INDIRECT SYSTE 1. Tex 2. Denier 1. Ne: No of yards weighting in One pound 2. Nm: No of kilometer yarn weighting in one kilogram 3. Tex:. Weight grams of 1000meter (1 kilometer)yarn 4. Denier: Weight in grams of 9000 meter (9 kilometer yarn For the determination of the count of yarn, it is necessary to determine the weight of a known length of the yarn. For taking our known of yarns, a wrap-reel is used. The length of yarn reeled off depended upon the count system used. One of the important requirements for a spinner is to maintain the average count and count variation within control. 1.1 Yarn Count Variation The term count variation is generally used to express variation in the weight of a lea and this is expressed as C.V%. The number of samples and the length being considered for count checking affects this. While assessing count variation, it is very important to test adequate number of less. After reeling the appropriate atmosphere for testing before it’s weight is determined. 1.2. Conversion Table For Yarn Counts Tex Ne Den Nm Tex Den/9 1000/Nm Ne 590.54/Tex 5314.9/Den Nmx.590.5 ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… 2.0. Yarn Twist Twist is is Defined as the spiral disposition of the components of yarn, which is generally expressed as the number of turns per unit length of yarn, e.g turns per inch, turns per meter, etc. With increase in twist, the yarn strength increases first reaches a maximum and then decreases. Depending on the end use, two or more single yarns are twisted together to form ``plied yarns’’or’’ folded yarns and a number of plied yarns twisted together to form ``cabled yarn’’ Among the lied yarns, the most commonly used are the doubled yarns, wherein two single yarns of identical twisted together in a direction opposite to that of the single yarns. Thus for cabled and plied yarns, the direction of twist and the number of turns per unit length of the resultant yarn as well as of each component have to be determined for a detailed analysis. Direction of twist is expressed as ``S’’-Twist or ``Z’’-Twist. Direction depends upon the direction of rotation of rotation of the twisting element. Twist take up is defined as , `` The decrease in length of yarn on twisting, expressed as a percentage of the length of yarn before twisting. 2.1 Twist Standards Cotton combed knitting T.M=3.4 to 3.6 cotton Combed weaving T.M=3.7 to 3.8 cotton carded Knitting T.M=3.8 to 4.0 cotton carded weaving T.M=3.9 to 4.2 3.0 Yarn Strength & Elongation Breaking strength, elongation, elastic modulus, resistance abrasion etc are some important factors, which will represent the performance of the yrn during actual use or further processing. Strength testing is doradly classified into two methods 1. Single End Strength Testing 2. Lea Strength 3.1. Tensile strength of single yarn During routine testing, both the breaking load and extension the yarn break are usually recorded for assessing the yarn quality. Most of the instruments record the load-elongation diagram also. Various parameters such as initial elastic modulus, the yield point, the tenacity or elongation at any stress or strain, braking load, breaking extension etc can be obtained from the load-extension diagram. Two types of strengths can be determined for a yarn 1. Tensile strength-load is applied gradually 2. Ballistic strength-applying load under rapid impact certain drawbacks. Firstly, in most of the subsequent processing, such as winding, warping or weaving, yarn is used single stranding not in the form of a skein expect occasionally when sizing, bleaching, mercerizing or dyeing treatments are crried on hanks. Secondly, in the method used for testing skein strength the rupture for the whole skein, Further, this method of tesr does not give an indication of the extensibility and elastic properties role during the weaving operations. However, such a large size sample is used in a skein test as against that ibn a single strand test can be used for determination of the liner density of the yarn a well. After finding out skein strength, broken sleins are also weight to determine the liner density. The most common skein used is the lea and the results of lea strength tests are expressed as C.S.P, which is the product of the liner density (count) of the yarn in the English system (Ne) and the lea breaking strength expressed in lbs. In view of the fact that C.S.P in much less dependent on yarn count than on strength. Especially when count different as small, C.S.P in the most widely used measure of yarn quality. 4.0. Yarn Evenness Non-uniformity in variety of properties exists in yarns .There can be variation twist, bulk, strength, elongation finesses etc. Yarn evenness deals with the variation in yarn fineness. This is the property, commonly measured, as the variation in mass per unit length along the yarn, is a basic and important one, since it can influence so many other properties of the yarn and of fibric made from it. Such variations are inevitable, because they arise from the fundamental nature of textile fibers and from their resulting arrangement accordingly, there are limits to the achievable yarn evenness. 4.1 Unevenness/ Irregularity The mass per length variation due to variation in fibre assembly is generally known as ``IRREGULARIRT’’ OR ``UNEVENNESS’’. It is true that the diagram can represent a true reflection of the mass or weight per unit length variation in a fiber assembly. For a complete analysis of the quality, however, the diagram alone it not enough. It is also necessary to have a numerical value that represents the mass variation. The mathematical offer 2 methods. 1. The irregularity U%: It is the percentage mass deviation of unit length and is caused by uneven fiber distribution along the length the strand. 2. The coefficient of variation C.V%. 4.2 Imperfection Yarns spun from staple fibers contain ``IMPEWRFECTION ‘’. They are also referred to as frequently occurring yarn faults. They can be subdivided into three groups 1. Think places 2. Thick places 3. Neps The reasons for three different types or fults are due to raw material or improper preparation process. A reliable analysis of these imperfections well provide some references to the quality of the raw material used the standard sensitive levels are as follows • Thin place -50% + Thick place+50% Neps +200% Thin places and thick places in yarn can on the one hand, quite considerable affect the appearance of a woven og knitted fabric. Furthermore, an increase in the number of thin places and thick places refer to a particularly valuable indication that the raw material or the method of processing has become worse. On the other hand, it cannot be concluded from the increased number of thin places faults this yarn, the
Posted on: Mon, 18 Nov 2013 06:59:09 +0000
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