FIBRE TESTINGFIBRE ELONGATION:There are three types of elongation Permanent elongation: the length which extended during loading did not recover during relaxation Elastic elongation:The extensions through which the fibres does return Breaking elongation:the maximum extension at which the yarn breaks i.e.permanent and elastic elongation together Elongation is specified as a percentage of the starting length. The elastic elongation is of deceisive importance, since textile products without elasticity would hardly be usable. They must be able to deforme, In order to withstand high loading, but they must also return to shatpe. The greater resistance to creasefor wool compared to cotton arises, from the difference in their elongation. For cotton it is 6 -10% and for wool it is aroun 25 - 45%. For normal textile goods, higher elongation are neither necessary nor desirable. They make processing in the spinning mill more difficult, especially in drawing operations. FIBRE RIGIDITY: The Torsional rigidity of a fibre may be defined as the torque or twisting force required to twist 1 cm length of the fibre through 360 degrees and is proportional to the product of the modulus of rigidity and square of the area of cross-section, the constant of proportionality being dependent upon the shape of the cross-section of the fibre. The torsional rigidity of cotton has therefore been found to be very much dependent upon the gravimetric fineness of the fibres. As the rigidity of fibres is sensitive to the relative humidity of the surrounding atmosphere, it is essential that the tests are carried out in a conditional room where the relativehumidity is kept constant. THE SLENDERNESS RATIO: Fibre stiffness plays a significant role mainly when rolling, revolving, twisting movements are involved. A fibre which is too stiff has difficulty adapting to the movements. It is difficult to get bound into the yarn, which results in higher hairiness. Fibres which are not stiff enough have too little springiness. They do not return to shape after deformation. They have no longitudinal resistance. In most cases this leads to formation of neps. Fibre stiffness is dependent upon fibre substance and also upon the relationship between fibre length and fibre fineness. Fibres having the same structure will be stiffer, the shorter they are. The slendernesss ratio can serve as a measure of stiffness,

slender ratio = fibre length /fibre diameter Since the fibres must wind as they are bound-in during yarn formation in the ring spinning machine, the slenderness ratio also determines to some extent where the fibres will finish up.fine and/or long fibres in the middle coarse and/or short fibres at the yarn periphery. TRASH CONTENT:In additon to usuable fibres, cotton stock contains foreign matter of various kinds. This foreign material can lead to extreme disturbances during processing. Trash affects yarn and fabric quality. Cottons with two different trash contents should not be mixed together, as it will lead to processing difficulties. Optimising process paramters will be of great difficulty under this situation, therefore it is a must to know the amount of trash and the type of trash before deciding the mixing. SHIRLEY TRASH ANLAYSER: A popular trash measuring device is the Shirley Analyser, which separates trash and foreign matter from lint by mechanical methods. The result is an expression of trash as a percentage of the combined weight of trash and lint of a sample.

This instrument is usedto give the exact value of waste figures and also the proportion of clean cotton and trash in the material to select the proper processing sequence based upon the trash content to assess the cleaning efficiency of each machine to determine the loss of good fibre in the sequence of opening and cleaning. Stricter sliver quality requirements led to the gradual evolution of opening and cleaning machinery leading to a situation where blow room and carding machinery were designed to remove exclusively certain specific types of trash particles. This necessitated the segregation of the trash in the cotton sample to different grades determined by their size. This was achieved in the instruments like the Trash Separator and the Micro Dust Trash Analyser which could be considered as modified versions of the Shirley Analyser. The high volume instruments introduced the concept of optical methods of trash measurement which utilised video scanning trash-meters to identify areas darker than normal on a cotton sample surface. Here, the trash content was expressed as the percentage area covered by the trash particles. However in such methods, comparability with the conventional method could not be established in view of the non-uniform distribution of trash in a given cotton sample and the relatively smaller sample size to determine such

a parameter. Consequently, it is yet to establish any significant name in the industry. RAW MATERIAL AS A FACTOR AFFECTING SPINNING: Fineness determines how many fibres are present in the cross-section of a yarn of particular linear density. 30 to 50 fibres are needed minimum to produce a yarn fibre fineness influencesspinning limit yarn strength yarn evenness yarn fullness drape of the fabric lustre handle productivity productivity is influenced by the end breakage rate and twist per inch required in the yarn Immature fibres(unripe fibres) have neither adequate strength nor adequate longitudinal siffness. They therefore lead to the following,loss of yarn strength neppiness high proportion of short fibres varying dyeability processing difficulties at the card and blowroom Fibre length is one among the most important characteristics. It influnces spinning limit yarn strength handle of the product lustre of the product yarn hairiness productivity It can be assumed that fibres of under 4 - 5 mm will be lost in processing(as waste and fly). fibres upto about 12 - 15 mm do not contribute to strength but only to fullness of the yarn. But fibres above these lengths produce the other positive characteristics in the yarn. The proportion of short fibres has extremely great influence on the following parameters spinning limit yarn strength handle of the product lustre of the product

yarn hairiness productivity A large proportion of short fibre leads to strong fly contamination, strain on personnel, on the machines, on the work room and on the air-conditioning, and also to extreme drafting difficulties. A uniform yarn would have the same no of fibres in the cross-section, at all points along it. If the fibres themeselves have variations within themselves, then the yarn will be more irregular. If 2.5% span length of the fibre increases, the yarn strength also icreases due to the fact thatthere is a greater contribution by the fibre strength for the yarn strength in the case of longer fibres. Neps are small entanglements or knots of fibres. There are two types of neps. They are 1.fibre neps and 2.seed-coat neps.In general fibre neps predominate, the core of the nep consists of unripe and dead fibres. Thus it is clear that there is a relationship between neppiness and maturity index. Neppiness is also dependent on the fibre fineness, because fine fibres have less longitudinal stiffness than coarser fibres. Nature produces countless fibres, most of which are not usable for textiles because of inadequate strength. The minimum strength for a textile fibre is approximately 6gms/tex ( about 6 kn breaking length). Since blending of the fibres into the yarn is achieved mainly by twisting, and can exploit 30 to 70% of the strength of the material, a lower limit of about 3 gms/tex is finally obtained for the yarn strength, which varies linearly with the fibre strength. Low micronaire value of cotton results in higher yarn tenacity.In coarser counts the influence of micronaire to increase yarn tenacity is not as significant as fine count. Fibre strength is moisture dependent. i.e. It depends strongly upon the climatic conditions and upon the time of exposure. Strength of cotton,linen etc. increases with increasing moisture content. The most important property inflencing yarn elongation is fibre elongation.Fibre strength ranks seconds in importance as a contributor to yarn elongation. Fibre fineness influences yarn elongation only after fibre elongation and strength. Other characters such as span length, uniformity ratio, maturity etc, do not contribute significantly to the yarn elongation.Yarn elongation increases with increasing twist. Coarser yarn has higher elongation than finer yarn. Yarn elongation decreases with increasing

spinning tension. Yarn elongation is also influencedby traveller weight and high variation in twist insertion. For ring yarns the number of thin places increases, as the trash content and uniformity ratio increased For rotor yarns 50%span length and bundle strength has an influence on thin places. Thick places in ringyarn is mainly affected by 50%span length, trash content and shor fibre content. The following expression helps to obtain the yarn CSP achievable at optimum twist multiplier with the available fibre properties.

Lea CSP for Karded count = 280 x SQRT(FQI) + 700 - 13C

Lea CSP for combed count = (280 x SQRT(FQI) + 700 - 13C)x(1+W)/100

where,FQI = LSM/FL = 50% span length(mm)S = bundle strength (g/tex)M = Maturity ratio measured by shirly FMTF = Fibre fineness (micrograms/inch)C = yarn countW = comber waste%Higher FQI values are associated with higher yarn strength in the case of carded counts but in combed count such a relationship is not noticed due to the effect of combing Higher 2.5 % span length, uniformity ratio, maturity ratio and lower trash content results in lower imperfection. FQI does not show any significant influence on the imperfection. The unevenness of carded hosiery yarn does not show any significant relationships with any of the fibre properties except the micronaire value. As the micronaire value increases, U% also increases. Increase in FQI however shows a reduction in U%. Honey-dew is the best known sticky substance on cotton fibres. This is a secretion of the cotton louse. There are other types of sticky substances also. They are given below.honey dew - secretions fungus and bacteria - decomposition products vegetable substances - sugars from plant juices, leaf nectar, overprodcution of wax, fats, oils - seed oil from ginning

pathogens synthetic substances - defoliants, insecticides, fertilizers, oil from harvesting machines In the great majority of cases, the substance is one of a group of sugars of the most variable composition, primarily but not exclusively, fructose, glucose, saccharose, melezitose, as found, for example on sudan cotton. These saccharides are mostly, but not always, prodced by insects or the plants themselves, depending upon the influence on the plants prior to plucking. Whether or not a fibre will stick depends, not only on the quantity of the sticky coating and it composition, but also on the degree of saturation as a solution.

Sugars are broken down by fermentation and by microorganisms during storage of the cotton. This occurs more quickly the higher the moisture content. During spinning of sticky cotton, the R.H.% of the air in the production are should be held as low as possible. The following table shows the degree of correlation between the various cotton fibre quality characteristics and those of the yarns into which these fibres are spun - RING SPUN YARNS

yarn evenness

imperfection and classimat faults

breaking tenacity

breaking elongation

hairiness

fibre length

micronaire value

nep, trash, leaf, microdust, fibre fragments

1/8" breaking strength

1/8" elongation

colot/reflectance

significant correlation

good correlation

little or no correlation

The following table shows the degree of correlation between the various cotton fibre quality characteristics and those of the yarns into which these fibres are spun - ROTOR SPUUN YARNS.

yarn evenness

imperfections and classimat faults

breaking tenacity

breaking elongation

hairiness

fibre length

micronaire value

nep, leaf, trash,microdust, fibre fragments

1/8" breaking strength

1/8" breaking elongation

color/ reflectance

significant correlation

good correlation

little or no correlation

Fiber testing

IMPORTANCE OF RAWMATERIAL IN YARN MANUFACTURING: Raw material represents about 50 to 70% of the production cost of a short-staple yarn. This fact is sufficient to indicate the significance of the rawmaterial for the yarn producer. It is not possible to use a problem-free raw material always , because cotton is a natural fibre and there are many properties which will affect the performance. If all the properties have to be good for the cotton, the rawmaterial would be too expensive. To produce a

good yarn with this difficulties, an intimate knowledge of the raw material and its behaviour in processing is a must. Fibre characteristics must be classified according to a certain sequence of importance with respect to the end product and the spinning process. Moreover, such quantified characteristics must also be assessed with reference to the followingwhat is the ideal value? what amount of variation is acceptable in the bale material? what amount of variation is acceptable in the final blend Such valuable experience, which allows one to determine the most suitable use for the raw material, can only be obtained by means of a long, intensified and direct association with the raw material, the spinning process and the end product. Low cost yarn manufacture, fulfilling of all quality requirements and a controlled fibre feed with known fibre properties are necessary in order to compete on the world's textile markets. Yarn prodcution begins with the rawmaterial in bales, whereby success or failure is determined by the fibre quality, its price and availability. Successful yarn producers optimise profits by a process oriented selection and mixing of the rawmaterial, followed by optimisation of the machine settings, production rates, operating elements, etc. Simultaneously, quality is ensuredby means of a closed loop control system, which requires the application of supervisory system at spinning and spinning preparation, as well as a means of selecting the most sutable bale mix. BASIC FIBRE CHARACTERISTICS: A textile fibre is a peculiar object. It has not truly fixed length, width, thickness, shape and cross-section. Growth of natural fibres or prodction factors of manmade fibres are responsible for this situation. An individual fibre, if examined carefully, will be seen to vary in cross-sectional area along it length. This may be the result of variations in growth rate, caused by dietary, metabolic, nutrient-supply, seasonal, weather, or other factors influencing the rate of cell development in natural fibres. Surface characteristics also play some part in increasing the variablity of fibre shape.

The scales of wool, the twisted arrangement of cotton, the nodes appearing at intervals along the cellulosic natural fibres etc. Following are the basic chareteristics of cotton fibrefibre length fineness

strength maturity Rigidity fibre friction structural features STANDARD ATMOSPHERE FOR TESTING: The atmosphere in which physical tests on textile materials are performed. It has a relative humidity of 65 + 2 per cent and a temperature of 20 + 2° C. In tropical and sub-tropical countries, an alternative standard atmosphere for testing with a relative humidity of 65 + 2 per cent and a temperature of 27 + 2° C,may be used. FIBRE LENGTH: The "length" of cotton fibres is a property of commercial value as the price is generally based on this character. To some extent it is true, as other factors being equal, longer cottons give better spinning performance than shorter ones. But the length of a cotton is an indefinite quantity, as the fibres, even in a small random bunch of a cotton, vary enormously in length. Following are the various measures of length in use in different countries mean length upper quartile effective length Modal length 2.5% span length 50% span length Mean length:It is the estimated quantity which theoretically signifies the arithmetic mean of the length of all the fibres present in a small but representative sample of the cotton. This quantity can be an average according to either number or weight. Upper quartile length:It is that value of length for which 75% of all the observed values are lower, and 25% higher. Effective length:It is difficult to give a clear scientific definition. It may be defined as the upper quartile of anumerical length distributioneliminated by an arbitrary construction. The fibres eliminated are shorter than half the effective length.

Modal length:It is the most frequently occurring length of the fibres in the sample and it is related to mean and median for skew distributions, as exhibited by fibre length, in the follwing way.

(Mode-Mean) = 3(Median-Mean)where,Median is the particular value of length above and below which exactly 50% of the fibres lie. 2.5% Span length:It is defined as the distance spanned by 2.5% of fibres in the specimen being tested when the fibres are parallelized and randomly distributed and where the initial starting point of the scanning in the test is considered 100%. This length is measured using "DIGITAL FIBROGRAPH". 50% Span length:It is defined as the distance spanned by 50% of fibres in the specimen being tested when the fibres are parallelized and randomly distributed and where the initial starting point of the scanning in the test is considered 100%. This length is measured using "DIGITAL FIBROGRAPH". The South India Textile Research Association (SITRA) gives the following empirical relationships to estimate the Effective Length and Mean Length from the Span Lengths. Effective length = 1.013 x 2.5% Span length + 4.39Mean length = 1.242 x 50% Span length + 9.78 FIBRE LENGTH VARIATION: Eventhough, the long and short fibres both contribute towards the length irregularity of cotton, the short fibres are particularly responsible for increasing the waste losses, and cause unevenness and reduction in strength in the yarn spun. The relative proportions of short fibres are usually different in cottons having different mean lengths; they may even differ in two cottons having nearly the same mean fibre length, rendering one cotton more irregular than the other.It is therefore important that in addition to the fibre length of a cotton, the degree of irregularity of its length should also be known. Variability is denoted by any one of the following attributesCo-efficient of variation of length (by weight or number) irregularity percentage Dispersion percentage and percentage of short fibres Uniformity ratio

Uniformity ratio is defined as the ratio of 50% span length to 2.5% span length expressed as a percentage. Several instruments and methods are available for determination of length. Following are someshirley comb sorter Baer sorter A.N. Stapling apparatus Fibrograph uniformity ration = (50% span length / 2.5% span length) x 100uniformity index = (mean length / upper half mean length) x 100 SHORT FIBRES: The negative effects of the presence of a high proportion of short fibres is well known. A high percentage of short fibres is usually associated with,- Increased yarn irregularity and ends dddown which reduce quality and increase processing costs- Increased number of neps and slubs whiiich is detrimental to the yarn appearance- Higher fly liberation and machine contttamination in spinning, weaving and knitting operations.- Higher wastage in combing and other oppperations.While the detrimental effects of short fibres have been well established, there is still considerable debate on what constitutes a 'short fibre'. In the simplest way, short fibres are defined as those fibres which are less than 12 mm long. Initially, an estimate of the short fibres was made from the staple diagram obtained in the Baer Sorter method

Short fibre content = (UB/OB) x 100 While such a simple definition of short fibres is perhaps adequate for characterising raw cotton samples, it is too simple a definition to use with regard to the spinning process. The setting of all spinning machines is based on either the staple length of fibres or its equivalent which does not take into account the effect of short fibres. In this regard, the concept of 'Floating Fibre Index' defined by Hertel (1962) can be considered to be a better parameter to consider the effect of short fibres on spinning performance. Floating fibres are defined as those fibres which are not clamped by either pair of rollers in a drafting zone.Floating Fibre Index (FFI) was defined asFFI = ((2.5% span length/mean length)-1)x(100)The proportion of short fibres has an extremely great impact on yarn quality and production. The proportion of short fibres has increased substantially in recent years due to mechanical picking and hard ginning. In most of the

cases the absolute short fibre proportion is specified today as the percentage of fibres shorter than 12mm. Fibrograph is the most widely used instrument in the textile industry , some information regarding fibrograph is given below. FIBROGRAPH:Fibrograph measurements provide a relatively fast method for determining the length uniformity of the fibres in a sample of cotton in a reproducible manner. Results of fibrograph length test do not necessarily agree with those obtained by other methods for measuring lengths of cotton fibres because of the effect of fibre crimp and other factors. Fibrograph tests are more objective than commercial staple length classifications and also provide additional information on fibre length uniformity of cotoon fibres. The cotton quality information provided by these results is used in research studies and quality surveys, in checking commercial staple length classifications, in assembling bales of cotton into uniform lots, and for other purposes. Fibrograph measurements are based on the assumptions that a fibre is caught on the comb in proportion to its length as compared to toal length of all fibres in the sample and that the point of catch for a fibre is at random along its length.

FIBRE FINENESS: Fibre fineness is another important quality characteristic which plays a prominent part in determining the spinning value of cottons. If the same count of yarn is spun from two varieties of cotton, the yarn spun from the variety having finer fibres will have a larger number of fibres in its cross-section and hence it will be more even and strong than that spun from the sample with coarser fibres. Fineness denotes the size of the cross-section dimensions of the fibre. AS the cross-sectional features of cotton fibres are irregular, direct determination of the area of croo-section is difficult and laborious. The Index of fineness which is more commonly used is the linear density or weight per unit length of the fibre. The unit in which this quantity is expressed varies in different parts of the world. The common unit used by many countries for cotton is microgrammes per inch and the various air-flow instruments developed for measuring fibre fineness are calibrated in this unit. Following are some methods of determining fibre fineness.

gravimetric or dimensional measurements air-flow method vibrating string method Some of the above methods are applicable to single fibres while the majority of them deal with a mass of fibres. As there is considerable variation in the linear density from fibre to fibre, even amongst fibres of the same seed, single fibre methods are time-consuming and laborious as a large number of fibres have to be tested to get a fairly reliable average value. It should be pointed out here that most of the fineness determinations are likely to be affected by fibre maturity, which is an another important characteristic of cotton fibres. AIR-FLOW METHOD(MICRONAIRE INSTRUMENT): The resistance offered to the flow of air through a plug of fibres is dpendent upon the specific surface area of the fibres. Fineness tester have been evolved on this principle for determininG fineness of cotton. The specific surface area which determines the flow of air through a cotton plug, is dependent not only upon the linear density of the fibres in the sample but also upon their maturity. Hence the micronaire readings have to be treated with caution particularly when testing samples varying widely in maturity. In the micronaire instrument, a weighed quantity of 3.24 gms of well opened cotton sample is compressed into a cylindrical container of fixed dimensions. Compressed air is forced through the sample, at a definite pressure and the volume-rate of flow of air is measured by a rotometer type flowmeter. The sample for Micronaire test should be well opened cleaned and thoroughly mixed( by hand fluffing and opening method). Out of the various air-flow instruments, the Micronaire is robust in construction, easy to operate and presents little difficulty as regards its maintenance. FIBRE MATURITY: Fibre maturity is another important characteristic of cotton and is an index of the extent ofdevelopment of the fibres. As is the case with other fibre properties, the maturity of cotton fibres varies not only between fibres of different samples but also between fibres of the same seed. The causes for the differences observed in maturity, is due to variations in the degree of the secondary thickening or deposition of cellulose in a fibre. A cotton fibre consists of a cuticle, a primary layer and secondary layers of cellulose surrounding the lumen or central canal. In the case of mature fibres, the secondary thickening is very high, and in some cases, the lumen is not visible.

In the case of immature fibres, due to some physiological causes, the secondary deposition of cellulose has not taken sufficiently and in extreme cases the secondary thickening is practically absent, leaving a wide lumen throughout the fibre. Hence to a cotton breeder, the presence of excessive immaturefibres in a sample would indicate some defect in the plant growth. To a technologist, the presence of excessive percentage of immature fibres in a sample is undesirable as this causes excessive waste losses in processing lowering of the yarn appearance grade due to formation of neps, uneven dyeing, etc. An immature fibre will show a lower weight per unit length than a mature fibre of the same cotton, as the former will have less deposition of cellulose inside the fibre. This analogy can be extended in some cases to fibres belonging to different samples of cotton also. Hence it is essential to measure the maturity of a cotton sample in addition to determining its fineness, to check whether the observed fineness is an inherent characteristic or is a result of the maturity. DIFFERENT METHODS OF TESTING MATURITY:MATURITY RATIO:The fibres after being swollen with 18% caustic soda are examined under the microscope with suitable magnification. The fibres are classified into different maturity groups depending upon the relative dimensions of wall-thickness and lumen. However the procedures followed in different countries for sampling and classification differ in certain respects. The swollen fibres are classed into three groups as followsNormal : rod like fibres with no convolution and no continuous lumen are classed as "normal" Dead : convoluted fibres with wall thickness one-fifth or less of the maximum ribbon width are classed as "Dead" Thin-walled: The intermediate ones are classed as "thin-walled"

A combined index known as maturity ratio is used to express the results. Maturity ratio = ((Normal - Dead)/200) + 0.70where,N - %ge of Normal fibresD - %ge of Dead fibresMATURITY CO-EFFICIENT:Around 100 fibres from Baer sorter combs are spread across the glass

slide(maturity slide) and the overlapping fibres are again separated with the help of a teasing needle. The free ends of the fibres are then held in the clamp on the second strip of the maturity slide which is adjustable to keep the fibres stretched to the desired extent. The fibres are then irrigated with 18% caustic soda solution and covered with a suitable slip. The slide is then placed on the microscope and examined. Fibres are classed into the following three categoriesMature : (Lumen width "L")/(wall thickness"W") is less than 1 Half mature : (Lumen width "L")/(wall thickness "W") is less than 2 and more than 1 Immature : (Lumen width "L")/(wall thickness "W") is more than 2 About four to eight slides are prepared from each sample and examined. The results are presented as percentage of mature, half-mature and immature fibres in a sample. The results are also expressed in terms of "Maturity Coefficient" Maturity Coefficient = (M + 0.6H + 0.4 I)/100 Where,M is percentage of Mature fibresH is percentage of Half mature fibresI is percentage of Immature fibresIf maturity coefficient isless than 0.7, it is called as immature cotton between 0.7 to 0.9, it is called as medium mature cotton above 0.9, it is called as mature cotton AIR FLOW METHOD FOR MEASURING MATURITY:There are other techniques for measuring maturity using Micronaire instrument. As the fineness value determined by the Micronaire is dependent both on the intrinsic fineness(perimeter of the fibre) and the maturity, it may be assumed that if the intrinsic fineness is constant then the Micronaire value is a measure of the maturityDYEING METHODS:Mature and immature fibers differ in their behaviour towards various dyes. Certain dyes are preferentially taken up by the mature fibres while some dyes are preferentially absorbed by the immature fibres. Based on this observation, a differential dyeing technique was developed in the United States of America for estimating the maturity of cotton. In this technique, the sample is dyed in a bath containing a mixture of two dyes, namely Diphenyl Fast Red 5 BL and Chlorantine Fast Green BLL. The mature fibres take up the red dye preferentially, while the thin walled immature fibres take up the green dye. An estimate of the average of the sample can be visually assessed by the amount of red and green fibres.

FIBRE STRENGTH: The different measures available for reporting fibre strength arebreaking strength tensile strength and tenacity or intrinsic strength Coarse cottons generally give higher values for fibre strength than finer ones. In order, to compare strength of two cottons differing in fineness, it is necessary to eliminate the effect of the difference in cross-sectional area by dividing the observed fibre strength by the fibre weight per unit length. The value so obtained is known as "INTRINSIC STRENGTH or TENACITY". Tenacity is found to be better related to spinning than the breaking strength. The strength characteristics can be determined either on individual fibres or on bundle of fibres.SINGLE FIBRE STRENGTH:The tenacity of fibre is dependent upon the following factorschain length of molecules in the fibre orientation of molecules size of the crystallites distribution of the crystallites gauge length used the rate of loading type of instrument used and atmospheric conditions The mean single fibre strength determined is expressed in units of "grams/tex". As it is seen the the unit for tenacity has the dimension of length only, and hence this property is also expressed as the "BREAKING LENGTH", which can be considered as the length of the specimen equivalent in weight to the breaking load. Since tex is the mass in grams of one kilometer of the specimen, the tenacity values expressed in grams/tex will correspond to the breaking length in kilometers. BUNDLE FIBRE STRENGTH:In practice, fibres are not used individually but in groups, such as in yarns or fabrics. Thus, bundles or groups of fibres come into play during the tensile break of yarns or fabrics. Further,the correlation between spinning performance and bundle strength is atleast as high as that between spinning performance and intrinsic strength determined by testing individual fibres. The testing of bundles of fibres takes less time and involves less strain than testing individual fibres. In view of these considerations, determination of breaking strength of fibre bundles has assumed greater importance than single fibre strength tests. YARN HAIRINESSINTRODUCTIONYarn hairiness is a complex concept, which generally cannot be completely defined by a single figure.The effect of yarn hairiness on the textile operations following spinning,

especially weaving andknitting, and its influence on the characteristics of the product obtained and on some fabric faultshas led to the introduction of measurement of hairiness. FACTS ABOUT YARN HAIRINESS:Hairiness occurs because some fibre ends protrude from the yarn body, some looped fibres archout from the yarn core and some wild fibres in the yarn. Pillay proved that there is a high correlation between the number of protruding ends and thenumber of fibres in the yarn cross-section. Torsion rigidity of the fibres is the most important single property affecting yarn hairiness. Other factors are flexural rigidity, fibre length and fibre fineness. Mixing different length cottons-No substantial gain in hairiness. Although the hairiness of a yarn could be reduced to some extent by the addition of a longer and finer cotton to the blend. The extent of reduction is not proportional to the percentage of the longer and finer component. This is probably due to the preferential migration of the coarser and shorter component, which has longer protruding ends, from the yarn body. The addition of wastes to the mixing increases the yarn hairiness; the effect of adding comber waste is greater than that of adding soft waste. Blending-not a solution to hairiness. The blended yarns are rather more hairy than expected from the hairiness of the components; a result similar to that found in cotton blends. This may be due to the preferential migration of the shorter cotton fibers; a count of the number of protruding ends of both types of fiber shows that there is more cotton fiber ends than expected, although the difference is not very great. The number of protruding ends is independent of twist, whereas the number of loops decreases whenthe yarn twist increases because of a greater degreee of binding between hte fibres owing to twist.The number of wild fibres decreases only very slightly with twist because of their position on theyarn periphery. The proportion of fiber ends that protrude from the yarn surface, counted microscopically has been found to be about 31% of the actual number of ends present in the yarn. If the length of the protruding fibre ends as well as that of the loops is considered, the mean

value of the hairiness increases as the cross-sectional area increases and decreases with the lengthof the loops. The hairiness is affected by the yarn twist, since an increase in twist tends to shortenthe fibre ends. Wild fibres are those for which hte head alone is taken by the twist while the tail is still grippedby the front drafting rollers. Fibre length influences hairiness in the sense that a greater length corresponds to less hairiness. Cotton yarns are known to be less hairy than yarns spun from man-made fibres.

The possible reasonfor this is the prifile of the two fibres.Because of taper, only one end, the heavier root part of thecotton fibre, tends to come out as a protruding end in a cotton yarn. With man-made fibres, both endshave an equal probability of showing up as protruding ends. If the width of the fibre web in the drafting field is large, the contact and friction with thebottom roller reduce the ability of the fibres to concentrate themselves and hairiness occurs. Thiseffect is found more in coarse counts with low TPI. This suggests that the collectors in thedrafting field will reduce yarn hairiness. The yarn hairiness definitely depends on the fibres on the outer layer of the yarn that do notdirectly adhere to the core. Some of them have an end in the core of the yarn gripped by other fibres,whereas others, because of the mechanical properties of the fibre(rigidity, shape, etc.) emerge tothe surface. During the twisting of the yarn, other fibres are further displaced from their centralposition to the yarn surface. Greater the fibre parallelization by the drawframe, lower the yarn hairiness. An increase in roving twist results in lower yarn hairiness, because of smaller width of fibreweb in the drafting field.

The number of fiber ends on the yarn surface remains fairly constant; the number of looped fibers reduces in number and length on increasing twist. Combed yarn will have low yarn hairiness, because of the extraction of shorter fibres by the comber. Yarn hairiness increases when the roving linear density increases . Yarn spun from double rovingwill have more hairiness than the yarn spun from single roving. This is due to the increased number offibres in the web and due to higher draft required to spin the same count. Drafting waves increase hairiness. Irregularity arising from drafting waves increases with increasing draft. Yarn hairiness also may be accepted to increase with yarn irregularity, because fibers protruding from the yarn surface are more numerous at the thickest and least twisted parts of the yarn. The yarns produced with condernsers in the drafting field, particularsly if these are situatedin the principal drafting zone, are less hairy than those spun without the use of condensers.Higher spindle speed – high hairiness. When yarns are spun at different spindle speed, the centrifugal force acting on fibers in the spinning zone will increase in proportion to the square of the spindle speed, causing the fibers ends as they are emerging from the front rollers to be deflected from the yarn surface to a greater extent. Further, at high spindle speed, the shearing action of the traveller on the yarn is likely to become great enough to partially detach or raise the fibers from the body of the yarn. As against the above factors, at higher spindle speeds the tension in the yarn will increase in proportion to the square of the spindle speed, and consequently more twist will run back to the roller nip, so that it is natural to expect that better binding of the fibers will be achieved. The increase in hairiness noticed in the results suggests that the forces involved in raising fibers from the yarn surface are greater than those tending to incorporate them within the body of the yarn at higher spindle speeds. Higher draft before ring frame-less hairiness. There is a gradual reduction of hairiness with increase in draft. In other word, as the fiber parallelization increases hairiness decreases. Reversing the card sliver before the first drawing head causes a reduction in hairiness, the effect being similar to that resulting from the inclusion of an extra passage of drawing. Smaller roving package-less hairiness. Yarn hairiness decreases with decrease in roving (doff) size, and yarn spun from front row of roving bobbins is more hairy and variable as compare to that spun from back row of

rowing bobbins. It may be noted that though the trends are consistent yet the differences are non-significant: The spinning tension has a considerable influence on the yarn hairiness. The smaller the tension,the greater the hairiness. This is the reason why heavier travellers result in low yarn hairiness.If the traveller is too heavy also , yarn hairiness will increase. Spindle eccentricity leads to an increase in hairiness. Small eccentricities influence hairinessrelatively little, but, from 0.5 mm onwards, the hairiness increases almost exponentially with eccentricity. The increase in hairiness due to spindle eccentricity, will be influenced by the diameter of ring,dia of bobbin, the shape of the traveller,the yarn tension, etc. Yarn hairiness will increase if the thread guide or lappet hook is not centred properly. Heavier traveler- less hairiness. The reduced hairiness of yarns at higher traveller weights can be explained by the combined effect of tension and twist distribution in the yarn at the time of spinning. The spindle speed remains constant, but the tension in the yarn will increase with increasing traveller weight, and better binding of the fibers would be expected.Parallel fibers-less hairiness. The improvement of yarn quality on combing is mainly ascribed to the reduction in the number of short fiber improvement in length characteristics, and fiber parallelization. There is a marked difference in hairiness of the carded yarn and the combed yarns, even with a comber loss of only 5%, but the effect on hairiness of increasing the percentage of comber waste is less marked. Combing even at low percentage waste causes a marked drop in hairiness relative to that of the carded yarn. In the case of combed cotton yarns the average value of hairiness decreases with increase in count, whereas in the case of polyester/ viscose blend yarns the hairiness increases with increase in count. In the case of polyester/ cotton blend yarns trend is not clear.Flat and round travellers do not influence yarn hairiness, but a greater degree of hairiness wasobserved with elliptical travellers and anti-wedge rings. Traveller wear obviously influences hairiness because of the greater abrasion on the yarn.Yarn hairiness increases with the life of the traveller. Bigger the ring diameter, lower the yarn hairiness. Yarn spun in a dry atmosphere is more hairy.

Hairiness variation between spindles is very detrimental. Because these variation can lead toshade or appearance variaion in the cloth. The variation in hairiness within bobbin can be reduced considerably by the use of heavy travellersalone or by balloon-control rings with travellers of normal weight. In both the cases yarn is preventedfrom rubbing against the separators. Yarn hairiness is caused by protruding ends, by the presence of a majority of fibre tails.

This suggests that these tails will become heads on unwinding and that friction to which theyarn is subjected will tend to increase their length. It is therefore logical that a yarn should be morehairy after winding. Repeated windings in the cone widning machine will increase the yarn hairiness and after threeor four rewindings, the yarn hairiness remain same for cotton yarns. Winding speed influences yarn hairiness, but the most important increase in hairiness is producedby the act of winding itself. Because of winding, the number of short hairs increases more rapidly thatn the number of long hairs. In two-for-one twisters (TFO), more hairiness is produced because, twist is imparted in two steps.Yarn hairiness also depends upon the TFO speed, because it principally affects the shortest fibre ends. Hairiness varitions in the weft yarn will result in weft bars. Hairiness Testing of YarnsHairiness of yarns has been discussed for many years,but it always remained a fuzzy subject. With the advent of compact yarns and their low hairiness compared to conventional yarns,the issue of measuring hairiness and the proper interpretation of the values has become important again.Generally speaking,long hairs are undesirable, while short hairs are desirable (see picture ). The picture shown below just give a visual impression of undesirable and desirable hairiness at the edge of a cops.Figure:

RING YARN COMPACT YARNThere are two major manufacturers of hairiness testing equipment on the market,and both have their advantages and disadvantages. Some detail is given below.USTERUSTER is the leading manufacturer of textile testing equipment. The USTER hairiness H is defined as follows . H =total length (measured in centimeters) of all the hairs within one centimeter of yarn .(The hairiness value given by the tester at the end of the test is the average of all these values measured, that is,if 400 m have been measured,it is the average of 40,000 individual values) . The hairiness H is an average value,giving no indication of the distribution of the length of the hairs. Let us see an example

0.1cm 0.2cm 0.3cm 0.4cm 0.5cm 0.6cm 0.7cm 0.8cm 0.9cm 1.0cm total

yarn 1

100 50 30 10 5 6 0 2 1 0 398

yarn 2

50 10 11 5 10 0 5 10 0 11 398

Both yarns would have the same hairiness index H, even though yarn is more desirable,as it has more short hairs and less long hairs,compared to yarn 2.This example shows that the hairiness H suppresses information,as all averages do. Two yarns with a similar value H might have vastly different distributions of the length of the individual hairs. The equipment allows to evaluate the variation of the value H along the length of the yarn. The "sh value "is given, but the correlation to the CV of hairiness is somehow not obvious.A spectrogram may be obtained.2.ZWEIGLEZweigle is a somewhat less well known manufacturer of yarn testing equipment. Unlike USTER,the Zweigle does not give averages. The number of hairs of different lengths are counted separately, and these values are displayed on the equipment. In addition, the S3 value is given,which is defined as follows: S3 =Sum (number of hairs 3 mm and longer)In the above example,the yarns would have different S3 values: S3yarn 1 =2 . S3yarn 2 =4 .

A clear indication that yarn 2 is "more hairy "than yarn 1. The CV value of hairiness is given a histogram (graphical representation of the distribution of the hairiness) is given.The USTER H value only gives an average,which is of limited use when analyzing the hairiness of the yarn.The Zweigle testing equipment gives the complete distributionof the different lengths of the hairs. The S3 value distinguishes between long and short hairiness, which is more informative than the H value.HAIRINESS IN YARNI am very happy to add this article written by Mr.Kamatchi Sundaram , All india Service Manager of VOLTAS LTD. INDIA, in my site. He is one among the good technologists who has indepth knowledge about textile technology and spinning machines. I hope this information is of use to the technical people who browse through this site.Hairiness is a measure of the amount of fibres protruding from the structure of the yarn. In the past, hairiness was not considered so important. But with the advent of high-speed looms and knitting machines, the hairiness has become a very important parameter. In general, yarn spun with Indian cotton show high level of hairiness due to the following reasons. 1. High short fibre content in mixing. 2. Low uniformity ratio.3. High spindle speeds.Hence most of the Indian yarns have a hairiness index above 50% Uster standards. However, as this parameter is becoming more and more important, Indian spinners are concentrating more on this aspect and try to reach at least 25% standards by conducting lot of trials. He has conducted a lot of such studies on hairiness and he is pleased to share his learning’s with you.Hairiness is measured in two different methods.1. USTER HAIRINESS INDEX: This is the common method followed in India. The hairiness index H corresponds to the total length of protruding fibres within the measurement field of 1cm length of the yarn.2. ZWEIGLE HAIRINESS INDEX:This zweigle hairiness measurement (S3) gives the number of protruding fibres more than 3 mm in length in a measurement length of one meter of the yarn.From the above you can infer that Uster hairiness index give the total length of hairs whereas zweigle hairiness testers give the absolute number of fibres.

Though the later measurement is more accurate, most of the Indian spinners are still following Uster hairiness index only.The factors effecting hairiness can be sub divided into 3 major components.a) The fibre properties.b) Yarn parameters.c) Process parameters.a)THE FIBRE PROPERTIES:Fibre length, Uniformity ratio, Micronaire and short fibre content are the properties exerting high influence on hairiness. Among the above the length and short fibre content exerting major influence. For a particular count, higher length of fibre leads to lesser hairiness and high short fibre content leads to high hairiness.b)YARN PARAMETER:Hairiness is dependent on the number of fibres present in the cross section of the yarn. Hence coarser yanrs have more hairiness compared to finer yarns. The yarn twist is another major factor and higher twists lead to less hairiness up to a certain extent. This is the main reason while hosiery yarns normally have high hairiness compared to warp yarns. However in a mill condition, the fibre parameters and yarn parameters cannot be adjusted. Hence the next topic, process parameters, assumes very high significance, as this is the only available option at the mill level to reduce the hairiness. C) PROCESS PARAMETER:The preparatory machines do not have a big influence on hairiness. The Speed frame, Ring frame and the Cone winder are the only machines to be attended for reduction in hairiness. I give below the various process parameters that can be attended for reducing the hairiness.a)SPEED FRAME:1. Roving hank: It plays a major role in the reduction of hairiness. For a particular count, the hairiness of the yarn goes down, as the roving hank is made finer and finer.For example: If 30s yarn is spun with 0.8 and 1.0 hank, yarn made with 1.0 hank will give lesser hairiness than the yarn made with the 0.8 hank. Hence please conduct a trial with finer roving hank to reduce the hairiness.

The results of the study conducted recently at a leading mill are given below for your reference on this point. TRIALS ON HAIRINESSEFFECT OF ROVING HANK ON HAIRINESS

Ring rail bottom po Ring rail top postion

COUNT 24 ch 24 ch 24 ch 24 ch 24 ch 24 ch

ROVING HK

1.0 0.9 0.8 1.0 0.9 0.8

SPACER 3.0 3.0 3.0 3.0 3.0 3.0

U% 8.75 8.8 8.72 8.61 8.54 8.68

thin (-50%)

0 0 0 0 0 0

thick (+50%)

10 15 15 9 11 14

Neps (+200%)

12 18 21 12 14 18

Total IPI 22 33 36 21 25 32

Hairiness Index

7.52 7.86 8.45 6.4 6.48 7.09

Sh(-) 1.31 1.3 1.48 1.19 1.27 1.41

You would note from the above that the hairiness as well as imperfections have improved significantly by using finer hank of the roving. 2. Spacer Size: It is the normal tendency of the technicians to use spacer as thin as possible to reduce the U% and imperfections. But thinner spacers lead to higher hairiness. Hence please conduct a trial with a spacer, which is 1.0 to 1.5 mm thicker than existing spacer.b)RING FRAME:1. Ring Traveller: It is generally opined by many technicians that the traveller plays a major role in hairiness. Though selection of the traveller plays a small role in hairiness (specially with reference to the yarn clearance), it’s effect is quite less. This is because the yarn contact point with the traveller is quite far away from the ring and traveller contact point. Hence even if the traveller is run for a long time, the hairiness will not increase. But the breakage rate will increase. 2. Ring: It is the general opinion of some technicians that imported rings give lesser hairiness than Indian rings. It is also believed by technicians that older rings give more hairiness. Recent studies / trials conducted by us recently at a leading mill indicate this not to be true. Please refer the table below.EFFECT OF RINGS ON HAIRINESS

RING COPS TRAIL (TOP POSITION OF THE RING RAIL)

PARAMETERS old lmw rings new lmw rings bracker rings

NOMINAL COUNT

30s CH 30s CH 30s CH

U% 9.37 9.59 9.59

Thin (-50%) 0 0 0

Thick (+50%) 24 28 24

Neps (+200%) 51 52 58

Total IPI 75 80 82

Hairiness Index 5.4 5.26 5.33

Sh(-) 1.18 1.13 1.17

RING COPS TRAIL (BOTTOM POSITION OF THE RING RAIL)

PARAMETERS old lmw rings new lmw rings bracker rings

NOMINAL COUNT

30s CH 30s CH 30s CH

U% 9.24 9.18 9.24

Thin (-50%) 0 0 0

Thick (+50%) 26 19 27

Neps (+200%) 49 44 46

Total IPI 75 63 73

Hairiness Index 6.11 6.06 6.22

Sh(-) 1.27 1.26 1.29

You would note from the above trials that:a) There is no significant difference in hairiness between Imported & Indian rings.b) There is also no significant difference in hairiness between a new and a one-year-old ring. However if the condition of the ring is highly worn out , it will affect the hairiness. In short the ring and traveller do not play a major role on hairiness compared to other process parameters, which are explained below.3) SPACER SIZE: Size of the spacer plays significant role in reducing the hairiness. Many technicians have a tendency to use the thinnest spacer for reduction in U% and imperfections. However it leads to significant increase in hairiness.

A study conducted recently at a leading mill proves this point. Please refer the table below for the above study. EFFECT SPACER SIZE ON HAIRINESS

Ring rail bottom position Ring rail Top position

COUNT 24s CH 24s CH 24s CH 24s CH

ROVING HK 0.8 0.8 0.8 0.8

SPACER 3.0 4.0 3.0 4.0

U% 8.7 9.06 8.58 8.76

thin (-50%) 0 0 0 0

thick (+50%) 8 15 7 12

Neps (+200%) 14 16 16 19

Total IPI 22 31 23 31

Hairiness Index

7.32 6.72 5.87 5.35

Sh(-) 1.27 1.19 1.07 1.06

You would note from the above that there is a significant reduction in hairiness by using thicker spacer. However the imperfection has also increased. .The spacer should be selected such that optimum results are achieved with respect to imperfections as well as hairiness. We request you to conduct a trial with a spacer, which is 0.5 to 1mm thicker than the existing spacer. It is needless to mention that using thicker spacer will increase the imperfections. However if the reduction in hairiness is more significant than increase in imperfections it can be allowed.4) TPI IN THE YARN: Increasing the TPI leads to reduction in hairiness and this is more significant in the case hosiery yarn. Hence if the hairiness is a bigger problem faced by mill, trials can be conducted by increasing the TPI up to the allowable limit for achieving reduction in hairiness. 5) LAPPET HEIGHT: Reduction in lappet height leads to direct reduction in hairiness. However care should be taken to ensure that the yarn does not touch the tip of the Empties. Please conduct trials with reduced lappet height (Formula: Lappet height = 2D+5mm).

6) SUCTION TUBE SETTING: The suction tube should be set such that the yarn does not touch the tip of the suction tube in running. If the yarn touches the suction tube due to improper setting, it will lead to increase in hairiness. 7) TRAVELLER SIZE: Usage of heavier traveller leads to reduction in hairiness. For Example: If the breakage rate in 30s carded hosiery count is same with 4/O and 6/O traveller, using 4/O traveller will give lesser hairiness than 6/O traveller. 8) LIFT AND RING DIAMETER: Using lesser lift and lesser ring diameter will lead to direct and significant reduction in hairiness. For Example: If 30s carded hosiery count is spun with 170/38 and 180/40 combination, spindle speeds remaining the same, the former combination will give much lesser hairiness than the later combination because of a reduction in the height and diameter of the yarn balloon while spinning. C) CONE WINDER:There will be a significant difference between the hairiness of the yarn at cop stage and at cone stage. The cone winding process increases the hairiness by 15 to 20%, which is unavoidable. However, if the modern AutoConers are not tuned properly, it will lead to increase in hairiness of much more than 20%. In this case the following points need attention.1. WINDING SPEED: The speed of winding plays a significant role on increase in hairiness. The increase in winding speed leads to direct increase in the hairiness. The results of the study conducted recently at a leading mill are given below for your reference on this point. EFFECT OF WINDING SPEED ON HAIRINESS

PARAMETERS Cop resultwinding speed 1200 m/min

winding speed 1400 m/min

winding speed 1600 m/min

NOMINAL COUNT

30 s CH 30 s CH 30 s CH 30 s CH

U% 9.37 9.59 9.6 9.53

Thin (-50%) 0 0 0 0

Thick (+50%) 16 14 15 17

Neps (+200%) 39 41 41 50

Total IPI 55 55 59 50

Hairiness Index 5.04 7.13 7.47 7.5

Sh(-) 1.08 1.59 1.66 1.73

You would note from the above that the hairiness increases more and more with the increase in the winding speed. However it is not economically feasible to run the AutoConer at slow speed just for achieving lesser hairiness. But all the AutoConers have a provision to adjust the speed of winding according to the stage of the cop and this is called variable speed arrangement. By selecting the right speeds at different stage of the cop the increase in hairiness can be controlled to a great extent.2. YARN TENSION DURING WINDING: By optimizing the yarn tension the increase in hairiness can be controlled. The results of the study conducted recently at a leading mill are given below for your reference on this point.

PARAMETERStension 25 grams

tension 32 grams

NOMINAL COUNT

30/1 CH 30/1 CH

U% 9.73 9.68

Thin (-50%) 0 0

Thick (+50%) 23 19

Neps (+200%) 52 48

Total IPI 75 67

Hairiness Index 7.41 7.72

Sh(-) 1.74 1.79

You would note from the above that the hairiness can be reduced by optimizing the winding tension. This trial may be conducted at your mills for controlling the hairiness. 3. WAX PICK UP: It is the normal practice of many mills to apply wax on the hosiery yarn during winding. By controlling the wax pick up, the increase in hairiness can be reduced. The detail of the study recently conducted at a leading mill is given below for your reference. EFFECT OF WAX PICK UP ON HAIRINESS

PARAMETERS wax pick up 0.8 gms/kg wax pick up 1.2 gms/kg

NOMINAL COUNT

30/1 s CH 30/1 s CH

U% 9.84 9.91

Thin (-50%) 0 1

Thick (+50%) 32 30

Neps (+200%) 89 112

Total IPI 121 1459

Hairiness Index 8.13 7.89

Sh(-) 1.84 1.87

We request you to conduct a study of this aspect at your mills for control of hairiness. Thus, there are several process parameters that can be optimized for controlling the hairiness. Unless the ring and traveller are in a worn out condition, the role played by the ring and traveller on hairiness is quite negligible on modern ring frames like LG5/1 and LR/6. YARN EVENNESS TESTERDIAGRAMThe mass variations or weight per unit length variations are recorded and printed as a Diagram bythe Evenness tester. The diagram is an extremely important part of evenness testing. It contains alarge amount of information which cannot be provided by the wavelength spectrum, U% value, and theimperfections. Diagrams help to understand the following seldom occuring events long wave-length variations periodic mass variations with wave-lengths which are longer than 40m(which can not be confimedby the spectrogram. extreme thick and thin places randomly occurring thick and thin places which tend to be available in batches. slow changes in the mean value step changes in the mean value with periodic faults, it can be determined whether the fault is permanently availabe or occursonly in batches with measurements "within a bobbin", seldom occurring events can be found and changes in the meanvalue taking place over a number of kilometers can be confirmed. with unusual measured values, it can be proved in many cases by means of the diagram whether theserefer to a faulty or to a correct measurement. RELATIVE COUNT:It is a measure used to calculate the count variations using capacitance method of USTER TESTER.It calucalates a value called "Average Value Factor AF". This factor is

proportional to the mean countof the tested sample length. The relative count describes the variation of count between separate measurements within a sample. Thesingle values are calculated such that they are in direct reference to the mean value of the samplewhich is always considered to be 100%. The relative count is always estimated with reference to atest length of 100m or 100 yards. From the single-overall report, it is possible to recognize immediately which samples are lying aboveor below the mean value. The standard deviation provides a reference to the variation in count betweensamples. As the mean value is always 100%, the standard deviation also provides a reference to thecoefficient of variation. If the samples are from the same bobbin this would indicate the "within bobbin"variation and if the samples are from the same bobbin this would indicate the "within bobbin" variationand if the samples are from different bobbins this would indicate "between bobbin" variation. VARIANCE LENGTH CURVE:The variance-length curve is generally regarded as the most useful technique for expressing theyarn irregularity data. Any fibre assembly has a TOTAL IRREGULARITY CV(T), and this coefficient ofvariation is made up of two terms. These are the coefficient of variation within length ,CV(L) and the coefficientof variation between lengths CB(L). The co-efficient of variation at different cut lengths provided by the evenness testers provide invaluableinformation with regard to the variations prevalent at the specific cut lengths. Therefore independently, theshor, medium and long term variations could be studied by estimating the coefficient of variation ofthe required length. However, such numerical values, cannot directly provide complete information onthe source of faults. The spectrogram provides a possibility of localizing the source of fault but with aspectrogram, only faults of periodic nature could be identified and that too,

in most cases, only if proceededby some other means of identifying the machine / processing stage responsible for the fault. When thevariations prevailing at different cut lengths are simultaneously represented graphically, it providesthe possibility of segregating cut lengths at which abnormal variations occur and consequently identifythe process stage which is most likely to be responsible. This is made possible by the "VarianceLength Curve" which is a standard feature of most evenenss testers. A variance-length curve can be set out in quite a simple manner by cutting a fibre assembly into piecesand determining gravimetrically the mass of these pieces. The CV value is then calculated from each of theseseparate values. If this procedure is repeated for various cut lengths and the CV value drawn out,one obtains the variance-length curve. Uster tester can be used to obtain the curve in a much shortertime than is possible by manual analysis. For constructing the variance length, the measuring fieldlength is taken as the basic cut length at which the CV is calculated and plotted. For variations atother cut lengths, the mass of successive portion of material are added up and the CV calculated.Strictly speaking, the variance-length curve is only a straight line on double logrithmic paper in themedium length range of approx.1 cm to 100m. For cut lengths shorter than 1 cm and longer than 100m,the variance-length curve tends to become flatter. One can easily comprehend that the curve for thesame raw material and same ideal processing conditions will always be a straight line with an unchangedangle of inclination. Deviations from the straight line must therefore indicate porblems due to themachine or the raw material. THEORETICAL LIMIT FOR IRREGULARITY:The spinning process is based primarily on a procedure which evenly mixes the fibre, separates eachfibre from its neighbour, lays the fibres parallel to each other and draws these out to produce a

? final count. The mixing leads, however, to the fact that each single fibre has the same probabilityof appearing in any chosen section of the fibre mass. The fibres are therefore equally distributed inthe fibre assemblies.

The number of fibres in any section considered is dependent on random variations.The fibres overlap each other and result, even under the best conditions, in a spun material whichhas a certain minimum irregularity. With the natural fibres, in contrast to the synthetic staple fibres,there is an additional irregularity because the single fibres themselves have differences in their fibrecorss sectional size. The theoretical investigations have helped to arrive at a formula which will help us to calculatethe limiting irregularity.CV(lim) = 100 /(sqrt(N)where,N = mean number of fibres in the cross section. CALCULATION OF NUMBER OF FIBRES IN THE YARN CROSS-SECTION:The number of fibres in the cross section of a yarn can be calculated if the fibre fineness and yarncount in tex are available, or can be converted into tex(gram per 1000m) N = T/Tfwhere,N = number of fibres in the cross sectionT = count of the fibre material in TEXTf= Fibre fineness in TEXINERT TEST:The uster evenness testing installations offer two possible modes of operation which are referred toas the Normal test Inert test With the "NORMAL TEST" , a signal is obtained from the tested masterial which is in reference to the measuringfield length of the applied measuring slot.

In the operating mode "INERT TEST", the signal obtained from the test material is passed through anelectrical filter arrangement. Normally, the signal from the test material consists of short and long-term variations which are superimposed on each other. By means of this filter procedure, the shorter-termvariations are suppressed in a certain manner, so that only the mean value variations, i.e thelong-term mass variations, will be traced out in the diagram. This testg serves primarily to provide, an indication of the random mean value variations in the test material a means of localizing and indicating long term periodic variations in the test material a means of facilitating the setting of the mean value at the yarn signal instrument. If medium-term varitaions appear in a diagram, one can make these more distinctive by choosing a suitablediagram feed and suitable material speed and operating with the mode Inert test.

CONSTANTS AND CALCULATIONS:

FIBRE FINENESS, YARN COUNTS AND CONVERSIONS:

Micronaire value(cotton) : The unit is micrograms per inch. The average weight of

one inch length of fibre, expressed in micrograms(0.000001 gram).

Denier(man-made fibres): Weight in grams per 9000 meters of fibre.

Micron:(wool): Fineness is expressed as fibre diameter in microns(0.001mm)

Conversions:

Denier = 0.354 x Micronaire value

Micronaire value = 2.824 x Denier

YARN COUNTS:

It is broadly classified into 1. DIRECT and 2.INDIRECT system.

DIRECT SYSTEM:

English count (Ne)

French count(Nf)

Metric count(Nm)

Worsted count

Metric system: Metric count(Nm) indicates the number of 1 kilometer(1000 meter)

lengths per Kg.

Nm = length in Km / weight in kg (or)

Nm = length meter / weight in grams

INDIRECT SYSTEM:

Tex count

Denier

CONVERSION TABLE FOR YARN COUNTS:

tex Ne den Nm grains/yd

tex den/9 1000/Nm gr.yd x 70.86

Ne 590.54/tex 5314.9/den Nm x .5905 8.33 / gr/yd

den tex x 9 9000/Nm gr/yd x 637.7

Nm 1000/tex 9000/den 14.1 / gr/yd

grains/yd tex / 70.86 den / 637.7 14.1/Nm

Where, Nm - metric count, Nec - cottoncount

CONVERSION TABLE FOR WEIGHTS:

ounce grains grams kilograms pounds

ounce 437.5 grains 28.350 grams

grains 0.03527 ounces

0.0648 grams

grams 0.03527 grains 15.432 grains 0.001 kgs

kilograms 35.274 ounces 15432 grains 1000 grams 2.2046 pounds

pounds 16.0 ounces 7000 grains 453.59 grams 0.4536 kgs

CONVERSION TABLE FOR LINEAR MEASURES:

yard feet inches centimeter meter

yard 3 feet 36 inches 91.44 cms 0.9144 meter

feet 0.3333 yards 12 inches 30.48 cms 0.3048 meter

inches 0.0278 yards 0.0833 feet 2.54 cms 0.254 meter

centimeter 0.0109 yards 0.0328 feet 0.3937 inches 0.01meter

meter 1.0936 yards 3.281 feet 39.37 inches 100 cms

CALCULATIONS:

grams per meter = 0.5905 / Ne

grams per yard = 0.54 / Ne

tex = den x .11 = 1000/Nm = Mic/25.4

Ne = Nm/1.693

DRAFT = (feed weight in g/m) / (delivery weight in g/m)

DRAFT = Tex (feed) / Tex(delivery)

DRAFT = delivery roll surface speed / feed roll surface speed

No of hanks delivered by m/c = (Length delivered in m/min) / 1.605