irregular shape package:The result of improper operation of the winding mechanism.

Extremely loose or tight winding, poor yarn clearing, snarlings, Mixing of yarns, Greasy and

dirty yarn, and Slack knots or knots with long tails are also among winding faults.

2.11.2 Faults and wastes in Weft Winding

Faults can be due to troubles in some mechanisms of the automatic weft winders and

carelessness on the part of operator. The main faults in weft winding process are:

Oversize or under size weft pirns

Pirns of irregular shape due to improperly installed traverse after breakage elimination

Loose or over tight winding as a result of improperly set tension devices

Improper knotting or overlaps which cause yarn breakage on the looms in weaving



Pirns with yarns of different linear density and dirty pirns

Winding wastes are formed by ends remaining at breakage elimination, by winding-off spinning

faults, and by the ends remaining on bobbins after incomplete yarn withdrawal. A great amount

of wastes increases the manufacturing cost of products.

Exercise on winding

Instruction: Describe the followings

1) Demonstrate the yarn passages and the purpose of each machine part

2) Show and explain the purpose of anti balloon device

3) Identify the type of tensioners installed and explain how an adequate tension of yarn is

maintained during winding?

4) Demonstrate how empty cone is fixed on the spindle? Explain the movements of the

entire parts of the spindle

5) Explain how doffing is taking place when the required package is attained

6) Explain the operation of automatic stop motion during yarn breakage and normal

condition

7) Describe the function of cap bar in the cone winding machine?

8) What are purposes of spindle on the cone winding machine? Explain the working

position and idle position of spindle

9) Identify the type and explain the purposes of winding drum on cone winding machine

10) Describe the different parts and the purpose of over head blower of cone winding

machine?

11) Explain how motion is transmitted to different parts of the cone winding machine?

12) Describe how objectionable faults are removed



13) Identify the types of package driving and traversing mechanisms

14) Describe the causes of three winding defects and their remedies

15) What are your suggestions to increase the production of cone winding at KTSC from

your practical observation?

Solved problem:

Pb#1 An automatic winding machine which has 50 spindles runs at an average speed of 1000

m/min with an efficiency of 0.8 processing a 20 tex yarn.

(a) Calculate the actual production of the machine per shift of 8 hours

(b) How many packages of cones will be produced per day if the weight of each package be 2.5

kg?

(c) What would be the average length of yarn wound on each package?

Solution

(a) Actual production per shift of 8 hours

Pb#2 An automatic winding machine which runs at an average speed of 1200 m/min with an

operation factor of 0.85 processing 30 tex of yarn, produces 2644 kg of yarn per day. What

would be the total number of spindles in the machine if all the spindles are functioning?



Pb#3. A precision winder is used to wind 40 tex cotton yarn on to cheese of 16 cm traverse

length build on a 120 mm diameter and the nominal wind per double traverse is found to be 8.

Calculate the actual value of traverse ratio to give close winding assuming that the yarn diameter

(d) is equal to√0.037× yarn linear density (tex).



Additional solved problems:

Q1. What is winding? Why winding is necessary for weaving?

Ans: Winding; Winding is the process of transferring yarns from ring, bobbin, hank etc into a

suitable package. It may be electrical or mechanical.

Warp cone, cheese, flanged bobbin. Weft pirn, cop.

Objects or necessary:

1. To transfer yarn from one package to another suitable packages, this can be conveniently used

for weaving purposes.

2. To remove yarn faults like hairiness, neps, slubs of foreign matters.

3. To clean yarn.

4. To improve the quality of yarn.

5. To get a suitable package.

6. To store the yarn.

Q2. Explain – ―Yarn Tensioning Device‖.

Ans : During winding for controlling yarn tension, the yarn is passed into the device which is

called Tensioning device. Yarn Tension plays an important role in winding. Too high a tension



can damage the yarn, where as too low a tension can lead to unstable packages which will not

unwound clearly.

Q3. What are the requirements of Winding?

Ans :

1. Minimum fault: During winding always should be observed if yarn fault become less. (To

minimize the yarn faults).

2. No damage of yarn: There is a dame of yarn i.e. the yarn must not be damaged in any way in

the winding process.

3. Easy unwinding: Yarn to be wound so that it can be unwound easily.

4. Suitable size and shape of the package: Size and shape should be proper.

5. Economical condition: The package size should be controlled the particular economic

requirements.

6. Avoid excess loosened and tightness: Should be taken care.

7. Cheap cost of package: The package should be cheap. Above all the process must be

profitable.

Q4. Describe different types of winding packages. Describe parallel wound package or parallel

winding. Describe Near parallel wound package. Describe cross wound package What are the

packages used both cotton and jute winding?

Ans :

Types of Packages:

1. Parallel wound package: (a) warp yarn, (b) weavers yarn.

2. Near parallel wound package: (a) pirn, (b) cop, (c) Flanged bobbin.

3. Cross wound package: (a) cone, (b) cheese, (c) spool.

Description:

1. Parallel wound package or parallel winding: This comprises threads laid parallel to one

another as in a warp beam. It is necessary to have a flanged package or beam; otherwise the

package would not be stable and would collapse.There is no necessity of traversing.

Advantages:

1. Many yarn can be wound at a time.

2. No need of traversing machanism.

3. Side withdrawl is possible.

4. The density of yarn is more.



5. No change of number of turns per inch.

Disadvantages:

1. Two sides of the package need flanged.

2. For yarn unwinding need separate mechanism.

3. Cannot be over withdrawl.

2. Near parallel wound package: This package comprises one or more threads which are laid

very nearly parallel to the layers already existing on the package.

Advantages:

1. No need of flanged.

2. Can be side withdrawl.

3. No change of number of yarn turns per inch during winding.

Disadvantages:

1. Need of traversing mechanism.

2. Cannot be over withdrawl.

Cross wound package: This type usually consists of a single thread which is laid on the package

at an appreciable helix angle so that the layers cross one another to give stability.

Advantages:

1. .No need of flanged.

2. Can be over withdrawl.

3. Yarn package is stable.

Disadvantages

1. Number of yarn turns per inch is changed in this method.

2. Quality of yarn is less.

3. Need of traversing mechanism.

Package used for winding:

Cotton: cone, cheese, bobbin, pirn.

Jute: cop, spool.

Q5. Describe precision and non precision winding.

Ans :



A. Precision winding: In this type of winding, successive coils of yarn on a package are laid

parallel or nearly parallel to each other. Hence a very dense package is formed which contains

maxm amount of yarn in a given volume.

Feature:

1. Package is wounded with a reciprocation traverse.

2. Package contain maxm amount of yarn.

3. Low stability.

4. Hard and more compact.

5. Flang may be used.

6. Dense package.

7. Unwinding process or rate is low & process is harder.

8. The wound coil is arranged parallel or near parallel.

9. Yarn tension is comparatively high.

B. Non precision winding: This type of winding, the package consists of a single thread which

is laid on the package at appreciable helix angle that the layers cross one another and give

stability.

Features:

1. Only one coil used.

2. Cross wound coil.

3. Less dense package.

4. Minimum yarn is stored.

5. High stability.

6. Flanged not necessary.

7. Unwinding rate is high & process is easier.

8. Soft & less compact.

9. Yarn tension is comparatively less.

Q6. Write down the faults in winding.

Ans :

Faults in winding :

1. Yarn breakage : The main causes –

a) Improper slub catcher setting.



b) Incorrect tension level.

c) Improper winding speed.

2. Stitch : The main causes of formation of stitch -

a) Excessive spindle speed.

b) Worn out spindle speed.

c) Large tension variation during winding

d) Defective release of Yarn after knotting.

e) Improper alignment of tension bracket.

f) Worn out or damaged grooves in the drum

g) Improper setting of travers restricters.

3. Patterns or Ribbons : The main causes of formation of patternsa)

a)Defunct antipatterning motion.

b) Incorrectly set antipatterning motion.

c) Cone or chese loose filting on winding spindle.

4. Entanglements : The main causes –

a) Repeated knotter fibre

b) Strong suction pressure

c) Lack of care while knotting and releasing yarn

d) Defunct warp stop motion

e) Improper setting stop motion

5. Wild Yarn :

a) Yarn waste wrapped on hands of workers.

6. Snarls : The main causes –

a) Faulty release of yarn after knotting

b) Strong suction pressure in the slack tube

c) Inadequate setting of twist.

7. Chaffed yarn : The main causes –

a) Defunct stop motion

b) Rough damaged grooves in drum

c) Defective yarn path.

8. Formation of patches on the yarn



9. Tension variation

10. Soft bobbin

11. Tight bobbin

12. No. of less removal of slubs, neps, dirt loose fibres

13. Incorrect shape of packages.

14. The faulty shape may be due to :

a) Faulty traverse motion

b) Faulty yarn guide

c) Faulty drum guide

d) Faulty building device

15. Too much knot in the yarn

16. Two end winding

17. Slack knots or knots with long tail.

18. Overlapping

19. Mixing of yarn of difference linear density.

Q7. State the Importance or Effects of tensioning Device.

Ans :

Too high tension:

(a) Can damage the yarn.

(b) Breakage rate may greater.

(c) Elongation properties may change.

Too low tension:

(a) Can lead to unstable or loose packages which will not unwind cleanly.

(b) Variation in yarn tension in different parts of a wound package can cause

undesirable effects.

For MMF(manmade fiber):

Too high tension :-

(a) Can cause molecular change which effects dye ability.

(b) Random variation in colour shading.

For Staple or Spun yarn:

Too high tension :-



(a) May breakage at thin place.

Mathematical Problem

Q1. Calculate the time required winding 400 lb of 12`s cotton on 10 drums. The actual

production per drum per min 560 yds.

Ans :

Actual production per drum per hr = (560*60)/(12*840) lb

=3.33lb

Time required = 400/3.33*10

=12Hrs(Ans)

Q2. How much time will be required to wind 2388 lbs of 20s cotton on 40 drums of a super

speed cone winder, if the calculated of winding is 1298 yds per min & the efficiency is 80%.

Ans : Actual production per drum per hr = Calculated rated of winding in min *Efficiency*60

= 1298*80/100*60yds

= 1298/840*80/100*60 Hank

=74.17 Hank

Time required = 2388*20

74.17*40

=16 Hrs(Ans)

Q3. Calculate the production of a super speed cone winding machine

from the following particulars :

R.P.M of the winding drum = 4956

Diameter of winding drum = 3 inch

Efficiency of the machine = 30%

Production/min = ?

Ans :

Production = π*diameter of winding drum* r.p.m of drum *efficiency

36*100

=3.14*3*4956*80 yds



36*100

=1037.456(Ans)

Q4. Calculate the production of a cone winding machine from the following particulars :



No. of drums = 120

Count of the yarn = 32s


Production/hrs = ?

Ans :

Production = π*dia of drum*60min*hr*efficiency*no. of drums lbs

36*840*100*count of yarn

=3.14*4*1200*60*8*70*120 lbs

36*840*32*100

= 628 lbs(Ans)

Q5. Calculate the production of a super cone winding machine from the following particulars :



No. of drums = 120

Count of the yarn = 32s (Ne)


Production/8hrs = ?

Ans :

Production = π*dia of drum*r.p.m. of drum*60min*hr*efficiency*no. of drums lbs

36*840*count of yarn*100

= 3.14*3*3012*60*8*90*120

36*840*100*32

= 1519.98 lbs(Ans)

Q6. Calculate the time required for winding 60,000 lbs of 54s yarn on 500high speed winding

drums each of which has a calculated reate of winding of 630 yds. The efficiency 90%.



Ans :

Actual production per drum per hr = 63*90*60 yds

100

= 3420 yds

Time required = Quality of yarn to wound in lb

Actual production in lb / spindle per hr*No. of drum

= 60000*54 hrs

3420/840 *500

= 160hrs (Ans)

Q7. Calculate the time required to prepare 9 sets of a 8 warpers beam each on 2 super speed

beam warping m/c. The calculated prodn of the m/c is 30,000 yds per hr & the length of warp on

each beam is 20,000 yrds. Assume 85% efficiency.

Ans :

Total length of warp in yards to be warped =20000*9*8 yds

= 1440000yds

Actual production per hr per m/c =30000 *85 yds

100

= 25500 yds(Ans)

Time required = total length of warp in yds

actual production per hr per m/c* no. of m/cs

= 1440000

25500*2

= 28.24 Hrs(Ans)

Q8. The rate of winding (calculated) of modern high speed cone winding m/c is 800 yds per min.

Calculate the no. of drums required to wind 388 lbs of 40s frinaring bobbin in 8 hrs. If efficiency

is 84 % , Allow 1% for waste & left on the bobbins.

Ans :

Actual production per drum per hr = 800*60*84

840*100

= 48 hanks



Quality of yarn to be wound =388- 1% =384 lbs

No. of drums required = 384*40 yds

48*8

= 40(Ans)

Q9. The winding drum of a high speed cone winder having a diameter of 3 inch makes 2870

r.p.m. The actual amount of yarn wound in 9 hrs was found to be 332,838 yds. What is the

efficiency?

Ans :

Calculated production in 9 hrs = 405531 yds.

Efficiency= Actual production *100

calculated production

= 332838 *100

405531

= 82%(Ans)

Q10. Production of pirn winding m/c per shift per spindle is 10 lbs for 30s cotton yarn. If the m/c

runs at 600 yds/min calculate efficiency.

Ans :

Calculated production per spindle per shift = 600 yds per min

= 600*60*8 yds per hr

= 288000 yds per hr

Actual production per spindle per shift = 10*840*30yds

= 252000 yds

Efficiency = Actual production *100

calculated production

=252000 *100

288000

= 87.5 %(Ans)

Q11. Calculate the no. of warper beam & length of warp that can be made from 1500 cones, each

of which contains 1.5 lbs of 40s cotton yarn. Total no. of ends required is 3000.

Ans :

Total wt. of yarn in lb =1500 *1.5 lbs

=2225 lbs



Length of warp in yds =wt of warp in lb* count *840

No. of ends

= 2225*40*840 yds

3000

= 2520 yds (Ans)

No. of beams= Total no. of ends

No. of cones

= 3000/1500

=2 (Ans.)

Q12. An ordinary slow speed warping m/c is working with 40s. The prodn of the m/c is 21,000

yds per day of 9 hrs. If it is required that creeling is to be wounded on the supply package,

allowing 5% for wastage & mtl left on the bobbins.

Ans :

Length of yarn = 21000 +21000*5/100 yds

=22050 yds.

wt. of yarn to be wound on each bobbin = 22050 lbs

840*40

=0.656 lb per 9 hrs (Ans)

Exercise on weft winding


2) Describe the main parts of weft winding machine

3) What are the properties of weft yarn improved during weft yarn preparation? How?

4) Demonstrate the difference between Automatic warp winders and automatic weft winder?

5) Demonstrate the function of the three motions in weft winding machine?

6) Identify the type of tensioning device and explain how the adjustment techniques

7) Explain the techniques to transport the empty pirn and presented to the winding heads.

8) Explain how motion is transmitted to different parts of the weft winding machine?



UNITE THREE: WARPING

Introduction

Warping is a process of transferring yarn from a predetermined number of single-end packages,

such as cones or cheeses, into a sheet of parallel yarns of a specified length and width. The

individual warp yarns are uniformly spaced across the whole width of the beam. In warping, the

sheet of parallel yarns is wound onto a flanged beam called a warper‘s beam [10]. The function

of warping is primarily to transfer large lengths of yarns from a number of large wound packages

to a warper‘s beam containing a predetermined number of yarn ends (threads), so that it runs

without interruption at a high speed. Removing faults from yarns during warping is not

recommended because it affects the efficiency of the process. A single break makes several

hundred other good warp yarns inoperative, thus affecting productivity[1,2,12].

If the creeling capacity is equal or higher than the number of warp threads, the warping would

simply entail the direct winding on the warp beam of the threads coming from the creel.

Generally this condition does not take place and, even with creels of high capacity, the number

of creeling positions never corresponds to the number of threads, which is always by far higher

than the number of bobbins which the creel can contain. This problem has been solved by

dividing the warping operation into two phases:

1st phase: unwinding of the threads from the bobbins and their winding on intermediate carriers,

till attainment of the required total number of warp threads;

2nd phase: simultaneous rewinding of all these threads and subsequent winding on the weaver‘s

beam; the contemporaneity of these two operations is the prerequisite to produce a beam where

all threads show same tension and length[1,2].

3.1 objectives

The main objective of warping process is to present a continuous length of yarn to the

succeeding process with all ends continuously present and with the integrity and elasticity of the

yarn as wound fully preserved. Warping is aimed at preparing the weaver‘s beam to be set up on

the weaving machine. Warping carries out following operations:

creation, out of a limited number of warp threads (creel load), of a warp composed of any

number of threads with the desired length;

arrangement of above-mentioned threads according to the desired sequence;



manufacturing of a warp beam with said characteristics.

3.2 Technical Requirements of the Process

The warping process should met the following technical requirements

1. The tension of all wound ends must be uniform

2. Warping should not impair the physical and mechanical properties of the yarn

3. The density of the yarn throughout the package must be uniform as possible and its shape

should be cylindrical

4. All ends should be of the same length

5. While the yarn end break or slough-off occurs, the beam must stop before 5 meter

displacement

6. The production rate of warping should be as high as possible

3.3. Warping Machines and Mechanisms

Depending up on the package replacement method, there are two types of warping are used.

Intermittent warping

Continuous warping

In intermittent warping, all the packages on the creel are changed after the stopping the warper,

and in continuous warping, the packages are replaced without stopping the warper.

Depending up on the kind of yarn and the manufacturing process, warping machines can be

groped into three categories

Beam warping (High speed beaming) machine

Sectional warping (Horizontal mill warping) machine

Specialist warping machines

In beam warping process, a part of known length of threads is wound on to a warping beam

followed by their joining and winding on to the weavers beam. Moreover, it is used for the same

colored yarns.

In sectional warping process, yarn ends are first wound in succession as sections on the warping

drum and further these sections are simultaneously wound from the warping drum on to the

weavers beam. Moreover, it is used for complicated colored pattern warp yarns[2,8,9,10,12].



3.4 Warping Systems

There are two basic systems of warping, namely, the direct system and the indirect system

(depending on the kind of intermediate carrier used, the industrial warping process can be carried

out), as shown in Fig. 3.1. In the direct system the warp yarns from a creel are wound directly

onto a flanged warper‘s beam. This system is most widely used for mass production of warper‘s

beams containing only one type of warp yarns. Because of the difficulties involved in setting up

a pattern of different types and colors of warp yarns, the direct system is not normally used for

the preparation of a patterned warper‘s beam [1]. Any pattern that is required to be produced is

adjusted by combining beams of different colors during the slashing operation. The cumbersome

work of setting the pattern at the slashing stage is time intensive and inefficient. In the indirect

system, a number of sections of patterned warp, containing different colors, are wound

sequentially on a section beam, as shown in Fig. 3.1. Once a desired number of sections (desired

number of total ends) are wound on a section beam, the warp is transferred onto a weaver‘s

beam[2,3].

Fig. 3.1 Warping systems[3].

3.4.1 Direct System preparatory beam warping or beam warping

In beam warping, the yarn is parallel wound on a warping. Up on warping ‗n‘ beams with ‗m‘

ends on each, a set of beams with a total number of ends, M = n ×m is formed, which is

necessary to produce the given fabric. The reasons of having limited number of ends in a beam is



that it makes the arrangement of the package will be easy to accommodate and manage.In the

direct system of warping, a predetermined number of yarn packages are placed in a large creel,

as shown in Fig. 3.2. Each yarn package is firmly inserted on a package holder,. The yarn from

each package is then threaded through its own stop motion and a tensioner at the front of the

creel. Yarns from all packages are brought together to form a warp sheet, which is taken to the

head stock where it is uniformly spaced by passing through dents of a comb and where the actual

winding of the yarn sheet on a beam takes place. The beams thus prepared are known as section

beams, warper‘s beams, or back beams. The required number of these beams is placed at the

back of the sizing machine. The type of creel, tensioner, warp stop motion, head stock, and

control devices on warping machines may vary depending on the manufacturer; however, their

basic functions remain the same[3].

The main parts of beam warping machine are:

(i) Creel

(ii) Package drive mechanism

(iii) Adjustable reed

(iv) Measuring device

(v) Braking Mechanism

Fig. 3.2 Direct warping system[3].



Creels

Independently of the warping system, the threads are fed from bobbins placed on creels. The

creels are simply metallic frames on which the feeding bobbins are fitted; they are equipped with

yarn tensioning devices, which in modern machines are provided with automatic control and

centralized tension variation. Moreover the creels are equipped with yarn breakage monitoring

systems. The creel capacity is the parameter on which the number of warping sections or beam s

depends; it should be as high as the installation type and planning permit; the usual creel capacity

amounts today to 800-1200 bobbins. Various solutions have been designed to reduce the time

required to load the creel and thus increase the warping performance . When standard creels are

used, the most cost effective solution is, provided that there is sufficient room available, to use

two creels for one and the same warping machine; in fact, while one of the two creels is used for

warping, the other creel can be creeled up again. In this case it is advisable that the reserve creel

is equipped with comb holder and that the warp threads are already drawn through the dents of

the combs. This way the loss of time caused by creel change can be minimized.

There are six general purpose types of creels in common use, continuous chain, truck, magazine,

duplicative, swiveling, and 'automatic', with specialist creels for tricot, polyolefin tape, and

sizing machine service[1,2,3].

a. Continuous chain type (Reversible) creel

The reversible creel, allows the position of the old packages and the new ones to be reversed at

the end of a run. Creel changes inside cycle can be completed using such a system in less than 15

minutes, and significant reductions of creel-change time. There is considerable storage space

within the creel for storage of creel trolleys[2,3].

Fig 3.3. Continuous chain type (reversible) creel[3]



b. Truck or mobile creel

This creel type is similar to the standard creel, but is formed by trolleys which can be taken

individually out of the creel. The bobbins are creeled up on each trolley outside the creel. During

the creeling up of a series of trolleys, the second series of trolleys is brought back to the outside

of the creel to feed the warper. This reduces considerably the waiting time. The mobile creel

comes in handy especially when there is insufficient room to permit the use of two

standard creels.It uses ‗trucks‘, or mobile package carrier units, each consisting of a number of

columns and tiers on either side so that when inserted on the axis of the creel frame it becomes a

part of the creel. This is not a low cost solution as many reserve trucks are essential and these are

not inexpensive units[3].

Fig 3.4. Truck or mobile creel[3]

c. Magazine creel

Each package position is duplicated with one package in the running position and the other in the

reserve position tied nose to tail. The package holders swivel to enable the empty cones to be

removed and new cones tied in nose to tail to the running package whilst the machine is in

operation. Space requirements are not so great for this type of package and a creel with

magazining features can be accommodated within a reasonable area. this kind of creel is used

when several warps of similar type must be prepared in sequence, that is when large lots of

similar yarns need to be processed. Level with each tensioner, two bobbins are positioned: one

operating and the other as reserve[1,2,3].



Fig 3.5. Magazine creel[3]

d. Duplicative creel

One duplicate spare creel is kept ready with creeled packages. After exhaustion of the first creel,

the headstock or creel can be moved relative to each other to bring in front of the new creel. This

system is versatile and saves a lot of time, but it will be necessary to re-thread the warp at the

beaming headstock before commencing the new run.

(i) Mobile creel (ii) Fixed creel

Fig 3.6. duplicate creels[1]

e. Swiveling creel

This creel has been designed to reduce the large space requirement of truck creel and frequently

used for very large creel packages which makes the trucks difficult to maneuver. Two

arrangements are possible. The creel can be loaded from outside with inside draw-off or vice

versa by rotating about its center point. The former arrangement is preferable as it not only

provides a straighter thread-path but is easier to load[1].



Fig 3.7. Swiveling creel[1]

f. Automatic creel

It is essentially a truck creel with automatic chain loading and unloading and with two features to

reduce creel change time. As the truck is pushed forward it automatically threads and separates

the ends according to creel tiers and columns[1].

Fig 3.8 Automatic creel[1]

3.4.2. Package driving mechanisms

There are two ways to drive the package.

i. Indirect (Drum driven) drive

ii. Direct drive

Indirect drive (Drum driven)



The package is driven by frictional contact from a driving drum and its effectiveness

depends on friction.

The yarn speed would be constant throughout the beam build-up.

Speed is limited up to 600 yd/min (548.64 m/min).

Programmed braking is not possible.

Direct (spindle) drive

Speed can be increased up to 1000 m/min by using thyristor-controlled DC motor with a

press roll and synchronous braking of all rotating masses (beam, pressroll and measure

roll)

If the beam revolutions per minute were constant, the yarn speed would increase as the

beam diameter increased which cause the tension in the yarn sheet to increase and the

yarn on the inside of the beam to be compressed and become damaged.

There is no friction problem.

Programmed braking is possible.[2,3]

3.4.3. Adjustable reed

It ensures the threads to spread uniformly across the warp sheet by arranging one thread per dent

and also used to set the width of the warp sheet to the exact distance between the flanges of the

beam[2,3].

1 - Needle bars

2 - Supports

3&4 - Plates

5 – Screw

Fig 3.9. Adjustable reed[1]



3.4.4. Measuring motion

The measuring roller acts as a guide and connected to a measuring device, which is preset

according to the length of yarn required on the beam. The counter of the measuring device runs

backwards and, when it reaches zero, the machine will be stopped automatically for a beam

change[1,12].

3.4.5. Braking mechanism

It is used to stop the machine up on achieving the required length of warp or in the case of yarn

breakage.

Brake Torque: Braking shoes for slow motion and hydraulic brakes for high speed warping

machines can be used to stop the motion of all machine parts at once during end breakage or up

on achieving the preset length of warp.

Brake torque (Tb) can be calculated as

Tb =m*k2*α

Where: m = Weight of the beam

k = Radius of gyration

α= Angular retardation

But, for uniform distribution of mass, the radius of gyration can be calculated as:

k = 0.25× d , where d = diameter of beam

3.5. Automatic stop motion of yarn

In warping, each end passes through the porcelain front guide reed and wire loop. The tensioned

yarn retains the loop in upraised position and presses it against guide rod. With the loop in this

position, contact plate is separated from brass rod. In case of yarn breakage the loop falls down,

contact plate comes in contact with brass rod and closes the stop electromagnet circuit and brings

the machine to standstill. As the machine stops, a signal lamp lights up indicating the group of

ends in which breakage has occurred.



Fig 3.10 Automatic stop motion

1- Guide reed

2- Wire loop

3- Guide rod

4- Brass rod

5- Contact plate

3.6. Indirect System, sectional warping (conical drum or dresser warping)

Unlike the direct system, warping and the preparation of a weaver‘s beam takes place on the

same machine but in two consecutive steps. In the first step, the warp is prepared in sections on a

large drum with one conical end, as shown in Fig. 3.11. Then the rewinding of the entire warp

sheet from this drum to a weaver‘s beam is done in the second step. The operations in the first

and the second step are commonly known as warping and beaming, respectively. For preparing

the sections on a drum, the warp yarn is withdrawn from the creel through a tension device and

stop motion (similar to the one described in the previous section) and is in turn passed through a

leasing reed. Then all the sectional warps are condensed into a section of the desired width by

passing them through a V-shaped reed guide and over a measuring roller to the drum. The

density of the warp in a given section is the same as the number of ends per unit width required

in the weaver‘s beam for producing a fabric with a given color pattern and specification. The

length of each section is generally equal to the length of the warp required in a weaver‘s beam

plus due allowance for the waste in the process. One end of the warping drum is conical shaped,

as shown in Fig. 4.15. This is necessary for providing support to the outside ends of the first

section to prevent the yarns from sloughing off at the end of the drum[10,11,12].



The leading end of each section is attached to the drum such that the edge of the section is placed

exactly on the nose of the conical portion of the drum or by the nose formed due to winding of

the previous section. During the process of winding a section on the drum, a slow continuous

traverse is imparted to the section of warp being wound. After the initial few turns of the warping

drum, a lease thread is inserted in each section with the help of a leasing device. This is

necessary for maintaining the correct order of the warp ends as required by the multicolored

pattern. These one -and- one leases inserted during warping are helpful during drawing-in of

warp ends in the harnesses of the loom [3, 12].

Fig. 3.11 Schematics of section warping[3].

After completing the warping operation, the full sheet of warp built on a warping drum contains

the exact number of ends and width of warp required on the weaver‘s beam. This warp sheet is

then rewound on a weaver‘s beam ready for weaving if the yarns do not require sizing. The yarns

that require sizing are also processed exactly in a similar manner, but additional split strings are

inserted during one-and-one leasing. These split strings are later replaced during slashing by split

rods. The beam prepared on such sectional warpers can be conveniently sized on a slasher

without much loss in time because the introduction of one-and-one leases ensures perfect

arrangement of all warp threads according to the pattern set during warping, and the counting

and arrangement of threads in the expansion comb of the slasher are no longer required[3,12].

As already mentioned, by this warping system several ″sections″ are wound in sequence and

parallel to each other on a dresser or on a drum; the warping sections are as many as necessary to

obtain, with the available creel capacity, the total number of threads composing the warp.



Sectional warping is cost-effective for short and striped warps (cotton and wool fabrics). The

warping speed is about 800 m/min, while the beaming speed is about 300 m/min.

Before carrying out warping, following calculations are necessary:

Section number = Total number of warp threads

Creel loading capacity

If the calculation does not give an exact number, the last section will be produced with a number

of threads lower than the other sections, or the number of threads composing each section will be

reduced so as to get all sections with one and the same number of threads[3].

Section width = Reed width

Number of sections

This way the total number of warp threads will occupy on the dresser a width equal to the width

of the weaver‘s beam on which they will be finally wound.

Example:

Given:

Total number of warp threads: 10,000

Creel capacity: 1,100

Number of sections = 10,000

1,100

= 9 + 100 threads

There are two possibilities: either to warp 9 sections with 1,100 threads each and 1 section with

100 threads; or to warp 10 sections with 1,000 threads each (therefore all of them equal) using

only part of the creel capacity. In this last case the result will be:

Section width= 140

10

= 14 cm

Relationships between drum storage capacities to beam flange diameter



There is a relationship between the capacity of the warping drum and the maximum flange

diameter of the beam which can be filled from the drum.

The thickness of the yarn (h) will be:

h=D –d

2

Where:

D = maximum flange diameter of the beam

d = warping drum diameter or barrel diameter

θ = cone angle

The volume of yarn (V) on the drum can be:

V=π/4*(D2-d

2)*w

W= si𝑛𝑖=1

tanϴ= h/t

Where:

w= widths between flanges

s = headstock feed or section width

t = traverse displacement

h= depth of yarn on the drum

Hence, the density of yarn on the drum (ρ)

ρ=m/v

Where: M = the weight of yarn on the package

3.7. Warping Machines Productivity

The productivity of warping machines can be expressed by the amount of yarn wound on a

warpers beam or a weavers beam per given time[3].



The actual productivity of a beam warping machine can be:

P = V × t ×T × m×Εx10-6

(kg/hr)

Where:

V = average speed of warping machine (m/min)

t = rated time (min)

T = linear density of yarn (tex)

m= number of ends wound simultaneously onto a beam

ε = machine efficiency

Time required to produce a full beam (tb) or each section

tb= L/V

where: L= piece length of warp in a beam and V = average speed of warping machine

The running efficiency of the warping machine:

ε= tb *100

(tb +ts ) ,ts= Idle time of the machine

The yarn breakage is usually assumed per million meters of single yarn. Hence, the number of

operations for eliminating breakages per warping or weavers beam (no) is

no= (n* m* L)/1000000

Where:

n1 = number of breakages per million meters of singl

m = number of ends

L = length of warp in a beam

Number of warping beams (nb) or sections (ns)

nb =l/L

ns=m/c

Where:

l = length of yarn on the supply package including warping waste

C= creel capacity



3.8 Warping Defects and Wastes

Some of defects that may occur during warping are:

Lapped ends which occur when the broken end is not tied to the end on the warping

beam but wound around it. It can be the result of operative carelessness or

disarrangements in the machine stop motion, when the yarn broken end is wound around

the warping beam and the operative fails to find it.

Piecing which is occurs when one broken end is pieced to another yarn end on the

warping beam and due to operative carelessness.

Incorrect form of build which is caused by non-uniform spreading of ends in the guide

reed and its improper setting, incorrect shape of the warping drum or improper setting of

supporting levers.

Slackness and non-uniform tension which is caused by improper setting of tension

devices or when the yarn escapes from under the washer.

Incorrect warping length which is caused by incorrect setting or troubles in the counter,

improper adjustment of measuring roller, non-uniform coating of measuring roller with

felt, or when the felt is worn out.

Mixing up of wrong count which is due to operative carelessness

Warping wastes occur as a result of yarn losses at the elimination of breakages and at gaiting. In

intermittent warping yarn losses are also caused by re-creeling. The amount of wastes depending

upon the method of warping and the yarn count is from 0.02 to 0.15%.

Solved exercise on warping

Pb#1. Suppose the following parameters are given:

Average speed of warping machine (V)= 750 m/min

Length of yarn on the supply package (l) = 90,000 m

The piece length of warp on a beam (L) = 18,000 m

Number of ends in a beam (m) = 400

Linear density of yarn (Nm) = 20

Working time (t) = 8 hours

Ideal time of the machine(ts)= 2 hours

Calculate



(a) The actual productivity of the machine

(b) The time required to produce a full beam

(c) Number of warpers beam obtained per supply package.

Solution

Conversion of the linear density of yarn in to tex system

T=1000/Nm

=1000/20

=50 tex

Conversion of working time

t= 8hr*60mint/hr =480mint

Determination of machine efficiency:

ε=(t-ts/t)*100

=8-2/8 *100

= 75%

(a) Actual productivity of warping machine (P)

P =V*t*T* ε *10-6

=750m/mint*480mint*50tex*400*0.75*10

-6

=5,400kg/shift

(b) The time required for a full beam:

tb= L/V

= 18000m/750m/mint

= 24mint

(c) Number of beams produced per supply package:

nb= l/L

= 90,000/18,000

=5 beam

Pb#2 In the sectional warping machines the following particulars has been observed

Linear density of yarn (T) = 20 tex

Drum barrel diameter (d) = 1.5 m

Inclination angle (θ) = 27°

Piece length of yarn in a beam(l) = 4,000 m

Total ends (m) = 5,000



Width between flanges (L) = 2 m

Density of warp in a beam (ρ) = 0.5 g/cm3

Calculate the traverse displacement (t).

Solution

Weight of yarn in a beam (M):

M =T*n*l/1000

=20*5000*4000/1000

= 400,000 g

Maximum flange diameter of beam (D)

The volume of yarn in a beam (V) can be calculated by either of the two equations

V=M ρ----------------(1)

V= π/4*(D2-d

2)*L………………….(2)

Equating equation 1 & equation 2, By rearranging the above equation:

D=√4/ π(M/ ρ*L)+d2

=√4/ π(400,000 g/0.5g/cm

3*200cm) +(150cm)

2

= 166 cm

Depth of the yarn on the beam (h)

h= D-d/2

= 166 cm-150cm/2

=8cm

Hence, the traverse displacement per section (t) can be calculated from depth of yarn on the

beam and cone angle

t=h/tanϴ

=8cm/tan270

= 16 cm(Ans.)

Warping

Q. Describe the problems in warp yarn & how can you solve these problems?

Ans:

1. Warp off centre of the beam: Due to not carefully placing of creel wraith & flanged beam.

Remedy: Beam & wraith placed properly.

2. Ridgy or uneven warp beam: This defect due to



(a) Winding of small no. of ends on larger beam.

(b) When the dents are bent or the spacing between dents are uneven.

(c) Mixed count.

Remedy: Higher no of ends be used.

3. Crossed ends: Due to

(a) Faulty knotting after yarn breakage.

(b) Tying of broken ends.

(c) Loose warp.

Remedy: Knotting & tension controlled.

4. Snarl formation in the warp: Due to

(a) Over tension.

(b) Improper twist

(c) Position of guide.

Remedy: By proper tension & twist.

5. Missing ends: Due to

(a) Faulty stop device.

(b) Exhausted cone or bobbin

(c) Absence of cone or bobbin on creel.

Remedy: By correct stop device used.

6. Hard beam: Due to high tension.

Remedy: By correct stop device used.

7. Unequal length of warp: Due to faulty measuring device.

Remedy: Tension & pressure maintained.

8. Broken ends:

Remedy: To be joined carefully the yarn.

9. Entanglement of warp.

10. Large knot.

11. Sandy warping.

12. Slack ends.

13. Uneven tension of warp.

14. Uneven shape of beam.



15. Wild yarn.

16. Defective beam flange.

17. Warp ends round the creel peg.

18. Unequal length of warp.

19. Unequal size or weight of cone or cheese in the creel.

20. Lapped ends.

21.piecing.

22. Soft end on the warping beam.

23. Warp ends round the creel peg (spindle) & result broke.

Q. Compare between High speed warping & Sectional warping.

Ans:

S.No High speed warping Sectional warping

1 To produce common fabric (colour &

grey fabric.)

To produce fancy fabric.

2 High production Lower prodn

3 Large amount of yarn reqd. Small amount of yarn reqd.

4 Weavers beam is produced after sizing. Weavers beam is produced after warping.

5 Creel capacity is greater than 12000. Creel capacity is 300-400.

6 Flanged bobbin is used as beam. Tapered beam or drum is used as beam.

7 Single yarn is used. Twist yarn is used.

8 Cheap process. Costly process.

9 Uniform tension. Non-uniform tension.

10 Used very much. Not used.



Q. Describe the functions of components of creel and head stock that are used in warping m/c.

Ans :

Function of components of creel:

1. Cone or cheese spindle of high speed & peg for sectional warping.

2. Thread guide: To pass through the yarn in the reqd way.

3. Tensioner: To keep the yarn always in a uniform tension.

4. Yarn cleaner: To remove various faults of yarn like slubs, neps etc.

5. Suction fan or blower: To remove the dirt & dust from the yarn.

6. Breakage indicator: To indicate breakage in package.

7. Stop device: To stop the m/c when yarn will be broken.

Features of components of Head stock:

1. Adjustable or variable v-reed or wraith: To control the width of the warp beam.

2. Measuring & making device: Measure the amount of warp yarn on the beam & marks the

yarn.

3. Yarn speed controlling device: To control the speed of yarn.

4. Pneumatic pressure unit: To press the warp beam with the surface contact of driving drum.

5. Break assembly: It stop the m/c after reqd length is wound on beam.

6. Driving drum: Beam is in contact & control with driving drum.

7. Stop motion: Used to stop the m/c after reqd length is wound on beam.

8. Beam bracket: To support & hold the beam.

9. Lease rod: Used for separation of yarn individually.

Mathematical Problems

Q. Calculate the no. of warper beams & the length of warp that can be made from 440 bobbins,

each of which contains ½ lb of 60s cotton. The no. of ends of warp reqd is 2200. Allow 5%

waste & yarn left on the bobbins.

Ans :

Total wt. of yarn =440*1/2-5%

=209lbs

Length of warp =wt. of warp in lb*count *840 yds



No. of end

=209*60*840/2200

=4788 yds(Ans)

No. of beam =Total no. of ends/No. of bobbins

= 2200/440

= 5 (Ans.)

Q. Calculate the quantity of yarn in lbs which will be reqd for a set of 6 back beams to be

produced on a modern high speed beam warper. The length of warp on each beam is 24000 yds

& there are 462 ends on each beam count 36s. Allow 1 *1/2% or 1.5% for waste during warping.

Ans :

Length of warp reqd per beam =24000+1* ½%

= 2460 yds

Wt. of yarn in lbs reqd for the set =Total length of yarn in yds/count *840

Total length of yarn for the set = Length of warp in yds reqd per beam* no. of ends per beam

*no. of beams

=24360*462*6

=67525920 yds

Wt. of yarn in reqd for the set =67525920/36*840

= 2233 lbs(Ans.)

Q. Calculate the production of a modern high speed beam warpn m/c from the folloeing

particulars: Rpm of winding drum =260, diameter of winding drum = 22‖, no. of ends = 420,

time = 8hrs, efficiency = 80%, count = 32, production/8hr in pound?

Ans :

Production = π*dia. of drum* r.p.m. of drum* hr*efficiency* no. of ends

36*840*count*100

= 3.14*22*260*8*80*420 lbs

36*840*32*100

=2993.466 lbs?(Ans.)



Q. Calculate the production of a modern high speed beam warping m/c from the following

particulars:

R.P.M. of winding drum = 260

Diameter of winding drum = 22‖

Efficiency = 80%

Time = 8 hrs

Production/8hr = ?

Ans :

Production/8hr = π*dia of drum *r.p.m. of the winding drum *hr* efficiency /36*100

= 3.14*22*260*60*8*80/36*10

= 191581.860 yds(Ans)

Exercise

Describe the following question as per your observation your practical Textile Share

Company:

1) Demonstrate the yarn passages and explain the purpose of each machine part of a

warping machine

2) Identify the type of warping creel and also Show and explain the purposes of different

parts of warping creel

3) Describe the different parts of automatic stop motion

4) How automatic stop motion in warping actuated?

5) What is the use of the glass winding guard? Demonstrate the purpose of an eccentric

roller at the headstock

6) Identify the type of tension device and explain how tension adjustment

7) How could you increase or decrease the tension of yarn on the beam warping machine?

8) What is the purpose of adjustable reed? How is it adjusted?

9) Identify the type of breaking mechanism and demonstrate how it can be actuated?



10) Explain the parts and symbols of the of the right and left hand control panel of the

warping machine?

11) Show and demonstrate the working principles of yarn clearer

12) Explain the operation of measuring motion

13) How constant density of the warping beam is achieved?

14) If you are assigned supervisor of the preparatory department what you will do to increase

the production of warping machine?

15) Explain how motion is transmitted to different parts of the warping machine

16) Identify the type and demonstrate the drawing in operation?

17) Identify the type of tying in machine and explain how the operation is done



UNIT FOUR: SIZING

Introduction

During weaving process, the warp yarn is subjected to aconsiderable friction and the action of

variable stretching forces. As the result, the yarn becomes damaged and single fibers are

detached from it, which finally results end breakage.

The tensions imposed on the warp yarn can be

(i) Constant tension, which includes the tension due to the relative movement of let-off and take-

up motions. This tension comprises tension due to stretch and crimp and also do not causes warp

breakage[3].

(ii) Cyclic tension, which includes tension variation due to large shed opening and heavy beat

up. Both causes warp breakage.

(iii) Transient tension is those tensions which may rise for a very short period of time and leads

to breakage of warp yarns. This tension occurs when large knots unable to pass through the reed

and when fibers or broken filaments or yarns are entangled[1,2,3,12].

Hence, the warp yarn should be subjected to a special treatment known as Sizing to make it more

resistant for the above complex weaving stress and reduce the resulting end breakage.

The primary purpose of sizing is to produce warp yarns that will weave satisfactorily without

suffering any consequential damage due to abrasion with the moving parts of the loom. The other

objective, though not very common in modern practice, is to impart special properties to the

fabric, such as weight, feel, softness, and handle. However, the aforementioned primary

objective is of paramount technical significance and is discussed in detail herein. During the

process of weaving, warp yarns are subjected to considerable tension together with an abrasive

action. A warp yarn, during its passage from the weaver‘s beam to the fell of the cloth, is

subjected to intensive abrasion against the whip roll, drop wires, heddle eyes, adjacent heddles,

reed wires, and the picking element. The intensity of the abrasive action is especially high for

heavy sett fabrics. The warp yarns may break during the process of weaving due to the complex

mechanical actions consisting of cyclic extension, abrasion, and bending. To prevent warp yarns



from excessive breakage under such weaving conditions, the threads are sized to impart better

abrasion resistance and to improve yarn strength. The purpose of sizing is to increase the strength

and abrasion resistance of the yarn by encapsulating the yarn with a smooth but tough size film.

The coating of the size film around the yarn improves the abrasion resistance and protects the

weak places in the yarns from the rigorous actions of the moving loom parts[3].

4.1. Functions of the sizing operation

To lay in the protruding fibers in the body of the yarn and to cover weak places by

encapsulating the yarn by a protective coating of the size film. The thickness of the size

film coating should be optimized. Too thick a coating will be susceptible to easy size

shed-off on the loom[3].

To increase the strength of the spun warp yarn without affecting its extensibility. This is

achieved by allowing the penetration of the size into the yarn. The size in the yarn matrix

will tend to bind all the fibers together,as shown fig 4.1. The increase in strength due to

sizing is normally expected to be about 10 to 15with respect to the strength of the

unsized yarn. Excessive penetration of the size liquid into the core of the yarn is not

desirable because it affects the flexibility of the yarn[3].

To make a weaver‘s beam with the exact number of warp threads ready for weaving.

Fig. 4.1 Fiber–size binding in a yarn[3].



4.2 Technical Requirements of Sizing Process

The sizing process should suit the following provisions

i. The sized warp must be sufficiently strong, smooth, and elastic

ii. The sizing process must ensure the applications of the required amount of size on the yarn

iii. The tension of the yarn must be uniform throughout its length

iv. The package must have cylindrical shape, the necessary winding density and yarn length

v. Yarn stretch and loss in elongation should be with in the admitted limit

vi. The process must be efficient, economical and ensure the production of high quality sized

warp.

4.3. Influence of sizing on yarn properties

Sizing increases the mass of yarn

Sizing decreases Hairiness which in turn increases smoothness and results lustrous yarn

Sizing Increases yarn strength but decreases elongation or stretch

Stretch or elongation

The elongation of sized yarn depends up on its stretching in sizing machine.

In proper sizing condition, the stretch for cotton warp yarn should not exceed 1.5 % and

for viscose staple about 5 %. With excessive stretch, the quality of sized warp is

impaired which results in high end breakage on looms.

Stretch of warp yarns (S) can be calculated in terms of:

S = (V2-V1)/V1 *100

Where: S = Stretch

V1 = Speed of feeding component

V2 = Speed of delivering component

Figure 4.2 illustrates various possible conditions that may occur in practice depending upon the

properties of the size employed. This emphasizes the importance of an optimal balance between

the penetration of the size into the yarn and providing a protective coating around the yarn, as

shown in Fig. 4.19d. The flow properties of the size liquid and the application temperature have

important effects on the distribution of the size within the yarn structure. More size at the

periphery of the yarn will tend to shed off on the loom under the applied forces because the size

is not well anchored on the fibers. Too much penetration, as shown in Fig. 4.19a, may leave too



little size around the yarn surface to protect it against the abrasive action. To rectify such a

condition, a higher size add-on is required to provide the required protective surface coating .

Fig. 4.2 Schematics showing size distribution; (a) too much penetration, no surface coating; (b)

too much penetration, more size added to provide surface coating; (c) too little penetration, no

anchoring of yarn structure; (d) optimal distribution[3].

4.4. The chemistry of sizing compounds

Up until the development and commercial use of manmade fibers, the sizing materials employed

in the textile industry had to meet the needs of the natural fiber weaving industry. The sizing

material used primarily in the cotton manufacturing industry used natural starches. The natural

starches such as corn, wheat, tapioca, and the like have a tendency to form very stiff films. To

overcome the stiffness of the natural starches, weaving was carried out at very high humidities.

Nevertheless, natural starches performed a useful function, and they still do in the cotton

industry. Because the starches have a chemical nature that is similar to that of cotton, the starches

adhere very well to cotton as well as to rayon—the first commercially made manmade fiber

which has a chemical structure similar to cotton[3].

The desizing of starch can be carried out by enzymatic treatment and making the degraded

product water soluble. The starch materials are relatively inexpensive and they still find

widespread use in the textile industry. The starches need to be cooked and applied at a relatively

high temperature, which poses some processing problems for rayon. For sizing of rayon a gelatin

type natural protein sizing material derived from hides and skins of animals was developed. This

material could be applied at temperatures lower than that used for natural starches. This material

proved adequate for sizing rayon without causing any ‗‗hot-wet‘‘ damage. A protein-digesting

protein is employed to desize the material. This state of affairs prevailed until the 1940s when



the first truly synthetic fibers appeared on the scene. In 1938 nylon fiber, which is thermoplastic

in nature, appeared on the scene, requiring the development of sizing material that could be

applied at lower temperatures and also adhered to the hydrophobic surface of the fibers.

The new types of sizing materials included such chemical compounds as carboxymethyl

cellulose (CMC), polyvinyl alcohol (PVA), copolymers of acrylic acids, and other such water-

soluble materials that did not require cooking before use. The chemistry of these materials made

the desizing simpler and easier. By controlling the degree of polymerization of these compounds,

sizes with considerably different physical and solubility properties have been made. Some of

these sizes are also blended with starches to balance the cost of sizing while at the same time

improving the processing properties of yarns during weaving[3].

Another class of materials called ‗‗binders‘‘ has also been developed to improve adhesion and

properties of size films formed by synthetic materials. The chemical sizing materials available in

the market offer the textile technologists to engineer the sizing ingredients to meet the processing

requirements of various types of fibers and high speed weaving. In this chapter, the chemical

nature and the various chemical and physical properties of the sizing ingredients will be

discussed[3].

4.5 properties of size materials

There are a number of desirable properties which a warp size should possess. These are

summarized in Table 41. A good sizing material should have most if not all of these properties;

however, sizes that are deficient in some of these properties still may be used. For example,

starch is a useful sizing material even though it has a high biological oxygen demand (BOD),

lacks bacterial resistance, and is sensitive to overdrying; cannot be recovered; and must be

cooked to achieve uniform properties besides other disadvantages. Yet it is a useful size material

primarily because it is inexpensive, is easily desized, is a renewable resource, has good adhesion

to cellulosic fibers, and can be modified and/or derivatized to yield a wide range of size film

properties. In other words the usefulness of a size material for a specific application will depend

upon the nature of the fibers of yarns being sized (e.g., cellulosic, nylon, polyester,

etc.), the type of yarn (ring-spun, open-end, air-jet), the type of weaving machine being

employed (shuttle, air-jet, rapier, projectile, etc.), and the characteristics of the fabric being

woven (style, construction, weave, twist, yarn count, etc.). For example, what may be a suitable

size for a ring-spun yarn may not work for an open-end or an air-jet spun yarn, especially if a

yarn is made from blends of dissimilar fibers[3].



The primary size materials that act as ‗‗film formers‘‘ are

Starch (modified and unmodified)

Polyvinyl alcohol

Carboxymethyl cellulose

Acrylic (various addition polymers)

Table 4.1 Properties of a Good Sizing Material[3]

Environmentally safe (nonpolluting)

Good film former

Reasonable use economics

Penetration of yarn bundle

Elasticity

Good film flexibility

Good specific adhesion

Good frictional properties (lubricity)

Transparency

Bacterial resistance (mildew)

Reasonable strength

Controllable viscosity (fluidity)

Water soluble or water dispersible

Good hygroscopicity characteristics

Uniformity

Clean split at bust rods

Improves weaving efficiencies

No effect on drying

Reasonable extensibility

Recoverable and reusable (or treatable)

Low static propensity

No skimming tendency

Easily removed (desized)

Easily prepared

Lack of odor

No beam blocking

Compatible with other ingredients

Good abrasion resistance

Neutral pH

High fold endurance

Insensitive to high heat (overdrying)

Low BOD



Rapid drying

No redeposition of size

Insensitive to changes in relative humidity

No build-up on dry cans

Reduced shedding

4.5.1. STARCH

Starch was at one time the primary sizing agent for textiles, and it is still used extensively either

alone or in blends with other sizing agents. Large quantities are also used by the paper and food

processing industries, for medicinal and adhesive applications, in the fermentation of alcoholic

beverages, and even as explosives. It is one of the most abundant agricultural ‗‗renewable‘‘

resources found in nature. Starch occurs widely in plants but is found in its purest form in the

seeds (such as in wheat, corn, rice, and sorghum), in the roots and tubers (such as in potato,

tapioca, and arrowroot), or in the stem pith of plants (such as in sago). These sources constitute

the bulk of the world‘s supply of commercial starches. In the United States, the endosperm

portion of the kernels of the hybrid yellow dent corn (which is about 90% starch) provides the

major source of starch used in textile applications. Starch { n (C H O ) 6 10 5 } which is a

complex carbohydrate and ‗n’ depends on the kind of starch can be used as natural gum. Some of

them are Maize, potato, wheat …

Starch (big granules) can be broken by hot water, chemical agent and steering[3].

(C6 H10 O5)n {Dextrin + Glucose}

4.5.2. Chemical agents

It is used for splitting to a certain degree the macromolecules of starch. Eg. Chloramines

Chloramines ensure a uniform splitting of starch granules without impairing its chemical

structures[3].

4.5.3. Softners

When splitting of starch is effected by means of acids or alkalies, a chemical modification of

starch in to dextrin and glucose is possible which forms a hard rigid film on the yarn surface after

sizing and makes the yarn stiff. Hence, to make the film somewhat flexible softners are used.

Some of the softners in use are

Vegetable and animal fats

Glycerin

Cotton seed oil.



Soap

4.5.4. Deliquescent

It can be used to increase the hygroscopic properties of sized yarn and for preserving the

flexibility of starch film. It can be used rarely since constant moisture content is obtained by

automatic sizing regulators[1,2,3].

Eg. Common salt, Ca cl2, Glycerin

4.5.5. Wetting and Antifoaming agent

Foams are bubbles which can put-off size penetration inside the yarn and hence Antifoaming

agents are used to prevent foam formation. The introduction of wetting agents improves the

penetration of size between the fibers and to have a uniform penetration of sizing solution on the

yarn surface.

Eg. Silicones, Ethers, water insoluble alcohol ….

4.5.6. Preservatives

When the size warp or grey cloth is to be stored for a long period of time microorganisms can be

developed and destroy the fabric. Antiseptics such as Sulphates of copper, phenol, boracic acid

etc. are introduced in to the size to prevent the development of microorganisms.

4.5.6. Water

It is a solvent in the preparation of sizes. Only clean water without suspended admixtures and

considerable amount of calcium or magnesium salts (hard water) should be used.

4.6. Sizing Parameters

The sizing parameters includes

Size concentration (C)

Size add-on or size (A)

Size pick up (W)

(i) Size concentration (C) can be

C= (Oven dry weight of size)*100

Weight of size liquor

(ii) Size add-on (A) can be calculated as

A = (Oven dry weight of size)*100

Oven dry weight of unsized yarn



(iii) Size pick-up (W) can be calculated as

W= (Weight of liquor after the nep poiont)*100

Oven dry weight of unsized yarn

= A/C *100

Size pick up can be affected by

the concentration of size

the pressure on the squeezing roller

the speed of the machine

the density of the warp sheets

the yarn structure (twist)

Size concentration affects the viscosity or thickness of the size solution.The viscosity of size

depends up on

the temperature

the gum content

uniform splitting of the starch particles

4.7. Sizing–Weaving Curve

A typical sizing–weaving curve is as shown in Fig. 4.3. Initially the warp breaks decrease with

the increase in size add-on level. This is due to the associated increase in yarn strength and

reduction in yarn hairiness. The coating of the protective size film around the yarn provides

improved resistance[2,3,12].

Fig. 4.3 A typical sizing–weaving curve[3].

to abrasion and also affords adequate protection to the weak places in the yarn.

The reduction in warp breakage rate with an increase in size add-on reaches a point beyond

which further size add-on will not show any significant improvement in yarn performance on the

loom. The weaving efficiency, which is inversely proportional to warp yarn end breakage rate,



reaches its peak when the warp breakage rate is at its minimum. The optimal range of size add-

on is usually between points A and B as shown in the typical curve in Fig. 4.20. Increasing the

size add-on beyond the optimum, in fact, has a detrimental effect on weaving performance since

the warp breaks increase. Excessive size add-on leads to an increased penetration of the size,

which makes the yarn inflexible. Also, higher size add-on may tend to coat the yarn with a very

thick film of size which is not sufficiently anchored to the fibers. Such a thick coating of size

film may have a lower extensibility compared to the extensibility of the warp yarn itself.

Inflexibility of the yarn and a size film not bound securely have a net effect of size film shedding

due to its easy rupturing, thus making the yarn vulnerable to intensive abrasion action and

leading to a higher warp breakage rate. The best weaving efficiency region consistent with

optimal size add-on is usually achieved in practice by trial and error[2,3].

4.8. Sizing Machines

The essential components of a sizing machine to slash spun warp yarns may be categorized as

follows:

1. Creels—unwinding zone

2. Size boxes—sizing zone

3. Drying cylinders—drying zone

4. Bust rods—splitting zone

5. Head stock—weaver‘s beam preparation zone

6. Controls and instrumentations

Figure 4.4 shows a schematic diagram of a typical sizing machine and its essential components.

Warp yarns from warping beam placed in a creel are withdrawn and fed to the size box by a feed

roll. The yarns are then impregnated in size liquor preheated to a desired application temperature.

Then the yarns are passed through a pair of rolls, commonly known as squeeze rolls, to squeeze

out excessive size before they are subjected to the drying cylinders of the drying zone. This is

necessary to minimize the drying energy required to dry the warp yarns. The yarns wet with size

solution are passed over and under the heated drying cylinders to dry the sheet of warp yarns to a

desired level. The dried yarn sheet is then passed through a series of bust rods in the splitting

zone to separate the yarns. In the final phase, the separated yarns are passed through a guide

comb and wound onto a weaver‘s beam. The following sections will deal with each function and

component of the sizing machine separately.



Fig. 4.4 Schematic of sizing operation[3].

4.8.1. Creels—Unwinding Zone

The creel on a modern slasher is available in several different forms. Basically it must be well

built and of robust construction, capable of carrying heavy warper‘s beams. The primary

function of the creel is to allow smooth and steady unwinding of the warp yarn sheet without a

side to side swinging of the warper‘s beam and without entangling two adjacent warp sheets

being unwound. Also, the ends from either side of the warper‘s beam should not touch the beam

flanges. To prevent the sideways swinging of the beams and allow a smooth unwinding of the

warp sheet, modern creels are equipped with ball bearings to support the end shafts of the

warper‘s beams. This also helps in eliminating unwinding tension variations in the warp sheet.

Both fixed and movable (on wheels) types of creels are available. The advantage of the movable

creel is that while slashing is in progress from one set of beams, the loading of another set can be

done on another stand-by creel, which can be attached to the back of the sizing machine later

without loss of much time. Consequently, the next set on the sizing machine can be started with

much less down time, thus increasing the slashing efficiency[2,3].

The major creel types housing multiple beams are:

Over/under

Equitension

Inclined

Vertical stack

Over/Under Creel. In the over/under creel, as the name implies, the warp yarn passes over one

beam, under the next beam, again over the next beam, and so on, as shown in Fig. 4.5. This type

of creel is most commonly used for slashing spun warp yarns of cotton and synthetic fibers. The

threading pattern of warp from the beams in this type of creel varies depending upon the number

of size boxes used. For heavy to medium construction fabrics, where two size boxes are used in

industrial practice, all top beams in the creel may be threaded over and under and then straight to



the first size box, as shown schematically in Fig. 4.6. All bottom beams are threaded over and

under and then straight to the second size box , as shown in Fig. 4.6. Equitension Creel. In this

type of creel, the warp sheet is withdrawn from the individual beam and is passed over a guide

roll mounted on the creel framework[3].

Fig. 4.5 Over/under creel[3]

Thus the yarn sheet from each warper‘s beam is drawn individually and passed over a guide roll;

it then joins the yarn coming from other beams of the top or bottom tier, respectively, and then

passes forward directly to the size box, as shown in Fig. 4.7. This type of creel is more useful for

lightweight fabrics of open constructions.

Inclined Creel. The inclined creel may be either double tier or single tier. Obviously, the single

tier creel requires much greater floor space, and two tier creels are therefore more commonly

used in the industry. The double tier inclined creel is commonly used for filament warps. As

shown in Fig. 4.8, the inclined creel allows a direct path of the yarn from each beam through the

hook reed to the size box.

Vertical Creel. This type of creel is most suitable where a large number of warper‘s beams are

used. This creel allows the operator easy access to all the warper‘s beams. The beams are

supported on vertical stands in three decks in several modules, as shown in Fig. 4.9. The passage

between each pair of

Fig. 4.6 Over/under creel for two size boxes.



Fig. 4.7 Equitension creel[3].

Fig. 4.8 Inclined creel[3].

Fig. 4.9 Vertical creel[3].

As the beam diameter decreases to maintain a uniform yarn tension from start to finish of the

warping beams. The deadweight system is substituted by pneumatic cylinders in the pneumatic

braking system. The pneumatic pressure in such cylinders on the individual warping beam can be

integrated into a central regulator accessible to the operator. The centralized pneumatic braking

system, integrated with the sizing machine drive controller, is very efficient because it applies a

higher braking force only when the slasher is decelerated.

This prevents the application of excessive tension during the normal working of the slasher. A

more precise system is the automatic pneumatic braking system in which a sensor is placed

between the creel and the size box for measuring the tension in the whole warp sheet. The

desired tension in the warp sheet is preadjusted by the operator depending upon the yarn type,

yarn count, and style of the fabric being produced. The air pressure in the pneumatic cylinders is

automatically adjusted in proportion to the tension fluctuations registered during acceleration or



deceleration, and also from start to finish of the warper‘s beams. This system assures a constant

unwinding tension of the warp yarns from the warp beams for the entire sizing process, with

minimal operator intervention[3,12].

4.8.2. Size Boxes—Sizing Zone

The size box and all parts that remain in contact with the size solution are made of stainless steel

to prevent corrosion. The shape of the size box from the bottom is contoured with no sharp ends.

The size liquor in the size box is normally heated by steam supplied through a steam coil placed

at the bottom of the size box. The steaming coils placed in the size box should ensure uniform

heating of the size liquor in the entire size box[3,12].

Fig. 4.10 Rope or belt braking system[3].

The type and the design of the coil vary depending upon the size box manufacturer. The entry of

the high pressure steam in the size box also creates a turbulence which results in the agitation of

the size liquor. This is favorable in the case of a starch-based size used for sizing spun yarns

because the agitation prevents gelling and scumming of the size near the corners. For filament

slashing, a size box with direct heating coils is not desirable as the agitation of the size liquor

may disturb the filaments. Also, the bottom of the size box should have an outlet to the effluent

disposal system so that the size box can be completely drained when cleaning is required[3].

The configuration of size boxes is quite diverse and they are available in a variety of different

forms depending upon the sizing machine manufacturer. However, the basic function of all size

boxes is to impregnate the warp sheet in the size liquor at a predetermined application

temperature and to squeeze out the excess size liquor before the yarn sheet reaches the drying

zone. Most slashers are equipped with a single sizing box having two pairs of squeezing rolls and

an immersion roll. Figure 4.10 shows a typical size box. A sheet of warp yarn is drawn from the



warper‘s beams and fed to the size box over a pair of guide rolls with a slack rod or tension roll

riding on the warp between the two guide rolls. The sheet of yarn is immersed in a size solution

by one or two immersion roll(s). The immersion roll is normally movable. It is mounted on the

size box with a rack and pinion mechanism so that it can be freely lowered and raised. The

amount of size that will be picked up by the yarns will depend upon the depth of the immersion

roll and the level of size liquor in the size box. At a given constant size level in the box, the

lower the position of the immersion roll, the greater the pick-up of the size by the yarns, as it

allows a longer time for the yarns to remain in the size liquor and vice versa. The yarn sheet with

wet size on it then passes through one or two pairs of squeezing rolls, as shown in Fig. 4.10[3].

The purpose of the squeeze rolls is to remove the excess size liquid from the yarns. For filament

yarn sizing a single squeeze size box is usually used; however, in case of spun cotton and

synthetic yarns where higher size addon is required, double squeeze size boxes are normally

preferred. The bottom roll in a pair of squeeze rolls is made up of stainless steel and the top roll

is made from cast iron material covered with rubber. The top roll is usually under pressure in

addition to its own weight of around 180 to 250 kg. The pressure is usually applied by

compressed air operating on pneumatic cylinders or pneumatic diaphragms[3].

Fig. 4.11 Schematics of size box[3].

In modern slashers, the trend is to use a high squeezing pressure to save energy in drying and to

make it possible to use higher concentrations of the size liquor to obtain the predetermined size

addon. In high pressure squeezing, the squeeze roll loading is up to approximately 9000 kg

(20,000 lb), which is about 15 times the loading used in a conventional size box . In high

pressure squeezing, the quantity of water evaporating during the drying process will be lower,

thereby allowing not only savings in drying energy, but also an increase in sizing machine



productivity. The drawback of the high pressure squeezing is that the top squeeze rolls deflect or

bend when loaded at such high pressure. This results in a nip size variation across the width of

the roll, as shown in Fig. 4.29. An uneven nip zone width causes a variation of squeezing

pressure across the roll width, resulting in variation in size add-on from the selvedge to the

center of the warp sheet. For narrow size boxes (1.4-m width of yarn sheet) West Point Co.

research has found that the variation in size add-on due to top roll bending is not significant.

Nevertheless, in the case of wider size boxes corrective action incorporating ‗‗crowned‘‘ squeeze

rolls should be used to obtain a uniform nip width[2,3,12].

Fig. 4.12 Schematics showing nip deformation in high pressure squeezing[3].

A crowned squeeze roll is produced by grinding the rubber cover top roll to a slightly larger

diameter in the center than at the ends. This compensates for the possible bending of the top roll

while under high pressure and provides a reasonably uniform nip width and squeezing pressure

across the entire width of the roll.

A double squeeze size box with twin rolls is also used for slashing light and heavy warp sett spun

yarns. The twin immersion rolls allow both sides of the yarns to be exposed to the size mixture,

thus ensuring uniform coating and penetration of the size liquor. Both squeeze rolls are equipped

with independent loading and lifting controls. This provides flexibility to the slashing operator in

using either one or both rolls depending upon the requirement. A size box having double roller,

double immersion with high pressure squeezing, as shown in Fig. 4.13, is also used. In such a

size box, one set of immersion and squeeze rolls is followed by another set of immersion and

squeeze rolls. A recent development is the Equi-Squeeze Size Box, shown in Fig. 4.14. In this

system the top squeeze roll position is adjustable. A unique bracket and loading system allows

the positioning of the roll to the rear 15 or 30 degrees off the top center position, as shown in Fig.



4.14. By moving the roll to the rear, the adherence of yarns to the roll as they leave the squeezing

nip is minimized[3,12].

Fig. 4.13 Schematic of double squeeze rollers, double immersion with high pressure squeezing.

(1) Driven dry feed rollers; (2) guide roller; (3) immersion roller; (4) rubber covered squeeze

roller; (5) finishing roller; (6) size level float switch; (7) size circulating pump[3].

Fig. 4.14 Equisqueeze size box[3].

4.8.3. Drying Cylinders—Drying Zone

There are two principal types of drying methods used, namely,

1. Cylinder, or can, dryers

2. Hot air, or convection, dryers

4.8.3.1. Cylinder Dryers.

These are most widely used as they are the most energy efficient. The cans or cylinders are about

75 cm in diameter and are used in a multiple unit containing a series of five, seven, nine, or

eleven cylinders, usually arranged in two tiers to save floor space. The maximal working

pressure of steam in these cylinders is about 4.92 kg/cm2 (70 psi). The cylinders are made of



stainless steel. These cylinders are mounted on ball bearings and driven positively by a chain and

sprocket. This eliminates undue tensioning of the yarns while they are dried. The cylinders are

also coated with nonstick coating, e.g. Teflon, for preventing the size and yarns from sticking

while the warp is partially dried. Usually the first three cylinders from the front are coated with

Teflon in any sizing machine containing five, seven, and nine cylinder systems. For an eleven-

cylinder drying system, usually the first four cylinders are coated with Teflon. In the case of

filament sizing, usually all cylinders are coated with Teflon[1,2,3,12].

The cylinders in a drying section are usually arranged either horizontally or vertically. The

horizontal system is generally used because it allows easy access to the cylinders for threading

and mending a break, whereas the vertical system is useful in cases where floor space is limited

and when more cylinders are required because a greater number of size boxes are used. The

horizontal system of drying cylinders usually consists of seven, nine, or eleven cylinders,

depending upon whether one or two size boxes are used[2,3].

The number of drying cylinders required in a typical slasher will be decided by the density of the

warp and the slashing speed that is used. For a higher number of warps and faster slashing

speeds, a greater number of drying cylinders will be required. With faster slashing operation, the

time available for the warp yarns to be dried will be less, and therefore a high heat transfer rate is

required. On a multicylinder machine, in practice, it is desirable to increase the drying

temperature during the first phases of drying and to decrease it during the final phases. However,

too high of a drying temperature is detrimental to the quality of the sized warp and also too much

penetration of size will take place. Typically the temperature range from 80 to 1050C is used in

practice[2,3].

4.8.3.2. Convection Drying

In this system, hot air is used as a drying medium instead of the steam used in cylinder drying.

The heated air is passed through the drying chamber. The warp yarn through its passage in the

drying chamber comes into contact with the heated air circulation, as shown in Fig. 4.15. The air

is heated either by electric coil or steam. The advantage of the hot air convection drying system

is that the whole yarn surface is subjected to a uniform drying temperature in contrast to cylinder

drying where only a part of the yarn surface is in contact with a hot cylinder. The surface of the

yarn in contact with the hot cylinder is likely to be overdried. Cylinder drying is therefore

expected to result in uneven drying, with a resultant uneven distribution and migration of size in

the yarn . Modern multiple-cylinder drying systems overcome this drawback by subjecting both



the top and bottom sides of the yarns to drying by allowing the yarns to pass over and below the

hot cylinders, resulting in progressive and uniform drying[2,3,12].

4.8.3.3. Infrared and Microwave Drying.

Other forms of drying methods, though not yet widely used in practice for sizing, are infrared

drying and microwave drying systems. These systems aim to conserve energy through the

efficient and cost-effective use of drying energy to replace conventional steam-based conductive

drying. Infrared drying energy can be sourced either electrically or from gas. In an electric

system, a series of infrared lamps with reflectors are mounted above and/or below the warp yarn

sheet to be dried. The cost of electricity-based infrared drying is usually higher than that of

conventional steam-based conductive drying. Gas-based infrared energy can be achieved by

heating refractory materials to incandescence. This drying energy is similar to hot air drying

based on the convection principle. The heat produced due to the combustion of gases is also

circulated. The yarn can be passed through a number of infrared-radiating gas burners for

drying[3].

Fig. 4.15 Schematic of convection dryer[3].

Microwave radiation is an inexpensive form of energy generation widely used in many industrial

practices. Microwave energy can be obtained easily without causing pollution and therefore

receives attention for the drying of textiles where large amounts of energy are consumed. The

major problem of the conventional form of microwave energy radiation is the lack of uniform

heating, resulting in randomly occurring hotspots which cause overheating in some areas and

underheating in others. This problem has been corrected recently by the introduction of

appropriately designed ‗‗waveguides‘‘ systems where microwave energy is transmitted back and

forth across the material. This improvement in uniformity of distribution in microwave radiation

has opened up new opportunities for its use in textile drying applications. Industrial microwave

systems designed for specific purposes are now available which can be retrofitted to the existing



conventional fossil fuel burning ovens or drying chambers that can be used as pre- or post-

dryers. The use of microwave drying in sizing is in an early stage of development and has yet to

replace the conventional drying methods based on conduction and convection[3,7,8,12].

4.8. 4.Lease Rods—Splitting Zone

The function of the lease rods in the splitting zone is to separate the individual yarns which are

stuck together because of the drying of the size film in the drying section. To achieve this, a

series of lease or bust rods, with one large diameter busting rod, are used, as shown in Fig. 4.16.

The lease rods are generally chromium-plated hollow cylindrical bars flattened at both ends to be

placed firmly in the brackets. The number of lease rods used is determined by the number of

warper‘s beams being used in the creel. The yarn sheet emerging from the drying section is

divided into two sections by one large lease rod, as shown in Fig. 4.16, and each section is

further subdivided into two subsections by successive lease rods. The pattern of dividing by lease

rods in the splitting section is usually kept similar to the pattern of combining the sheet in the

unwinding section, which helps in maintaining the order of the warp sheet, thus facilitating the

subsequent drawing-in operation. Also, the leasing-in of the sized yarns to the weaver‘s beam is

facilitated by inserting leases in the top few layers of the warp. Even under normal operating

conditions, the splitting zone imposes tension in the warp by offering resistance to the forward

movement of the dried warp sheet. However, under stable running conditions, the tension

imposed on the warp sheet is not affected significantly[3,12].

Fig. 4.16 Schematics of splitting zone[3].

4.8.5. Head Stock

The head stock is a take-up unit supporting the weaver‘s beam and necessary drive gears. The

drive equipment imparts necessary beaming tension for compact and straight winding of the

warp yarn on the weaver‘s beam. The configuration of the head stock is available in a variety of



widths and styles. The width of the head stock is determined by the width of the weaver‘s beam

and the number of weaver‘s beams being wound side by side. Usually head stocks are available

which allow winding on a single beam, two beams side by side, and two beams positioned

vertically or half beams run in center. Double beam head ends with vertical arrangement are

primarily used for towel, gauze, and leno warps, which contain so few warps that winding on

only one beam may either lead to the warp being overdried or else the full drying efficiency of

the cylinder surfaces not being used[3].

A typical head stock is shown in Fig. 4.17. Irrespective of the configuration, the head stock is

equipped with a positively driven roll, commonly known as the delivery roll or draw roll. The

cork and rubber covered draw roll is placed between two heavy chrome-plated nip rolls, as

shown in Fig. 4.18, to assure that the yarn sheet being drawn is wrapped well around the draw

roll. The delivery roll moves at a constant speed for any sizing machine, and the speed of the

weaver‘s beam is adjusted to impart the necessary winding tension. This poses a problem of

driving the weaver‘s beam at a constant tension from start to finish of the beam, because the

surface speed of the beam keeps increasing as the diameter of the beam increases, and

consequently the winding tension also increases. This requires that the driving arrangement of

the weaver‘s beam must incorporate a proportional reduction in the rotational speed of the

weaver‘s beam to assure winding at a constant surface speed. On most modern sizing machines

this is automatically controlled. Depending upon the type of arrangement used, the head stock

driving system may be grouped as controlled tension beam drive, DC multimotor drive, or digital

drive[3,12].

Fig. 4.17 Head end of a sizing machine[3].



The arrangement and the principle used vary from machine to machine and the techniques

employed by various manufacturers differ considerably, although the objectives remain the

same.

Controlled Tension Beam Drive. This system is the most accurate; is reliable, easy, and

inexpensive to maintain; and is used widely. The drive is purely mechanical and utilizes a

pneumatically loaded clutch to transfer the input torque to a positive infinitely variable (PIV)

speed variator. In this system, the position of the pulleys in transmission is adjusted by

comparing the revolutions of the clutch input shaft to the output shaft. With the increasing beam

diameter the torque required to drive the beam also increases; however, the revolution of the

beam should decrease to keep the surface speed constant, so the slippage across the clutch should

be increased. This will lead to a reduction in the clutch output speed at the constant input speed.

The automatic adjustment of speed and torque thus continues until the beam is full. While

placing the new empty beam, the operator is required to reset the system to the proper ratio of

barrel to full beam diameter. In this type of system, normally a single DC motor drive is used for

the whole sizing machine[3].

Fig. 4.18 Side view of a typical head stock[3].

Multimotor Drive. This system uses two DC motors, one for driving all components of the sizing

machine, except the beam, and the other exclusively for driving the beam. The motor driving the

beam provides constant winding tension as the beam diameter increases. This system is very

simple mechanically but very complicated electrically. This system does not require resetting

before beginning the new beam[3].

Digital Drive. This system comprises an electrical analog to the mechanical line shaft drive. The

components of the sizing machine such as head end, dryer section and size box, etc., are driven

by an individual motor. The digital system used for regulating the speed is most accurate.



4.9. Controls and Instrumentation

There are a variety of controls available on modern sizing machines. The essential functions of

all these controls are to provide optimal quality of warp at a minimal cost. The controls usually

act on the basis of information provided by the particular sensors placed on the machine. Figure

4.19 is a sketch of a typical two–size box slasher with locations of various sensors and

controls.The most important of these are summarized here:

1. Automatic tension control. In the direction of the yarn path, from the creel to the

weaver‘s beam at the head stock, controls are placed to monitor tension and effectively

regulate the speed of the sizing machine. The controls are placed in the creel to

maintain uniform unwinding of the warp beams in the creel, in the size box for a

smooth drive of the dry feed rolls, in the drying section to drive cylinders, and in the

head stock to drive the weaver‘s beam[3,12].

Fig. 4.19 Sensors and controls on a typical two–size box slasher[3].

2. Automatic size box level regulator, with a warning indicator for low size level or overflow.

3. Electronic stretch indicators and controllers with digital display for yarn elongation. Excessive

yarn elongation (stretch) resulting from the applied tension is detrimental to the quality

performance of the warp during weaving. The loss in elongation results in an increase in warp

breaks on the loom. Surface speed sensors, mechanical or electronic, in direct contact with the

warp sheet are placed from the creel to the front roll in each zone. The automatic controls adjust

the size box roll speeds to maintain a constant stretch.

4. Electronic moisture detectors, used to regulate the slashing speed automatically or steam

pressure in the drying cylinders.



5. Steam pressure controllers in the cylinders which may be interfaced to drive the controller to

reduce the steam pressure during the slow or creep speed operation.

6. Temperature controls for the drying cylinders which can be used for maintaining accurate

temperature and effective condensate removal.

7. Squeeze roll pressure release system designed to decrease the squeezing pressure when

operating the machine at creep speed or maintaining proportional pressure with respect to the

operating speed of the sizing machine.

8. Size liquor filtration and circulation system designed to filter out yarn waste and fibers (wild

yarns and short fibers) found in the sizing system.

9. Creel braking systems to decelerate the warper‘s beams effectively, thereby preventing over-

run and maintaining the unwinding tension at a constant speed operation.

10. Microprocessor controls interfaced to a computer for effective management of the operating

variables of the sizing machine.

11. Wet pick-up measurement and size add-on control. In this device, microwave energy which

is absorbed by water is used to continuously measure the wet pick-up immediately after the yarn

sheet leaves the size box. The on-line refractometer monitors the size solids in the size mix. The

size add-on, which is the product of the wet pick-up and size solids in the size mixture, is

automatically calculated by the microprocessor. The correction in the size addon is made by

automatically adjusting the squeeze roll pressure to keep the add-on practically constant

throughout the sizing operation.

12. On-line size encapsulation measurement. Size encapsulation is the measure that defines the

degree of reduction of the yarn hairiness due to sizing. One on-line yarn hairiness sensor is

placed on the unsized and the other on the sized yarn sheet. The difference between the two,

expressed as percentage, is the measure of size encapsulation[3].

4.10. Effect of Sizing Machine Parameters

The different zones of sizing machines—namely, creel, size box, drying, and head end—have to

be controlled effectively for producing a good loom or size beam. Although the design and

configuration of the sizing machine have some influence, the effect of different sizing parameters

on the quality of size beam in general will be considered in this section. The quality of sizing

will have a profound effect on the weaving efficiency and the quality of the woven fabric. Since

modern shuttleless looms are running at four to ten times faster than the speed of the



conventional shuttle loom, effective sizing—by exercising all the necessary controls on the

sizing parameters from creel to head end—is important[3].

4.10.1Creel Zone

The warping beams are the heart of the creel zone for ensuring effective unwinding of the warp.

Therefore, the physical quality of the beams must be good. The edges should be smooth and free

of burrs so that the warp ends do not cling to the edges during the process of unwinding.

This may cause the warp yarn to break or be damaged due to abrasion. The mill should ensure

that the warp beams are cleaned and polished at regular intervals. Also, the distance between the

flanges of the beams should be constant and these flanges must be at right angles to the barrel.

This must be measured before warping so that it does not create a problem when beams are

delivered to the sizing section. The quality of warping on the beams should be good, with no

cross-ends nor buried or embossed ends at the edges near the flanges. The density of the warping

beam should be as uniform as possible to ensure uniform unwinding during sizing. The warping

tension must be controlled and beam density (hardness) must be measured with a suitable

pressure gauge (e.g., durometer). Warping beam preparation data such as slack selvedges, broken

ends, laps, and cross-ends must be recorded and supplied to the sizing machine operator to

enable effective control and correction of various problems[3,10,11,12].

On the sizing machine, the warping beams must be aligned properly in the creel. The distance

between the front end of the creel to the back of the size box must be fixed on both sides to avoid

slack or tight ends on the selvedges. The beam journals should be adequately tight, and bearings

should work freely to ensure proper tension is maintained. The effect of the braking system has

been described previously in this section. The control of yarn stretch between the back of the

creel and the size box is critical. It should be as low as possible but should not exceed 0.4 to

0.8%, and it should be checked frequently[2,3,4,5,6].

4.10.2. Size Box

The major features of modern size boxes were discussed previously in this section. Positive

feeding of yarns from the creel to the size box is necessary for ensuring a minimal stretch in the

creel zone. The purpose of the size box is to allow the immersion of the yarns in the size box for

a uniform and thorough penetration of the size and coating of the surface of the yarn. The

following sizing variables should be checked and controlled where necessary:

Viscosity of the size solution



Sizing machine speed

Size add-on levels

Concentration of the size mixture

Volume of the size box (both quantity and size level)

Threading arrangements

Condition of squeeze rolls

Squeezing pressure

Hardness of squeeze rolls

Diameter of squeeze rolls

Number of size boxes

Yarn count and size box warp density per unit space

Size viscosity is dependent on the concentration of the size and the application temperature in the

size box. Viscosity influences the size pick-up and consequently the size add-on of the yarn

being sized. The continuous heat losses in the size box are caused by the incoming warp sheet,

which is at a lower temperature; convection and radiation losses from the surface of the size to

the atmosphere; and conduction losses of the size box itself. Unless the heat is uniformly applied

to replenish the loss, the size solution will be cooled and a resultant increase in the viscosity is

unavoidable. Heating of the size in the box is usually done by injecting steam into the size

mixture. The quality of steam, therefore, is important. Excessive moisture in the steam will dilute

the size due to condensation, thereby reducing the effective solid content of the size mixture.

This, in turn, lowers the viscosity and affects the size pick-up and size add-on of the yarn being

sized. Squeeze roll configuration, thickness and hardness of covering, surface finishes, roll

diameter, speed of the sizing machine, and squeezing pressureare a few important parameters

which affect the sizing quality. A wide variety of size box configurations is available to fulfill

the specific needs of various constructions and styles of fabrics for a particular mill[3,7,8,9].

Roll hardness of the rubber-covered squeeze roll influences the level of size add-on of the yarn.

The suitability of the squeeze roll is dependent upon the particular sizing application (style and

construction of fabric, spun or filament yarns, blend of spun yarn, yarn counts, etc.) and the

sizing chemical being used (e.g., starch, PVA, acrylics, auxiliaries etc.). Harder rolls enable a

sharper nip and lower pressure than softer rolls, thereby squeezing more size from the yarn and

resulting in a lower pick-up. A soft roll makes a flatter nip at the same squeeze pressure so



resultant size pick-ups are higher. As the thickness of the rubber covering the squeeze roll

decreases, the nip becomes sharper causing the size pick-up to decrease. The prolonged exposure

to high heat and constant use tend to harden the rolls and can cause permanent deformation of

the coverings of the squeeze roll, which affects sizing due to uneven squeezing, lapping on rolls

due to broken ends, and build-up of size on rolls[1,2,3].

Periodic buffing of the squeeze rolls should take place, and the rolls should be re-covered when

necessary. An impression of the nip should be made periodically and the record should be

maintained. All settings, such as temperature, pressure, switches, and monitors, should function

well at all times to ensure good quality of sizing.

The size box level determines the contact time between the yarn and size mixture. If the size

level in the box is low, the yarn contact time will be shorter and vice versa. With shorter contact

time, the size may not penetrate into the yarn, and the coating of the yarn may not be adequate.

Ultimately, a low size level in the size box influences the size add-on, size coating, film

characteristics, and control of yarn hairiness, besides affecting other properties.

Devices to monitor and control the size level should be installed to eliminate the adverse effect

of differences in size level on sizing. The control of the yarn stretch between size box and drying

zone is also important. Yarns being wet in the size box tend to elongate depending upon the fiber

and yarn characteristics. Appropriate devices should be utilized to monitor the stretch. Space

between yarns in the size box is an important criterion to ensure sufficient penetration by and

adequate encapsulation of the size[2,3].

This cannot occur if the yarns are too close together (i.e., crowded). This crowding of yarns in

the size box creates a problem, particularly with spun yarns where the protruding fibers of

adjacent yarns become entangled and cemented together. Consequently, higher energy may be

required during splitting after drying. This will also increase yarn breakage during sizing,

increase yarn hairiness and clinging on the loom, increase yarn breakage during weaving, and

increase size shedding on loom. Too small spacing between yarns will also result in matting and

entanglement, and this is especially acute in hairy yarns having long protruding fiber ends. To

reduce this problem, the spreading of yarns further apart must be done to increase spacing

between them. The distribution of the yarns in the size box may be expressed as percent yarn

occupation:

Percent occupation = number of ends in the sizing sett *100

(Number of threads per cm at 100% occupation * distance between flanges of warp beam in cm)



The distance between the flanges of the warping beam provides the information on the total

working space in the size box since it represents the width of the warp sheet. The actual number

of ends is the total number of yarns in the fabric style being sized. The normal percent occupancy

is about 50% for yarns sized for shuttle looms and about 60 to 80%for yarns sized for air-jet

weaving. Another parameter used for expressing the yarn spacing in the size box is equivalent

yarn diameter (EYD). If the space between adjacent yarns in the size box is equal to 1 yarn

diameter, the EYD is 1, which corresponds to a size box occupation of 50%. Similarly, yarn

spaced 2, 3, and 4 diameters apart would have EYD of 2, 3, and 4, respectively, which

correspond to percent yarn occupations of 33, 25, and 20%, respectively. Spun yarns normally

require an EYD of 1.1 to 1.5[2,3].

Drying: About 75 to 80% of the total energy used in sizing is for drying the warp sheet. The

water in the warp sheet is evaporated by converting it into steam that can be readily removed.

Out of the three methods of heat transfer, namely, conduction, convection, and radiation, the

conduction method is most commonly used, where multicylinder drying is employed. The

mechanism of cylinder drying is explained in Fig. 4.20. The heat of vaporization of the

superheated steam transfers to the wet yarn through the walls of the drying cylinder. The amount

of water to be evaporated from the wet yarn depends upon the size add-on levels and the solid

content of the size. This relationship is graphically presented in Fig. 4.38. For example, a yarn

sized at 12%addon with 8%solid content in the size box requires 1.38 kg of water to be removed

through evaporation for each kilogram of yarn being sized[3].

The drying configuration employed depends upon the number of size boxes used, number of

yarns in the sett, wet splitting, percent yarn spacing or EYD employed, number of drying

cylinders available, size add-on level, solid content of the size mixture, etc. If only one size box

is used, the yarn sheet is generally split in two and each sheet is dried on a separate set of drying

cylinders and then combined again for final drying. By increasing the spacing between the yarns,

the cylinders are not overloaded and the yarns actually dry faster, and this allows increase in

sizing speed. If two size boxes are employed, there will be four sheets of wet warp, each dried

separately before combining them for the final drying. Yarns sized using the high pressure

squeezing technique require much less drying energy (fewer cylinders); additionally higher

sizing speeds can be employed because they contain less water[3,12].



The rate of evaporation (drying rate) and the threading of yarns through the cylinders are critical

for uniform drying. The temperature of the first drying cylinder is normally set at the lowest

possible temperature so that sticking of yarns on the cylinder is avoided. Such sticking causes a

rough yarn surface which tends to increase shedding of size both on the sizing machine and on

the loom during weaving. Moreover, sticking of yarns to the cylinder increases hairiness of yarns

as the fibers are pulled from the yarn bundle during transfer to the next cylinder. After the first

cylinder, the temperature is gradually increased to ensure thorough drying. If possible, the last

drying cylinder should be set relatively cool to prevent false moisture regains and to control

tension variations. Most sizing machines are fitted with Teflon-coated drying cylinders to

minimize the sticking of the yarns. These coatings must be safeguarded and should be free of

scratches or worn surfaces. Too high temperature of the drying cylinders should be avoided as it

tends to cause the size to migrate due to sudden conversion of water into steam. The size is

blown away from the yarn when in contact with very hot cylinders, causing an inadequate

coverage of the yarn due to a lack of encapsulation or else excessive size on some yarns[2,3].

Fig. 4.20 cylinder drying in sizing[3]

Mechanism of cylinder drying in sizing:

1. Steam enters the dry cans and strikes cylinder wall.

2. Steam condenses to water giving up its latent heat of vaporization(980 BTU/lb)

3. The latent heat transfers to the cylinder wall.

4. The cylinder wall transfers the heat to the wet yarn.

5. The water in the vaporizes.

6. The steam trap lets the condenser water inside the cylinders out through the diphon

pipe for return to boiler

7. More steam enters. Backs to step 1



Yarn Stretch. The most critical issue in sizing is to control the yarn stretch. As yarns pass

through the long path from creel to head stock, the tension applied in the process will tend to

elongate it. If this elongation is not controlled, the deformation so introduced will be

permanently set in the yarn[3].

The control of yarn elongation (stretch) between the squeezing rolls of the size box and the first

drying cylinder is critical, since the wet yarns under high heat undergo stretching even at low

tensions. This must be controlled by proper selection of the drive system, such as digital or

variable speed differential transmission, between the size box and the drying unit.

The tension develops when the yarn is passed through the drying cylinders for ensuring proper

drying. The surface speeds of all drying cylinders should be controlled, and if they are uniform,

no stretch will develop in the drying zone. Despite good control, the variable speed transmission

employed is susceptible to some output variation resulting from the variation in input speeds and

loads. This results in a variation in tension, particularly in the wet warp sheet and during periods

of acceleration and deceleration of sizing speeds[2,3].

The newer sizing machines are fitted with better controls and mechanisms to control stretch more

precisely. The number of drying cylinders required to dry the yarns—based on the drying

loads—can be determined from the data of wet pick-up (WPU), solid content of the size, speed

of the sizing machine, number of ends in the sett, and yarn count. The following calculations

represent a typical example:

Wet pick up = weight of sizing solution (Kg)

Weight of upsized yarn (kg)

= size add on to yarn (%)

Solid sizing solution (%)

Drying load= sizing speed(m/mint)* totalends* WPU*(100-%solids insolution)* yarn count (tex)

1000*1000*100

The drying load is expressed in kilograms of water evaporated per minute. For example, a sizing

machine is operated at a speed of 73.2 m/min, there are 6000 ends in the sett, 8% is the solid

content in the solution, 10% is the size add-on, and the yarn count is 22.7 tex. Then the

calculation is



WPU= 10/8

=1.25 kg of solution per kg of yarn drying load

= 73 .2 *6000* 1. 25*(100-8)*22.7

1000*1000*100

= 11.46 kg of water evaporated per minute

Thus it will require six drying cylinders for two-shed drying.The above example provides an idea

of the minimum number of drying cylinders for predrying; spreading of warp yarns over as many

drying cylinders as available will result in the best drying of the warp, with adequate

encapsulation, control of hairiness, and size penetration[3].

Head Stock. The properly dried warp ends coming out from the drying zone must be handled

well by separating individual ends and be wound on the weaver‘s beam at uniform tension. If the

ends are not separated well, the size film is damaged when the yarns pass through the lease rods.

The size coating on the yarn surface is damaged and the yarns become vulnerable to breaks on

the loom during weaving. If the spacing between the yarns is adequately set, there is no

entanglement of the fibers of two adjacent yarns, which prevents damage to the size films. The

proper splitting of yarns at the first leasing rod is an indication of proper sizing. A low splitting

force indicates that the yarn hairiness will not be increased due to splitting.

The bust rods (lease rods) should be of large diameter and well polished to prevent the damage to

the warp sheet. The yarn sheets should be evenly split between the lease rods such that the

individual sheets represent the warping beam from which they came. This minimizes the yarn

tension and size shedding in the splitting zone. The lease rods should be adjusted to ensure

uniform spacing and leveled warp sheets to ensure that they do not touch each other while

entering the front comb.

The density and height of the comb wires should be sufficient to ensure uniform winding of the

warp on the weaver‘s beam. Uneven spacing between the dents and the crossed ends should be

avoided to ensure a uniform distribution of the warp sheet. A traversing V or slant comb reed is

used to help in providing an even distribution of the warp yarns and for avoiding abrasion

between the yarns, which causes size shedding. To avoid abrasion and size shedding the yarns

should never touch the bottom of the comb. It is recommended that the spread of the warp sheet

exiting the drying cylinders should be the same as the distance between the flanges of the

weaver‘s beam on which the warp is wound. If the distance between the flanges of the weaver‘s



beam is higher, then the yarns are drawn at an angle which produces undue stresses and strains,

which may result in size shedding, yarn breaks, and attendant problems during weaving.

The winding of the warp on the weaver‘s beam is done at a constant speed by means of a

precision mechanism. The winding tension and uniformity of the ends should be controlled. The

yarn should be drawn by the delivery roller and presented straight to the weaver‘s beam. The

press rolls on the beam should be clean and smooth to ensure correct pressure and beaming

tension[2,3,12].

If too high a pressure is used, then the beam density will be too high and yarn slackening may

occur during winding; while too soft a pressure will result in a very soft weaver‘s beam, which

will cause problems during weaving. As the beam diameter increases, the surface speed also

increases if the rotational speed is not decreased proportionately. This will exert high winding

tension,which is detrimental. In modern precision winding mechanisms, the revolutions of the

beam are reduced to keep the surface speed constant.

4.11. SINGLE-END SIZING SYSTEMS

Single-end sizing systems are widely used for sizing a wide variety of multifilament yarns, such

as zero twist flat, textured, and low twisted fine denier yarns. Modern single-end sizing machines

operate at extremely high speeds of up to 500 m/min. The sizing system is very versatile and it

has simplified the yarn passage to produce high quality sizing beams. The single-end sizing

systems consist of a creel and a warper, beam-to-beam sizing of the warper beams, and a beamer

to assemble sized section beams into a weaver‘s beam. Figure 4.21 illustrates the single-end

sizing system[3].

Fig. 4.21 Single-end sizing systems[3].

About 800 to 1500 supply packages can be placed in the creel, and the ends delivered from these

packages are wound onto a large warper‘s beam on a warping machine at uniform tension. The

broken ends or filaments in a supply package can be repaired or removed during this process to



ensure a defect-free warper‘s beam. The warper‘s beam is placed on the supply stand at the back

of the sizing machine. The yarns are sized by impregnating them in the sizing solution and then

dried and wound onto a sectional beam on the beam-to-beam sizing machine. Figure 4.21 shows

a schematic of the beamto- beam sizing machine. The yarn is fed to the sizing section by a

positively driven feed roller and the squeezing roller. A high pressure squeezing of 15kN is used

to ensure adequate squeeze and reduction in subsequent drying load. The squeezing pressure is

automatically controlled in accordance with the sizing speed. The sizing machine comprises both

cylinder drying and hot air chamber drying. The cylinder drying acts as a predrying step, with the

number of drying cylinders varying from three to seven depending upon the yarn type and sizing

speed. The hot air drying chambers enable the contactless drying of the sized yarn to ensure

undisturbed size coating and smooth yarn surfaces without adversely affecting the yarn or its

properties. The drying temperatures in the chambers can be adjusted to between 150 and 160oC

for high-speed operations and to between 120 and 130oC for low-speed operations[3].

Since the warper‘s beam thus prepared is free of yarn defects, the sizing machine generally runs

without interruptions, therefore making it feasible to operate at a high production speed and

efficiency with very little downtime. The yarns are sized, dried, and wound onto a sectional

warper‘s beam at a distance of almost 1 mm apart, thus eliminating crowding during sizing and

intermingling during subsequent unwinding. The required numbers of section beams are placed

on the beam creel of the beamer so as to assemble a weaver‘s beam[3].

The versatility of this system allows it to be used as a nonsizing system by skipping the sizing

process, making it particularly suitable for high-twisted filament yarns. Warper‘s beams are

prepared on a warper, and waxing or oiling, if required, is applied during the process. Such

unsized section beams can then be assembled on a beamer into a weaver‘s beam. Alternatively,

the system can also be used as a creel to the beam sizing system, where the yarns delivered from

the packages mounted in the creel can be directly sized, dried, and wound straight onto a section

beam. The sized section beams are then placed on the beam creel of a beamer to wind onto a

weaver‘s beam. This system is suitable for high quality filament yarn packages containing a

minimum number of yarn defects, and in such cases the system ensures a high level of

performance and quality preparation of beams[3,12].



Fig. 4.22 Beam-to-beam sizing machine[3].

4.12.Sizing Machine Productivity

The sizing speed (V) for cotton yarn can be determined as:

V= C*106

a*m*T*60

Where:

V = Linear speed of sizing, m/min

C = Amount of moisture evaporated in the drying section, kg/hr

a = Ratio of moisture weight to yarn weight

m = Total number of ends

T = Linear density, Tex

Hence the actual productivity of the sizing machine (P) can be

P= (V* m* t*T/106)*ϵ

= C/ a*ϵ

Where:

ε = Efficiency

t = Working time

4.13. Sizing Defect and Wastes

Some of the most common sizing defects are

Undersized yarn which is due to improper size concentration, improper working squeeze

roller, and dilution of size paste

Oversized yarn caused by high size concentration due to non-splitting of starch

granules, depth of immersion, and longer duration in size box

Sticky warp due to improper drying, high speed sizing, and low drying temperature



Improper build of weavers beam caused by improper spreading of ends in the

adjustable reed, and improper functioning of compressing devices

Incorrect warp length caused by disarrangement of measuring roller and marking

mechanism.

Non uniform size regain due to irregular heating of size in the size box and non

uniform pressure on the squeeze roller.

Crossed and lost ends occur when the lease rods are set too far apart, when broken

ends are improperly pieced-up.

Solved problem on sizing

Pb#1 In a typical sizing process a 40 tex cotton yarn which has a standard moisture regain of

8 % is estimated to have a size add-on of 10 %. Calculate the oven dry mass of size added

per one kilogram of unsized yarn.

Solution

From the definition of moisture regain,

Moisture Regain(R)= Moisture absorbed (W) *100

Oven dry weight of yarn( D)

8=W/D*100W/D=0.08

W =0.08*D………………Eqn (1)

From the given parameters

W+D =100------------------------Eqn (ii) because 1Kg=1000g

From eqn 1 and 2

(0.08*D)+D=1000

(1.08*D)=1000

D =1000/1.08

=926g

W =1000-D

=1000-926

=74 g

By definition side add on(A) can be calculated as

Size add on(A)= OvendryWeight of size *100

Oven dry weight of unsized yarn(D)



Oven dry weight of size =A*D/100

=10*926/100

=92.6 g

Therefore, Oven dry weight of size (kg)/1Kg of unsized yarn =0.0926

Q. Define sizing?

Ans:

The process of applying a proective adhesive coating upon the yarns surface is called sizing. This

is the most important operation to attain maxm weaving efficiency especially for blended &

filament yarns. Duo to sizing, increases elasticity of yarn, yarn strength, weight of the yarn,

smoothness, frictional resistance.

Q. Why sizing is done in weaving?

Ans:

Objects of sizing:

1. To improve the weave ability of warp yarn.

2. To maintain god fabric quality by reducing hairiness, weakness and by increasing smoothness,

strength of yarn.

3. To increase the tensile or breaking strength for cellulose yarn.

4. To increase the elasticity.

5. To remove the projecting fibres.

6. To reduce electrostatic formation for synthetic or blended yarn.

Q. What factors are to be considered for choosing size ingredients?

Ans:

1. The recipe should be that which gives fewest end breakage.

2. It should be that which gives the least exfoliation.

3. It should be easily washable i.e. permits easy desizing.

4. It should give good fabric characteristics.

5. It should be compatiable with the machinery & associated parts.

6. It should not cause any degradation of the textile mtl.

7. It should not cause any health hazard.

8. It should be cheap.

9. Size ingredients should be neutral.

10. It should be available.



Q. Describe different types of sizing.

Ans:

1. Light sizing: This is used for dyeing and printing. 10 to 15% sizing ingredients are use on the

weight of yarn.

2. Pure sizing: When sizing is done in yarn which produces unbleached fabric is called pure

sizing. Size ingredients are used on the weight of yarn 15% to 25%.

3. Medium sizing: For increasement of strength & weight of the yarn 25 to 50%. Sizing

ingredients are used on the weight of yarn.

4. Heavy sizing: To increase weight of the yarn its application on twisted yarn & lower count of

yarn. Above 50% sizing ingredients are used on the weight of yarn.

Q. Write down the properties of size ingredients.

Ans:

1. It should be easily removed during wet processing process.

2. It should not do any harm to the fibre or yarn.

3. Adhesive substances should be more adhesive.

4. It should give good fabric characteristics.

5. It should have ability to dry instantly after sizing.

6. It should not cause any degradation of the textile mtl.

7. It should not change the colour of coloured yarn or shed.

8. It should be cheap and available.

Q. Write down the names of warp sizing m/cs.

Ans:

A) Cylinder drying i) Two cylinder types.

ii) Multi cylinder types.

B) Hot air drying.

C) Combined Hot air and cylinder type.

Q. Describe with sketch the slasher sizing m/cs. Q. Dividing unit.

Ans:

This is the mostly used sizing process. About all types of yarns can be sized by slasher

sizing process. In this process the warp is passed through a size luquor bath then through

a separating unit & cooling unit.



The slasher sizing m/c consists of the following seven units.

1. Back beam unit: In single end sizing yarns are taken from a creel rather than from a beam.

This unit contains 7 to 12 carriers from where yarn is supplied. Indirect & direct process of yarn

supply is frequently used for spun yarns. In case of indirect method beam creel is used. This

beam creel can be arranged in various ways.

2. Sizing unit: In this unit a size box is used to apply size to the yarn. The warp sheet is guided

through the solution means of the immersion roller & then through the squeeze roller where the

yarns are pressed to maintain the reqd size to up percentage by the yarn. The size box temperature

is controlled by flowing steam through pipe.

3. Drying unit: Two or more heated cylinder consists of drying unit. This unit is reqd to dry the

wet sized yarn rapidly, thoroughly & uniformly. A two cylinder dryer is too slow

& it is difficult to maintain by it. But a multi-cylinder dryer is a good one to main in such a way

that after drying. Yarn contains 6% water.

4. Cooling unit: In this unit there is cooling fan & a guide roller. The cooling fan supplies cool

air which extinguish the yarn temperature & also remove the moisture.

5. Dividing unit: In order to prevent adhesion betn the yarns, it is necessary to separate each

sized end from the others. For this lease rod or breaker rods are used to divide the main warp

sheet into single end.

6. Measuring & marketing unit: This unit consists of colouring bowl which contains easily

removable colour. This colour is used for making on sized yarn. Also there is a measuring roller

which measures the length of sized warp yarn.

7. Beaming unit: Finally the sized warp is wound on weavers beam.

Q. What is size take-up %?

Ans:

The amount of size material added on the yarn surface is called size take-up percentage.



Size take - up % = wt. of sized yarn - wt. of unsized yarn *100

wt. of unsized yarn

=wt. of size material*100

wt. of unsized yarn

Q. State the functions of size ingredients.

Ans:

1. Adhesive:

a) To improve strength

b) To increase smoothness.

c) To increase elasticity & stiffness.

d) Reduce extension percentage.

e) Impart adhesion.

2. Lubricant or softener:

a) To make the yarn soft & slippery.

b) To smoothen the yarn.

c) To reduce stiffness.

d) Reduce flexibility & friction.

3. Antiseptic or anti-mildew agent:

a) To prevent mildew formation.

b) To preserve size mtl for a long time.

c) To help to store the sized yarn.

d) To protect yarn from bacteria or fungus.

Q. Describe the changes in yarn due to sizing.

Ans:

Properties of yarn after sizing or sized yarn properties:

Due to sizing, there is a change in different properties of yarn as –

1. lasticity of yarn: Higher.

2. Yarn strength: Higher.

3. Frictional resistance: Increase.

4. Hairiness: Lower.

5. Flexibility: Lower.



6. Smoothness: Higher.

7. Absorbency: Lower.

8. Weakness: Lower.

9. Yarn diameter: Higher.

10. Wt. of the yarn: Higher.

11. Static electricity: Lower.

Q. Describe the technological changes of yarn due to sizing.

Ans:

1. Increase in breaking strength: During sizing, adhesive mtl creates bonds betn fibres to fibre

which increase the strength of yarn. It increases 20 to 40% breaking strength of the fibre.

2. Increase abrasion resistance: After sizing the gap betn fibres are filled with size & coating on

the outer surface of the yarn takes place.

3. Increase in stiffness: After sizing, flexibility or pliability of yarn is decrease & stiffness is

increased.

4. Increase in elasticity: As extensibility of the sized yarn decreases, more force has to be

applied to extent the yarn. Hence elasticity increases.

5. Increase frictional resistances: Application of size mtls makes outer surface of the yarn

smooth & hence occurs less friction.

6. Increase yarn diameter: Sizing means coating adhesive on their outer surface of the yarn.

Hence, sizing causes increases of diameter of yarn,

7. Decrease in extension: After sizing, the gap between the fibres are filled with size mtls. So,

the slippage between the fibres does not occur easily. So, the extension decreased.

8. Decrease in electrostatic charge: Electrostatic charge is formed due to the friction

betn yarns & roller. Size mtls contain moisture which reduces static friction.

9. Subpress hairiness: During sizing protruding hairs of yarn fix with yarn end so yarn hairiness

subpressed.

Q. State the uses of Antifoaming agent.

Ans:

To prevent foam formation, antifoaming agent is used.

Q. List the different sizing faults & state the causes of these faults.

Ans:



1. Size spot: Size mtl should be added gradually to the mixing tank for good mixing. If it is

added at once, spot are appeared on the yarn.

2. Repeating warp streaks: This defect is due to uneven tension in the pre-beam.

3. Shinnery: this defect due to the friction betn the yarn & drying cylinder.

4. Sandy warp: Due to not crushed or grind the size mtl properly.

5. Ridge Beam: This fault occurs due to uneven distribution of yarn in wraith.

6. Hard sizing: If the size mtls are applied too much, the size becomes hard which causes hard

sizing.

7. Improper drying:

Under drying

Bacteria form

Yarn breakage.

Over drying

Hard sizing.

8. Sizing dropping: This defect due to not optimum the viscosity of the size solution.

9. Size stitching: Due to improper drying after sizing.

10. Uneven sizing:

Due to over or under sizing.

Due to over or under concentration of size liqour.

Q. Describe ordinary size mixing or conventional method of mixing or cooking.

Ans:

Procedure:

1. Add reqd amount of water into the mixing tank making an allowance for evaporation &

condensation.

2. Stirring start & continue until the end of the process.

3. Add antiseptic & stir for 10 mins.

4. Gradually add starch mtls & stir for 30-45 mins.

5. Pass steam & bring temp. to boil.

6. Add softener & boil for 15-20 mins.

7. Continue steaming the correct viscosity is obtained.

8. Test & adjust pH 6 to 8 by adding soda ash, alkali or acid.

9. Total time of cooking is 120-150 mins.



10. Transfer the size mtls to storage

Q. What are the drying systems used in sizing? Describe briefly.

Ans:

1. Cylinder drying: In this type of m/c, drying is done by passing over hot cylinders.

a) Two cylinder drying:

In this drying process, two copper cylinder are used in which one cylinder is large

diameter & other is small comparatively.

Firstly warp sheet is passed below the small cylinder & then over the bigger one.

The yarn is dried while traveling through the circumstances of the cylinder.

Advantages:

1. Simple process & cheap.

2. Less risky.

3. Temp. uniform.

4. Almost uniform drying.

Disadvantages:

1. Slow process.

2. Drying efficiency is low.

3. Irregular drying.

4. Due to sticky property of cylinder uneven drying.

(b) Multi cylinder drying:

In this type of m/c, the drying unit consists of 5 to 7 or 11 cylinders having same

diameter are used.

All cylinders may be steel cylinders or first two cylinders are teflon coated & rest of are

steel cylinder.

The cylinders are heated by passing steam.

Heat in initial cylinder is low & gradually increases when moved towards final cylinder.

If large amount of heat is given to the initial, the sized may be backed.

If finer yarn is used, then no need to use excess cylinder.

Advantages:

1. High speed process.

2. Uniform drying.

3. Non- sticky so smooth drying.



4. Drying efficiency high.

5. Less time required.

Disadvantages:

1. For high viscosity, stick properly may observed.

2. For friction, yarn hairiness.

3. Shinning effect.

4. Yarn shape may hamper.

5. Possibility of yarn flaten.

2. Hot air drying:

In this m/c, the drying unit is a closed chamber containing a number of guide rollers through

warp yarn.

Hot air blown into the chamber causing the moisture in the yarn to evaporate.

Exhaustion should be used to throw away the moisture.

If moisture remains inside the chamber it may condense & again fall on the yarn.

Hot air should be continuously passed through the chamber, so the process becomes

somewhat costly.

Advantages:

1. Regular drying.

2. Not shinning effect.

3. Non-sticky property.

4. High speed drying.

Disadvantages:

1. Costly process.

2. For closed chamber, reqd more time.

3. Less suitable for fine yarn.

4. Difficult to maintain temperature.

3. Infrared drying:

In this machine, the heating chamber consists of a plate which is constantly heated by gas

flame.

The warp sheet is passed over the plate & dried in the process.

When gas flames are not used, then electronic plate may be used.



Arrangement should be made to through out the moisture removed from the yarn. This

m/c is not used singally.

Advantages:

1. No shining effect.


Disadvantages:

1. Yarn may burn.

2. Higher cost.

3. Difficult to maintain uniform heating.

4. Risk of accident.

4. Combined drying:

In this type of m/c, preheating is done as cylinder drying method.

And final drying is done by hot air drying method or infrared drying method.

Advantages:

1. Regular drying.


3. Speedy process.

Disadvantages:

1. Shinning effect.

2. High cost.

Q. What are the factor that influences size take up percentage?

Ans:

1. Fibre characteristics: Immature fibre-s.t.p. .

2. Yarn characteristics, Hairiness – s.t.p.

3. Wet ability, higher, s.t.p. due to absorption.

4. Linear density or yarn count: coarser yarn – s.t.p.

5. EPI: EPI – s.t.p. due to density of yarn in warp sheet.

6. Uniformity of warp yarn: Uniform yarn – s.t.p.

7. Warp tension: Tension – s.t.p.

8. Roller wt.: Squeezing roller wt. s.t.p.

9. Roller diameter, – s.t.p.

10. Nature of roller covering: rough & soft : s.t.p.



11. Contact length in size: yarn contact in size, s.t.p.

12. Running speed – s.t.p. due to short time of penetration of yarn.

13. Size concentration – s.t.p.

14. Total ends.

15. Environmental condition.

16. Ingredients: Adhesive power of starch is greater than flour.

17. Preparation condition: Shape of sizing mtls should be finer.

18. Temperature: 600C.

Mathematical problem

Rules:

1. Total wt. of size on warp = wt. of sized warp – wt. of unsized warp.

2. The wt. of size to be put on warp = wt. of unsized warp% of size reqd to be put on warp.

3. The wt. of unsized warp = length of warp in yds*no.ofends* wt. of size

840*count

4. Wt. of sized warp = wt. of size*100

wt. of unsized warp

5. % of size on warp = wt. of size*100

wt. of unsized warp

6. Count of sized yarn = length of warp in yds* no. of ends

840* wt. of sized warp (in lbs)

7. Count of sized yarn = count of unsized yarn*100/(100+% of size)

Q. Calculat the production of a slasher sizing m/c from the following particulars:

Circumference of drawing roller = 29.25‖

PPM of drawing roller = 36

Efficiency = 80%

Production/8hrs = ?

Ans:

Production=circumference of drawing roller *rpm of drawing roller *60min *hr *efficiency yds

36*100

=29.25*36*8*80 yds



36*100

production / 8hrs =11232 yds(Ans)

Q. Calculate the production in lb of a slasher sizing m/c from the following

particulars;

Circumference of drawing roller = 29.25inch.

PPM of drawing roller = 36

No. of warp ends = 2100

Yarn count = 32

Efficiency = 80%

Production/8hrs = ?

Ans:

Production= π*Dia of drawing roller *rpm of drawing roller* 60min *hr* eff. *no. of warp ends

36*840*yarn count*100

= 29.25*36*60*80*2100 lbs

36*840*32*100

= 877.5(Ans)

= 877.5/2.204 kg

= 398.14 kg(Ans)

Q. Calculate the no. of loom are neede from the following particulars:

Production/hr of a slasher sizing m/c = 1354 yds.

Production/hr of a loom = 4 yds

warp regain or crimp = 6%

wastage = 0.5%

no. of looms = ?

Ans

No. of looms = production / hr of a slasher sizing m/c

production / hr of a loom*(100+crimp %)/100*(100+w%)/100

= 1334

4*(100+6)/100*(100+0.5)/100



=313(Ans)

Q. A warp containing 2800 ends is required to be sized to 25%. The length of the

sized warp on the beam is required to be 1080 yds. If the counts of the yarn 40s.

Find

i)The wt. of the size to be put on the warp of the given length.

ii) The wt. of sized warp

iii) The count (Ne) of sized warp.

Ans:

i)The wt. of the size to be put on the warp = wt. of unsized warp*% of size

840*count

= 2800*1080*25%

840*40

= 22.5 lbs(Ans)

ii) wt. of sized warp = wt. of unsized warp + wt. of size on it

= 90+22.5

= 112.5 lbs(Ans.)

iii) The count of the sized warp = length of warp in yds*no. of ends

840*wt. of size warp in lbs

= 2800*1080

840* 112.5

=32 Ne(Ans.)

OR, Count of the sized warp= count of unsized * 100/(100+% size)

= 40*100/(100+25)

= 32 Ne(Ans.)

Q. The calculated production of a high speed slasher is 100 yds per min. If the

efficiency of the m/c is 75%, calculate the followings

a.The actual production per day of 8 hrs.

b. Total length of yarn if the total ends is 3520.

c. The total wt. of sized warp, if it is sized to 10% & the count of unsized are 40s.

Ans:



a. Calculated production per day of 8 hrs = 100*60*8 yds

= 48000 yds

The actual prodn per day of 8hrs = 48000 *75/100 yds

= 36000 yds(Ans.)

b. The total length of yarn sized = Total length of warp* no. of ends.

= 360000 * 3250 yds

= 117000000 yds(Ans.)

c. Total wt. of sized warp =Total length of warps +10%

840* count

= 117000000 + 10%

840 *count

=3482 + 10%

= 3830 lbs(Ans.)

Q. A warp containing 2800 ends, is required to be sized to 25%. The length of the

sized warp on the beam is required to be 1080 yds. If the counts of the yarn is 40s.

Find out –

a. The wt. of the size to be put on the warp of he given length.

b. The wt. of sized warp.

c. The count of the sized warp.

Ans:

a. The wt. of the size to be put on the warp= wt. of unsized warp* % of size reqd to be put.

=1080 *2800 *25%

840*40

= 22.5 lbs(Ans.)

b. Wt. of sized warp = wt. of unsized warp + wt. of size

wt. of unsized warp =length of warp in yds*no. of ends

840* count

= 1080 *2800 lbs

840*40

=90 lbs



wt. of sized warp = 90 + 22.5 = 112.5 lbs.

c. Count of sized warp = count of unsized * 100/(100+ size%)

= 40*100/(100+25)

=32 Ne(Ans.)

Q. A warp containing 2400 ends of 44s sized to 10%. If the sized warp wt. lbs.

Calculate the length of the sized warp & total length of sized yarn.

Ans:Count of the sized warp = count of unsized*100/(100+% size)

= 44* 100/(100+10)

= 40 Ne

Total length of sized warp = 120*count

=120 *40

= 4800 hanks. (Ans)

Total length of yarn sized = Total length of warp

no. of ends

= 4800/2400

= 2 hanks(Ans.)

Ans:

a) The wt. of size on the yarn = wt. of sized warp – wt. of unsized warp

Wt. of unsized warp = length of warp in yds* no. of ends

840* count

= 1050*3000

840*50

= 75 lbs

Wt. of size = 82.5 – 75 = 7.5 lbs (Ans)

b) Percentage of size put on the yarn = wt. of size100%

wt. of unsized warp

= 7.5/75 *100

= 10%(Ans.)

c) Count of sized warp = count of unsized *100/(100+% size)

= 50* 100/(100+10)

= 45.45 Ne(Ans.)



Exercise

Describe the following question as per your practical observation in Textile Share Company.


2) Why the top squeezing roller is rubber coated?

3) How the size level is controlled in the size box?

4) Why the first four cylinders are Teflon coated? How the temperature is maintained

constant in drying section?

5) Describe the techniques used to improve the size penetration in the size box

6) Describe the techniques used to calculate yarn stretch at sizing

7) Explain how the moisture of sized yarn is controlled at sizing machine and demonstrate

the different parts of the controlling unit

8) Describe the main parts of the sizing creel along with their purpose

9) How constant unwinding tension is controlled in the sizing creel?

10) Explain briefly how size solution is prepared for different types of warp yarns

11) Why we need to have a pneumatic braking on the ruffle of each warping beam during

sizing? How the mechanism is actuated?

12) How is the prepared size solution delivered to the sizing box? Describe the purpose of

reserve tank.

13) Identify the type of size box and drying section installed in KTSC?

14) How the warp sheets and ends in a sheet separated in the head stock

15) Explain the parameters controlled and adjusted by the control panel of the head stock

16) How the density of the weavers beam is controlled? Which machine parts are responsible

for it?

17) Explain how motion is transmitted to different parts of the sizing machine?



UNIT FIVE LOOMING

5.1. Objective

correct yarn preparation for weaving process

To obtain satisfactory weaving performance.

It is essential to have not only a correct yarn preparation, but also an efficient organization

which permits to have warps available at the right moment, thus avoiding any dead time with

style or beam change. All these prerequisites aim at ensuring to the weaving mills a sufficient

flexibility and at permitting them to cope promptly with a variable market demand. Currently

several weaving mills have installed weaving machines which enable to perform the quick style

change (QSC), leading to a considerable reduction of the waiting time of the machine. The

following chart presents the possible alternatives for the preparation of the weaving

machine[1,2,3,12]:

Changing style means producing a new fabric style, weaver’s beam changing means going on

weaving the same fabric style just replacing the empty beam with a full beam of same type.

5.2. Drawing-in

Drawing-in consists of threading the warp yarns through the drop wires, the healds and the reed

(fig. 5.1). Depending on the styles of the produced fabrics and on the company‘s size, this

operation can be carried out manually, by drawing-in female workers



Fig. 5.1 Drawing-in[1]

operating in pairs (a time consuming activity which requires also skill and care), or by using

automatic drawing-in machines. Fig. 5.2 shows one of the most established heald drawing-in

machines. The drawing-in begins by placing the weaver‘s beam, the harness and the row of

healds on the proper anchor brackets, then the drawing-in program is typed in on the computer

and the machine is started. A sort of long needle picks up in sequence the threads and inserts

them with only one movement into the drop wires, the healds and the reed dents, which are

selected each time and lined up to that purpose. The computer controls the different functions

and supervises them electronically, ensuring the exact execution of the operation and interrupting

it in case of defects[1,2,3,12].

Fig. 5.2 Heddle drawing-in machine[1]

The machine can be used with the usual types of healds, drop wires and reeds and can process a

wide range of yarn types and counts, from silk yarns to coarse glass fibre yarns. The drawing-in

speed can in optimum conditions exceed 6,000 threads/hour. Fig. 5.3 presents another automatic

drawing-in machine which carries out same functions as previous machine, however without

needing the weaver‘s beam. In fact it is fed by a common cotton twine which it inserts among the

various elements of the warp stop motion, of the harness and of the reed according to the



program set up on the computer and under its control and supervision. At the end of the drawing-

in, the drawn-in devices are moved on the frame of a knotting station in which an automatic warp

tying-in machine joins the drawn-in threads together with the threads of the beam. This operation

can be made also on board the loom[1,2].

Fig. 5.3 Automatic drawing-in machine[1]

This machine offers the advantage of working always under optimum operating conditions (use

of same yarn), independently of the quality of the warp to be prepared and in advance in respect

to warping, therefore with higher flexibility. The drawing-in rate can reach 3600 threads/hour.

Fig. 5.4 shows a harness and a reed with already drawn-in threads, ready to be brought to the

knotting station[1,2].

Fig. 5.4 A harness and a reed with drawn-in threads ready to be moved to the knotting station[1].

The main requirements of carrying out the drawing-in process efficiently are:

(i) The operators should be aware of the principles of drawing-in and be trained to do the job

speedily because any mistakes or delays in carrying out the process would prove to be costly.

(ii) The healds and reeds should be in good condition and of suitable specification for ensuring

that these are not the cause of warp breaks on the loom and of defects in the fabric.

(iii) The dressing of the beam should be done properly to avoid crosses-ends on the loom.



(iv) Suitable precautions should be taken to reduce the incidence of extra ends and to compensate

for the missing ends during weaving of the beam.

5.3. Tying-in (Knotting)

The operation of knotting or tying-in is used where the ends of the new warp beam have to pass

through the healds and reed dents, exactly the same way as the old warp, so that when the

individual ends are knotted with the corresponding ends of the old warp, the ends of the new

warp can be passed through the respective heald-eyes and dents of the reed, simply by pulling

the old warp from the front rest side of the loom. Knotting or tying cannot be used where the new

warp is not similar to the old warp in all respects. The operation of knotting can be carried out

mechanically only, by using a fully automatic knotting machine. It can be performed on the loom

or separately in the preparatory room. In the former case, the work involved in the carrying of

the old warp with the healds and the reed is eliminated. It also eliminates the operation of gaiting

up the warp on the loom. But the loom remains out of production until the operation of knotting

is completed.

The operation carried out by the automatic tying-in machines can be summarised as;

(i) Selection and knotting of the ends.

(ii) Cutting the tail ends of the knotted ends.

(iii) Stopping the machine in the event of a thread found missing or broken[1,2,3].

The piecing-up of the warp yarns (Fig. 5.5) permits to the weaving mills which are in a position

to use it (not many mills at the moment) to simplify and speed up considerably the loom starting

operations in case of warps which were drawn-in or tied-up outside the weaving machine. The

warp threads are laid into a uniform layer by the brush roller of the piecing-up machine and

successively pieced-up between two plastic sheets respectively about 5 cm and 140 cm wide,

both covering the whole warp width.

The plastic sheet can be inserted into the weaving machine simply and quickly, avoiding to

group the threads together into bundles; the threads are then pieced-up on the tying cloth of the

take-up roller[1,2,3].



Fig. 5.5. Piecing-up[3]

If a new drawing-in operation is not necessary (this expensive operation is avoided whenever

possible) because no style change is needed, the warp is taken from the beam store and brought

directly to the weaving room, where it is knotted on board the loom to the warp prepared with

the knotting machine. As an alternative to the usual knotting on board the loom, the knotting

outside the loom or stationary knotting of a new warp with an already drawn-in warp can be

carried out in the preparation department. The devices bearing the threads of the old warps are

taken from the weaving machine and the knotting can be started in the preparation room under

better conditions, leaving the weaving machine free for rapid cleaning and maintenance

operations[1,2,3].

The stationary knotting, in particular, takes place in following stages:

Taking out of the loom the prepared beam with the harness

Transport of the beam into the weaving preparation department

Fastening of the heald frames and of the reed on the proper frame

Knotting

Passing of the knots by proper drawing

Warp piecing-up

Temporary maintenance of the new warp with the harness

Transport of the new warp inclusive of harness with proper carriage

Loading of the weaving machine and start of the weaving process using plastic sheet

Weaving



The automatic knotting machines can process a wide range of yarn types and counts at highly

reliable and rapid operating conditions (up to 600 knots/minute), with mechanical or electronic

control on double knots and on the sequence of warp patterns in case of multi-coloured warps.

Fig. 5.6 shows a knotting machine in operation on a warp with colour sequence, tensioned on the

proper frame[1,3].

Fig. 5.6. A knotting machine in operation on a warp with colour sequence, tensioned on the proper frame[3].

Fig. 5.7.Harness loading in the weaving machine[3].

5.4 faults and wastes in drawing in and tying in processes.

1. Faults in drawing-in of the warp are mainly caused by the carelessness or inattention of

the drawers or attendants.

The main faults are as follows:

Misdraws caused by missing reed dents or healds or by drawing-in surplus ends

through them.

Broken pattern caused by drawing-in without adhering to the repeat of draft.



Crossed ends as a result of improper laying of ends in the clamp or rack, as well as

due to carelessness or inexperience of the attendant

Imperfect selvedge due to inadequate number of reed dents is occupied, lost ends,

etc.

2. Faults at tying-in of the new and old warps may be caused by disarrangements of the

tying-in machine and carelessness of the worker attending to the machine.

The main faults in tying-in are:

Yarn breakage due to different tension of separate yarns or their excessive tensioning

The yarns are tied in pairs, as the needle of improper number is employed

Weak knots are tied

End missing due to disarrangement of the yarn selector

Wastes in drawing-in and tying-in depend upon the yarn length on the beam, the proper

operation of drawers and attendants of tying-in machines and the method of warp storage and

transport. Usually the wastes in the drawing room are from 0.05 to 0.15%.

Exercises:

1. Differentiate the type of drawing in and tying in machine found in Textile Company on your

practical observation.

2. Explain the working mechanism of drawing in and tying in machine with necessary sketches.

3. mentioned the main requirements of carrying out the drawing-in process efficiently.

4. What is the basic difference between drawing in and tying in?

5. List out the possible defect on drawing in and tying in processes and give the possible remade

of the defects.

6. Mention different type of drawing in and tying in machine . What are the basic future of each

machines.



UNIT SIX WEAVING MACHINES

6.1. General remarks

Actually the research work on the shuttle loom was dropped in the first half of the 70‘s, with the

arrival on the market and the prevalence of systems using for weft insertion other ways than the

shuttle. The new shuttleless machines are simply called ″weaving machines″, this term implying

looms working without shuttle[2,12,13].

The weaving machines present following advantages over traditional looms:

1. Total elimination of any spooling operation

2. Production increase, thanks to the fact that these machines can work at high speed, owing to

the reduction or elimination of moving masses

3. Reduction of the shed size, therefore lower tension of the warp threads and consequently

reduction in the number of yarn breaks

4. Noise reduction thanks to the elimination of the shuttle pick

5. Automation of various devices.

Fig. 6.1.General scheme of a weaving machine[3].

The warp threads wound on a beam (1) are bent on the back rest roller (2), support special drop

Wires (3), pass through the healds (5) and through the dents of the reed (8) fastened to the slay

(7), along which the vehicle transporting the weft runs (9). The fabric produced is then drawn by

a take-down roller (10) and wound on the cloth beam (11). The warp let-off (4) and the motor

driving the fabric takedown (6).



6.2. Classification of looms

General classification of looms:

On the basis of the system used for weft insertion, the weaving machines can be divided into:

A) Machines with mechanical weft insertion system:

by rigid rapiers

by flexible rapiers

by projectiles

B) Machines with non-mechanical weft insertion system:

by jets of compressed air

by jets of compressed water

Furthermore the machines can be divided into:

A) mono-phase weaving machines (inserting one weft at a time)

B) Multi-phase weaving machines (inserting several wefts at a time)

6.3. Classification of loom motions

The motions of a plain loom can be broadly classified as:

1) Primary motions:

a. Shedding - forming shed by splitting warp threads into two layers

b. Picking - inserting pick into the shed

c. Beating - pushing weft thread towards the fell of the cloth

2) Secondary motions:

a. Let-off - releasing warp from the weaver‘s beam and keeping necessary tension in the

warp

b. Take-up -moving cloth forward at a constant rate for required pick spacing



3) Auxiliary motions:

a. Warp protectors -protecting warp from damage when shuttle trap occurs in the shed

during weaving

b. Weft fork -preventing cracks and thin places in cloth by stopping loom when weft is

broken or exhausted

c. Brake -asserting motion of the crank shaft when stoppage of the loom occurs

d. Temples - preventing width way contraction of the cloth at the fell

e. Top rollers - assisting reversal of healds.

f. Box swell - arresting momentum of incoming shuttle and running shuttle at box smoothly

g. Check strap - arresting momentum of incoming shuttle in the box.

h. Oscillating backrest - regulating tension in the warp during pick cycle for plain

weaving[2,12,13].

6.4 Sheding

It is separating the warp threads, which run down the fabric, into two layers to form a

spacefor the passage of weft threads

Table 6.1. Types of Sheds[13]

Type of sheding Centre closed shed: Bottom closed shed Open shed Semi open shed

Advantage

1.Rising thread is

balanced by falling

thread.

2) Power

consumption is low.

3) Wear and tear of

spare parts is low.

Good cover is

obtained in the

fabric

1) Rising thread

balances the

lowering threads.

2) Minimum time

required to form a

shed.

3) Strain upon warp

is low.

4) Loom can run at

high speed.

5) Strain upon the

warp is less.

Requires less time to

form a shed.

2) The strain upon

the warp is low.

3) The loom can run

at high speed.

4) Power

consumption is low.

Dis advantage Strain upon the warp Long time required 1) It is difficult to

repair broken ends.

1) It becomes

difficult to repair the



is more. to produce a shed.

2) Not suitable for

high speed looms.

3) Strain upon the

warp is high.

4) Wear and tear is

more.

5) Power

consumption is more

A heald leveling

mechanism is

required.

2) As the shed is

always open,

breakages may result

when the yarn is

weak.

broken ends.

2) Breakages may

result when the yarn

is weak.

Use For centre shed

dobbies, centre shed

jacquards and

handlooms.

For single lift

dobbies and single

lift jacquards.

1) Used on plain

looms.

2) Used for double

lift dobbies and

double lift jacquards

Many double lift

dobbies and double

lift jacquards form

semi-open shed.

5.3 _

Types of shedding mechanisms:

Tappet shedding mechanism

Dobby shedding mechanism

Jacquard shedding mechanism

1. Tappet Shedding

Simple and robust

Inexpensive with regard to both initial cost and maintenance,

Improbable to cause faults in the fabric

The speed of the loom is not limited

Limitation:

Restriction in patterning possibilities

Limited to 8 or 10 ends and 8 or 10 picks/repeat

Inconvenient for frequent pattern changes

2. Dobby Shedding

More versatile

Usually controls at least 16 and can goes to 36 heald shafts

No limit to the number of picks per repeat

the lifting of the shafts is controlled by some form of pattern chain



Relatively easy to change the weave

Produce any structure, weave, or combination of weaves.

Limitation:

More complicated and much more expensive initially

Maintenance costs are higher because they have many more parts, which eventually have

to be replaced owing to wear

More liable to produce fault in the fabric than tappets

Limitation in the speed of the loom (Max. possible up to 500 ppm)

3. Jacquard Shedding

It is made in a wide variety of sizes to control from 100 to 2000 or more ends per repeat

The lifting of the ends is controlled by a chain of punched cards or by a loop of punched

paper

Simpler in principle than dobbies and patterning possibilities virtually unlimited

Used for a wide variety of purposes from ties to carpets

Limitations:

High initial cost

Relatively costly to install and maintain since it contains many more moving parts.

A medium-sized jacquard for controlling 600 ends in the repeat has 600 or 1200

wire hooks for raising the ends, 600 or 1200 wire needles for controlling the hooks,

and as many cords as there are ends in the warp for connecting the hooks to the

ends they control

More liable to produce faults in the fabric than dobbies

Imposes limitations on loom speeds (Max. possible up to 300 ppm)

Table 6.2. Comparison of shedding systems

Cam Dobby Jacquard

Maximum number of different

lifts 6-10 16-36

5376 or 8000;

1344 is standard

Maximum picks per repeat 8 24 000+ 20 000+

Degree of complexity Minimal Quite complex Simple in principle but many

parts

Ease of pattern change More time Very quick Very quick

Amount of maintenance Low Low to medium Highest

Likelihood of faults Low More possible Greatest likelihood

Capital cost Low Quite high Highest



6.4.1. Negative Tappet Shedding Mechanism:

The principle of tappet shedding motion consists in using a tappet which impinges upon an anti-

friction roller, supported in a treadle, the heald shaft being directly or indirectly connected to the

treadle from which it is operated. The most elementary form of tappet shedding is one which is

constructed to control two healds. The latter (healds) receive a reciprocating motion and produce

a plain weave[1,2,313],.

The heald shafts are either raised or lowered by the mechanism but are returned by the action of some external device.

Fig 6.2. Negative tappet shedding mechanism[13]

The figure shows negative shedding tappets for plain weave with their requisite connections. The

healds are connected with tappet treadles below and with pulleys at the top of the loom.

A & B - Tappets

C - Bottom shaft

D & E - Treadle levers

F - Fulcrum

G & H - Lamb rods

J & K - Heald shafts

L & M - Leather straps

N - Top reversing roller (Smaller dia)

P - Top reversing roller (Bigger dia)

Q - Top reversing roller shaft

R & S - Bowls

T - Heald eye

U - Heald eye

V - Weft yarn

W - Lease rods

X - War p sheet

Y - Cloth



A and A‘ are two plates of a negative tappet, both fixed on the tappet shaft beneath the centre of

the healds C and C‘. Two treadles D and D‘ move on a fulcrum pin E, and each carries an anti-

friction roller F, F‘ upon which the tappet plates act as they rotate.

G and G‘ are straps and chords which connect the treadles to the bottom of the heald shafts.

Cords and straps, H, H‘, connected to the upper heald shafts, are secured respectively to the

peripheries of two rollers K, K‘, which may be either fast or loose upon a shaft B.

When these tappets are in motion, the treadles are alternately depressed and the

underconnections impart a similar downward movement to the healds; but as the tappets are

incapable of lifting either the treadles or the healds, the upward motion is entirely due to the top

connections and pulleys[1,2,3,13].

Thus, as one heald shaft is depressed by a treadle, the strap H is unwound from the roller K, and

H‘ is wound upon K‘ or vice versa; therefore a sinking (falling) heald is made to lift the other

one, and the negative action of a tappet is converted into a positive one by the roller and

strap[13].

6.4.2 Positive tappet shedding motion:

In this type of shedding mechanism, the heald shaft is both raised and lowered by the shedding

tappet.

Fig.6.3. Positive Tappet Shedding Mechanism[13]

The given figure shows a positive tappet shedding mechanism. The tappet shaft ‗A‘ carries the

tappet ‗B‘ that has a groove ‗C‘ in which a bowl ‗D‘ is placed. The bowl is



connected in turn to a tappet lever ‗E‘, link rods ‗G‘, links ‗J‘ and a heald shaft. Each shaft is

separately connected to a tappet through link rods and tappet levers. ‗F‘ and ‗H‘ are fulcrums for

tappet lever and links ‗G‘ respectively.

When the tappet is rotated, the bowl is also rotated. According to the shape of the groove, the

bowl is moved up or down or still. If the bowl is moved up, the tappet lever moves to the right

through the links ‗G‘ and ‗J‘ and the heald shaft is lowered.

If the bowl is moved down, the tappet lever moves to the left and the heald shaft is raised. Since

the heald shaft is raised and lowered by the tappet, the mechanism is known as Positive Tappet

Shedding Mechanism. When the bowl stands still, the heald shaft is said to be in the ‗Dwell‘

stage[1,2,3,12,13].

6.5. Dobby shedding:

Dobby is a shedding device place on the top of a loom in order to produce figured pattern by

using a large number of healds than the capacity of a tappet. It is used to produce small figures

by means of warp threads and healds. The scope of the dobby is limited between the use of

tappets and jacquards. When the number of heald shafts to be controlled or the picks to a repeat

of the design is beyond the range of a shedding tappet, but is at the same tine too small to be

produced economically by a jacquard, a dobby is employed. The number of heald shafts which

can be actuated by a dobby varies between 6 and 48[2,13].

It is used for manufacturing fabrics of complicate weaving patterns with a big warp and weft

repeats

Main units:

(i) The heald lifting motion : a system of knives performing a return stroke and a

system of hooks connecting in certain way to actuate lifting and lowering of the

healds.

(ii) The pattern mechanism: comprises a cylinder and a card, and determine the

consecutive order of hook engagement with the knives, which in turn determines the

order of heald lifting and lowering in accordance with the kind of fabric.

Main parts:

Top motion : lifting the healds.

Middle motion: transmitting the movement from top motion to the healds.

Lower motion or the under motion: designed for lowering the healds.



6.5.1 Classification of dobbies shedding:

1. Depending on the means to raise and lower the healds:

Negative dobby shedding: the shafts are raised by the dobby and lowered by some

spring under motion.

Positive dobby shedding: the dobby machine both raise and lower the shafts

2. Depending the cycle of knife motion:

Single-lift dobbies: the full cycle of the knife movement is performed during one

revolution of the main shaft

Double-lift dobbies: the full cycle of the knife movement is performed during two

revolutions of the main shaft

3. Depending on the number of cylinder used: one or two cylinder

4. Depending on the the kind of ties in the heald drive: flexible or rigid dobbies

5. Depend on the arrangement of dobby: right-hand dobby or left hand dobby. Generally

dobby shedding classified as:

(a) Positive dobby



(b) Negative dobby

The Negative dobbies tend to be simpler, and, because they are satisfactory except for heavy

fabrics and high loom speeds, they are commoner than positive dobbies, except in woollen and

worsted weaving and for high-speed unconventional looms.

6.6 Jacquard Shedding

It is used for producing large-pattern fabrics with a great number of warp and weft threads in the

repeat, when it is necessary to lift not only groups of threads but single threads as well.When the

design becomes very large, it becomes impossible for controlling the warp threads by using

heald shafts. This is because as the design becomes very large, the number of heald shafts

required to make this design also becomes very large. Thus it becomes very difficult to

accommodate these healds in the available space on the loom. Hence tappet shedding and dobby

shedding cannot be used. It is for this reason that a new type of shedding mechanism came into

existence called as jacquard shedding. By using a jacquard, there is virtually no limit on the size

of the design[13]. There are many kinds of jacquards in use.

Main units:

(i) Mechanisms of lifting: lifting the warp yarns to a certain height

(ii) Pattern mechanism: deflecting certain hooks according to the fabric design

Types of jacquard machines:

The Single or double lift type can be with one or two cylinders

Single-lift jacquard machines: Actuated from the loom main shaft and effect one full

working cycle during its revolution



The double lift jacquard machines: Usually actuated from the middle shaft and perform

full cycle for two revolutions of the main shaft. The mechanical jacquards are mainly of

the single lift single cylinder, double lift single cylinder & double lift double cylinder

types.

6.6.1 Single Lift Single Cylinder Jacquard:

The figure shows a schematic representation of a single lift single cylinder jacquard.

In this machine, we have one needle and one hook for every end in the repeat. Common sizes

have 200, 400, or 600 needles[2,13].

Fig. 6.4. Single lift single cylinder jacquard[13]

A six hundred needle jacquard for example would have twelve horizontal rows of needles with

50 needles in each row. Each needle is linked around a vertical hook, which it controls. Coil

springs press the needles towards the right. There is a lifting knife for each row of hooks, the

knives being fixed in a griffe, which reciprocates one every pick and is normally driven by crank

or by chain and sprocket from the crank shaft[13].

The design is punched in pattern cards, one for each pick in the repeat, and the cards are laced

together to form a continuous chain. The cars are presented to the needles by a card cylinder,

which has a square section in the diagram, but may also be pentagonal or hexagonal.

After presenting a card to the needles, the cylinder moves away from the needles a distance

sufficient to allow itself to be turned to present the next card. If there is a hole in the card

opposite to a particular needle, the needle will enter the hole (the cylinder being perforated to

receive it) and the needle spring will cause the hook to engage its knife. This particular hook and

the ends it controls will therefore be lifted when the griffe rises[2,12,13].

If there is no hole opposite to a particular needle, it will be forced to the left as the cylinder

moves inwards. The hook it controls will be moved out of the path of its knife, so that the hook

and the end it controls will not be lifted.



This jacquard generally forms a bottom closed shed. There is therefore much wasted movement.

The cylinder must reciprocate and turn and the griffe must rise and fall every pick. These

considerations dramatically limited the speed at which the loom cam be run[2,13].

6.6.2 Double lift double cylinder jacquard:

The double lift double cylinder jacquard is a development over the single lift single cylinder in

the manner that, each harness cord and each end in the repeat is controlled by two needles and

two hooks. There are two selective cylinders, one carrying the odd number and the other carrying

the even numbered cards[1,2,13].

If it is assumed that the left hand cylinder in the given figure carries the odd numbered cards, it

will be presented to its needles on odd picks, the right hand cylinder being presented on even

picks. The jacquard has two sets of knives each mounted in a

griffe. The two griffes move up and down in opposite over a two pick cycle.

Fig.6.5 Double lift double cylinder jacquard[13]

Imagine that the hook D is about to descend and the hook C is about to be raised. The harness

cord it controls will be lowered to the centre shed position as the hook D descends. When it

reaches the centre position, it will be taken over by the hook C, which will return to the raised

position. The result is and end required to remain up for two or more consecutive picks is

lowered half way between the picks. Thus a semi open shed is formed. The speed of the machine

is higher compared to the previous one because of reduced time required for selection.

6.7 Picking:

Picking is the second the primary motions in weaving. it is passing the weft thread, which

traverses across the fabric, through the shed. It consists in passing a pick of weft between the



upper and lower lines of a divided warp. The shuttle is the vehicle of weft for picking in the

conventional and automatic looms[13].

The mechanism of shuttle picking is negative. Negative picking is of two types:

(i) Overpicking

(ii) Underpicking

Positive picking is carried out in the machines where the weft is carried across the shed by some

other means instead of a shuttle.

The successful positive picks are:

(i) Carrier pick

(ii) Rapier picking

(iii) Air jet pick

(iv) Water jet pick

The mechanism of propelling a shuttle in the powerloom is negative and includes the picking

device, shuttle guards, swells, fast or loose reed appliances, check straps, pickers etc. The

picking mechanism is elaborate in construction and is the least satisfactory part of the whole

loom[13].

6.7.1 Cone Over-pick Mechanism:

The over pick motion is extensively used in cotton mills. The figure shows a cone over pick

mechanism; a picking stud B is positioned in the hole of the vertical shaft A.

The stud B is parallel with the nose end ‗N‘, when the nose is at the centre of the roller or cone

D. The nose end is then at right angle to the cone, as shown by the dotted line XY.



Fig.6.6 Cone Over Pick Mechanism[13]

The cone over pick motion consists of a vertical shaft A, which is placed either inside or outside

the loom framing. The shaft A serves as the fulcrum of a picking lever ‗C‘.

It is held against the loom framing by a common (top) bearing near the top, and a footstep

bearing at the bottom. This foot-step is bolted to the loom framing. The stud ‗B‘ is either passed

through a slot in A secured by screw and nut, or it occupies a fixed position upon A.

The long picking arm ‗C‘ is of wood, and is attached to a ring E on the top of A having radiating

teeth on it‘s upper surface, for a ring with smaller teeth on the underside to fit into. These teeth

form a rigid connection and facilitate adjustment. A grooved cap M is bolted over the picking

arm ‗C‘ to hold all secure. From the forward end of C, a leather strap passes, down to a picker,

which is freely mounted upon a spindle placed over the centre of the shuttle box.

The picking tappet is keyed upon and end of the shaft ‗S‘ inside the loom framing. In revolving

its nose N, the tappet strikes the cone-shaped antifriction roller on the stud

B, and partly rotates the shaft A and the picking arm ‗C‘, and causes the picker to move inward

with sufficient velocity to drive a shuttle across the loom[2,13].



6.7.2 Lever Under-pick Motion:

When the picking stick moves from the bottom of the shuttle box and the fulcrum of the stick is

below the shuttle box, it is called an under motion.

The lever under-pick motion is one of the best known under pick motions. The lever ‗A‘ is

fulcrummed at C upon the loom framing ‗P‘. The free end of the treadle lever has a connector

leather band T attached to it. The other end of the leather is fastened to the picking arm H. A

coiled spring J is fastened to the framing with the view that the picking arm is held normally at

the outer end of the shuttle box I. The crank shaft wheel R drives the large bottom shaft wheel

‗S‘. Now, on the rim of the bottom shaft wheel there is a picking bowl B, which is mounted

freely upon a stud with the revolving movement of the bottom shaft, the bowl B will strike the

metal piece E, fixed upon the treadle level A, once for two picks[2,13].

Fig.6.7 Lever Under-Pick Mechanism[13]

The action of the bowl upon A will cause the leather band T to be pressed down; and as a result

of this, the picking arm H will go forward with the picker throwing the shuttle into the shed from

that side of the loom. Same mechanism is fitted at the other side of the loom. Same mechanism is

fitted at the other side of the loom, but the striking bowls B, oppose each other.

6.7.3 Cone Under-pick Mechanism:

A picking tappet is fixed to the bottom shaft B. The picking tappet has a nose bit ‗C‘.

A cone D is fixed to the side shaft E, which in turn is connected to a lug strap F. A picking stick

G is connected to the lug strap. The top of the picking stick carries a loosely mounted picker H,

which is free to move along with the picking stick. The bottom of the picking stick is pivoted

(fulcrummed) and connected to a spring J.



When the bottom shaft rotates in the direction shown, the picking tappet also rotates. When the

nose of the tappet cones against the cone, it strikes the cone. This causes a partial rotary

movement of the side shaft. The end of the side shaft thus pulls the lug strap and hence the

picking stick and shuttle moves with great velocity. The picking stick is returned to its original

position by the reversing spring. For the next pick the mechanism situated on the other side of

the loom will actuate and the shuttle moves in the opposite direction[2,3,13].

Fig.6.8 Cone Under-pick Mechanism[13]

Power Required for Picking

The energy usefully expended in accelerating the shuttle is equal to the kinetic energy when it

leaves the picker

Energy/pick = 2

1MV

2

Where: M = Mass of the shuttle or weft carrier, Kg

V = the average speed of the shuttle, m/s

But, Power = time

workdone

If ppm is the loom speed in picks/min, then

Power for picking = 2

1MV

2 x

60

ppmx

1000

1 kW

The time for the passage of the shuttle or weft carrier will be,



Time (t) = pppm

x6

60

360

s

and the distance moved by the shuttle or weft carrier

Distance (d) =

100

LR m

Where: R= Reed space

L= Length of the shuttle

= degree of crank shaft rotation for the shuttle passage

If 'V' is the average speed of the shuttle during it passage through the shed, it can be calculated

as,

V=

xLRxppmxppmx

xLR

)()(6)(6

100

10

-2 m/s

then,

time

donework

2

1MV

2 =

4

2

22

10)()(18

xLRxppmM

J

Hence the power for picking = 2

1MV

2 x

1000

1

60

)(x

ppm kW

Power for picking = 8

2

23

10)()(3

xLRxppmM

kW

6.8. Beat-Up Mechanism:

The beating up is the third of the primary motions in weaving. It consists in driving the last pick

of weft to the fell of the cloth. This is accomplished by the forward movement of the reed fixed

in the sley. The sley is given a quick and sudden movement towards the fell of the cloth by the

cranks in the crankshaft.



Fig. 6.9 Beat-up Mechanism[13]

The figure shows the mechanism of the beat-up motion. A is the Sley. B is the sleysword, C is

the rocking shaft, and D is the crank. X is the crank shaft, and D is the crank. X is the crank

shaft, E the crankarm, F the connecting pin, and G a metal plate on the sley sword. It is a

separate lath fixed in the horizontal way, in the groove provided in the sley. The reed Y is held in

position between the reed cap and the sley. The rocking shaft ‗C‘ is supported in bearing, bolted

to the end framing. The crank arm E is fulcrummed to the sleysword B, by the connecting pin F

and is bent on the crank shaft. As the crank D revolves, swinging motion is given to the sley

when the latter is pulled from the fabric, the shuttle is driven across; the shuttle is driven across;

when it is pushed towards the fabric, the weft thread is forced into position by the reed Y. The

bolt K is adjusted to vary the position of the warp line to suit different fabrics[2,3,12,13].

6.8.1 Eccentricity of Sley’s motion:

The sley has primarily got two functions to perform. When at it‘s forward position it must have

sufficient velocity to firmly beat-up the last pick to the fell of the cloth. At the backward

position, it‘s movement must be slow to allow sufficient time to pass the shuttle across.

The movement of the sley is therefore, unequal, variable or eccentric. The traverse of unequal

spaces by the sley in equal intervals of time is called as it‘s eccentric movement.

The amount of eccentricity of sley‘s motion depends upon the following factors:

(a) The size of the crank

(b) The length of the crank arm

(c) The position of the crank arm in relation to the connecting pin.



Fig.6.10 Eccentricity of sley[13]

A – Position of the connecting pin at fell

B – Position of the pin at back centre

CD – Crank arm

ED – Crank

―The eccentricity of the sley is defined as the equal distances moved by the sword pin (sley) in

unequal intervals of time.‖

The velocity of the sley will be more as it approaches the forward most position and it decreases

as it approaches the backward most position. This helps in giving more time for the passage of

shuttle and also increases the effectiveness of beat-up. Sley eccentricity can be also defined as

―the ratio of length of cranks (r) to the length of the crank arms (l).

Sley eccentricity, e = r / l

Timing Diagram of Primary Motions

The timing diagram which is depends on the type of fabric and loom shows the timing of

each motion.

Timing diagram



6.9 Take-up motion

Cloth control (take-up) is the withdraws fabric from the weaving area at the constant rate

that will give the required pick[1].

6.9.1 Objectives of take-up motion:

The objective of the take-up motion is to draw the fabric to the cloth roller as it is regularly

woven. Texture of a fabric largely depends upon the number of ends and picks per unit space i.e.

per centimetre or per inch. It is the take-up motion that determines in conjunction with the let-off

motion that determines the number of picks of weft per inch and contributes to the uniform

texture of the fabric[1,2,3,13].

6.9.2 Types of take-up motions:

a. negative take-up motion : Here, the amount of cloth drawn forward at each pick is

determined by the force employed by the reed to the fell of the cloth at the time of beat-up. The

drive to the take-up roll is negative.

Fig. 6.11 Negative Take Up[13]

A simple type of negative take-up motion is shown in the figure. ‗D‘ is a cam fixed on the crank

shaft ‗C‘ at an end opposite to the loom pulley. ‗AB‘ is a two armed lever fulcrummed at ‗E‘.

The cam ‗D‘ actuates the lever AB at a point indicated by the arrow. The arm B supports dead

weights K upon it. A catch F is held immediately above the ratchet J. On the same stud of J is a

small pinion I, which engages with the beam wheel H. G and G1 are the detaining catches. Now



when the cam depresses AB, the arm B rises up and along with it the catch F gets lifted against

the force of the weights. When the cam moves round, it releases lever AB, and immediately, the

catch F plunges upon the ratchet J, causing a drag upon the cloth, and this action takes place just

at the time of beat-up. The force of beat-up on the cloth fell and the drag is responsible for the

take-up of the fabric. The dead weights can be regulated by moving these either near to or farther

from the fulcrum, the greater becomes the drag[2,3,13].

b. Positive take-up motion: Here, the cloth is drawn forward by the take-up roll which is

positively driven through a number of gear wheels, at a uniform rate. The number of pick per

inch can be regulated to the required extent and pick density can be kept uniform throughout the

weaving operation.

Examples:

1. Seven wheel take-up motion

2. Worm and worm wheel continuous take-up

3. Ruti-C take-up, etc.

c. Five wheel take-up motion:

Fig. 6.12 Negative Take Up[13]

The five wheel take-up motion is an intermittent positive motion. It consists of a train of five

wheels. The rack or ratchet wheel is fixed on a short shaft and on the opposite end of the same



shaft is fixed a change wheel B. The change wheel meshes with a stud wheel ‗C‘ which is

compounded with the stud pinion D. The stud pinion drives the beam wheel E. The change wheel

is a driver wheel and hence, a larger change wheel increases the cloth take-up speed giving more

picks / inch and vice versa. In this take-up motion, the motion is primarily imparted from the sley

sword. The finger K is bolted to the sley sword. This finger enters into the slot of the take-up

lever, which is fulcrummed at J. A pushing pawl is mounted on a stud and the stud is secured to

the top end of the takeup lever within a slot. The pushing pawl operates on the ratchet A, either

one tooth at a time or two teeth, as required, when the sley swings backward. The detaining catch

prevents the ratchet wheel from rotating in the opposite direction. The movement of the pushing

pawl can be regulated by altering the position of finger K and the position of the pushing pawl in

their respective slots[2,3,12,13].

d. Seven wheel Take-up motion:

Fig. 6.13-Wheel Take-Up Motion[13]

The seven wheel take-up motion is a positive intermittent take-up motion. It is also known as

―Picks seven wheel take-up motion‖. The figure shows the take-up lever H, which is centred at I,

having a pawl M, pivoted upon it. A finger G is bolted and adjustable to a sley word and passed

through a slot in H. A swinging motion is given to H, and this will cause the pawl M to drive the

ratchet wheel D, and set the train of wheels in motion. The amount of movement in M depends



upon the position of G in the slot of H. The cloth is wound onto the cloth roller as the sley moves

forward, because here the fulcrum I is below the pulling pawl.[1,2,3]

M. In this motion, the change wheel B, is a driven wheel and larger wheel will, therefore, give

more number of picks, and a smaller wheel will give lesser number of picks per inch in the cloth.

The wheel A, on the ratchet D, is also sometimes changed and is termed as the standard wheel,

which is a driver wheel. A smaller wheel will therefore give more number of picks and a larger

wheel will give less no. of picks/inch[2,12].

The figure shows a commonly used seven wheel take-up motion. The take-up roller A is driven

through a gears consisting of seven wheels. The first wheel B called a ratchet wheel is driven by

means of a pawl operated by the sley S. The other wheels in the mechanism include a standard

wheel ‗C‘, a change wheel D, a swing pinion E, a carrier wheel F, a compound pinion G and a

beam wheel H. The retaining catch K prevents the ratchet wheel from turning in the reverse

direction[13].

The number of teeth on each wheel, except the change wheel, and also the circumference of the

take-up roller are constant, so that a direct relation is possible between the picks / inch and the

number of teeth on the change wheel. For example, a 40 teeth change wheel would give 40 picks

/ inch. In this mechanism, the ratchet wheel is turned by one teeth for every pick inserted.

Normally standard is of 36 teeth, however for very high or low pick densities, it can also be

changed along with the change wheel[1,13].

6.10 Let-Off Motion

Let off motion is a secondary motion of weaving, by which, the warp is released every pick from

the weavers beam. The following are the objects of the let-off motion[1,12,13]:

(i) To maintain the necessary tension upon the warp.

(ii) To regulate the amount of warp delivered from the warp beam during weaving.

(iii) To influence the number of picks per unit space.

(iv) To supply the warp exactly in lengths i.e., taken up by the take-up roller.

The warp let-off motions are divided into two classes:

(a) Negative let-off and

(b) Positive let-off

a) Negative let-off: Here the tension in the warp is controlled by means of chains, levers and

dead weights. The tension is regulated by moving the dead weights manually.



b) Positive let-off: Here the tension in the warp is regulated automatically by a positive drive to

the beam which facilitates in delivering the warp for every pick at a constant tension[13].

6.10.1 Negative let-off

In negative let-off motions, the warp is controlled by means of ropes or chains, levers and

weights; whereas, in positive let-off motions, the warp beam rotates to deliver warp every pick

automatically. The negative let-off motions are classified as[2,13]:

(i) Brake let-off motion

(ii) Frictional let-off motion

(iii) Rope or chain, lever and weight let-off motion.

6.10.2 Negative let-off motion

Chain, Lever and Weight Let-off Motion, this type of negative let-off motion is generally used in

cotton mills. This motion allows horizontal warp to be withdrawn from the warp beam whenever

a taking up lever is activated. The ropes and weights reciprocate with the shedding motion, for

when a shed opens, the warp is drawn from a beam A, and when it closes, any surplus length is

wound on again. But ropes and weights do not keep and equal tension upon the warp in all its

varying positions. A change occurs at every revolution of the beam, caused by the withdrawal of

a layer of yarn, without altering it‘s circumference where the ropes act. To rectify this would

necessitate a reduction of weights B in proportion to the decreased diameter of the

coiled[1,2,3,12,13].

Fig. 6.14 Negative Let-Off Mechanism[13]

It is clear from the figure that the efficiency of the weights is increased by suspending them from

simple levers as at F, and uniting the chains, and levers. But this renders a warp beam less

sensitive to movement in the shedding healds and less capable of taking any excess of warp then



where balance weights are used. The warp beam has ruffles J, which prevent ropes and chains

from channelling it. When required, weights on the leverage should be increased without

increasing the no. of coils on the ruffles. If the strain on the warp is more, great force is required

to form a shed and the picks will not be driven closer. If the strain is less, slack warp will permit

one pick to ride upon the other and form ridges in the cloth. To ensure uniform tension, a

vibrating backrest (oscillatory back rest) is used to slacken a warp when the shed opens and to

lighten it when the shed closes. This is known as the tappet or warp easing motion[1,2,12,13].

Exercise:

1. Describe the weaving mechanics with sketch?

2. Classify the loom with their working mechanism.

3. What are the basic working principles of dobby and jacquard shedding?

4. Describe the Negative Tappet Shedding Mechanism and Positive tappet shedding motion

with sketch.

5. Describe the Cone Over-pick Mechanism and Lever Under-pick Motion with sketch.

Describe the Beat-Up Mechanism with sketch.

6. What does it mean Eccentricity of Sley‘s motion?

7. Describe the types of take-up motions with sketch.

8. Describe the Five and seven wheel take-up motion with sketch.

9. Describe-Off Motion with sketch.

10. Describe Negative let-off?



Reference:

1. Reference books of textile technology: weaving (october 2000), ACIMIT italian association

of textile machinery producers moral body.

2. Lord, P.R.; Mohamed, M.H. Weaving: Conversion of Yarn to Fabric, 2nd edition: Merrow,

Durham, England; 1982.

3. Just, M. Package Dyeing: Clemson University Short Course, Clemson, SC; May 30–31, 1989.

4. Goswami, B.C. Yarn packages for dyeing, Internal Communication; Clemson

University: Clemson, SC, May 30–31, 1989.

5. Rebsamen, A. New possibilities of package building with microprocessors. Int. Text. Bull.

3/1988, 18–32.

6. Rebsamen, A. New possibilities of package building with microprocessors, Paper presented at

the Reutlingen Colloquy on ‗‗Process Control in Textile Technology,‘‘

Schweiter Mettler Report; Schweiter Ltd.: Switzerland, 3/1988.

7. Schweiter Corporation Report on ‗‗Schweiter Digital Winding‘‘; Schweiter Ltd.:

Switzerland, 3/1988.

8. Uster_ Statistics 1997. Zellweger Uster Publications: Knoxville: Tennessee.

9. What is new in slasher instrumentation. Standberg Engineering Laboratories, Inc:

Greensboro: North Carolina.

10. Textile Yarns: Technology, Structure & Applications. Goswami B. C., Martindale

J. G., Scardino F. L., Eds.; John Wiley and Sons: New York, 1977.

11. Seydel, P. V.; Hunt, J. R. Textile Warp Sizing; Seydel Wooley & Co. Phoenix

Printing: Atlanta, Georgia, USA, 1981.

12. Ormerod, A.; Sondhelm, W. S. Weaving: Technology and Operations; The Textile

Institute: Manchester, UK, 1995.

13.Teaching Material On Woven Fabric Manufacture I, Sajid Ahmed Qureshi, M.Tech (Ph.D).,

Lecturer, Department of Textile & Leather Engineering Institute of Technology, Wollo

University, Kombolcha.

Documents

Woven Fabric -I Teaching Materials