Yarn Faults And ClearingIt is still not possible to produce a yarn without faults for various reasons. Stickiness of cotton can contribute to the formation of thick and thin places. Fly liberation in Ringframe department is one of the major reasons for short faults in the yarn because of the fly gets spun into the yarn. Hence it is not possible to have fault free yarn from ringspinning, it is necessary to have yarn monitoring system in the last production process of the spinning mill. As physical principle for electronic yarn clearing the capacitive and the optical principle have established. Both principles have their advantages in specific applications.Depending upon the rawmaterial, the machiery set up, production and process parameters, there are about 20 to 100 faults over a length of 100 km yarn which do not correspond to the deisred appearance of the yarn. This means that the yarn exhibits a yarn fault every 1 to 5 km. These faults are thick and thin faults, foregin fibres and diry places in the yarn.The yarn faults which go into the woven or knitted fabric can be removed at very high costs or can not be removed at all. Therefore the yarn processing industry demands a fault free yarnThe difference between frequent yarn faults and seldom occuring yarn faults are mainly given by the mass or diameter deviation and size. These faults are monitored by classimat or clearer installation on windingEach yarn contains, here and there, places which deviate to quite a considerable extent from the normal yarn corss-section. These can be short thick places, long thin places , long thick places or even spinners doubles. Eventhough such events seldom occur, they represent a potential disturbance in the appearance of the fabric or can negatively influnece subsequent processing of the yarn.Short thick places are those faults which are not longer than approximately 8 cms, but have a cross-sectional size approx. twice that of the yarn. These faults are relatively frequent in all spun yarns. To an extent they are the result of the rawmaterial ( vegetable matter, non-seprated fibres, etc). To a much larger extent, these faults are produced in the spinning section of the mill and are the result of spun in fly. Short thick places are easily determinable in the yarn. In many cases, they cause disturbances in subsequent processing. Once they reach a certain size( cross-section and length) , and in each case accoridng to the type of yarn and its application, short thick place fults can considerably affect the appearance of the finished product.Long thick places are much more seldom-occuring than the short thick places and usually have a length longer than 40cms. In some cases, their length can even reach many meters. Their cross sectional size approx. + 40% to +100% and more with respect of the mean cross-section of the yarn. Long thick places will affect the fabric apperance. Faults like spinners doubles are difficult to determine in the yarn, with the naked eye. On the other hand, they can produce quite fatal results in the finished product. A spinners double in the warp or in yarn for circular knitting can downgrade hundreds of meters of woven , or knitted fabric.Thin places occur in two length groups. Short thin places are known as imperfections, and have a length approx. three times the mean staple length of the fibre. Their frequency is dependent on the rawmaterial and the setting of the drafting element. They are too frequent in the yarn to be extracted by means of the electronic yarn clearing.Long thin places have lengths of approx. 40cms and longer and a cross-sectional decrease with respect to the mean yarn cross-section of approx.30 to 70%. They are relatively seldom-occuring in short staple yarns, but much more frequently-occuring in long staple yarns. Long thin faults are difficult to determine in the yarn by means of the naked eye. Their effect in the finished product however, can be extremely serious.The quite extensive application of electronic yarn clearing has set new quality standards with respect to the number of faults in spun yarns.It is therefore necessary to evolve a method of yarn fault classification before clearing the faults in winding. The most important aspect is certainly the determination of the fault dimensions of cross-sectional size and length. With such a cross-section and length classification and by means of the correct choice of the class limits, the characteristic dimensions of the various fault types can be taken into consideration, then a classification system will result which is suitable primarily for satisfying the requirements of yarn clearing and yet allows, to quite a large extent, for a selection of the various types of faults.Types of Electronic Yarn ClearersElectronic Yarn Clearers available in the market are principally of two types -capacitive and optical. Clearers working on the capacitive principle have mass'as the reference for performing its functions while optical clearers function with diameter' as the reference. Both have their merits and demerits and are equally popular in the textile industry. Besides the above basic difference in measuring principle, the basis of functioning of both the types of clearers are similar if not exactly same. Since most of the other textile measurements like, U% / CV%, thick and thin places etc., in various departments take into account mass as the reference parameter, the functioning of the capacitive clearer is explained in some detail in the following sections.Functioning PrincipleThe yarn is measured in a measuring field constituted by a set of parallely placed capacitor plates. When the yarn passes through this measuring field (between the capacitor plates), an electrical signal is produced which is proportional to the change in mass per unit length of the yarn. This signal is amplified and fed to the evaluation channels of the yarn clearing installation. The number and type of evaluation channels available are dependent on the sophistication and features of the model of the clearer in use. Each of the channels reacts to the signals for the corresponding type of yarn fault. When the mass per unit length of the yarn exceeds the threshold limit set for the channel, the cutting device of the yarn clearer cuts the yarn.Yarn Clearer SettingsThe yarn clearer has to be provided with certain basic information in order to obtain the expected results in terms of clearing objectionable faults. The following are some of them -A. Clearing LimitThe clearing limit defines the threshold level for the yarn faults, beyond which the cutter is activated to remove the yarn fault. The clearing limit consists of two setting parameters - Sensitivity and Reference Length.i. Sensitivity - This determines the activating limit for the fault cross sectional size.ii. Reference Length - This defines the length of the yarn over which the fault cross - section is to be measured. Both the above parameters can be set within a wide range of limits depending on specific yarn clearing requirements. Here, it is worth mentioning that the reference length' may be lower or higher than the actual fault length'. For a yarn fault to be cut, the mean value of the yarn fault cross-section has to overstep the set sensitivity for the set reference length. B. Yarn CountThe setting of the yarn count provides a clearer with the basic information on the mean value of the material being processed to which the clearer compares the instantaneous yarn signals for identifying the seriousness of a fault.C. Material NumberBesides the yarn count there are certain other factors which influence the capacitance signal from the measuring field like type of fibre (Polyester / Cotton / Viscose etc.) and environmental conditions like relative humidity. These factors are taken into consideration in the Material Number'D. Winding SpeedThe setting of the winding speed is also very critical for accurate removal of faults. It is recommended that, instead of the machine speed, the delivery speed be set by actual calculation after running the yarn for 2-3 minutes and checking the length of yarn delivered. Setting a higher speed than the actual is likely to result in higher number of cuts. Similarly a lower speed setting relative to the actual causes less cuts with some faults escaping without being cut. In most of the modern day clearers, the count, material number and speeds are monitored and automatically corrected during actual running of the yarn.Fault ChannelsThe various fault channels available in a latest generation yarn clearer are as follows: 1. Short Thick places

2. Long Thick Places

3. Long Thin Places

4. Neps

5. Count

6. SpliceThe availability of one or more of the above channels is dependent on the type of the yarn clearer. Most of the modern clearers have the above channels. Besides detection of the various types of faults, with latest clearers, it is also possible to detect concentration of faults in a specific length of yarn by means of alarms(cluster faults).Contamination ClearingDetection of contamination in normal yarn has become a requirement in recent times due to the demands by yarn buyers abroad. Therefore, some of the optical yarn clearers have an additional channel to detect the contamination in yarn. This is mostly used while clearing cotton yarn. The various facilities available in the yarn clearers nowadays enable precise setting and removal of all objectionable faults while at the same time ensure a reasonably high level of productivity.

WindingRing spinning produces yarn in a package form called cops. Since cops from ringframes are not suitable for further processing, the winding process serves to achieve additional objectives made necessary by the requirements of the subsequent processing stages.Following are the Tasks of Winding Process Extraction of all disturbing yarn faults such as the short, long thick ,long thin, spinners doubles, etc Manufacture of cones having good drawing - off properties and with as long a length of yarn as possible Paraffin waxing of the yarn during the winding process Introduction into the yarn of a minimum number of knots Achievement of a high machine efficiency i.e high produciton level The winding process therefore has the basic function of obtaining a larger package from several small ring bobbins. This conversion process provides one with the possibility of cutting out unwanted and problematic objectionable faults. The process of removing such objectionable faults is called as yarn clearing'Practical experience has proven that winding alters the yarn structure.This phenomenon does not affect yarn evenness, but affect the following yarn properties Thick Places Thin Places Neps Hairiness Standard Deviation of Hairiness Winding TensionIf winding tension is selected properly, the following tensile properties are not affected Tenacity Elongation Work- to- break But excessive tension in winding will deteriarate the above said tensile properties.Characterestics Of Bobbin Formation Stretch Length It is the length of the yarn deposited on the bobbin tube during each chase (one up and down movement of ringrail ) of ring rail. The length should be around 3.5 to 5 meters. It should be shorter for coarser yarns and longer for fine yarns. Winding RatioIt is the ratio of the length of yarn wound during the upward movement of the ring rail and the length wound during the downward movement of the ringrail. Bobbin TaperThe ratio of the length of the upper taper of the cop (bobbin with yarn) to the diameter of the bobbin must be 1:2 or greater. Winding SpeedIt depends upon the following factors Count Type of Yarn, (type of fibre, average strength and minimum strength) Type and Charactersitics of Bobbin Package Taper Final Use of Package The best winding speed is the speed which allows the highest level of production possible for a given type of yarn and type of package, and with no damage whatsoever to the yarn.(abrasion and breaks due to excessive tension)Winding ProductionIt depends upon the following factors Winding speed Time required by the machine to carry out one splicing operation Bobbin length per bobbin( both bobbin weight and tpi to be considered, because TPI will affect the bobbin length). This decides the number of bobbin changes The number of faults in the yarn and the clearer settings, this decides the clearer cuts Count The number of doffs. It depends upon the doff weight. Higher the doff weight, lower the number of doffs The time taken for each doff either by the doffer or by an operator Down time due to red light. It depends upon, number of red lights, number of repeaters setting for red lights, clearer settings like off count channel, cluster setting which will result in red lights and others Bobbin rejections, it depends on weak yarn, wrong gaiting, double gaiting, bobbin characteritics etc. Following are Some of the Winding Package Defects which will result in complaints Yarn Waste in the Cones This is due to loose yarn ends that are wound on to the cone Stitch, Drop Over, Web Yarn is visible on the small or on the big side of the cone either across the side , around the tube, or going back in the cone Damaged Edges or Broken Ends on the Cone The yarn is broken on the edges or in the middle of the cone. Ring Formation The yarn runs in belt formation on to the package, because it is misguided Without Transfer Tail The desired transfer tail is missing or too short Ribbon Formation Pattern or ring formation are made by the drum when rpm are staying the same Displaced Yarn Layers yarn layers are disturbed and are sliding towards the small diameter of the cone Misguided Yarn The yarn is not equally guided over the hole package Cauliflower On the smaller side of the package, the yarn shows a wrinkle effect Soft and Hard Yarn Layer Some layer of yarn are pushed out on the small side of the cone Soft and Hard Cones Great difference in package density from one winder head to anotherA bobbin change occurs when yarn on the bobbin is fully exhausted during winding. But if a bobbin is changed with yarn still left on it, we call it Rejected Bobbin'. The quantity of yarn on the bobbin may vary from full bobbin to only few layers of yarn.The Various Reasons of Bobbin Rejections are as follows:1. Bobbin Quality Long Tail End Kirchi/Lapetta Deshaped Bobbin Overfilled Bobbin Bottom Spoiled Bobbin Ring Cut Bobbin Soft Bobbin Sick Bobbin2. Bobbin Feeding in Magazine Presence of under-winding and back-winding while feeding the bobbins in the magazine leads to rejection3. Top Bunch Transfer Failure Top bunch position is lower with respect to bobbin tip. Blowing device does not come down to concentrate blow at the bobbin tip. Very few numbers of coils at the bobbin tip. Removal of top bunch due to fault in cutter at the bobbin preparatory or any other reason. Very few numbers of coils at the top bunch.4. Fault in Winding Unit, Splicing Failure5. Yarn Quality High degree of objectionable fault Count variation High Hairiness BobbinBobbin Quality Checking for Best WindingWhenever there is a count change in ring frame, the cop quality should be checked. Proper quality of cop ensures higher winding efficiency. The cop quality is checked as per the following parameters:1. Bobbin Parameters2. Cop Content : Depending on the spindle lift and ring diameter, the cop content (in gms) should be checked3. Diameter of the Cop : The Actual cop diameter' must be checked against Standard cop diameter'. The standard cop diameter depends on the ring diameter. Standard Cop Diameter = Ring Diameter - 3mm.4. Back Winding : The number of back winding coils should be around 1.5 to 2.5 and the maximum length of back winding should not be more than 80cms5. Under Winding : The number of under winding coils should be around 2 to 3 and the maximum length of back winding should not be more than 20cm. As the under winding and back winding increases, more time is wasted to open them up before feeding in the magazine and also hard waste is increased.6. Top Clearance : The clearance from bobbin tip to yarn body of a full cop should be approx 10 mm. If the top clearance is too less, it may cause slough off at the start of the bobbin unwinding7. Bottom Clearance : The clearance from bobbin bottom to yarn body of should be approx. 10mm. If the bottom clearance is too less, it may cause bottom spoiled bobbin8. Yarn Length per Chase : The length of yarn per chase should be around 3.5 to 5.5 m. If the length is too long, it may lead to slough of during high speed unwinding.9. Bobbin Hardness : The bobbin hardness should be around 50 to 55. Soft bobbins results slough off. Besides the above mentioned points, the cops should be also checked for long tail end, deshaped bobbin, kirchi & lapetta, ring cut, overfilled and bottom spoiled bobbin to ensure high production efficiency in winding.Due to the ever-increasing emphasis on better quality of yarn for the competitive market and process performance, the normal parameters of yarn tenacity, unevenness and imperfections are not adequate to completely define today's quality. Besides the above mentioned traditional parameters, so many factors influence the performance of the yarn in the subsequent process such as process parameters in ring spinning & cone winding, work procedures in ring spinning & cone winding and ambient conditions. So to attain the expected quality for any applications such as weaving or knitting, one should focus mainly on the fault free feed material preparation because it contributes more than any other factor. Best winding capabilities can be achieved through best bobbin quality.A high degree of yarn quality is impossible through knot, as the knot itself is objectionable due to its physical dimension, appearance and problems during downstream processes. The knots are responsible for 30 to 60% of stoppages in weaving.Splicing is the ultimate method to eliminate yarn faults and problems of knots and piecing. It is universally acceptable and functionally reliable. This is in spite of the fact that the tensile strength of the yarn with knot is superior to that of yarn with splice. Splicing is a technique of joining two yarn ends by intermingling the constituent fibres so that the joint is not significantly different in appearance and mechanical properties with respect to the parent yarn. The effectiveness of splicing is primarily dependent on the tensile strength and physical appearance. Splicing satisfies the demand for knot free yarn joining: no thickening of the thread or only slight increase in its normal diameter, no great mass variation, visibly unobjectionable, no mechanical obstruction, high breaking strength close to that of the basic yarn under both static and dynamic loading, almost equal elasticity in the joint and basic yarn. No extraneous material is used and hence the dye affinity is unchanged at the joint. In addition, splicing enables a higher degree of yarn clearing to be obtained on the electronic yarn clearer.Splicing technology has grown so rapidly in the recent past that automatic knotters on modern high speed winding machine are a thing of the past. Many techniques for splicing have been developed such as Electrostatic splicing, Mechanical splicing and Pneumatic splicing. Among them, pneumatic splicing is the most popular. Other methods have inherent drawbacks like limited fields of application, high cost of manufacturing, maintenance and operations, improper structure and properties of yarn produced.Pneumatic SplicingThe first generation of splicing systems operated with just one stage without proceeding to trimming. The yarn ends were fed into the splicing chamber and pieced together in one operation. Short fibres, highly twisted and fine yarns could not be joined satisfactorily with such method. Latest methods of splicing process consist of two operations. During the first stage, the ends are untwisted, to achieve a near parallel arrangement of fibres. In a second operation the prepared ends are laid and twisted together.Principle of Pneumatic SplicingThe splicing consists of untwisting and later re-twisting two yarn ends using air blast, i.e., first the yarn is opened, the fibres intermingled and later twisted in the same direction as that of the parent yarn. Splicing proceeds in two stages with two different air blasts of different intensity. The first air blast untwists and causes opening of the free ends. The untwisted fibres are then intermingled and twisted in the same direction as that of parent yarn by another air blast Structure of SpliceAnalysis of the longitudinal and transverse studies revealed that the structure of the splice comprises of three distinct regions/elements brought by wrapping, twisting and tucking / intermingling. Yarn WrappingThe tail end of each yarn strand is tapered and terminates with few fibres. The tail end makes a good wrapping of several turns and thus prevents fraying of the splice. The fibres of the twisting yarn embrace the body of the yarn and thus acts as a belt. This in turn gives appearance to the splice.Yarn TwistingThe two yarn ends comprising the splice are twisted around the body of the yarn, each yarn strand twists on the body of the yarn on either side of the middle of the splice. The cross-section of this region distinctly shows the fibres of the two yarn strands separately without any intermingling of the fibres.Yarn Tucking / Yarn InterminglingThe middle portion of the splice is a region (2-5 mm) with no distinct order. The fibres from each yarn end intermingle in this splice zone just by tucking. The studies on quantitative contribution of splice elements showed that intermingling/tucking contributes the most to the strength of splice (52%), followed by twisting (33%) and wrapping (about 15%). The lower strength of the splice is attributed to the lower packing coefficient of the splice zone. Spliced yarn has a lower breaking elongation than normal yarn. Breaking elongation is mainly affected by intermingling. Wrapping and twisting provides mainly transverse forces. The absence of fibre migration gives lower breaking elongation to splice.Effect of Variables on the Properties of the Spliced yarnSeveral studies have been conducted on the effect of various variables on the properties of the spliced yarn.Effect of Fibre Properties and Blend Fibre properties such as torsional rigidity, breaking twist angle and coefficient of friction affect splice strength and appearance. The lower torsional rigidity and higher breaking twist angle permit better fibre intermingling. Higher coefficient of friction of fibres generates more inter-fibre friction to give a more cohesive yarn. Thus, these properties of fibre contribute to better retention of splice strength. In blended yarn, usually the addition of polyester to other fibre blend like P/W, P/C both for ring and rotor spun yarn increases splice strength.Effect of Yarn FinenessSeveral studies on cotton, polyester and wool report that coarser yarns have higher breaking strength but a moderate extension. The coarse yarn cross section contains more fibres and provides better fibre intermingling during pre-opening, hence the splice is stronger than that of finer yarns.Effect of Yarn TwistAn increase in the twist significantly increases the breaking load and elongation, even at higher pneumatic pressure. This could be due to better opening of the strands at higher pneumatic pressure. Splicing of twisted ply yarn is more complicated than single yarn due to the yarn structure having opposing twists in the single and doubled yarns. Twisted yarns also require a relatively longer time for complete opening of the yarn ends.Effect of Different Spinning MethodsYarn produced with different spinning methods exhibit different structure and properties. Therefore, these yarns show significant differences in splice quality. The ring spun yarn lent best splicing but the potential of splicing is affected by the spinning conditions. The breaking strength percentage of ring spliced yarns to a parent yarn is 70% to 85% for cotton yarn. However, the breaking strength and extension of splice vary with fibre and yarn properties. Rotor spun yarns, due to the presence of wrapper fibres, make it difficult to untwist and the disordered structure is less ideal for splicing. The breaking strength retention varies from 54% to 71% and is much lower compared to the splice of ring spun yarns. In case of friction spun yarns, the highest relative tensile strength obtained at the spliced joints can be above 80%, but a number of splicing failures occurs due to unfavourable yarn structure. The air-jet-spun (MJS) yarn and the cover spun yarn are virtually impossible to splice. Only very low tensile strengths and elongation values can be attained due to the inadequate opening of the yarn ends during preparation of the splicing. The coefficient of variation of these properties is also generally high.Effect of Opening PressureA study on 50/50 polyester cotton, 25 tex ring spun yarn shows a rise in tensile strength up to a certain opening pressure. However, long opening time deteriorates the strength. An increase in pressure up to 5 bar caused release of fibre tufts and fibre loss from the yarn ends in P/C blend which is due to intensive opening, but beyond this pressure, drafting and twisting in the opposite direction may also occur.Effect of Splicing DurationWith a given splicing length, when the splicing is extended for a long period of time, the breaking strength of the spliced yarn and also their strength retention over the normal value of the basic yarn increases because of increased cohesive force resulting from an increased number of wrapping coils in a given length. The effects are more pronounced at higher splicing lengths. It is desirable however, that splicing duration be as short as possible. The splicing duration alone has no conclusive effect on elongation properties of splice yarn. It has also been observed that, for maximum splice strength, different materials require different durations of blast. These are between 0.5 to 1.8 seconds. Effect of Splicing LengthStudies on splicing of flyer and wrap spun yarns spun with different materials, showed that regardless of the splicing material, the breaking strength and strength retention of both yarn types increase with the splicing length because of the increased binding length of the two yarn ends. Elongation at break and retention of elongation of both flyer and wrap spun spliced yarns increase with the splice length. Compared to the splicing duration, the splicing length has more pronounced effect on the load-elongation properties of the spliced yarn. It can be therefore be stated that the splices made on longer lengths and for longer period of time have more uniform strength.Effect of Splicing ChamberThe factors like method and mode of air supply and pressure along with type of prism affect the splicing quality. It was observed that irregular air pressure has advantages over constant pressure for better intermingling in the splicing chamber, which varies with different staple fibres, filament yarns, and yarns with S and Z twists. It is not possible to make a general comment regarding potential of the splicing chamber due to the multiplicity of factors influencing splicing.Comparison of Dry and Wet SplicingThe comparative studies on dry and wet splicing with water showed that the breaking load retention for wet spliced yarns are significantly greater than dry spliced yarns. In fact, wet splicing is more effective for yarn made from long staple fibres and for coarse yarn. This may be due to higher packing coefficient resulting from wet splicing.Assessment of Yarn Splice QualityThe two important characteristics of a splice are appearance and strength. Although quality of splice can be assessed by methods like load-elongation, work of rupture, % increase in diameter and evaluation of its performance in down stream process etc., the appearance can be assessed either by simple visual assessment or by comparing with photograph of standard splice.

What is Ply Yarn / What is Plying / Plying DefinitionFor sewing threads as well as for some speciality industrial yarns , it is necessary to ply (to double or fold) the yarns to give them a smoother and less hairy character.Doubling improves the evenness and plying balances torque if carried out correctly and binds some of the hairs on the component yarns.PlyingPlying is a process used to create a strong, balanced yarn. It is done by taking two or more strands of yarn that each have a twist to them and putting them together. The strands are twisted together, in the opposite direction than that in which they were spun. When just the right amount of twist is added, this creates a balanced yarn, which is a yarn with no tendency to twist upon itself. Almost all store bought yarns are balanced, plied yarns.A two-ply yarn is thus a yarn plied from two strands, a six-ply yarn is one from six strands, and so on. Most commercial yarns are more than a two ply. Embroidery floss is generally a six ply yarn.Plying YarnRegular plying consists of taking two or more singles and twisting them together, the opposite way. This can be done on either a spinning wheel or a spindle. The most important thing to remember though is that the twist must go the opposite direction. If in spinning the single the wheel was spinning clockwise (which is called a "Z" twist, as on any given side the fibres appear to cross diagonally in the same direction as the diagonal of a "Z"), in order to ply it the wheel must spin counter-clockwise (an "S" twist). This is because otherwise you are not balancing the twist, just twisting it more. The concept is similar to when a heavily twisted piece of yarn is folded, and it twists up on itself. It is most common for singles to be spun with a "Z" twist, and then plied with an "S" twist.Novelty YarnsMany novelty yarns make use of special plying techniques to gain their special effects. By varying the tension in the strands, or the relative sizes of the strands, or many other factors different effects can be achieved. For example, when a soft, thick strand is plied against a tightly twisted thin strand, the resulting yarn spirals. Another example is boucl, which is a yarn where one strand is held loosely and allowed to make loops on the other yarn while plying.