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Yarn hairiness, its causes and effect to the fabric

 Introduction

Hairiness significantly influences the properties of yarns and fabrics. Hairiness in warp yarns can cause considerable breakage and hence stoppage of weaving looms, thus reducing the efficiency of production. It causes pilling on fabrics, resulting in poor appearance. Yarn hairiness is very complex, but this parameter is now as routinely tested as the other parameters of yarns. Hairiness can be defined as the state of migrated fibre ends and fibre loops pushed to the surface of the yarn body. The factors causing yarn hairiness can be studied in three different ways; the physical properties of fibres, yarn parameters and machine parameters used. Several investigations have been carried out on the influence of the ring traveller. In some studies, it was observed that yarn hairiness decreased as the weight of the traveller increased, whereas in some others it was stated that as the traveller weight is increased the hairiness gradually decreased to a certain point, and then started to increase.

The effect of yarn hairiness on the textile operations following spinning, especially weaving and knitting, and its influence on the characteristics of the product obtained and on some fabric faults has led to the introduction of measurement of hairiness.The quality of yarn in a textile mill is normally defined in terms of various parameters but is based principally on two measures – mass variation along the length and yarn strength. The importance of yarn hairiness as a quality parameter, though felt by the industry for quite some time, has failed to register universal popularity. A major factor for this situation was the lack of an accurate method of estimation and the limitation with regard to the reproducibility of the hairiness measure.

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SummaryThe awareness has been rapidly increasing among textile mills to estimate and control the hairiness levels within acceptable limits. This has particularly been necessitated by a steady increase in the production speeds of spinning and winding machinery, which tend to abrade the surface of the yarn resulting in higher hairiness. It is worth mentioning here that an increase in hairiness is not always a negative feature, a certain amount of hairiness being necessary for obtaining a good cover of the woven or knitted fabric, but a high level of hairiness variation is certainly undesirable.Periodic variation in hairiness has been traced to be a cause for alternate thin and thick bands in fabrics:1. It affects performance of yarn in subsequent stages. Adjoining warp threads cling together in the loom shed because of long hairs in yarn, which in turn resist separation of sheet during shedding. This leads to more warp breaks and fabric defects like stitches and floats.2. Excessive lint droppings in sizing, loom shed and during knitting are encountered with hairy yarns because of shedding of hairs and broken hairs.3. In printed goods, prints will be hazy and lack sharpness if yarn is hairy.4. In sewing breakages will be high with hairy yarns and removal of hairiness by singeing is invariably practiced.5. Pilling tendency will be more with higher hairiness. Pilling is a major problem with knitted and polyester blend fabrics.6. Increases air drag on rotating packages and balloon.With the availability of yarn hairiness characteristics in different forms such as the diagram, spectrogram, etc, in the Uster Tester 4 installation, similar to mass variation characteristics, the hairiness variations, their periodicities, etc, can be effectively analyzed. Important is the fact that the introduction of yarn hairiness can be traced to machine sources and consequently corrective measures may be introduced.

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Facts about yarn hairiness:
Hairiness occurs because some fiber ends protrude from the yarn body, some looped fiber arch out from the yarn core and some wild fiber in the yarn.§  Pillay proved that there is a high correlation between the number of protruding ends and the number of fiber in the yarn cross-section.§  Torsion rigidity of the fiber is the most important single property affecting yarn hairiness. Other factors are flexural rigidity, fiber length and fiber fineness.§  Mixing different length cottons-No substantial gain in hairinessAlthough 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 when the yarn twist increases because of a greater degree of binding between the fibers owing to twist. The number of wild fiber decreases only very slightly with twist because of their position on the yarn 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 fiber 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 length of the loops. The hairiness is affected by the yarn twist, since an increase in twist tends to shorten the fiber ends.
§  Wild fibers are those for which the head alone is taken by the twist while the tail is still gripped by the front drafting rollers.§  Fiber 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 fiber.

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Causes and recovery of yarn hairiness:*      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 condensers: The yarns produced with condensers in the drafting field, particularly if these are situated in 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:a.       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.b.      The increase 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.c.       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.a.       Flat and round travelers do not influence yarn hairiness, but a greater degree of hairiness was observed with elliptical travelers and anti-wedge rings.b.      Traveler wear obviously influences hairiness because of the greater abrasion on the yarn. Yarn hairiness increases with the life of the traveler. c.       Bigger the ring diameter, lower the yarn hairiness.d.      Yarn spun spun in a dry atmosphere is more hairy.e.       Hairiness variation between spindles is very detrimental. Because these variation can lead to shade or appearance variation in the cloth.f.       The variation in hairiness within bobbin can be reduced considerably by the use of heavy travelers alone or by balloon-control rings with travelers of normal weight. In both the cases yarn is prevented from rubbing against the separators. Yarn hairiness is caused by protruding ends, by the presence of a majority of fiber tails.g.      This suggests that these tails will become heads on unwinding and that friction to which the yarn is subjected will tend to increase their length. It is therefore logical that a yarn should be more hairy after winding.h.      Repeated windings in the cone winding machine will increase the yarn hairiness and after three or four rewinding, the yarn hairiness remains same for cotton yarns. i.        Winding speed influences yarn hairiness, but the most important increase in hairiness is produced by the act of winding itself. j.        Because of winding, the number of short hairs increases more rapidly that the number of long hairs.k.      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 fiber ends.l.        Hairiness variations in the weft yarn will result in weft bars.

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Measurement of hairiness: Hairiness consists of protruding fibers, looped fibers and loosely wrapped wild fibers. The methods of yarn hairiness measurement are as follows:i)                    Subjective Methodsii)                  Microscopic Methodsiii)                Photoelectric Method  Subjective Methods:Yarns can be graded for hairiness by comparison of appearance. Relative levels of hairiness in two yarns can be easily judged by comparison of full bobbins. Wrapping the yarn on a blackboard and comparing them can also be employed for grading hairiness. Uster has developed yarn hairiness grade standard boards. This will assist in grading of yarns. Paired comparisons by a number of unbiased observers can determine statistically significant differences in hairiness through estimation of coefficient of consistency.Microscopic Methods:Before instruments were developed, hairiness was measured by viewing the yarn under a microscope. Image of yarn is projected on a screen and number of protruding hairs and loops in a known length are counted. Length of protruding hairs is also measured with the help of micrometer eyepiece scale. From this, total length of hairs per unit length is determined. Pillay projected the yarn on Projectina microscope and counted the number of protruding ends and loops in 10 mm length. Length of protruding fibers is measured by a curvimeter on a tracing of yarn image. Jedryka took photographs of yarn image under microscope with a magnification of 50x. The boundary levels of yarn were marked. Four zones parallel to the boundary line were drawn on either side. The lines were equidistant with space between adjoining lines being kept as half the diameter of yarn. Hairiness is determined by the number of intersections the fiber makes with the lines marking the zone on either side. This method gives the hairiness as per the length of the hairs. About 50 to 100 yarn samples are examined from which average hairiness is determined.Major difficulty in microscopic methods is in identifying the boundary of yarn. Looped fibers, wild fibers, low twisted portions, variation in yarn diameter and cross-section smudge the boundary. High variation in hairiness is found both within and between bobbins and as a result, large number of yarn specimens has to be examined to get a fairly reliable estimate. This makes the method laborious and time consuming.Photoelectric Method:Several instruments are available for measurement of hairiness based on photoelectric method.i.                    Shirley-Atlas Hairiness Testerii.                  Zweigle Hairiness Testeriii.                Meiners Dell Hairiness Testeriv.                Changling Hairiness Testerv.                  Uster Testervi.                Premier Electronic Testervii.              Weighing Techniqueviii.            Online Measurement a.     Shirley-Atlas Hairiness TesterA measuring head consisting of a photocell placed close to the yarn counts the number of interruptions made by the protruding hairs to an LCD beam. The measuring head is infinitely adjustable from 1 to 10 mm from the surface of yarn. This enables measurement of hairiness as per the length of hairs. Nip rollers at 50 to 300 m/min drive yarn by an electronic variable speed drive. Latest version is operated by a PC. Continuous chart of hairiness can also be obtained through a recorder or printer. A portable battery operated model is available for online measurement of hairiness with a standard measuring head of 3 mm. Portable model will enable detection of spindles giving high hairiness.b.     Zweigle Hairiness TesterThis also uses a measuring head with a photocell and a laser light source. The instrument measures hairiness of 9 length zones from 1 to 12 or 15 mm fiber length in a single run of the yarn and produces a running chart of hairiness. Faults of a periodic nature can be detected. . The equipment is controlled by a PC, which carries out statistical analysis of the results. There is a facility for checking and matching all the optical channels with the reference value set ex works. Calibration with the yarn that has been checked on a master Hairiness tester is also possible. The above facilities improve reproducibility of results. An automatic bobbin changer up to 24 bobbins is available which makes the instrument fully automatic. Most of the research work on hairiness is based on tests on this instrument.   c.      Mainers Dell Hairiness TesterThe instrument measures simultaneously hairiness of hair lengths from 1 to 10 mm in steps of 1 mm. A single run of the yarn gives hairiness for all lengths at a selected speed. A portable model is also available which enables online measurement of hairiness.d.     Changeling Hairiness TesterThis uses a laser light source and a sensitive integrated photocell for measuring number of projecting hairs. Measurements of hair number for lengths from 1 to 9 mm are possible.Apart from estimates of number of hairs, length-wise, another parameter that is commonly used is S3 value, which indicates the number of fibers, which protrude beyond 3 mm length.e.      Uster TesterUster Evenness Tester has a hairiness attachment. Measuring field consists of homogenous rays of parallel light from an infrared light source. Scattered light from the protruding hairs of yarn, placed in this field, reach an optical sensor, which converts it into an electronic signal. The body of yarn itself is dark as it is not transparent and so does not contribute to the measurement. The protruding fibers are bright and reflected light from these fibers alone contributes to measurement. Hairiness thus measured is an estimate of total length of protruding fibers in a cm length and is termed as Hairiness index. Hairiness index of 4 means that the total protruding length of hairs in 1 cm length is 4 cm.Uster has been publishing periodically Uster standards for hairiness based on survey of mills worldwide. While this method has the merit that it gives a single index to characterise the hairiness, it has the drawback that it does not provide information on long length and short length hairs separately. Thus two yarns may have the same hairiness index but one may have more long hairs and fewer short hairs than other. Since long hairs are more objectionable than short hairs, information on the level of hairs as per their length will be more useful. Uster tester further gives coefficient of hairiness over measured lengths 1 cm (normal) 10, 100, 300, 1000, 5000 cm or in other words variance length curve of hairiness. Presence of periodicity in hairiness can also be determined by spectrogram of hairiness.While some studies have shown a good correlation between hairiness by Shirley hairiness tester and Uster tester, others have found little association. While Uster hairiness index is based on all hair lengths, S3 is based on hairs 3 mm and longer. So these two measures will correlate well only when number of hairs vs hair length relation is similar. Good correlation exits between Uster hairiness index of compact and normal ring spun yarns spun from a number of cottons. But Zweigle hairiness S3 values of compact and normal ring spun did not show any correlation. This once again confirms that Uster hairiness index and S3 values do not always go hand in hand.f.       Premier Electronic TesterPremier Qualicenter, which is similar to Uster Tester, has an attachment to measure hairiness by hair count as well as Hairiness index method.Speed of testing affects hairiness results. Hairiness is found to reduce with test speed in SDL teste. Direction of hairs, air drag and rubbing action against guides affect hairiness results. This could be one of the reasons for the different results obtained on different instruments. Humidity conditions in testing room as also conditioning time of yarn, affect hairiness. ASTM standard D5647-01 (1995) gives a standard method for measuring hairiness with photoelectric instruments. This will be helpful to minimize variations from laboratory to laboratory.g.     Online MeasurementBarco Profile Optical Measuring Unit, Uster Quantum Clearer and Loepfe Yarn Spectra and Lab Pack enable online measurement of yarn diameter and hairiness. The unit is fitted on clearer of winding unit and on rotor machine and sets aside packages, which give hairiness beyond a preset limit. Online measurement monitors the entire production and enables identification and prompt correction of defective units, which give high hairiness.h.    Weighing TechniqueDifference in the mass of yarn before and after singeing is used as a measure of hairiness. Flaw in this method is that a large amount of yarn has to be singed to get an accurate estimate. Moreover singeing does not fully remove fully projecting hairs particularly of shorter length.

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Factors influencing yarn hairiness: i.                    Mode of formation ii.                  Yarn Parameters iii.                Process Parametersiv.                Ring framea.       Strand width.b.      Spindle speed.c.       Doff position.d.      Chase position.e.       Traveller.f.       Weight.g.      Profile.v.                  Cross section vi.                Traveler vii.              Ring a.       Flange number.b.      Wear and tear.c.       Lappet.viii.            Disturbed spindle centering ix.                Separator x.                  Spindle and bobbin variation xi.                Relative humidity xii.              Winding             a.     Mode of formationHairiness is produced at two zones in ring spinning. 1. At the delivery point of front roller. 2. In the ring/traveller junction. A small amount of hairiness is also made at lappet and separator. Selvedge fibers in the strand do not get fully integrated into yarn, as twist does not flow right up to the nip because of spinning triangle. The effect is more for the trailing portion of fiber, as the tension in the fiber drops to zero, the moment trailing end leaves front roller nip. Trailing portion of majority of selvedge fibers therefore show up as hairs. The leading portion of fibers at the extreme end of selvedge may also project as hair, because of their non-integration into strand. Some of the loosely bound leading as well as trailing portion of fibers will develop into hairs because of abrasion at traveller/ring junction.By dividing the yarn cross-section into 5 concentric zones of equal radial spacing, Wang et al found that the outer most zone formed 36% and outer two zones 64% of the total yarn cross-section. They therefore concluded that trailing hairs come from fibers in the outer two zones and leading hairs come from fibers in outer most zone of yarn. Spinning triangle at front roller nip is however not symmetric because the twist flow is more to the right side than to left side of the strand (in Z twisted yarns). This is because, as shown by Morton, front bottom roller does not permit folding under of left side of fringe. Fibers in left selvedge of strand therefore contribute more towards protruding hairs and wild fibers. This is confirmed by the studies of Wang et al. If the distance travelled by a fiber in the left side of spinning triangle could be reduced by some means, hairiness can be reduced. Towards this end, Wang and Cheng spun yarn on the spindle to the left of drafting roller on a woollen ring frame as this should reduce the height of spinning triangle at the left. Contrary to expectations, this resulted in more hairiness than conventional spinning. On the other hand, spinning yarn on a spindle to the right of drafting roller gave less hairiness than conventional and spinning on left side spindle.b.     Yarn ParametersCount and twist have considerable influence on hairiness. Coarser yarns have more hairiness than finer yarns because of higher number of fibers in cross-section in the former. Yarn count has the maximum influence on hairiness. Yarn hairiness chart therefore bears a close correspondence with irregularity chart, with coarser regions having more hairiness than finer portions. Hairiness reduces with increase in twist because of shorter spinning triangle and more effective twisting in of surface fibers into yarn. With firmly bound fibers chances of release due to abrasion at traveller/ring junction is minimized. Hairiness is therefore more in hosiery yarns, which have low twist.c.      Process ParametersPillay found fiber parallelization reduces on hairiness. Hairiness therefore comes down with increase in number of draw frame passages. With more draw frame passages, fiber orientation is increased and fiber hooks are reduced. As a result fiber extent along the length of strand is increased this is the reason for reduction in hairiness. For the same reason combed yarns have less hairiness than carded yarns. Further with combing, short fiber content is reduced which is another reason why hairiness is reduced. A compact roving by use of front zone floating condenser at speed frame will bring down hairiness, as this will reduce strand width at ring frame. Floating condenser can be used behind front roller at speed frame without any working problems in hanks 1.4 Ne and finer but with coarser hanks from short staple cottons choke up of condenser is encountered.d.     Ring FrameRing frame includes following parameters,


 

i)                    Strand width.ii)                  Spindle speed.iii)                Doff position.iv)                Chase position.v)                  Traveller.vi)                Weight.

vii)              Profile

 

Strand WidthStrand width at the front roller nip has the maximum influence on hairiness. Strand width is much wider than final yarn diameter and as a result twist does not flow right up to the nip of front roller. Selvedge fibers do not get fully twisted into yarn. If the strand width is reduced, twist will flow closer to front roller nip and spinning triangle will be smaller and fibers in selvedge will be integrated better into yarn. As will be discussed later, compact spinning was developed based on recognition of this fact. A coarser roving hank and higher ring frame draft will therefore increase hairiness. This is confirmed by studies by Pillay. Floating condenser behind front roller has been tried to reduce strand width but did not meet with success because of choke up fibers in the condenser. Further, front zone setting has to be increased to accommodate floating condenser and this will increase irregularity. Spindle speedHigher spindle speed is generally found to increase hairiness. This is because of the larger balloon at higher speed. With a larger balloon, traveller tilt will be more and this will reduce the space available for yarn passage and there will be chafing and abrasion of yarn. Twist flow at lappet will also be reduced. Moreover yarn will dash against separator with bigger balloon thereby generating hairiness. Doff positionDoff position and chase positions have a significant influence on hairiness. When comparing the hairiness of yarns at different doff positions in mills and it was found that hairiness is higher at cop bottom position. This is because of larger balloon found at cop bottom, which increases traveller tilt and causes dashing of yarn against separator. In some cases, an increase in hairiness is found towards the end of doff.Chase positionHairiness is more at the shoulder and reduces progressively towards the nose of the chase as shown in Figure 1. The balloon is bigger at shoulder and traveller tilt is more. Yarn also dashes against separator. Both these factors increase hairiness. The periodic variation in hairiness in the chase, thus caused, is sometimes a source of hairiness.A mill was experiencing high fabric rejections due to weft bar. The weft bar consisted of alternate thick and thin bands with varying amplitude and periodicity. Thick and thin band portions did not show any difference in pick spacing, count, twist or diameter of yarn. But the hairiness of yarn was found to be markedly higher in thick band portion compared to thin band portion.The yarn from thick band is found to be more hairy. As a result, hairs in this portion cover interspaces between yarns and more light gets reflected leading to a denser appearance. Length of yarn in one period of thick and thin band was found to be close the length of yarn in one chase of ring bobbin. The cloth was woven on Sulzer loom where 2 splits were made side by side. Cloth width in each split was close to one half of the length of yarn wound during chase movement of ring rail. As a result, yarn from shoulder regions goes to one split and that from nose goes to the next split. But as the yarn made during one half of chase movement is slightly longer than cloth width in one split, a gradual shift in poisoning of yarns from shoulder to the nose region takes place. Yarns from shoulder and nose regions group together alternately in the fabric leading to formation of thick and thin bands.WeightHeavier traveller up to a limit reduces hairiness because of improved flow of twist to front roller nip. As a result pilling of knitted material reduces. Higher tension associated with heavier traveller will also help to firmly twist the surface fibers into yarn.

 

ProfileElliptical traveller has a low bow size and as a result limited space is available for passage of yarn. Chafing of yarn will therefore be more resulting in increased hairiness. 'C' shape traveller has a high bow size, which provides ample space for passage of yarn. Hairiness will be least with this traveller. But as centre of gravity is higher with 'C', it results in unstable flight and traveller fly especially at high speeds. Further traveller profile does not match with profile of anti wedge rings, which leads to unsteady traveller flight and rapid wear.As a compromise, Clip and EM1 and EM2 travellers were developed. While having an elliptical profile these travellers have a higher bow size than elliptical. Hairiness will therefore be lower with these travellers compared to elliptical without compromising on speed. Bow size becomes more critical when rings are worn out.In one mill hairiness was high on 44s warp yarn, due to worn out condition of rings. The rings were No 1 flange antiwedge and traveller used was HRW clip. As change of ring will take time, and since spindle speeds were not high, 'C' type traveller was used in place of clip. A marked reduction of hairiness was found with 'C' as will be seen from Figure 2. As 'C' type traveller wears out fast, traveller replacement cycle has to be accelerated.  e.      Cross-section: Round wire or half round wire cross-section will give less hairiness than flat wire. This is because of reduced frictional resistance to yarn movement by the former.f.       Traveler: Weight, profile and type of cross-section of traveler have critical influence on hairiness 1.     Application of lubricant to travellerApplication of specially developed lubricant to the traveller has been found helpful in reducing hairiness by 20 – 30%. The reduction is more prominent immediately after application of lubricant and gradually reduces with passage of time. Application of lubricant once in 6 – 9 days is therefore necessary to good full benefits. It is important to ensure while choosing the lubricant that it does not stain the yarn. BTRA has developed lubricants meeting this requirement.Travellers with coatings, such as silver and ceramic coating and chromium plating, are available for reducing traveller wear and for extending traveller-changing frequency. Because of their smooth finish, friction between yarn and traveller is reduced, which brings down hairiness. Usta and Canoglu found that with heavier travellers, silver coating brings down hairiness.2.     Traveller Changing FrequencyHairiness is found to increase over the traveller replacement cycle because of traveller wear. Rate of increase is initially slow but after a point of time becomes rapid as shown in Figure 3. For hosiery, sewing threads and p/c blends, where low hairiness is desired, traveller replacement frequency has to be kept low. Hairiness increases with traveller wear because of unstable traveller flight and flutter which accompanies it.3.     New Traveller DesignNewer Ring and traveller designs like Spicon of BRT and Orbit by Rieter have been developed to reduce traveller wear. With such designs the traveller in its running position lies in a plane close to resultant of all forces acting on it and as a result traveller tilt is minimum. As a result hairiness is lower with such ring/traveller combinations. Moreover round wire cross-section could be used without compromise on speeds.g.     RingRing influence hairiness considerably by followings,i)                    Flange number.ii)                  Wear and tear.iii)                Lappet.Flange NoHigher flange number gives more space for passage of yarn and will reduce hairiness. But traveller wear will be more and higher speeds cannot be achieved in finer counts. Normally No 2 flange should be used up to 20s count and No 1 flange should be used for counts 30s and above. For bringing down hairiness No 2 flange may be used in counts of border range.Wear and tearWorn out ring is a major cause of hairiness and variation in hairiness in mills. When wear is pronounced, the bobbins are highly hairy and exhibit whisker like defects. Rings were not changed for 9 years in a mill and were extremely worn out. Upon replacing the rings a substantial reduction of hairiness is seen.When rings are more than 3 years old, hairiness starts increasing. Replacement of rings will bring significant reduction in hairiness.Yarns spun on pilot plant ring frame give lower hairiness and higher strength than those on mill's ring frame though same roving bobbins were used as feed material. This is because rings in pilot plant ring frame are worn out to a lesser extent than mills ring frame because of less running.LappetAbrasion against lappet is a source of hairiness. This gets aggravated when lappet is grooved or is worn out. Some manufacturers have come out with glass finish lappet, which minimizes friction and thereby reduces hairiness. Height of lappet above the ring bobbin has to be optimised to reduce not only end breaks but also hairiness. If lappet to bobbin tip distance is high, balloon will be longer. This will reduce twist flow and also increase area of contact between yarn and lappet. As a result hairiness will be higher. Controlled studies have shown a lower hairiness with reduction in lappet height. Care should however be taken to ensure that yarn does not touch bobbin tip while lowering lappet height.h.    Disturbed Spindle CenteringDisturbed spindle centering is one of the major causes for the spindle-to-spindle variation in hairiness. On spindles where cantering is disturbed, hairiness is found to be higher and upon accurate centering hairiness comes down significantly. When spindle is not centered traveler movement is not smooth because of peak tensions in yarn. Traveler tilts and flutters also increases leading to higher hairiness.0.     SeparatorPlastic separator will increase hairiness because of static generation. Disturbed, slanting and bent separators generate hairiness because of excessive dashing of balloon on separator.p.     Spindle and bobbin vibrationsVibration of spindle arises because of worn out spindle tip and bearing. Bobbin vibrations arise not only from spindle vibration but also from eccentricity in bobbin and improper fit. When bobbin vibrates hairiness increases because of uneven traveler flight.Plastic BobbinPlastic bobbins generally give more hairiness than wooden bobbins especially with polyester blend yarns. This is because of static generation.q.     Relative HumidityRecommended humidity in ring frame department is 55 – 60%. At higher humidity levels, fibers tend to stick to drafting rollers resulting in protruding hairs and loops. At low humidity levels static generation causes repulsion of fibers, particularly with p/v and p/c blends, leading to more hairiness.r.      WindingHairiness increases in winding. This is because of abrasion of yarn against tension disc, guide eyes, balloon breakers and winding drum. Extent of increase varies from 50 to 150%. Extent of increase in hairiness increases with winding speed. Lang et al showed, through a theoretical analysis, that hairiness increase takes place mainly at tension discs because of frictional resistance offered by disc surface to projecting hairs. As the yarn moves forward, these fibers get pulled out of yarn. Loosely bound surface fibers may also become projecting hairs because of rubbing action. The authors used a parameter K and a critical length to estimate the effect of winding on hairiness increase. Friction coefficient between yarn and friction disc has the maximum influence on K. Increase in initial tension of yarn will reduce generation of hairiness.A very interesting finding of practical significance is that initial level of hairiness in ring yarn has considerable influence on the extent of increase in hairiness in winding[16]. Ring bobbins judged to be more hairy and less hairy were selected from a ring frame in a mill spinning 60s. The yarns were separately wound on Autoconer.Short length hairs increase by 4 – 4.5 times with winding with 'Less hairy' yarns. But with 'More hairy' yarns, short length hairs do not increase with winding. Long length hairs however show an increase with winding with both 'Less hairy' and 'More hairy' bobbins.Longer hairs being on the surface of yarn are more likely to come in contact with tension disc and so get pulled out because of frictional resistance. This is the reason why they increase with both type of yarns. With 'More hairy yarns' the surface of yarn body and short length hairs are well buried under long length hairs and therefore do not come into contact with the tension disc. There is therefore no generation of short length hairs at tension disc and short length hairs therefore do not show an increase with winding with such yarns. Moreover, with 'Hairy' yarns, most of the fibers whose ends are loosely anchored on the surface have already developed into hairs in ring frame itself because of abrasion at traveller/ring junction. Therefore there are fewer such fibers that can develop into hairs during winding. This is not the case with 'Less hairy' yarns as there are many loosely anchored fibers in the yarns. The work of Dash et al supports this winding. The authors found that hairiness increase in winding is more in compact yarns (which have low hairiness) than normal yarns.  {mospagebreak}  Conclusions Yarn hairiness generally decreased as the traveler weight was increased, regardless of type or coating.Yarn tension increased with increasing traveller weight. Hence the weight of the traveller had a significant influence on reducing the yarn hairiness.The flat types of M2f and C2f travelers caused less hairiness than the M2dr half-round type travellers.It is generally accepted that yarn hairiness increased as the spindle speed is increased however, this observation appeared as only partly true in our investigation. Spinning with light weight travellers, the yarn hairiness increased regularly as the spindle speed increased; but spinning with heavy travellers, the results became irregular, e.g. higher hairiness was measured at the spindle speed of 7000 rpm than when spinning at 10,000 rpm.Yarn hairiness is reflected in pilling of the fabric produced. Consequently, as traveller weight increases, pilling of the fabrics generally decreased. It should be stressed that the fabrics did not show any pilling when yarns had been spun with C2f and M2f travelers of 106, 112 and 125 mg weight.We propose that the travellers of two counts heavier than the manufacturers’ specification must be utilised in spinning to produce less hairy yarns.In acrylic spinning, the use of M2f and C2f travellers can be preferred regarding the avoidance of hairiness in yarn, provided that they are not objectionable for other reasons.

 

     

 

 

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  1. I want to write textile article in wave side. how I want to know.
    I am a Textile engineer from textile university at 1993-94 seasons
    my email adress
    ranisur77@gmail.com

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