122 Fundamentals and Advances in Knitting Technology

122 Fundamentals and Advances in Knitting Technology Số trang: 329 trang Ngôn ngữ: English --------------------------------------------- About the book Description Fundamentals and advances in knitting technology looks at the history of knitting and how the process has evolved to the latest developments. Chapters discuss the principles involved in different types of knitting machines and the different types of loops and knitted structures. The science and quality aspects of knitting, calculations related to knitting, and the mechanics of knitting are also examined. The book is primarily based on the author's extensive experience of teaching and research in this particular area of textiles. With its distinguished author Fundamentals and advances in knitting technology is an important reference source for designers, engineers and technicians involved in the manufacture and use of knitted textiles and garments. It will also be helpful as a practical guide for academics and students.

advances in knitting technology

Fundamentals and advances in knitting technology

Sadhan Chandra Ray

New Delhi ● Cambridge ● Oxford ● Philadelphia

Woodhead Publishing India Pvt Ltd., G-2, Vardaan House, 7/28, Ansari RoadDaryaganj, New Delhi – 110002, India

First published 2011, Woodhead Publishing India Pvt Ltd

© Woodhead Publishing India Pvt Ltd., 2012

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The knitting technology has been playing a very vital role in our life stylesince 1000 B.C It not only produces fabrics and shaped garments forapparel and household purposes but also for various technical endapplications Knowledge developed in the past, particularly in the last 50years in the field of knitting technology has contributed significantly tothe developments of state-of-the-art machinery on one hand and highlysophisticated and specialised textile products on the other The basicprinciples of knitting technology as well as the recent developments inknitting are now-a-days included in the syllabi of the textile relatedundergraduate and postgraduate courses all over the country.

Prof (Dr.) Sadhan Chandra Ray has written a textbook on

“Fundamentals and Advances in Knitting Technology” to cater to the need

of the students, teachers and professionals dealing with knitting technology

I appreciate the efforts of Prof Ray for precisely covering the variousaspects of knitting technology in his book and Woodhead Publishing IndiaPvt Ltd Delhi for publishing the book Suggestions are invited from thereaders for the improvement of the book in future

University of Calcutta

Clothing is one of our basic needs in life The second most importanttechnique of manufacturing either clothing or clothing material is theknitting Apparently, knitting is a very simple technique of making fabric

or clothing, but it has complexity too The more we study and the more weresearch on knitting, more and more mysteries of knitting are beingunveiled and we become more confident to control the technology ofknitting for producing from simpler to complex fabrics for diversifiedapplications in addition to traditional apparels even at a very high speed.Moreover, knowledge is now recognized as key input for future prosperity

of knitting like other production techniques During my long teachingexperience I always have felt the need for a suitable text book on knittingtechnology encompassing together all scientific information available inother books and journals at one place in a form that is lucid and easilycomprehensible to students and researchers So the basic aim of writingthis book was to precisely combine the fundamental principles of knittingand related developments It is hoped that this publication will fulfill theneed for an updated comprehensive publication which remained overduesince long

The book introduces the basic concepts of knitting to a student with noexposure of knitting as well as the aspects of knitting science to apostgraduate student or researcher for better understanding the knittingtechnology and gaining an insight in to the mechanics of loop formation

in knitting Emphasis has also been given on recent developments andcomplicated things in knitting Naturally, a number of ideas from previousbooks and journals have been gained on this subject to enrich the presentbook I am indebted to all these authors

Presently, knitting technology has been included in the syllabi of textiletechnology and allied courses in various undergraduate and postgraduatedisciplines Keeping in view the above mentioned requirements, I haveendeavoured to bring out the present textbook based on my experience ofteaching and research in this particular branch of textiles I have attempted

to incorporate the following notable features in the text like basics of weftand warp knitting, production of different knitted structures, latestdevelopments in knitting (machine, process and products), knitting science,

mechanics of knitting, knitting related calculations, traditional andobjective measurements of knitted fabrics, concept of green business inknitting, etc For easy comprehension, the text has been supplemented byillustrations, tables and photographs wherever possible as well as abibliography at the end The book is intended for a wide spectrum ofreaders, including students, researchers and academics, as well asprofessionals in the clothing and textile industries.

I have personally gathered all the information, arranged those in aparticular sequence, typed the manuscript, prepared all the figures except

a few and repeatedly checked the whole matter in order to achieve goodquality with minimum errors However, all the readers are requested tosuggest necessary corrections and modifications for upgrading the quality

of the book in future publication

Finally, I would like to express my sincere gratitude to my numerousteachers, students, friends, colleagues, well wishers and my familymembers who have contributed directly or indirectly by way of theirinspiration, constructive suggestion and useful discussion for writing thisbook

Prof Sadhan Chandra Ray

Department of Jute and Fibre Technology

Institute of Jute TechnologyUniversity of Calcutta

35, Ballygunge Circular Road

Kolkata 700019

2.4 Comparison between weft knitting and warp knitting 17

3 Weft knitting elements and loop formation 19

3.6 Manufacturing and specifications of latch needle 22

4 General terms in weft knitting 34

4.4 Single-faced structures and double-faced structures 36

4.12 Floating and float Loop (or missing and miss loop) 41

4.14 Timing of knitting in circular double jersey machine 43

5.1 Introduction to basic weft-knitted structures 44

5.3 Features of plain (single jersey) knitting (machine, process

5.4 Features of rib knitting (machine, process and structure) 485.5 Features of interlock knitting (machine, process and structure) 495.6 Features of purl knitting (machine, process and structure) 505.7 Comparison between rib and interlock knitting 51

5.11 Some popular extended basic double jersey structures 55

6.6 High pile or sliver knitted fabric production 62

6.10 Loop transfer 65

7 Circular weft knitting machine and mechanism 69

9.10 Racked structures 112

10 Some aspects of weft-knitting science 117

10.3 Importance of knitted loop length and loop shape 118

10.9 Relation between properties and geometry of a loop 126

10.13 Prediction of finished weight and shrinkage of cotton 131

knits – The Starfish Project

11.7 Relationship between yarn properties and knitted fabric

11.8 Pre-requisites for faultless production in knitting 14111.9 Main factors affecting the dimensional properties of knitted

12 Warp knitting machines and knitting elements 144

12.3 Comparison between Tricot and Raschel type warp knitting

12.4 Knitting elements 147

13 Principles of loop formation in warp knitting 151

14.10 Common products of warp knitting machines 177

15 Double needle bar warp knitting machine 179

15.5 Tubular and branched fabrics on double needle bar machine 183

16 Some aspects of warp knitting science 185

16.1 Structural parameters of warp knitted fabrics 185

16.5 Loop length and loop model of warp knitted cell 18716.6 Standardization of chain link and machine gauge 188

16.8 Grey specification of warp knitted fabric 188

17.3 Developments in circular bed weft knitting 193

17.5 Technical textiles – the new product range in knitting 195

18.5 Conversion of count in one system to other system 202

18.15 Quality of cotton yarns used in circular weft knitting 20918.16 Relationship between machine gauge and yarn count 210

19 Application of electronics in knitting 213

19.2 Fields of applications of electronics in knitting 21319.3 Computer-aided designing and manufacturing 214

19.5 Types of CAD for knitting and other peripherals 21719.6 Some of the exclusive features of standard software 21819.7 Computer-aided manufacturing of knitted fabrics (CAM) 219

19.8 Data management system in electronic jacquard 219

20.5 Measurement of coefficient of yarn to needle and yarn to 235

yarn friction

21 Mechanics of loop formation in weft knitting 238

21.3 Experimental studies on single jersey knitting 24321.4 Experimental studies on double jersey knitting 250

22 Mechanics and mechanism of warp loop 262

formation

22.3 The three-dimensional analysis of the loop’s picture 266

22.5 Yarn tension and oscillation in the process of warp knitting 269

24 Production of spacer fabrics in knitting 283

24.3 Production of spacer fabric in weft knitting 285

24.4 Production of spacer fabric in warp knitting 28724.5 Common advantages of 3-dimensionally knited spacer fabrics 29024.6 Types of testing performed for spacer fabrics 29024.7 Warp knitted spacer fabric (WKSF) and its characteristics 291

25 Scope of knitting in garment manufacturing 293

25.7 Shaping during knitting in garment length machine 299

25.12 Potential benefits of seamless garment knitting 314

26.7 Low stress mechanical properties of fabrics 321

27 Scope of knitting in the manufacture of medical 326

textiles

27.4 Human body parts made of textile materials 32727.5 Advantages of knitting in the production of medical textiles 327

28 Concept of green business in knitting and 330

Classification of knitting

Abstract: Knitting is primarily classified as weft knitting and warp

knitting This classification is based on the direction of movement

of yarn with respect to the direction of fabric formation If the yarnsrun in the width or cross-wise direction with reference to the

direction of fabric formation during knitting, then the process ofknitting is called weft knitting In case the yarns run in lengthdirection, i.e the direction of fabric formation during knitting, theprocess is called warp knitting Accordingly, the structures are calledweft-knitted fabric and warp-knitted fabric, respectively, and themachines employed for the purpose are called weft knitting machineand warp knitting machine The detailed classification of the

machines and the comparison between weft knitting and warp

knitting are discussed in this chapter

Key words: weft knitting, warp knitting, knitted fabric, knitting

cross-in which such structures are produced are called weft knittcross-ing machcross-ines

In case the yarns run in length direction, i.e the direction of fabricformation during knitting, the process is called warp knitting The yarnsinside the knitted fabrics are just like the warp yarns in woven fabrics.Such knitted fabrics are called warp knitted fabrics, and the machine whichproduces such fabric is known as warp knitting machine Direction ofmovement of yarn in weft and warp knitting is shown in Figs 2.1 and 2.2.Till date, most of the fabrics we use in our daily life as apparel belong toweft knitting; and hence to knitting learners knitting means weft knitting

if not otherwise mentioned The terms weft and warp have been takenfrom the weaving developed much earlier than knitting.

2.2 Classification of weft knitting machines

Weft knitting machines are classified in various ways The main basis ofclassification is the needle bed Needle bed is the platform or frame onwhich needles are arranged at regular pattern There are grooves or cuts atregular interval to accommodate the individual needles so that those canmove up and down or to and fro along the needle axis for loop formationbut restricted to move laterally The number of needle bed in a machinemay be one or two and accordingly, the machines are called either singlebed (single jersey) or double bed (double jersey in UK and double knit inUSA) machines Further, the shape of the bed may be flat or circular Soaccording to the shape of the bed, knitting machine may be either flat bedmachine or circular bed machine Thus combining the number and shape

of the bed, a total combination of four types of machines is possible Flatsingle bed machines are generally horizontal or slightly angled But thetwo beds in flat machines are generally inclined making an angle of about

2.1 Weft-Knitting.

2.2 Warp-Knitting.

90° at the meeting point The single circular bed is cylindrical and vertical.But circular double beds are of two types – (a) two cylinders facing eachother, or (b) dial and cylinder type, i.e cylinder at the bottom and dial(a circular plate) at the top The dial and cylinder type machines are morecommon in commercial uses The same machines may be classified ashand-driven machine and power-driven machine according to the nature

of drive (mainly applicable to flat bed machine)

The types of structure produced in different machines are different Somachines may be classified according to the basic knitted structures theyproduce The four basic weft-knitted structures are (a) plain, (b) rib, (c)interlock and (d) purl The plain structure is made in single jersey / bedmachine whereas the other three are made in double jersey / bed machine.Sometimes different design elements/devices are fitted in knittingmachine and then those machines are given names according to the element/device attached to the machine For example such machines are

(a) knitting machine with pattern wheel

(b) knitting machine with jacquard

(c) knitting machine with multiple cam track arrangement

(d) knitting machine with intarsia facility

(e) knitting machine with CAD and CAM

Sometimes, some machine is developed and used to produce somespecial end product, and accordingly some specific name is given to thatmachine, i.e socks knitting machine, terry knitting machine, sliver knittingmachine, etc

Knitting machine can produce continuous fabric like weaving or canmake garment with proper shaping On the basis of the product, machinesmay be classified as fabric length machine or garment length machine.Garment length machines are more complicated and less productive.There is another type of weft knitting machine according to shape of theneedle bed equipped with bearded needles called straight bar frame It hasmuch similarity in appearance with Lee’s original hand frame knittingmachine This machine is mainly used for fashioning As neither the machinesare popular in India and neighbouring countries nor manufactured in goodnumber, so the details of the same is not included in the next chapters Thebrief classification of weft knitting machine is given in Fig 2.3

2.3 Classification of warp knitting machines

Based on the features of warp knitting, the machines available are classifiedinto two categories: Tricot and Raschel Both Tricot and Raschel may bemade with either single needle bar or double needle bar A briefclassification of warp knitting machine is given in Fig 2.4

2.3 Weft knitting classification.

2.4 Warp knitting classification.

2.4 Comparison between weft knitting and warp

knitting

The relative comparison between weft knitting and warp knitting(process, machine and structure) is shown in Table 2.1

Table 2.1 Comparison between weft knitting and warp knitting

1 Loop formation takes place course Loop formation takes place wale wise in wise in horizontal direction vertical direction

2 Yarn runs in horizontal or course Yarn runs in vertical or wale direction during direction during knitting knitting

3 Needles knit sequentially in a knitting Needles knit altogether in a knitting cycle cycle

4 Yarn is supplied generally in the form Yarn is supplied generally in the form of

of cone hold in a creel warp beam (number of beams may be 2 or

9 Less variety of structures can be Wide variety of structures can be made in

10 Change in pattern reduces the Change in pattern does not reduce the

11 Fabrics have less aesthetic value Fabrics have more aesthetic value

12 Fabrics are more resilient and Fabrics are less resilient and not suitable suitable for inner garments and for inner garments

15 Dimensional stability of the fabrics Dimensional stability of the fabrics are

16 Wide range of semi or full garment Limited range of garment length machine is length machines are available available

17 Machine may be flat or circular Machines are generally flat

18 Circular machine produces circular Mainly flat fabrics are produced but limited fabrics but both flat or tubular fabric range of circular fabrics can also be may be produced in flat machine produced.

Weft knitting Warp knitting

19 Weft insertion during loop formation Weft insertion during loop formation is

is not possible for producing highly possible for producing highly dimensional dimensional stable technical textiles stable technical textiles

20 Tailoring is difficult Tailoring is not difficult

21 Machines as well as the fabrics Machines as well as the fabrics produced produced are comparatively cheaper are comparatively costlier

The author has consulted in general and taken help of the following booksfor preparing the text and necessary diagrams in addition to the Journalsreferred in different chapters to make his dream successful for the greaterinterest of the student community in the field of textile technology andmany others who find interest to read this book.

An Introduction to Weft Knitting, J A Smirfitt, Merrow Publishing Co Ltd.,England

Circular Knitting, C Iyer, B Mammel and W Sehach, Meisenbach BambergFlat Knitting, Samuel Raz, Meisenbach GmbH, Bamberg

Handbook of Technical Textiles, A R Horrocks & S C Anand, WoodheadPublishing Limited, Cambridge in association with The Textile Institute,Abinton

Knitted Fabric Production, Prof P K Banerjee, Department of TextileTechnology, I I T., Delhi

Knitting – Reference Books of Textile Technologies (e-book), Carmine M &Paola Z., Fondazione, ACIMIT, Milano, Italy

Knitting : Fundamentals, Machines, Structures and Developments, N.Anbumani, New Age International Publisher, New Delhi

Knitting Technology, David J Spenser, Woodhead Publishing Limited,Cambridge, Pergamon Press

Knitting Technology, Prof D B Ajgaonkar, Universal Publishing Corporation,Mumbai

Warp Knitting Production, Dr S Raz, Verlag Melliand Textilberichte GmbH,Heidelberg

Warp Knitting Technology, D F Palling, Columbine Press (Publishers) Ltd.,Buxton, U.K., 1970

Wellington Sears Handbook of Industrial Textiles, S Adanur, TechnomicPublishing Co Inc., Lancaster, Pennsylvania, USA

Weft knitting elements and loop formation

Abstract: This chapter deals with the important knitting elements.

As needles are the main loop forming element, different types ofneedles have been discussed in detail The function of sinker andcam system which are also essential in loop formation has beenfocused The loop forming cycles using latch needle and beardedneedle have also been explained

Key words: knitting machine, needle, needle bed, sinker, cam

system

3.1 Introduction

Knitting is the technique of fabric formation by inter-looping The straightcontinuous length of yarn is bent into loops and those loops are inter-looped for fabric formation The main element responsible for such loopformation and subsequent inter-looping is the needle The needle takesthe help of sinker during loop formation, which applies necessary support

to the yarn for loop formation Moreover, needle has to move along itsaxis for performing the loop formation So some other element (cam) isalso required to impart the motion to the needle during loop formation.The designing of these elements with proper dimension should be doneprecisely as well as those should be placed accurately in the machine inorder to continue knitting smoothly

3.2 Types of needles

The main element used in knitting is the needle which actually makes theloop The three types of needles commonly used in knitting machines are(a) latch needle, (b) bearded needle and (c) compound or bi-partite needle.Whatever the type, needles are may be arranged on the needle bed atregular interval in such a way so that needles may move freely along theaxis without any lateral tilting For the purpose cuts or groves, technicallyknown as tricks, are made on the needle bed As discussed below, thelatch needle is the best and most widely used in the knitting industry The

position of the latch needle inside the trick of the cylinder bed of circularweft knitting machine is shown in Fig 3.1.

All the varieties of needles used in different types of knitting machines(warp and weft) are mainly manufactured and supplied by M/s Groz-Beckert established in 1852 In addition to their head quarter in Germany,they have numerous international production locations including India and

a dense sales network in more than 150 countries to cater the need ofmillions of knitting houses around the world

3.3 Latch needle

The different parts of a latch needle as shown in Fig 3.2 are as follows:(a) Hook, which draws the yarn, makes the loop and retains the same.The top of the hook is called crown

(b) Slot or saw cut on the stem which receives the latch blade

(c) Cheek or slot walls where the latch is riveted

(d) Rivet which fixes the latch on the slot of the needle stem

(e) Latch which moves around its fulcrum for opening and closing ofthe hook

(f) Latch has a spoon or cup at the end which imparts better closing of

the hook

(g) Stem – the main body of the needle

(h) Butt which receives the motion from cam system needed for loopformation

3.1 A latch needle inside cylinder bet trick.

(i) Tail, which is an extension of the stem below the butt, is used for

giving support to the needle inside the trick

Latch needles are mostly used in weft knitting as well as now-a-days inwarp knitting on account of the following advantages

● Needles are robust

● Needles are self-sufficient, i.e no extra element is required for hookclosure Latch moves up and down due to yarn tension

The newly developed spring-loaded latch needles guarantee high processreliability and precise stitch formation The only demerit of latch needles

is that very finer gauge is not possible

3.4 Bearded needle

The different parts of a bearded needle as shown in Fig 3.3(a) are asfollows:

(a) Stem the body of the needle

3.2 Main parts of latch needle.

(b) Head where the stem has been bent to make the hook.

(c) Beard, the flexible hook which can be pushed to the stem for hookclosure

(d) Groove or eye cut into the stem to accommodate the tip of the beard.(e) Shank, the bent bottom portion of the needle for connecting with aseparate machine part

Bearded needles are mainly used in tricot-type warp knitting machine.These needles are available in very finer gauge An additional part calledpusher is needed to close the hook during loop formation

3.5 Compound or bi-partite needle

Compound needles are more versatile and suitable for both weft and warpknitting Out of various types of compound needles, one has been shown

in Fig 3.3(b) It is a modified latch needle The main parts of this needleare as follows:

(a) Hook

(b) Stem

(c) Slot or hole inside the stem

(d) Sliding latch or hook closer

(e) Butt of the needle

(f) Butt or driving attachment of the hook closer

These needles are very robust and durable but can not be made of finervariety Moreover, motions are to be given separately on the needle andthe hook closer; and hence compound needles have very limitedapplications

3.6 Manufacturing and specifications of latch

The manufacturing process with the wire needle is the simplest andmost cost-effective one, while the die-cutting process gives bettertechnical results and imparts greater stiffness to certain sections of theneedle.

A critical feature of all needles is the gauge; it is directly connected tothe strength of the needle which must bear the stress and strain generatedduring the various technical cycles of the knitting process The gauge ofthe needle is directly proportional to the gauge of the machine; the needlemust be neither too thick (if so there would not be enough space between

a needle and the next one for looping the yarn) nor too fine since in thiscase the needle, besides being too weak, could compromise the resistance

of the binding pattern which would result poorly balanced

Table 3.1 shows the gauge of needles according to their thickness(approximate) The values are indicative, as the real value of the needlegauge is only given by the manufacturer’s specifications

The typical “European” specifications for a needle include a word, a

3.3 Main parts of bearded and compound needles.

number (usually a four digit number) and a final combination of lettersand numbers.

For example: Vota 78.60 G.02

The capital letter at the beginning of the word “V” identifies the origin

of the needle (obtained from a wire, pressed or die-cut), the type, thenumber of butts and the type of tail The other letters have a very precisemeaning, except for the vowels “e” and “a” which are added to make theword pronounceable, and indicate the shape and the height of the butt, theeventual existence of a groove and its size, the length of the tail and someother features of the needle The next group of numbers identifies theneedle according to the length and the gauge The first part (78 in theexample) indicates the whole length rounded off to the millimetres (in thepresent context that makes 78 mm); the second part indicates the gauge ofthe needle in hundredths of millimetres (in the example the gauge of theneedle is equal to 0.60 mm) The final group of letters and numbers has to

be read as follows The first capital letter indicates the needle manufacturer(For example, G for Groz-Beckert) The next number is used to distinguish

a specific needle among all the needles, particularly the technique of latchformation, produced by the same manufacturer

The primary knitting element next to needle is the sinker It is a thin metalplate positioned in between the needles The sinkers generally move toand fro in horizontal, i.e at 90° to the direction of movement of needlesand maintain a fixed height The old loops or the cloth falls rest on thesinkers The construction as well as the function of the sinker varies frommachine to machine Sinker is used in both weft and warp knitting incombination with latch needle as well bearded needle Sinkers may beunnecessary when knitting (circular weft) with two needle beds as the

Table 3.1 Needle gauge and needle thickness

Gauge of the Thickness (in mm) Thickness (in inches)

second bed restrain the fabric loops whilst the other set needles move.Sinker may perform one or more of the following functions dependingupon its shape and movement as well as the type of the machine:(a) loop formation, (b) holding down (c) knocking over.

The typical shapes of sinker commonly found in knitting machine areshown in Fig 3.4 The main parts are as follows:

(a) Throat which holds the yarn during loop formation

(b) Belly is the projected portion on which the old loops or fabric rests.(c) Butt which receives motion from a cam system

(d) Neb which prevents the yarns and fabric from moving up

The type of sinker used in circular weft knitting machine is known asholding down sinker, and it performs the following functions

(a) It helps in loop formation by holding or restricting the yarn.(b) It helps in take-down of the fabric by pushing the same after loopformation

The phases of operation of sinker in weft knitting can be viewed as –

● The held loop is positioned in the throat of the sinker when the sinkermoves forward and the needle moves upward for clearing The heldloop is retained by the throat and hence its movement along the needle

● Sinker remains in backward position and the needle descends to itsdown most position drawing the new loop through the old loop

● Before the needle ascends, the sinker moves forward to push theknitted fabric a little and to hold the old loop away from the head ofthe needle and to be in a position to control the fabric

Further the holding down sinkers enable tighter construction withimproved appearance to be obtained, the minimum draw-off tension isreduced, higher knitting speeds are possible and knitting can be commenced

on empty needles

In some modern weft knitting machines (Make: Mayer and Cie andJumberca), the sinkers also move in vertical direction in addition to itshorizontal movement in order to get higher knitting speed which istechnically known as CONTRA or RELANIT system

3.4

3.8 Knitting cam system

For the purpose of loop formation, needles are to move along the needleaxis inside the trick This axial movement of the needles is produced bymeans a cam system or cam profile Generally, a few pieces of cams(metallic plates) make a groove or channel The butts of the needles areplaced inside the channel and the relative displacement of the two forcesthe needles to follow the profile of the cam system According to the camprofile the needles either move up or down or remain idle which are neededfor loop formation There are different types of knitting machines producingdifferent types of structures So the profile of knitting cam system found

in different machines is different The line diagram of the typical shape orprofile of a knitting cam system found in circular single jersey weft knittingmachine is shown in Fig 3.5 The clearing cam (C) forces the needle torise up for clearing of the old loop and the corresponding guard cam (G)controls its rising motion and prevents it from jumping etc After clearing,the needle starts moving downwards under the control of the stitch cam(S) The downward movement of the needle is guided by the up-throwcam (U) As soon as the loop formation is completed by stitch cam theneedle slightly moves up to reach the level from where it started rising.The motion of the needle at this zone is controlled by up-throw cam or bythe yarn tension the needle is subjected to The level of the needle ismaintained by the running cams or guard cams (R) and (R) until the needle

is raised again for the next knitting cycle The position of the stitch camwith reference to the running height of the needles governed by the sinker

or verge level determines the stitch or loop length So for varying the

3.5 Knitting cam in circular single jersey machine.

position of the stitch cam as well as to maintain uniform gap betweenstitch cam and up-throw cam, these two cam pieces are fitted on a commonplatform the position of which can be adjusted by means of a spring loadedsetting knob The clearing cam is sometimes made in such a way so that

it can provide two or three different positions or levels during raising theneedles These positions are clearing, tucking and floating needed fornormal loop formation, tuck loop formation and float or miss loopformation respectively

The cam system found in circular double jersey (cylinder and dial)interlock knitting machine is shown in Fig 3.6 There are two cam tracks

in both the cam jackets The butts of short and long needles pass throughthe upper and lower cam tracks respectively during interlock knitting.However during rib knitting either short or long needles are to be takenout from both dial and cylinder and the working needles will pass throughone track only in each bed In addition the relative positions of the twocam jackets are adjustable for varying knitting timing

The cam systems used in old machines are generally linear in nature

3.6 Knitting cam in circular interlock machine.

An inherent limitation of the linear cams is the sudden change in needlevelocity as the needle but moves from one cam section to another At highercircumferential speed of the needle, the acceleration of needle movement

is so high that the movement of the needle butt becomes uncontrollable,needle but tends to fatigue and break off Replacement of conventionallinear cams by mathematically designed non-linear cams (Fig 3.7) is anattractive solution The various aspects of designing non-linear cam alongwith their performance have been dealt by Black and Munden [1] As pertheir finding properly designed non-linear cam permits smootheraccelerations and gives longer life to the essential components An eight(8) inch diameter commercial single jersey machine fitted with non-linearcam can run at a speed of 200 rpm which is about two times of theachievable speed with conventional linear cam The profile of a typicalnon-linear cam has been shown along with the same of traditional linearcam in order to visualize the difference between the two However theactual profile of the non-linear cam depends upon the boundary conditions

of the polynomial equation chosen for the purpose

3.7 Profile of non-linear and linear cams.

3.9 Knitting action of the latch needle

The knitting action of the latch needle, i.e., the position of a latch needle

as it passes through the cam system and moves up and down in its trickwith reference to the sinker level for completing one knitting cycle, isshown in Fig 3.8 The knitting cycle passes through a large number ofstages as described in the undergoing

i Rest position of the needle (a) The head or crown of the needle is at

a slightly higher level of the top of the verge or sinker The loopformed at the previous feeder or knitting cycle is in the closed hook

ii Latch opening (b) As the needle follows the cam profile, needle is

forced to gradually move up by the clearing cam The old loop which

is held down by the sinker as well as pulled by the take-down load,slides inside the hook, comes in contact with the latch and opens thelatch

iii Clearing height (c) As the needle reaches the top of the clearing cam,

the old loop is cleared from the latch and the latch is hanging down

iv Yarn feeding and latch closing (d and e) The needle starts to descend

under the control of the stitch cam The old loop which slides on theneedle stem comes under the latch At this height new yarn is fed tothe needle and the needle continues downward movement The loopcloses the latch on the hook and rides over the latch The sinkerstarts to move outward

v Casting-off (f) As the needle head approaches the verge or sinker

level, the old loop slides off the needle and the new loop is drawnthrough it The sliding off of the old loop from the needle is calledcasting-off and the old loop is called cast-off loop The sinkercontinues outward movement and allows the old loop to lie on thethroat

vi Loop formation (g and h) The needle with the new loop in its hook

descends further inside the trick and the loop size gradually increases.The needle ultimately reaches the bottom of the stitch cam, i.e., thedown most position and maximum length of yarn is drawn mainlyfrom the package and partly from the previous loop to complete theformation of the new loop The down most point is termed as knittingpoint The sinker starts inward movement

vii Attaining idle position (i and j) The needle with the new loop inside

the hook moves up The Sinker completes the inward movement andpushes the old loops or fabric to assist take-down The needle reachesthe idle position again

During loop formation the sinkers also move to and fro maintainingsame height or level However for the sake of simplicity, the different

positions of the sinker with respect to the needle are not shown in thefigures Only to have an idea of the same the position of the sinker atknitting point been shown in Fig 3.8(k).

3.10 Knitting action of the bearded needle

Like latch needle bearded needle also passes through different stages during

a knitting cycle The different stages of loop formation are shown inFig No 3.9

3.8 Latch needle loop formation cycle.

i Idle position of the needle (a) The head or tip of the needle is at a

slightly higher level of the top of the verge or sinker The loop formed

at the previous feeder or knitting cycle is inside the hook

ii Clearing height (b) As the needle follows the cam profile, needle is

forced to gradually move up by the clearing cam The old loop which

is held down by the sinker as well as pulled by the take-down loadslides inside the hook As the needle reaches the top of the clearingcam, the old loop is cleared from the hook, i.e., it reaches beyond thecontrol of the beard

iii Yarn feeding (c) The needle starts to descend under the control of

the stitch cam The old loop slides on the needle in upward direction

At this height new yarn is fed to the needle and the needle continuesdownward movement

iv Hook closing (d and e) The pusher or presser bar comes in contact

with the beard and closes the hook so that the old loop sliding on theneedle stem now can ride over the beard

v Casting-off (f) As the needle head approaches the sinker or verge

level, the old loop slides off the needle and the new loop is drawnthrough it The pressure bar is withdrawn The sliding off of the oldloop from the needle is called casting-off and the old loop is calledcast-off loop

vi Loop formation (g) The needle with the new loop in its hook descends

further inside the trick and the loop size gradually increases Theneedle ultimately reaches the bottom of the stitch cam, i.e., the downmost position and maximum length of yarn is drawn to form the loop.This is termed as knitting point

vii Idle position (h) The needle with the new loop inside the hook moves

up Sinker pushes the old loops or fabric to assist take-down Theneedle attains the idle position again

The author has consulted in general and taken help of the following booksfor preparing the text and necessary diagrams in addition to the Journalsreferred in different chapters to make his dream successful for the greaterinterest of the student community in the field of textile technology andmany others who find interest to read this book.

An Introduction to Weft Knitting, J A Smirfitt, Merrow Publishing Co Ltd.,England

Circular Knitting, C Iyer, B Mammel and W Sehach, Meisenbach BambergFlat Knitting, Samuel Raz, Meisenbach GmbH, Bamberg

Handbook of Technical Textiles, A R Horrocks & S C Anand, WoodheadPublishing Limited, Cambridge in association with The Textile Institute,Abinton

Knitted Fabric Production, Prof P K Banerjee, Department of TextileTechnology, I I T., Delhi

Knitting – Reference Books of Textile Technologies (e-book), Carmine M &Paola Z., Fondazione, ACIMIT, Milano, Italy

Knitting : Fundamentals, Machines, Structures and Developments, N.Anbumani, New Age International Publisher, New Delhi

Knitting Technology, David J Spenser, Woodhead Publishing Limited,Cambridge, Pergamon Press

Knitting Technology, Prof D B Ajgaonkar, Universal Publishing Corporation,Mumbai

Warp Knitting Production, Dr S Raz, Verlag Melliand Textilberichte GmbH,Heidelberg

Warp Knitting Technology, D F Palling, Columbine Press (Publishers) Ltd.,Buxton, U.K., 1970

Wellington Sears Handbook of Industrial Textiles, S Adanur, TechnomicPublishing Co Inc., Lancaster, Pennsylvania, USA

4 General terms in weft knitting

Abstract: The general terms related to loop formation in weft

knitting have been explained in the chapter Types of loop, loopparts and loop notations are shown The conditions of forming tuckand float loops are also explained

Key words: machine gauge, face loop, back loop, course; wale,

stitch density, loop length, stitch notation

4.1 Machine pitch and gauge

Both these terms are related to the density of needles in each bed of themachine Machine pitch (needle pitch) is defined as the distance betweenthe centres of two neighbouring needles in one needle set measured on thenominal machine diameter or width Although both English and Metricunits can be used, generally metric unit, millimetre, is preferably used toindicate the pitch of any knitting machine Machine gauge is also defined

in various units (systems) in various countries Definition of gauge alsodepends on the types of knitting machines Most popularly, it is defined inEnglish system as the number of needles per inch So the relationshipbetween these two parameters can be expressed as follows:

Pitch in mm =

[Nominal machine circumference (diameter × 3.14)

or width × 25.4]

No of needles in the machine

= (25.4 / Machine gauge in English system)

or Pitch in mm × Machine gauge in English system = 25.4

The selection of yarn (count and type) for knitting mainly depends onthe gauge of the machine

Loop means a shape produced by a curve that bends round and crossesitself In knitting it is the basic unit of a knitted structure It is produced