Fundamentals of yarn winding

Transcription

1 Fundamentals of yarn winding

2 Fundamentals of yarn winding Milind Koranne WOODHEAD PUBLISHING INDIA PVT LTD New Delhi l Cambridge l Oxford l Philadelphia

3 Published by Woodhead Publishing India Pvt. Ltd. Woodhead Publishing India Pvt. Ltd., 303, Vardaan House, 7/28, Ansari Road, Daryaganj, New Delhi , India Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge, CB22 3HJ UK Woodhead Publishing USA 1518 Walnut Street, Suite1100, Philadelphia First published 2013, Woodhead Publishing India Pvt. Ltd. Woodhead Publishing India Pvt. Ltd., 2013 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission. Reasonable efforts have been made to publish reliable data and information, but the authors and the publishers cannot assume responsibility for the validity of all materials. Neither the authors nor the publishers, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing India Pvt. Ltd. The consent of Woodhead Publishing India Pvt. Ltd. does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing India Pvt. Ltd. for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Woodhead Publishing India Pvt. Ltd. ISBN: Woodhead Publishing Ltd. ISBN: Woodhead Publishing Ltd. e-isbn: Typeset by Lalit Mohan Rawat, New Delhi Printed and bound by Replika Press Pvt. Ltd.

4 Preface Phenomenon of winding delivered yarn is observed at various stages of textile production such as winding at weaving preparation, soft dye package winding, rewinding of soft dye packages/ left over packages from warping creels, assembly winding prior to twisting, winding at unconventional spinning machines for taking up spun yarn, yarn singeing, single end sizing, take up winding at spinning lines of synthetic yarns, yarn texturising, sewing thread finish winding, winding of string wound filter cartridges etc. Technical developments in winding systems are taking place to offer new possibilities in package building. Efficient utilization of such technologies demands thorough understanding of various winding related aspects. This book intends to highlight on fundamental aspects of yarn winding in a broader perspective. The book contains eight chapters focusing on a range of topics on yarn winding. The first chapter introduces yarn winding as a weaving preparatory process. Basics of building winding packages are explained in second chapter clarifying frequently used winding related terminologies like random winding, patterning, precision winding, gain, open wind, close wind, head wind, after wind etc. Principles of various random, precision and step precision winding systems are covered in third chapter along with basic mathematics involved. The part of mathematics of Chapter 3 is based on author s fundamental understanding, research experience and interaction with the industries. There are diverse end uses of wound packages, each having its specific requirements. These can be achieved through optimal selection of various parameters related to package build which are discussed in Chapter 4. Chapter 5 is dedicated to various measures on winding machines employed to maintain optimum yarn tension during winding. Significance of yarn clearing and various yarn clearing devices are discussed in Chapter 6. The same chapter includes a detailed note on yarn splicing. Chapter 7 describes various methods of package driving and yarn traversing on winding machines. Various winding package faults and their remedies are discussed in Chapter 8. For ease of understanding, the text is supplemented by various self explanatory labeled diagrams and photographs. Main features of the latest

5 generation of winding systems of leading manufacturers are also included in the book. It is hoped that this book will prove to be a useful reference for students, academicians, textile technologists as well as persons from other engineering disciplines like chemical, mechanical, electrical, electronics, instrumentation and computer dealing with winding systems. I apologize in advance for any errors and omissions in the content and hope that there would be an opportunity later to rectify them. Milind Koranne milvako@yahoo.co.uk

6 Acknowledgements My sincere gratitude and thanks are due to all individuals and organizations that have directly or indirectly supported me in publication of this book. I would express my sincere gratitude to the following: Mr. Jean-Claude Alleman, Head, Textile Technology, SSM, readily shared his expertise and vast experience; and took pains to reply all my queries on various aspects of winding. Interaction with Mr. Jean-Claude Alleman has immensely helped in enriching the book content. Mr. Horst Luechinger, Director Sales Asia and Mr. A. T. Narayanan, General Manager, India, of SSM provided the necessary help. Mr. Thomas Elsener, Marketing Service of SSM took pain to provide me with all photographs I asked for. Dr.-Ing. Ansgar Paschen, Manager, Research & Development Textile Technology and Mr. Peter G. Gölden, Senior Manager, Textile Technology of Oerlikon Schlafhorst, Germany furnished valuable information on technical aspects of their range of Automatic winding machines. Mrs. Heike Scheibe provided with a wide range of photographs related to Oerlikon Schlafhorst range of products I required. Mr. Umang Kothari, National Manager (Service) and Mr. A. T. Kumar, Manager (Product Management) from Oerlikon Textile (India) Pvt. Ltd. readily interacted with me regarding various aspects of their range of products. Mr. K. C. Panchal. Assistant Manager (Service) of the same company provided required information source of Schlafhorst range of winding machines and discussed various technical aspects personally. Mr. S. J. Chokshi, General Manger CSS of Loepfe brothers provided information about Loepfe range of products. Mr. Nellaiappan, Head Product Support, from Uster Technologies (India) Private Limited provided the necessary information about Uster range of products. Mr. Bhargav Patel, Executive director, Mr. R. G. Yadav, GM (mfg), Mr. Ashok Singh, Dy. Mgr. (Electronics) and Mr. Anthony Francis Dy. Mgr. (Design) of Peass Industrial Engineers Pvt. Ltd. were always eager to extend me all kind of support and necessary information about products of their company. Mr. Pankaj Desai, General Manager, Fadis India helped in getting all necessary photographs of range of Fadis make machines along with necessary permission. Mr. Mrunal

7 Kansara, MD of NIF Mechanical Works Pvt. Ltd. permitted to publish the photographs and information of various winding drums manufactured by his company. I am extremely thankful to all other individuals/ organizations that have provided required photographs along with necessary permission. My wife Seema Koranne and daughter Trusha Koranne have always supported me during write up of this book. I have been able to write this book due to encouragement and support from my Professors, colleagues and technical staff at Textile Engineering Department of Faculty of Technology and Engineering, The M.S. University of Baroda. I am aware that it has not become possible to acknowledge full list of individuals and organizations due to space constraint. Milind Koranne

8 Winding as a weaving preparatory process 1 Yarn winding is an integral part of many textile production activities such as spinning, weaving, synthetic yarn manufacturing, etc. This chapter describes various weaving preparatory processes very commonly practiced where yarn winding is involved at some stages. 1.1 Weaving introduction In a woven fabric the lengthwise yarns forming the basic structure of the fabric are called the warp threads or ends and the widthwise threads are called the weft threads or picks or fillings. A woven fabric is produced through repeated cyclic process of shedding, picking and beating (Fig. 1.1). Figure 1.1 Weaving cycle For weaving the fabric, usually weaving machine (also known as loom) is required to be supplied with a weaver s beam which consists of thousands of warp threads wound on a weaver s beam in sheet form. Weaver s beam may be supplied to loom with warp threads which are already drawn through the heald shafts and dented through reed (with drop wire warp stop motions threading through drop wires may be additionally required) as shown in Fig. 1.2.

9 2 Fundamentals of yarn winding Figure 1.2 Warp supply on loom Form of weft supply on loom depends upon picking system. (a) For shuttle looms weft is wound on pirns. The pirn fits into a shuttle. The shuttle is projected into the shed. So, supply of weft is in the form of pirn wound with weft as shown in Fig Figure 1.3 Pirn in a shuttle Figure 1.4 Weft supply packages in creel of a shuttle-less loom (Courtesy: Picanol)

10 Winding as a weaving preparatory process 3 (b) For shuttle looms fitted with Unifil loom winder, pirn winding is done by a special mechanism on loom itself. So supply of weft is in form of packages such as cones or cheeses. (c) For looms in which insertion of weft is carried out without the use of the shuttle are called shuttle-less looms. In these looms (generally) weft insertion takes place from one side of the loom. The weft is withdrawn from the packages such as cones or cheeses and inserted into the shed by some carrier (gripper, rapier, air jet or water jet). Figure 1.4 shows a shuttle-less weaving machine with weft supply packages. Weaving productivity is influenced by quality of warp and weft supplied to loom. Poor quality of warp and weft causes frequent breakages which hampers fabric quality and loom productivity. Better performance in weaving cannot be realized with poor quality of warp and weft. 1.2 Quality requirements of warp and weft threads Broadly, a quality warp fulfils the following requirements: (1) To produce fabric of uniform quality, the tension of warp threads across the width of the cloth as well as along the weaver s beam should be as uniform as possible. (2) Warp threads should be free from places which are likely to cause breakages during weaving or hamper fabric appearance, such as a weak place can cause breakage during weaving. a thick place can cause breakage (Fig. 1.5) and give bad appearance in fabric. A thin place can cause bad appearance. Particularly, thinner place continuing over a long length, say 1m or 2m, will give bad appearance; as in that portion a fine crack-like appearance would be seen. (3) During weaving warp threads are kept under considerable tension and are subjected to the abrasive action of the healds, reed, and other moving parts and also of the neighboring warp threads. At heald eye an end is subjected to bending (flexing) and rubbing. To and fro movement of reed causes abrasion of reed dents with warp threads. At beat up the warp threads are subjected to sudden stress. Shed formation causes strain on warp threads. Therefore the warp threads should be strong enough to resist these actions without breaking.

11 4 Fundamentals of yarn winding Figure 1.5 Harm caused by thick places Broadly, quality weft fulfils the following requirements. As explained earlier, pirns or packages such as cones or cheeses can be weft supply packages. These packages should be built so as to give troublefree unwinding during weaving. The weft thread should also be free from any places which are likely to cause break during weaving or hamper fabric appearance. 1.3 Weaving preparatory processes The yarn received from spinning department is usually in the form of ring frame bobbins. To weave this yarn on loom, it must be converted into required form, i.e. warp and weft. The intermediate processes between spinning and weaving on loom employed to convert the yarn received from spinning department into suitable form that is required for weaving are called weaving preparatory processes. The processes converting yarns from spinning department into suitable warp form are called warp preparatory processes and into required weft form are called weft preparatory processes Warp preparatory processes The sequence of processes depends upon the type and quality of yarns, the type of fabric to be produced, and also on the equipment and other facilities

12 Winding as a weaving preparatory process 5 Figure 1.6 Warp preparatory processes available in the mill. The process flow chart is shown in Fig. 1.6 which shows the various stages of warp preparation. The solid lines indicate the basic process most commonly used and the dotted lines indicate some additional processes required for different types of fabrics. In winding, yarn from a number of ring frame bobbins or hanks is transferred in a long continuous length onto bigger packages such as cones or cheeses (Fig. 1.7). Some places in the yarn are likely to cause breaks in subsequent processes or hamper fabric appearance which are called yarn faults. Winding machine carries yarn clearer that breaks yarn at yarn faults. Faulty yarn portion is cut away and the yarn ends are rejoined. To introduce colored threads in warp or weft, it becomes necessary to dye yarn. Yarn dyeing can be done in any one of these three forms: hank/ muff, package (cone/ cheese) or warper s beam. If hanks are acquired from spinning department, they can be taken for hank dyeing. If ring frame bobbins are supplied from spinning department, usually yarn is wound onto bigger packages (cones/cheeses) eliminating yarn faults. Subsequently, hanks are obtained from these bigger packages on a reeling machine. Figure 1.10(a) shows photograph of a hank reeling machine. These hanks are dyed. A muff is

13 6 Fundamentals of yarn winding Figure 1.7 Autoconer X5 winding machine (Courtesy: Oerlikon Schlafhorst) Figure 1.8 Package dyeing (Courtesy: Ashima) Figure 1.9 Beam dyeing (Courtesy: Ashima) also a loose package like a hank without any supporting tube. This form of the package is used mainly for yarns with high shrinkage during dyeing. A muff is produced on a special winding machine. Dyed hanks/muffs are taken to a hank/muff to cone winder to obtain dyed cones/cheeses. For package dyeing, yarn from ring frame bobbins is usually wound onto bigger packages (cones/ cheese) eliminating yarn faults. These bigger packages are taken to a soft dye package winder which produces soft packages suitable for package dyeing. These soft packages are subjected to dyeing (Fig. 1.8). These packages being soft are not suitable for high speed unwinding.

14 Winding as a weaving preparatory process 7 Therefore, they are taken to a rewinding machine to produce compact packages suitable for subsequent processes. Yarn may be dyed in beam form, which is produced on direct warping machines. Figure 1.9 shows beams dyed in a beam dyeing machine. The object of direct warping (Fig. 1.10b) is to collect yarns from number of single end packages (winding packages from which a single thread is delivered on unwinding) mounted on a warping creel, convert into sheet form with ends uniformly spaced, and wind a specified length onto warper s beam. The warper s beam so obtained is a multi-end package (multiple ends are delivered on unwinding). The warper s beams for beam dyeing are soft wound and smaller in diameter with perforations to allow dye liquor flow. Figure 1.10 (a) Hank reeling machine (Courtesy: Fadis) (b) Direct warping machine (Courtesy: Prashant Gamatex) In sectional warping hundreds of warp threads are collected from creel. These threads are passed through a reed to form a narrow warp sheet with warp spacing closer to what is required on weaver s beam. Several sections of predetermined length of this sheet are wound on a large diameter drum (which is usually tapered at one end) side by side. Figure 1.11 shows a

15 8 Fundamentals of yarn winding Figure 1.11 Sectional warping machine (Courtesy: Prashant Gamatex) sectional warping machine. Subsequent stage is beaming in which ends from all sections are collected and wound onto a weaver s beam. Thus, at the end of the process, weaver s beam is obtained which may be sent to loom or for drawing-in. Warp threads are subjected to considerable stresses, strains, flexing and rubbing action during weaving. So warp threads are impregnated with size, whose main constituent is an adhesive substance. The size binds the constituent fibres in the yarn as well as forms a coating on yarn surface so Figure 1.12 Sizing machine (Courtesy: Prashant Gamatex)

16 Winding as a weaving preparatory process 9 Figure 1.13 Manual drawing in and denting that it can withstand stresses, strains, flexing and rubbing actions of weaving without breaking. At the back of sizing machine, warp sheets from number of warper s beams are combined to obtain a single sheet containing required number of ends for weaving. This sheet is impregnated with size, dried and wound on a weaver s beam. When beam from sectional warping is a supply package on sizing machine, it is called beam to beam sizing. Figure 1.12 shows a sizing machine. Thus, at the end of sizing, weaver s beam is obtained which may be sent for drawing-in and denting or directly to loom for end-to-end joining. The process of drawing in and denting consists of passing ends of warp sheet of weaver s beam through heald eyes of the heald shafts and through dents of reed, respectively. With drop wire stop motions additional operation of pinning may be involved. Figure 1.13 shows manual drawing in and denting. Automatic drawing in and denting machines are also available and used. On loom, if exactly the same fabric is to be reproduced after a weaver s beam is exhausted, warp threads of the new sheet are joined end by end with the old sheet. This operation is called tying-in or twisting depending upon the method of joining. Knotting machines are available to join the ends of exhausted beam and new beam one by one (Fig. 1.14). Thus, this process needs only weaver s beam wound with warp as a warp supply. But if other

17 10 Fundamentals of yarn winding Figure 1.14 Warp tying machine for end to end joining (Courtesy: Jaytex) variety of fabric is to be produced, a weaver s beam with warp threads drawn and dented is required. Old beam with its heald shafts and reed are removed and a new beam with its heald shafts and reed are reset on the loom. Figure 1.15 Weft preparatory processes

18 Winding as a weaving preparatory process Weft preparatory processes Figure 1.15 shows flow chart of weft preparatory processes. Flow chart is the same up to winding/rewinding. (In olden days, the end packages of weft ring spinning frames were directly used in the shuttle where no additional weft preparatory process was involved. This type of weft is known as direct weft). The yarn from bigger packages (cone/cheese or warper s bobbin from which objectionable faults are removed/ may be dyed) is wound on to pirns on pirn winding machines. These pirns are supplied to shuttle looms. The winding packages (cone/cheese) are supplied to automatic shuttle looms fitted with Unifil loom winder and shuttle-less looms (such as gripper, air jet, water jet or rapier). Unconventional spinning machines like OE spinning produce bigger packages which may be directly supplied as weft on shuttle-less weaving machines.

19 2 Basics of package building Yarn winding is basically a process of deposition of delivered yarn to form a suitable package that can meet requirements of its subsequent process. This chapter discusses some basic aspects related to package building. 2.1 End packages produced on winding machines Winding packages, which are very commonly used, can be divided into two groups: Parallel wound packages Cross wound packages Parallel wound packages Parallel wound packages are double-flanged bobbins, also known as warper s bobbins (Fig. 2.1a). Yarn is wound on these packages in such a way that the laid coils are almost parallel to one another. These packages were widely used in olden days. These packages may be built with parallel faces (Fig. 2.1b) or with bulging faces forming a barrel-shaped bobbin (Fig. 2.1c). Figure 2.1 also shows a winding machine with double-flanged bobbins. Flanges are needed on either side to support parallel laid coils. Without flanges, coils at the two ends would collapse. For given dimensions of a bare package, barrel-shaped bobbin accommodates more yarn. To withdraw the yarn from these packages, usually package has to be rotated by pull of yarn. Hence, high unwinding speed leads to excessive unwinding tension causing yarn break. When unwinding is stopped, the package continues to rotate due to its inertia and, therefore, yarn may continue to come out from package. Hence, this package is not suitable as a supply package where high speed unwinding takes place. These packages are usually used for yarns which do not form a stable cross wound package, like monofilament yarns.

20 Basics of package building 13 Figure 2.1 Parallel wound packages (Courtesy: Fadis) Cross wound packages To build a cross wound package, the supporting tube required is usually cylindrical or conical. The yarn is laid on the package in form of helices which reverse at extremes. Figure 2.2 shows how yarn is laid in form of helices on cylindrical or conical packages. Figure 2.2 Cross winding on packages

21 14 Fundamentals of yarn winding In this type of winding, the yarn wraps cross one another and therefore these packages are called cross wound packages. Because of reversal of helices at the extremes, usually there is no possibility of yarn coils collapsing at the two extremes. Hence these packages do not need flanges. The cylindrical cross wound package is commonly known as a cheese and the conical one as a cone. Figure 2.3 Over end withdrawal The yarn is usually withdrawn from cone and cheese over end (also known as nose unwinding). In over end unwinding, package remains stationary and yarn is pulled though a stationary yarn guide located on the package axis. The over end withdrawal allows unwinding at high speeds. As rotation of package during unwinding is not essential, yarn stops leaving the package almost at the same instant when withdrawal is stopped. Figure 2.3 shows over end withdrawal or nose unwinding from a cone and a cheese. Over end withdrawal adds or subtracts one twist from the delivered yarn which is not desired for some yarns. These packages are also suitable for side unwinding which is carried out for such exceptional cases. 2.2 Some definitions related to cross wound packages It is very essential to understand some definitions related to cross wound packages before understanding the basics of yarn laying. (a) Cone taper or semi-vertical angle Cone taper or semi-verticle angle is defined as the angle between the side of the cone and its axis as shown in Fig Cone taper generally ranges between 0 (cylindrical package) and Figure 2.4 Cone taper

22 (b) Wind Basics of package building 15 Wind is defined as the number of coils laid on a package in a single traverse (i.e. winding of the yarn from one end to other). As shown in Fig. 2.5(a), during traverse from left to right, i.e. from point A to C, 1.25 coils are laid. Hence wind at that diameter of the cheese is 1.25 ie or 4 4. Figure 2.5 Package wind and traverse ratio (c) Traverse ratio / crossing ratio / winding ratio Traverse ratio / crossing ratio / winding ratio is defined as the number of coils laid on the package during double traverse of the same wind point. As shown in the Fig. 2.5(b), yarn laying from A to C completes one single traverse. Moving from point C to E completes a double traverse. During this, 2.5 coils are laid during a double traverse [(A B = 1 coil) + (B C = 1/4 coil) + (C D = 1 coil) + (D E = 1/4 coil)] and hence traverse ratio is 2.5 ie or 2 2. (d) Coil angle or angle of wind It is defined as the angle f between instantaneous direction of yarn laid on the package and any plane perpendicular to package axis (Fig. 2.6a). This angle would be taken as coil angle in this book and would be used. (In some literatures, this angle is also called helix angle or winding angle). (e) Complimentary angle It is the angle (90 f), i.e. angle between instantaneous direction of yarn laid on the package and any plane parallel to package axis. Sometimes this angle is defined as the coil angle. (f) Crossing angle It is the angle at which yarn coils cross each other. Crossing angle is twice coil angle (Fig. 2.6 b).

23 16 Fundamentals of yarn winding Figure 2.6 Coil angle and crossing angle (A unique terminology and definition of angle at which yarn is laid is not used in all literatures. Therefore, its definition must be understood before going through any literature). 2.3 Traverse acceleration In case of a cheese, the surface area available for winding the yarn is same across the width of package due to uniform diameter. In case of cone the situation is different. The surface area available to wind the yarn decreases from base to nose as shown in Fig. 2.7(a). If two strips of same width at different diameters on cone are taken (Fig. 2.7b), and yarn is wound with same coil angle at both the strips then length of yarn crossing both the strips would be the same. Length wound across both the strips is same but area of strip towards base of the cone is greater than area of strip towards nose of the cone. So, taking into account amount surface area available, quantity of yarn deposited on strip towards nose is greater than that towards base. Upon continuing winding this way, the package diameter would build at greater rate towards nose than at base as Figure 2.7 Winding on a conical package

24 Basics of package building 17 package. This leads to non-uniform build up for cone as shown in Fig. 2.7(c) which is not desirable. To achieve uniform built up of cone, the length of yarn laid in given region of cone should be proportional to the area available to accommodate the yarn. If A 1 and A 2 are areas of strips at two locations along the length of the cone and L 1 and L 2 are yarn lengths crossing these strips respectively, then, L1 = A 1 L2 A2 \ L 2 = LA 1 2 A1 To shorten the length of yarn crossing the strip towards nose of the cone, coil angle should be kept greater than that at strip towards the base of the cone (Fig. 2.7d) so as to achieve uniform build up of cone (Fig. 2.7e). Speed of yarn traverse in relation to rotational speed of the package at given diameter influences coil angle. Faster the traverse speed greater is the coil angle and vice versa. In cheese winding as same coil angle is to be kept across the length of the package at given diameter, yarn need to be traversed at uniform speed from one end of the package to the other, i.e. acceleration is not involved. But in case of cone winding, to achieve uniform build up, coil angle should be increased from base to nose. Putting this in simple terms, yarn traverse speed must be increased from base towards nose and vice versa. Thus acceleration is involved in yarn traverse speed which is called accelerated traverse. In this way an accelerated traverse is required for cone winding, especially, with higher cone taper. Cone is preferred over cheese due to greater freedom of withdrawal. Because of conical shape, yarn can leave the package during unwinding with greater ease due to lesser chances of yarn getting dragged over the surface of the cone. But if the freedom of withdrawal of a full cone and an empty cone is compared, it is obvious that the chances of yarn dragging over the face of the cone are greater at bigger cone diameter than at smaller one (Fig. 2.8a). The phenomenon of yarn ballooning, i.e. yarn leaving the package is thrown away Figure 2.8 Foster cone

25 18 Fundamentals of yarn winding from the package surface, reduces the chances of yarn getting dragged against face of the package. But the intensity of ballooning depends upon unwinding speed and yarn linear density. At higher unwinding speeds and with coarser yarns, as yarn leaves the package, it is thrown away from the surface with higher intensity than that at very low unwinding speeds. Therefore, there are more chances of yarn getting dragged with the face of the package at slower unwinding speeds than that at higher speeds of unwinding. In an application like knitting, unwinding speeds are lower and an intense balloon is not formed. It is desired that yarn should leave the package with same freedom at all diameters of package. To maintain same ease of withdrawal, cone may be built purposefully in such a way that cone taper keeps on increasing from an empty to full cone. Hence during winding, yarn is laid in such a way that length of yarn laid in comparison with the area availability is more towards base than nose. So cone taper keeps on increasing as the cone builds up (Fig. 2.8b). To build such cone, yarn would be traversed much slower at base and faster at nose compared to uniform build up of cone. Hence acceleration involved in traverse would be greater. Therefore, traverse for cone for uniform build is called half-accelerated traverse while that with increasing taper is called fully accelerated traverse. A cone built up with increasing taper is called foster cone. 2.4 Building a cross wound package For building cross wound packages, two approaches can be thought: Building a package keeping constant traverse ratio throughout package build Building a package keeping constant coil angle throughout package build. For ease of understanding, winding of only cylindrical packages is discussed here Building a package with constant traverse ratio throughout package build Let a package be built with constant traverse ratio of 2 throughout its build. As shown in Fig. 2.9(a), one coil is laid in a single traverse moving from left to right and the other coil is laid while moving from right to left. Therefore, at the end of the double traverse, yarn arrives at the same point from where the laying was begun. If winding is continued, the yarn coils of second double traverse would be overlapped on coils of first double traverse. On further continuing winding, successive warps of double traverse will be laid

26 Basics of package building 19 exactly on top of one another and will form a thick ribbon or pattern. This phenomenon is called patterning or ribboning. The yarn will not be uniformly distributed on the surface of the package and therefore a satisfactory package would not be obtained. Thus, with constant traverse ratio of two, a satisfactory package would Figure 2.9 Package building with same traverse ratio not be built. Let us take case of package winding with a constant traverse ratio 3 (Fig. 2.9b). In this case too, the starting point of yarn after a double traverse comes out to be at the same place after a double traverse leading to pattern formation with yarn coils wrapping over one another. With traverse ratio of 2.5, the wraps of yarn will be laid on top of each other after completion of two double traverses as shown in Fig (a). Figure 2.10(b) shows coils viewed from side of the package. In this case yarn coils of every alternate double traverse would get overlapped on one another forming ribbons. Figure 2.10 Winding with traverse ratio 2.5 Thus, a constant traverse ratio of 2.5 is also not suitable for winding. The situation of winding with constant traverse ratio of 2.25( 2 1 ) is shown 4 in Fig. 2.11(a). If winding is started at say point A at left, yarn reaches the right end at point B laying (1 1 ) coil. From right side it reaches on left 8 side at point C at the end of first double traverse. Thus, starting point of yarn

27 20 Fundamentals of yarn winding on a face shifts through 1 4 rotation (from A to C, i.e. though 90 ). With shift of 1 4 rotation every double traverse, yarn would reach the same place after 4 double traverses, i.e. every 1 st, 5 th, 9 th... wraps of double traverses would be laid on top of one another. Similarly every 2 nd, 6 th, 10 th., 3 rd, 7 th, 11 th. and 4 th, 8 th, 12 th. wraps of double traverses would be laid on top of Figure 2.11 Winding with different traverse ratios one another. There would be only four starting points on the circumference on each side. With traverse ratio of 2.33 ( ), starting point on a face shifts by 1 3 rotation (120 ) and it would come to same place after three double traverses, i.e. every 1 st, 4 th, 7 th... wraps of double traverse would be laid on top of one another (Fig. 2.11b). For traverse ratio of 2.40 ( ), starting point on a face shifts by 2 5 rotation (72 ) and it would come to same place after five double traverses, i.e. every 1 st, 6 th, 11 th... wraps of double traverse would be laid on top of one another. Yarn starting point would come to same place after 5 double traverses, i.e. every 1 st, 6 th, 11 th... wraps of double traverse would be laid on top of one another (Fig. 2.11c) Relation between traverse ratio and number of double traverses after which yarn comes to same place

28 Basics of package building 21 Table 2.1 shows some traverse ratios and number of double traverses after which yarn come to same place. Table 2.1 Traverse ratios and number of double traverses after which yarn come to same place S. No. Traverse ratio Traverse ratio expressed as a fraction in form of x y Value of numerator, i.e. x Value of denominator, i.e. y Traverse ratio expressed in decimal Number of double traverses after which yarn comes to same place Some important conclusions can be derived from Table 2.1 as If traverse ratio is expressed in form of x, where x and y are natural y numbers without any common factors except 1, y indicates number of double traverses after which yarn comes to same place. The traverse ratios with small value of y (when expressed as a fraction in form of x ) would cause pattern formation. The most severe y patterns would be formed for whole numbers as traverse ratios, e.g. 2, 3, 4, etc. for which value of y is Building a satisfactory package with constant traverse ratio throughout package A smaller value of y (for a traverse ratio of x, where x and y are natural y

29 22 Fundamentals of yarn winding numbers without any common factors except 1) causes yarn to come to same place after fewer number of double traverses that leads to pattern formation and yarn is not laid across the entire package area. A traverse ratio of say 4 would not be suitable as successive wraps of yarns would be overlapped. What could be a suitable traverse ratio closer to number 4 to build a satisfactory package? Number 4 can also be expressed as an equivalent fraction, say If numerator is reduced marginally then we can get fractions like , , , 3979 etc. If winding is carried out with these traverse ratios, end 1000 point of a double traverse would lie before its starting point and overlapping can be avoided as the coils of next double traverse would get displaced as shown in Fig. 2.12(a). As value of denominator of traverse ratio is a larger number 1000, patterning would be avoided. The numbers , , 3997, are little lesser than 4. Difference between these numbers and 4 is highest for [4 ], i.e. it is the highest among all. Therefore displacement of yarn after a double traverse would be the greatest. This displacement would be the least for This displacement has to be at least equal to yarn diameter 1000 to avoid overlapping. Instead of taking numbers little less than 4, numbers exceeding it can also be taken, i.e. numbers such as , , , 4019 can be taken Figure 2.12 Winding with constant traverse ratio without overlapping

30 Basics of package building 23 With these numbers at the end point of a double traverse would lie beyond its starting point as shown in Fig. 2.12(b). Difference between , , , 4019 and 4 is the highest for 4019 and therefore the shifting of coils of next double traverse from previous one would be the highest. For , the difference is least and therefore the shifting of coils of next double traverse from previous one would be the least. Thus suitable traverse ratios for building a package with same traverse ratio throughout the package can be obtained by incrementing or decrementing a traverse ratio that would form patterns (with smaller value of y) in such a way that patterning is avoided and yarn coils shifts adequately at the end of pattern repeat. The traverse ratios with a smaller value of y leading to pattern formation are called nominal traverse ratios, like 4 ( 1 4 ), ( ), ( ), ( ), ( ) and ( ) which if expressed as decimal numbers are 4.00, 4.50, , 5.40, 8.25 and 4.75, respectively. With a nominal traverse ratio expressed in form of x, where x and y are y natural numbers without any common factors except 1, y indicates number of double traverses after which yarn comes to same place or it shows after how many double traverses pattern of laying repeats. Thus, for a traverse ratio of 9 pattern of laying repeats after two double traverses and for a traverse ratio 2 of 11 3 it repeats after 3 double traverses. Traverse ratios suitable for building satisfactory packages are obtained by suitably incrementing or decrementing nominal traverse ratios which are called actual traverse ratios Gain and precision winding Traverse ratios for building satisfactory packages are obtained by suitably incrementing or decrementing nominal traverse ratios so that the yarn coils at the end of pattern repeat displace adequately. Minimum displacement should be at least equal to diameter of the yarn at the end of pattern repeat so