Yarn Preparation PDF

Yarn Preparation for Subsequent Processes such as Weaving & Knitting Yarn preparation involves those processes that improve the yarn’s weave-ability or knit-ability; i.e. ability for the yarn to perform well during weaving or knitting.  Importance of Yarn Preparation The quality of ya...

Yarn Preparation for Subsequent Processes such as Weaving & Knitting Yarn preparation involves those processes that improve the yarn’s weave-ability or knit-ability; i.e. ability for the yarn to perform well during weaving or knitting.  Importance of Yarn Preparation The quality of yarn for weaving / knitting has a considerable influence on the efficiency of the weaving / knitting operation and the quality of the fabric produced.  Importance of Yarn Preparation In order to achieve maximum weaving / knitting efficiency, yarn breakage must be reduced to a minimum and this can be achieved by: winding onto a suitable package in the best possible way clearing yarn, i.e. remove thick and thin places as much as possible, for improved yarn quality and treating the yarn before using (knitting). Objectives of Winding Package the yarn Inspect and clear the yarn of defects Lubricate the yarn (optional)  Spinner’s Package During ring spinning process, yarn is wound from a ring frame onto small ‘spinners’ packages. The length of the yarn on the package can vary from a few hundred to a few thousand metres depending on the count of the yarn. Spinner’s Packages  Winding: Package One of the main purposes of winding is to transfer yarn from the spinner’s package to another suitable package for the particular end-use: as weft; for dyeing; for creeling of a warping machine. For efficient warping, long continuous lengths of yarn of the order of 50,000 metres or more are required. Winding: Package Yarn from a number of spinners packages is wound in a continuous length onto a large package, called a cone or cheese. A cone is quite conical and cheese, cylindrical in shape. The package size, shape, and build must be the most technologically suitable for the particular end use. Therefore, the yarn must be wound in such a way as to permit unwinding in the subsequent processes with minimum difficulty, good stability and at the required speeds. Yarn Winding Machines  Winding: Yarn Clearing The process of removing objectionable faults is called as yarn ‘clearing’. It is during this stage that objectionable thick and thin places in the yarn are eliminated. The fault level in the yarn must be reduced to an acceptable level. The yarn must not be damaged in any way in the winding process. Yarn winding machines are equipped with Electronic Yarn Clearers or clearing devices.  Electronic Yarn Clearing Device The electronic yarn clearing device is mounted on the winding machine.  Clearing Limit of Electronic Clearers The clearing limit defines the threshold level for the yarn faults, beyond which the cutter is activated to remove the yarn fault. The clearing limit consists of two setting parameters: o Sensitivity - This determines the activating limit for the fault cross sectional size. ii. o Reference Length – This defines the length of the yarn over which the fault cross – section is to be measured.  Yarn Splicing It is important to note that, when such objectionable faults are cut out, and/or to maintain continuity of the yarn in the wound package, the two ends have to be joined together by splicing as ends when a ring bobbin is exhausted. In other words, we are trying to replace a more serious fault with a relatively less serious one.  Yarn Splicing Splicing is a technique of joining two yarn ends, knot-free, by intermingling the constituent fibres so that the joint is not significantly different in appearance and mechanical properties with respect to the parent yarn. The splicing consists of untwisting and later re- twisting two yarn ends using air blast, i.e., first the yarn is opened, the fibres intermingled and later twisted in the same direction as that of the parent yarn. The effectiveness of splicing is primarily dependent on the tensile strength and physical appearance. Yarn Splicing Actions Yarn Splicing Device on Winders Treating the yarn before using it, esp. for knitting yarns  Yarn Preparation: Lubrication/Waxing Yarns are waxed or lubricated in order to improve their slide performance during knitting. Usually, staple yarns are waxed and, filament yarns are lubricated. The (surface) frictional properties of the treated yarn is thus changed: the value of the coefficient of yarn friction, μ, decreases. Thus, knitability improves.  Why is waxing needed? Application of proper waxing results in the production of better quality yarns by reducing friction coefficient and giving antistatic characteristics to the yarn. Through proper waxing, a uniform yarn tension is maintained throughout the knitting operation to obtain optimum productivity.  Yarn Folding/Doubling/Plying  Plied Yarn/ Le Fils Retors Le fil retors est un assemblage de deux ou plusieurs fils simples obtenu par torsion. Le Fils Retors Yarn Doubling/Folding/Plying The method of twisting two or more single yarns is called doubling or folding or ply twisting. Such yarns are designated as doubled yarn, folded yarn or plied yarn and the machines intended for the purpose are called doublers or ply-twisters. Types of yarn doubling/folding process: 1 - Ring doubling machine 2 - Two For One (TFO) twisting machine Ring doubling process: Ring doubling process is a one stage process. Two or more yarn packages are twisted together. The twisting system is the same as the ring frame. The difference of ring doubling from the ring spinning is: 1. No drafting 2. Creel in a system is different & creel contains yarn(No roving) Two For One (TFO) twister This is a two-stage process. In the first stage, two or more individual yarns are grouped/doubled or combine together, without twisting, with the help of an assembly yarn winding machine. The assembled yarn package is then supplied to a twister machine where the twist is applied in such a way that one revolution of rotating disc inserts two round of twist. The twisted yarn is then wound on a cone.  Yarn Folding Route for TFO Winding and clearing of single yarn (from spg) Assembly winding Doubling/Twisting Cone winding Two-For-One Twisting The term T.F.O stands for Two-for- One, indicating that two turns are inserted for each turn of the twisting element. In earlier times, the process involved transferring two yarns onto a doubler winder, which served as the feed package for T.F.O. However, in modern systems, two smaller packages are stacked vertically and extracted concurrently, replacing the older method. Final package is cone or cheese, no need for rewinding.  Principles of Yarn Folding It is customary to twist the ply yarn in the opposite direction to the twist of the single yarn (S singles with Z plied and vice- versa); F/S ratio: the folded to single twist ratio is the level of twist in the plied yarn relative to that of the single yarn components (e.g. S:700 tpm, D:350 tpm); The F/S ratio varies (0.5 to 2.0) F/S ratio affects the character of the folded yarn such as lustre, balance, elongation, strength etc. Différents Types de Fil Retors  Characteristics of a Ply Yarn Stronger; More regular, visually and tenacity; More voluminous; Depending on the twist direction: EITHER Less tendency to snarl, more balanced yarn for less skewness/spirality (moins de vrillage); OR more twist liveliness for crisp feel fabric Variable extensibility (fabric stretch) Production of novelty yarns, colour, fibre type, linear density, twist etc.  Uses of Ply Yarn Two-Fold: Poplin (Oxford weave); crepes, sewing threads Three-Fold: Sewing threads, hosiery, filter cloth etc. Multi-Ply: Cords, shoe laces, industrial yarns etc.  Yarn Costing: Ply v/s Single Why would a 60Nm/2 be more expensive than a 30Nm single yarn? Rate of Production More twist given to a finer yarn Less kg/hr for finer yarn Extra operation of twisting  End of Lecture on Yarn Winding & Folding