Contents of Weaving Technology

Contents of Weaving Technology 1 WEAVING PREPARATION 2 MECHANISMS OF a LOOM 33 BASIC WEAVING OPERATIONS 44 WOVEN FABRIC DESIGN 5 WOVEN FABRIC CONTROL INTRODUCTION Woven fabrics are composed of two sets of yarns, called warp and weft, and are formed by the interlacing of these sets of yarns. In a woven fabric, the lengthwise yarns, which run from the back to the front of the loom are called the warp or end. The crosswise yarns are the weft, also referred to as the pick. The weft yarns undergo less strain in the weaving process than warp yarns. Warp Weft INTRODUCTION Brief History of Weaving Weaving is the action of producing fabric by interlacing warp and weft yarns at right angles to each other. This action can be produced on a frame, hand loom or automatic loom. REF: http://commons.wikimedia.org/wiki/File:C%2BB-Weaving-Fig1-BeniHasanWeavingDepiction.PNG REF: http://blog.needsupply.com/2013/01/30/a-brief-history-of-weaving/ REF: http://www.itemausa.com/weaving-machines.php WEAVING PREPARATION After spinning, the yarn must be processed through several steps to prepare it for use in the loom. These steps are very important for successful weaving, and must be done properly from both efficiency and quality standpoints. Yarn Preparation Objectives Filling Yarns • Yarn must be wound on a suitable package properly for high speed unwinding Warp Yarns • Form supply package • Yarn strength must be increased • Yarn hairiness must be decreased • Yarn smoothness must be increased • Yarn elongation and flexibility must be sustained WEAVING PREPARATION You cannot start weaving operation imedeately after yarn production. In order to start weaving operations, some preparations needed to be fulfilled. Weft Yarns Warp Yarns Winding Winding Warping Quilling (For Shuttle Loom only) Slashing (Sizing) Drawing-in Tying-in WEAVING PREPARATION Winding Section Winding is the first stage in the weaving preparation Both weft and warp bobbins are prepared in the winding section. Winding is the process of transferring a yarn from one package to form another package that is more suitable for subsequent processing of the yarn. Winding is carried out for the following purposes 1 To change the type of package 2 To change the package density 3 To remove yarn faults After Winding; the weft bobbins are supplied directly to the weaving mill the warp bobbins are further treated in the warping section. WEAVING PREPARATION Warp Yarn Preparation Warping An operation where yarn is transferred from single packages of yarn to an even sheet of yarn representing hundreds of ends and then wound onto a warp beam. The purpose of warping is to arrange a convenient number of warp yarns so that they can be collected on a single warper’s beam. There are two main types of warping: (a) beam warping and (b) section warping. •Creels, i.e. apparatus for supplying a multiplicity of individual threads •Even tension for all warp threads •Accurate compliance with pattern •All warp threads must be of the same length •The width of the warp must match the length of the weaving reed beam warping sectional warping WEAVING PREPARATION Warp Yarn Preparation Sizing During the process of weaving, warp yarns are subjected to considerable tension together with an abrasive action. The warp yarns may break during the process of weaving due to the complex mechanical actions consisting of cyclic extension, abrasion, and bending. 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 WEAVING PREPARATION Warp Yarn Preparation Drawing-in This is the process of drawing every warp end through its drop wire, heddle eye and reed dent. WEAVING PREPARATION Warp Yarn Preparation Tying-in When mass production of the same fabric will be produced; then, by simply tying each end of a new beam to its corresponding end of the old beam is sufficient BASIC WEAVING OPERATIONS Beating up Shedding process mechanism Dobby system Picking mechanism Back rest weaves influence Machine operating back rest setting Warp stop speed - horizontal motion - vertical Breast bar Sand roller Warp Let- Warp beam off motion Warp tension Cloth Take-up Cloth beam range motion preselection, Weft sett [cm-1] Warp tension Weft sett approximatio correction 0.1 n weft density crimp influence influence, MECHANISMS OF a LOOM Shedding Mechanisms All weaving machines control the warp yarns to create a shed. This can be accomplished with the following systems: • Cam shedding or tappet shedding • Dobby shedding • Jacquard shedding Crank, cam and dobby mechanisms control the harnesses which lift the shafts. Jacquard machines control the individual warp yarns. Each system is outlined below: MECHANISMS OF a LOOM Shedding Mechanisms Link: http://www.youtube.com/watch?v=s0W0iDj7_hc MECHANISMS OF a LOOM Shedding Mechanisms Dobby Shedding Dobby shedding is more complex than crank and cam systems. The main advantage of dobby looms is that more intricate designs can be produced. Older dobby looms were operated by wooden lags with pegs, which rotated around a roller above the loom. The pegs in the lags correspond to the lifting plan, which controls which harnesses are lifted. Punched paper or plastic pattern cards can also be used. Recently modern dobby looms are controlled via an electronic system. The disadvantage of dobby systems is that faults are more likely to occur due to the complexity. MECHANISMS OF a LOOM Shedding Mechanisms Jacquard Shedding In jacquard weaving a device called a ‘jacquard’ selects and lifts the warp yarns individually. This type of machine is used for larger more detailed patterns, where all or most of the yarns in a repeat, move independently. There are single or double lift machines which use either mechanical or electronic systems, using CAD to control the harness lifting and lowering. Modern jacquards are capable of handling over 1200 harness cords which control the lifting and lowering of the warp yarns. REF: http://nptel.ac.in/courses/116102005/28 MECHANISMS OF a LOOM Weft Insertion Methods Shuttle MECHANISMS OF a LOOM Weft Insertion Methods Rapier: MECHANISMS OF a LOOM Weft Insertion Methods Projectile: Projectile machines carry yarn through the shed using a small bullet shaped object known as a ‘projectile’. This process can occur in the following ways: 1. A single projectile is fired from each side of the machine alternately and requires a bilateral yarn supply. 2. A yarn supply from one side of the machine is presented to the projectile. It carries the weft yarn across the machine and is then transported back to the other side by a conveyor belt. Several projectiles are in use at the same time to enable rapid pick insertion. Pick insertion rate can be up to 1300m min-1. MECHANISMS OF a LOOM Weft Insertion Methods Air jet: In air-jet weaving machines the filling yarn is inserted pneumatically. It is carried through the shed by compressed air flow supplied from a main nozzle and relay nozzles. This is the fastest type of weaving enabling pick insertion of 3000 m min-1. Water jet: Water jet weaving is the same principle as air jet weaving, water is used instead of air and a similar speed is achieved. One disadvantage is that only hydrophobic yarns can be used WOVEN DESIGN The design indicates the interlacement of warp and weft threads in the repeat of the design. It is made up of a number of squares, which constitute the repeat size of a design. The vertical direction of the squares indicate the picks and the horizontal direction indicates the ends. A blank in a square indicates that a warp goes below the corresponding weft and ‘X’ mark in the square or filled square indicates that the warp floats above the weft. WOVEN FABRIC DESIGN Plain Weave Twill Weave Satin Weave PLAIN WEAVE - It is the simplest of all weaves having a repeat size of 2. The range of application of this weave is wide. TWİLL WEAVES - are the weaves that find a wide range of application. They can be constructed in a variety of ways. The main feature of these weaves that distinguishes from other types is the presence of pronounced diagonal lines that run along the width of the fabric. SATIN WEAVES - Satin is a warp faced and sateen is a weft faced weave. Thus satin is the reverse side of sateen weaves. Use of move numbers (intervals of selection) is necessary to construct these weaves. WOVEN FABRIC CONTROL Classification of woven fabric - Yarn Faults Following faults cause problems on loom and are noted in the quality assurance forms..

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