YARN WAXING


It is common practice to wax staple-spun yarns for knitting applications, given the problems of friction associated with the many thread line deflection points of the thread guides and the knitting needles on knitting machines. For optimal running of yarns during knitting, there needs to be a uniform wax distribution along yarns and a minimum of wax rub-off.

The amount of wax deposited on the yarn has a marked influence on the dynamic frictional characteristics of the yarn. Figure 1a shows that, at a given running speed, the yarn coefficient of friction decreases to a minimum with increasing wax deposited and then increases with further yarn waxing. Of the three zones indicated, clearly, Zone II is the preferred range of deposition, usually 0.5 to 1.0 g/kg of yarn. Wax grades vary according to melting point, oil content, microstructure, and hardness. Little has been published in the way of selecting a wax grade for optimal running performance. However, it would seem that selection depends on many factors such as fiber type; yarn structure, count, and moisture content; as well as room temperature and humidity in the winding area and during storage and shipment.

The preference with the commonly used wax disc is for a coarse microcrystalline structure, which allows small wax particles to be removed and held onto the yarn surface as shown in Figure 7.17b, as this should enable a uniform distribution of deposition. Steaming or high-humidity conditioning of wax yarns can result in an increased friction coefficient. Steaming will melt the wax particles and also give a partial penetration of wax into the yarn. If the yarn has to be relaxed in this way, then the deposition should be increased to offset the effect.

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FIGURE 1 Yarn thread line friction with increased wax take-up. (Courtesy of W. Schlafhorst AG & Co.)

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END PACKAGES PRODUCED ON WINDING M/CS


Most of the common packages on which the yarns are wound can be divided in to two groups.

(1)Parellal wound packages

(2)Cross wound packages.

(1)Parellal wound packages:-

These are double flanged bobbins,also known as warper’s bobbins on which yarn is wound in such a way that the coils of yarn are laid parellel sided or barrel shaped,Flanges are needed on either sides to support parellely laid coils.If flanges are not provided then coils at the two ends will COLLAPSE.  To withdraw the yarn from these packages,package has to be rotated by pull of yarn.Hence high unwinding speed will lead to excessive unwinding tension & yarn will break.Also as the unwinding is stopped the package continues to rotate due to its inertia,hence yarn may continue to come out from package.So this package is not suitable for the process taking place at high speed.

(2)Cross wound packages:-

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In this case the yarn is wound on cylindrical tubes or conical tubes.The yarn is laid on this in form of helices at the two extremes. In this type of winding the yarn wraps cross one another hence these packages are called cross wound packages.Because of laying in cross fashion there is no possibility of yarn coils collapsing at the two extremes.Hence these packages do not need flanges. The cylindrical cross wound package is known as CHEESE & the conical one as CONE. The yarn can be withdrawn from cone & cheese overend (& side ways unrolling also).The over end withdrawal allows unwinding at high speed without extreme increase  in tension.Rotation of package for unwinding is not essential hence the unwinding from package stops almost at the same instant when withdrawal is stopped. For some special cases yarn is required to be withdrawn side ways also.

Bobbins may be made of card or plastic, the latter being perforated if the yarn is to be package dyed. Parallel-sided cheeses have tubular bobbins. For cones, the bobbin is of a conical form, i.e., a truncated cone; the angle of taper — the semivertical angle — depends on the end use for the resulting package. Table 1 lists four common tapers. The wound cone package may have a fixed taper, which gives it flat ends, in which case the package is referred to as straight-ended. Cones may also have an accelerated taper, where the taper of the package is greater than the bobbin, resulting in a concave end at the top (the nose) and a convex end at the bottom (the base) of the package. These are called dished ends.

Table :- Common Tapers for Random-Wound Cones

Cone taper
(semivertical angle)
End uses
3°30′ General purposes
4°2′ Wet processing (e.g., dyeing)
5°5′ Weft knitting: at final diameter taper may increase to 10°
9°1′ Weft knitting: at final diameter taper may be 14° to 18°

Comparison of cross and parallel wound package

Sr no. Cross wound Package Parallel wound package
1 Self supporting Package Flanges are required to support the yarn
2 Overhead Unwinding Side-end Unwinding
3 Package is Stationary during unwinding Package rotates during Unwinding
4 The yarn stops immideatly the unwinding Stops The yarn doesnot stop unwinding as the  package continues to rotating due to inertia
5 Suitable for High speed unwinding Not suitable for high speed unwinding
6 yarn is laid at an angle to each other The yarn is laid parallel to one another
7 eg., Warper’s Bobbin Eg, Cone, Cheese & Spool

Sampling


It is not possible or desirable to test all the raw material or all the final output from a production process because of time and cost constraints. Also many tests are destructive so that there would not be any material left after it had been tested. Because of this, representative samples of the material are tested. The amount of material that is actually tested can represent a very small proportion of the total output. It is therefore important that this small sample should be truly representative of the whole of the material. For instance if the test for cotton fibre length is considered, this requires a 20 mg sample which may have been taken from a bale weighing 250kg. The sample represents only about one eleven-millionth of the bulk but the quality of the whole bale is judged on the results from it.

The aim of sampling is to produce an unbiased sample in which the proportions of, for instance, the different fibre lengths in the sample are the same as those in the bulk. Or to put it another way, each fibre in the bale should have an equal chance of being chosen for the sample methods from the test lot.

• Test specimen: this is the one that is actually used for the individual measurement and is derived from the laboratory sample. Normally, measurements are made from several test specimens.

• Package: elementary units (which can be unwound) within each container in the consignment. They might be bump top, hanks, skeins, bobbins, cones or other support on to which have been wound tow, top, sliver, roving or yarn.

• Container or case: a shipping unit identified on the dispatch note, usually a carton, box, bale or other container which may or may not contain packages.

Fibre sampling from bulk

Zoning
Zoning is a method that is used for selecting samples from raw cotton or wool or other loose fibre where the properties may vary considerably from place to place. A handful of fibres is taken at random from each of at least 40 widely spaced places (zones) throughout the bulk of the consignment and is treated as follows. Each handful is divided into two parts and one half of it is discarded at random; the retained half is again divided into two and half of that discarded. This process is repeated until about nix fibres remain in the handful (where n is the total number of fibres required in the sample and x is the number of original handfuls). Each handful is treated in a similar manner and the fibres that remain are placed together to give a correctly sized test sample containing n fibres. The method is shown diagrammatically in Fig. 1. It is important that the whole of the final sample is tested.

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Fig:- Sampling by zoneing

Core sampling
Core sampling is a technique that is used for assessing the proportion of grease, vegetable matter and moisture in samples taken from unopened bales of raw wool. A tube with a sharpened tip is forced into the bale and a core of wool is withdrawn. The technique was first developed as core boring in which the tube was rotated by a portable electric drill. The method was then developed further to enable the cores to be cut by pressing the tube into the bale manually. This enables samples to be taken in areas remote from sources of power. The tubes for manual coring are 600mm long so that they can penetrate halfway into the bale, the whole bale being sampled by coring from both ends. A detachable cutting tip is used whose internal diameter is slightly smaller than that of the tube so that the cores will slide easily up the inside of the tube. The difference in diameter also helps retain the cores in the tube as it is withdrawn. To collect the sample the tube is entered in the direction of compression of the bale so that it is perpendicular to the layers of fleeces. A number of different sizes of nominal tube diameter are in use, 14, 15 and 18mm being the most common the weight of core extracted varying accordingly. The number of cores extracted is determined according to a sampling schedule and the cores are combined to give the required weight of sample. As the cores are removed they are placed immediately in an air-tight container to prevent any loss of moisture from them. The weight of the bale at the time of coring is recorded in order to calculate its total moisture content.

The method has been further developed to allow hydraulic coring by machine in warehouses where large numbers of bales are dealt with. Such machines compress the bale to 60% of its original length so as to allow the use of a tube which is long enough to core the full length of the bale.

Fibre sampling from combed slivers, rovings and yarn

One of the main difficulties in sampling fibres is that of obtaining a sample that is not biased. This is because unless special precautions are taken, the longer fibres in the material being sampled are more likely to be selected by the sampling procedures, leading to a length-biased sample. This is particularly likely to happen in sampling material such as sliver or yarn where the fibres are approximately parallel. Strictly speaking, it is the fibre extent as defined in Fig. 1.2 rather than the fibre length as such which determines the likelihood of selection. The obvious area where length bias must be avoided is in the measurement of fibre length, but any bias can also have effects when other properties such as fineness and strength are being measured since these properties often vary with the fibre length.

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Fig 2.:- The meaning of extenet

There are two ways of dealing with this problem:
1 Prepare a numerical sample (unbiased sample).
2 Prepare a length-biased sample in such a way that the bias can be allowed for in any calculation.

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Fig 3:- Selection of numerical sample

Numerical sample
In a numerical sample the percentage by number of fibres in each length group should be the same in the sample as it is in the bulk. In Fig.3, A and B represent two planes separated by a short distance in a sample consisting of parallel fibres. If all the fibres whose left-hand ends (shown as solid circles) lay between A and B were selected by some means they would constitute a numerical sample. The truth of this can be seen from the fact that if all the fibres that start to the left of A were removed then it would not alter the marked fibres. Similarly another pair of planes could be imagined to the right of B whose composition would be unaffected by the removal of the fibres starting between A and B. Therefore the whole length of the sample could be divided into such short lengths and there would be no means of distinguishing one length from another, provided the fibres
are uniformly distributed along the sliver. If the removal of one sample does not affect the composition of the remaining samples, then it can be considered to be a numerical sample and each segment is representative of the whole.

Length-biased sample
In a length-biased sample the percentage of fibres in any length group is proportional to the product of the length and the percentage of fibres of that length in the bulk. The removal of a length-biased sample changes the composition of the remaining material as a higher proportion of the longer fibres are removed from it.

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Fig4 :- selection of tuft sample

If the lines A and B in Fig. 3 represent planes through the sliver then the chance of a fibre crossing these lines is proportional to its length. If, therefore, the fibres crossing this area are selected in some way then the longer fibres will be preferentially selected. This can be achieved by gripping the sample along a narrow line of contact and then combing away any loose fibres from either side of the grips, so leaving a sample as depicted in Fig. 4 which is length-biased. This type of sample is also known as a tuft sample and a similar method is used to prepare cotton fibres for length measurement by the fibrograph. Figure  5 shows the fibre length histogram and mean fibre length from both a numerical sample and a length-biased sample prepared from the same material.

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Fig:5 Histogram of length based and numerical samples

By a similar line of reasoning if the sample is cut at the planes A and B the section between the planes will contain more pieces of the longer fibres because they are more likely to cross that section. If there are equal numbers of fibres in each length group, the total length of the group with the longest fibres will be greater than that of the other groups so that there will be a greater number of those fibres in the sample. Samples for the measurement of fibre diameter using the projection microscope are prepared in this manner by sectioning a bundle of fibres, thus giving a length-biased sample. The use of a length-biased sample is deliberate in this case so that the measured mean fibre diameter is then that of the total fibre length of the whole sample. If all the fibres in the sample are considered as being joined end to end the mean fibre diameter is then the average thickness of that fibre.

Random draw method
This method is used for sampling card sliver, ball sliver and top. The sliver to be sampled is parted carefully by hand so that the end to be used has no broken or cut fibres. The sliver is placed over two velvet boards with the parted end near the front of the first board. The opposite end of the sliver is weighed down with a glass plate to stop it moving as shown in Fig. 1.6. A wide grip which is capable of holding individual fibres is then used to remove and discard a 2mm fringe of fibres from the parted end. This procedure is repeated, removing and discarding 2mm draws of fibre until a distance equal to that of the longest fibre in the sliver has been removed. The sliver end has now been ‘normalised’ and any of the succeeding draws can be used to make up a sample as they will be representative of all fibre lengths. This is because they represent a numerical sample as described
above where all the fibres with ends between two lines are taken as the sample. When any measurements are made on such a sample all the fibres must be measured.

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Fig 6:- The random Draw method

Cut square method
This method is used for sampling the fibres in a yarn. A length of the yarn being tested is cut off and the end untwisted by hand. The end is laid on a small velvet board and covered with a glass plate. The untwisted end of the yarn is then cut about 5mm from the edge of the plate as shown in Fig. 7. All the fibres that project in front of the glass plate are removed one by one with a pair of forceps and discarded. By doing this all the cut fibres are removed, leaving only fibres with their natural length. The glass plate is then moved back a few millimetres, exposing more fibre ends. These are then removed one by one and measured. When these have all been measured the plate is moved back again until a total of 50 fibres have been measured. In each case once the plate has been moved all projecting fibre ends must be removed and measured. The whole process is then repeated on fresh lengths of yarn chosen at random from the bulk, until sufficient fibres have been measured.

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Fig7 :- The cut square method

Yarn sampling

When selecting yarn for testing it is suggested that ten packages are selected at random from the consignment. If the consignment contains more than five cases, five cases are selected at random from it. The test sample then consists of two packages selected at random from each case. If the consignment contains less than five cases, ten packages are selected at random from all the cases with approximately equal numbers from each case. The appropriate number of tests are then carried out on each package.

Fabric sampling

When taking fabric samples from a roll of fabric certain rules must be observed. Fabric samples are always taken from the warp and weft separately as the properties in each direction generally differ. The warp direction should be marked on each sample before it is cut out. No two specimens should contain the same set of warp or weft threads. This is shown diagrammatically in Fig. 8 where the incorrect layout shows two warp samples which contain the same set of warp threads so that their properties will be very similar. In the correct layout each sample contains a different set of warp threads so that their properties are potentially different depending on the degree of uniformity of the fabric. As it is the warp direction in this case that is being tested the use of the same weft threads is not important. Samples should not be taken from within 50mm of the selvedge as the fabric properties can change at the edge and they are no longer representative of the bulk.

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Fig 8:- Fabric Sampling

DREF Spinning


  • Introduction

Friction (DREF) spinning system is an Open-end and or Core sheath type of spinning system. Along with the frictional forces in the spinning zone the yarn formation takes place. The DREF spinning system is used to produce yarns with high delivery rate(about 300mpm). Still it has to gain its importance with the growth along with technical textiles in India. Amongst the spinning systems, DREF provides a good platform for production of core spun yarns due its spinning principle.It offers less spinning tension to the core and core will be positioned exactly at the centre of the yarn.
Development of DREF core-spun yarns unveils a path for new products including high performance textiles, sewing threads and in the apparels due to its exceptional strength, outstanding abrasion resistance, consistence performance in sewing operation, adequate elasticity for the stretch requirements, excellent resistance to perspiration, ideal wash  and wear performance and permanent press.

  • Principle of Friction (DREF) spinning Systems

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The friction spinning system consists of opening & individualization of fibres from slivers, reassembling of individualized fibres, twisting and winding of yarn. The figure 1 describes the DREF spinning principle where the opened fibres made roll with an aid of a mechanical roller for reassembling and twisting. Due to separate yarn winding and method of twist insertion, it has capability to go for high production rate.

  • DREF 1

DREF-1 friction spinning system was developed in 1973 by Dr.Fehrer.A.G. of Austria.The schematic diagram of DREF 1 spinner is shown in the figure 2.The fibres were opened with an opening roller and allowed to fall on a single perforated cylindrical drum slot ,which has negative pressure for fibre collection.The rotation of the drum impart twist to fibre assembly .

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The ratio of perforated drum to yarn surface is very large, hence the drum speed can be kept relatively low, even if one takes the unavoidable slippage into account. Due to the absence of positive control over the fibres assembly, slippage occurred between the fibre assembly and perforated roller, which reduced twist efficiency. Hence this development could not be commercialized.

  • DREF-2image

This is the development with earlier machine. DREF-2 was exhibited in the year 1975 at ITMA exhibition. The feasibility of using two perforated rotating cylinders, (as fibre collecting means), while at the same time the spinning-in of fibres into yarn occurred. It operates on the basis of mechanical/aerodynamic spinning system with an internal suction and same direction of drums rotation. The schematic diagram of the DREF-2 friction spinner is shown in the figure3. Drafted slivers are opened into individual fibres by a rotating carding drum covered with saw tooth type wire clothing. The individualized fibres are stripped off from the carding drum by centrifugal force supported by an air stream from the blower and transported into the nip of two perforated friction drums where they are held by suction. The fibres are sub-sequentially twisted by mechanical friction on the surface of the drums. Suction through the perforations of the drums assists this process besides helping in the removal of dust and dirt, thereby contributing to production of cleaner yarn. The low yarn strength and the requirement of more number of fibres in yarn cross-section(minimum 80-100 fibres) were restricted the DREF-2 spinning with
coarser counts (0.3-6s Ne).

  • DREF-3

The DREF-3 machine is the next version of DREF 2 for improving the yarn quality came to the market in the year 1981.Yarns up to 18s Ne. can be spun thro this system.

This is a core-sheath type spinning arrangement. The sheath fibres are attached to the core fibres by the false twist generated by the rotating action of drums. Two drafting units are used in this system, one for the core fibres and other for the sheath fibres. This system produces a variety of core-sheath type structures and multi-component yarns, through selective combination and placement of different materials in core and sheath. Delivery rate is about 300 m/min. DREF 3 schematic diagram is shown in the figure 4.

  • DREF-5

It was developed by Schalafhorst, Suessen and Fehrer Inc. The range of count to be spun from this system is from 16’s to 40’s Ne.Production speed is up to 200m/min.The schematic diagram of the DREF 5 is shown in the figure 5. The individualized fibres from a single sliver are fed through a fibre duct into the spinning nip at an angle to the yarn axis, so that they are stretched as far as possible, when fed into the nip[7]. This spinning system was not commercialized due to some reasons.

  • DREF-2000

It is the latest development in friction spinning demonstrated in ITMA 99. DREF-2000 employs a rotating carding drum for opening the slivers into single fibres and a specially designed system being used for sliver retention. The fibres stripped off from front the carding drum by centrifugal force and carried into the nip of the two perforated spinning drums. The fibres are subsequently twisted by mechanical friction on the surface of the drums, which rotates in the same direction. The process assisted by air suction through the drum perforations. Insertion of twist in ‘S’ and ‘Z’ direction is possible without mechanical alterations to the machine. Yarns upto 14.5s Ne can be produced at speeds of 250 m/min.

  • DREF-3000

In the ITMA 2003, the first public appearance of the DREF 3000 was made. The yarn can be spun form 0.3Ne to 14.5Ne.The features of DREF 3000 includes a drafting unit and opening head with infinitely variable drive control, spinning units with two infinitely variable suction spinning drums, take-off and winding units with infinitely variable speeds and filament guide with monitoring device. The drafting unit can handle all types of synthetic fibres, special fibres such as aramid, FR and pre-oxidized fibres, polyimides, phenol resin fibres (e.g. Kynol), melamine fibres (e.g. Basofil), melt fibres (e.g. PA, PES, PP), natural fibres (wool, cotton, jute, linen, flax, etc.), as well as glass fibres in blends with other materials. The DREF 3000 processes these fibres in the form of slivers composed of one type of fibre, or using slivers with differing fibre qualities at one and the same time. Slivers with a homogenous fibre mixture can also be employed. DREF 3000 core yarns offer high output, breakage-free spinning and weaving mill operation and thus up to 95% efficiency can be achieved.

  • Yarn formation in Friction spinning system

The mechanism of yarn formation is quite complex. It consists of three distinct operations, namely: Feeding of fibres, Fibres integration and Twist insertion.

  • Feeding:

The individualized fibres are transported by air currents and deposited in the spinning zone. The mode of fibre feed has a definite effect on fibre extent and fibre configuration in yarn and on its properties. There are two methods of fibre feed 1) Direct feed and 2)Indirect feed.

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In case of direct feed, fibres are fed directly onto the rotating fibre mass that outer part of the yarn tail. In indirect feed, fibres are first accumulated on the in-going roll and then transferred to the yarn tail. Figure 7 (a) and (b) are showing the above methods of fibre feed.

  • Fibres Integration:

The fibres through feed tube assembles onto a yarn core/tail within the shear field, is provided by two rotating spinning drums and the yarn core is in between them. The shear causes sheath fibres to wrap around the yarn core. The fibre orientation is highly dependent on the decelerating fibres arriving at the assembly point through the turbulent flow. The fibres in the friction drum have two probable methods for integration of incoming fibres to the sheath. One method, the fibre assembles completely on to perforated drum before their transfer to the rotating sheath. In the other method, fibres are laid directly on to rotating sheath.

  • Twist insertion:

There has been lot of deal with research on the twisting process in friction spinning. In friction spinning, the fibres are applied twist with more or less one at a time without cyclic differentials in tension in the twisting zone. Therefore, fibre migration may not take place in friction spun yarns. The mechanism of twist insertion for core type friction spinning and open end friction spinning are different,which are described below.

Twist insertion in core-type friction spinning:
In core type friction spinning, core is made of a filament or a bundle of staple fibres is false twisted by the spinning drum. The sheath fibres are deposited on the false twisted core surface and are wrapped helically over the core with varying helix angles. It is believed that the false twist in the core gets removed once the yarn is emerged from the spinning drums, so that this yarn has virtually twist less core. However, it is quite possible for some amount of false twist to remain in the fact that the sheath entraps it during yarn formation in the spinning zone.

Twist insertion in Open end type friction spinning
In open end type friction spinning the fibres in the yarn are integrated as stacked cone. The fibres in the surface of the yarn found more compact and good packing density than the axial fibres in the yarn. The Figure 8 shown the arrangement of fibres in the DREF-3 yarn as stacked cone shape .

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  • Structure of the yarn tail:

The yarn tail can be considered as a loosely constructed conical mass of fibres, formed at the nip of the spinning drums. It is of very porous and lofty structure.The fibres rotating at very high speed. Lord and Rust have been studied a number of short-duration photographs of the yarn tail during the yarn formation. In these photographs, they located an appendage protruding from the open-end of the yarn tail and called it as the tip of the tail. Observing through the perforated drums, they found this tip to be very unstable, flickering about like a candle flame a draught. With the help of the photographs, they have concluded that the yarn tail is enlarged and torpedo-shaped being squashed by the nip of the perforated drums and the fibres on its surface are loosely wrapped. Moving away from the tip, these wrappings have been shown to
become tighter. They have further added that the surface structure of the tail consists of outstanding fibres, which stand out almost radically.

  • Spinning Tension for DREF yarns

Figure 9 explains that the Friction spun yarns have less spinning tension during the yarn formation. Due to less tension during the spinning the core component can be placed exactly at the centre of the yarn.

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  • Friction Spun Yarns Properties:

Friction spun yarns (DREF) yarns have bulky appearance (100-140% bulkier than the ring spun yarns).The twist is not uniform and found with loopy yarn surface. Friction spun yarns with high %age of core have high stiffness. Friction spun yarns are usually weak as compared to other yarns. The yarns possess only 60% of the tenacity of ring-spun yarns and about 90% of rotor spun-yarns. The increased twist and wrapping of the sheath over the core improve the cohesion between the core and sheath and within the sheath.

The breaking elongation ring, rotor and friction spun yarns have been found to be equal. Better relative tenacity efficiency is achieved during processing of cotton on rotor and friction spinning as compared to ring spinning system.

Depending on the type of fibre, the differences in strength of these yarns differ in magnitude. It has been reported that 100% polyester yarns, this strength deficiency is 32% whereas for 100% viscose yarns, it ranges from 0-25%. On the other hand, in polyester-cotton blend, DREF yarns perform better than their ring-spun counterparts. A 70/30% blend yarn has been demonstrated to be superior in strength by 25%. The breaking strength of ring yarns to be maximum followed by the rotor yarn and then 50/50 core-sheath DREF-3 yarn.

DREF yarns have been seen to be inferior in terms of unevenness, imperfections, strength variability and hairiness. DREF yarns occupy an intermediate position between ring-spun and rotor spun yarns as far as short hairs and total hairiness s concerned. For hairs longer than 3mm, the friction spun yarns are more hairy than the ring spun yarns. Rotor spun yarns show the least value in both the values. DREF yarns are most irregular in terms of twist and linear density while ring spun yarns are most even.

Chattopadhyay and Banerjee have studied the frictional behaviour of ring, rotor, friction spun yarns of 59 and 98.4 Tex spun from cotton, polyester, viscose fibres, with varying levels of twist. The yarn to yarn and yarn to guide roller friction was measured at different sliding speeds and tension ratios. However for polyester fibres, the rotor spun yarn showed highest friction, followed by friction and ring spun yarns.

  • Advantages of Friction spinning system

The forming yarn rotates at high speed compare to other rotating elements. It can spin yarn at very high twist insertion rates (ie.3,00,000 twist/min). The yarn tension is practically independent of speed and hence very high production rates (up to 300 m/min) can be attainable. The yarns are bulkier than rotor yarns.

The DREF II yarns are used in many applications. Blankets for the home application range, hotels and military uses etc. DREF fancy yarns used for the interior decoration, wall coverings, draperies and filler yarn. Core spun yarns thro this friction spinning are used in shoes, ropes and industrial cable manufacturing. Filler cartridge for liquid filtration also effectively made with these yarns. Secondary backing for tufted carpets can be produced with waste fibres in this spinning system .Upholstery, table cloths, wall coverings, curtains, hand-made carpets, bed coverings and other decorative fabrics can be produced economically by DREF Spinning system. Heavy flame-retardant fabrics, conveyor belts, clutches and brake linings, friction linings for automobile industry, packets and gaskets are some examples were the DREF yarns can be effectively used.

The DREF-3 yarns made fabrics used in many applications like backing fabrics for printing, belt inserts, electrical insulation, hoses, filter fabrics and felts made from mono-filaments core. Hot air filtration and wet filtration in food and sugar industries these yarns made fabrics are used. It also used in clutch lining and brake lining for automotive industries.he multi-component yarns manufactured using DREF 3000 technology are mainly employed for technical textiles of the highest quality. They provide heat and wear protection, excellent dimensional stability, outstanding suitability for dyeing and coating, wearer comfort, long service life , as well as a range of other qualitative and economic advantages. These include cost savings due to the use of less expensive materials, special fibres and wires as yarn cores. Apart from their strength, DREF 3000 yarns are also notable for their good abrasion-resistance,uniformity and excellent Uster values compare to previous systems.

  • Limitations of Friction spinning system

Low yarn strength and extremely poor fibre orientation made the friction spun yarns very weak.The extent of disorientation and buckling of fibres are predominant with longer and finer fibres.Friction spun yarns have higher snarling tendency. High air consumption of this system leads to high power consumption.  The twist variation from surface to core is quite high; this is another reason for the low yarn strength. It is difficult to hold spinning conditions as constant.  The spinning system is limited by drafting and fibre transportation speeds.

Website: http://drefcorp.com

Magnetic Ring-Spinning-Revolutionizing the Tradition


BY:- Faissal Abdel-Hady, leader; Yehia El Mogahzy
(Auburn Textile Engineering)

“By replacing the traveler in ring spinning with a disc that rotates in a magnetic field, we hope to maintain the high quality of ring spun yarn, but at much higher speeds.”

In today’s spinning technology, at least 4 types of spinning systems are commercially available. These are the tradi-tional ring spinning, rotor spinning, air-jet spinning and friction spinning. Among them, ring spinning stands alone in providing high quality yarn suitable for any type of tex-tile end product. Other more recent systems enjoy much higher production speed than traditional ring spinning, but yarn quality restricts their use to only narrow ranges of tex-tile products. The primary technological limitation of ring spinning lies in the speed of the ring-traveler system. The traveler is a C-shaped thin piece of metal that is used for a limited period of time, disposed and replaced on a frequent basis. Three specific issues must be addressed to overcome this limitation:image
Close View of Magnetically Suspended Spinning Ring
• the dependence of the yarn linear speed (or delivery speed) on the rotational speed of the traveler
• the continuous need to stabilize yarn tension during spinning and the dependence of this stability on the traveler speed
• the impact of traveler speed on fiber behavior in the spinning triangle
Research to date has only provided about a 15% improve-ment in traveler speed without affecting the traveler/ring contact thermal load capacity. Ring spinning is still at a production rate disadvantage of 15 to 20 times in compari-son with other spinning systems. Therefore, the challenge is how to break the traditional paradigm of ring spinning and revolutionize its principle in such a way that very high speeds can be achieved without sacrificing the traditional quality of ring spun yarns.
Our design approach is to totally eliminate the traveler from the ring spinning system and replace it with a mag-netically suspended lightweight annular disc that rotates in a carefully pre-defined magnetic field (See Figure below). By creating a non-touching environment of the rotating element for ring spinning, this system provides super high spinning rotation without the limitations of the current trav-eler system.

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In the magnetic ring spinning system a bias flux is gen-erated from both permanent magnets across the air gap (shown in blue paths in Figure above), supporting the weight of the rotating disk in the axial direction. In case the floating ring is displaced from its central position, the permanent magnets will create a destabilizing force that at-tracts the ring even further away from the center. The con-trol system allows the current in the system to be controlled by feeding back information on the position of the rotor (obtained using four displacement sensors mounted radially to the floating ring) and adjusting the control currents based on this information. In simple terms, the control system re-duces the upper system current when the rotor is above the center position and increases the current when the rotor is below the center position. The total magnetic force will tend to bring the floating ring to its central position. We have now constructed the first prototype (See Photo below) and are optimizing its performance. The system was mod-eled using Simulink, to test how it performs. And the yarn balloon was analyzed using this model.

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PROCESS PARAMETERS IN DRAW FRAME


it is better to use two drawframe passages after combing. This will reduce long thick places in the yarn.
· In case of two drawframe passage, first drawframe passage will reduce the periodic variation due to piecing. Therefore the life of servomotor and servo amplifier will be more , if two drawframe passage is used. Quality of sliver will also be good, because of less and stable feed variation.
· For synthetic fibres (44 mm to 51 mm), 8 of a total draft can be employed both in breaker and finisher passage. The number of doublings depends upon the feeding hank and the total draft employed. Most of the modern drawframes are capable of drafting the material without any problem, even if the sliver fed is around 36 to 40 grams per meter.
· Especially for synthetic fibres with very high drafting resistance, it is better to feed less than 38 grams per meter to the drawframe.
· Break draft setting for 3/3, or 4/3, drafting system is as follows
1. For cotton, longest fibre +(8 to 12 mm)
2. For synthetic fibre, fibre length + (20 to 30% of fibre length)
· Break draft for cotton processing is normally 1.16 to 1.26. For synthetics it is around 1.42 to 1.6
· To meet the present quality requirements , finisher drawframe should be an autoleveller drawframe.
· Since the drawframe delivery speed is very high the top roller shore hardness should be around 80 degrees. It should not be less than that.
· It is advisable to buff the rubber cots once in 30 days(minimum) to maintain consistent yarn quality.
· Coiler size should be selected depending upon the material processed. For synthetic fibres, bigger coiler tubes are used. This will help to avoid coiler choking and kinks in the slivers due to coiling in the can.
· Speed of the coiler will also affect the coiling. Speed of the coiler should be selected properly. In drawframes like RSB D-30(RIETER) , any coiler speed can be selected through the variator type pully. Since, the option is open, there is also more probability for making mistakes. One should take enough care to set the coiler speed properly.
· Whenever coiler speed is adjusted, the diameter of the coil is also changed. Hence it is necessary to check the gap between the sliver and can. If it is more than 5 mm, then turn table position (can driving unit) should be altered so that the gap between coil outer and can inner is around 5 mm.
· Pressure bar depth plays a major role in case of carded mixing and OE mixings. If it is open, U% will be affected very badly.It should always be combined with front roller setting. If the pressure bar depth is
high,Creel height should be fixed as low as possible (esepcially for combed material).
· Top roller condition should be checked properly. While processing 100% polyester fibres, fibre scum should be removed by a wet cloth from the top roller atleast once in a shift. 3
· Sliver funnel size should be selected properly. Very wide funnel will affect the U%. But very small funnel will end up in more sliver breaks at the front.
· If the department humidity variation is very big, then corresponding correction to be made for checking the wrapping of sliver ( sliver weight). Otherwise, there will be unwanted changes in the drawframe which will affect the count C.V.% of yarn.
· Most of the Autoleveller drawframes are working on the principle of OPEN LOOP control system. Sliver monitor should be set properly. Whenever there is a problem in sliver weight, this will stop the machine.
Sometimes sliver monitor may malfunction. If it is found malfunctioning , it should be calibrated immediately.
AUTOLEVELLING:
· Most of the modern autolevllers are open loop autolevellers. This system is effective on short, medium and to some extent long tem variations.
· Mechanical draft should be selected properly in autoleveller drawframes. To decide about the mechanical draft, drawframe should be run with autoleveller switched off.If the sliver weight is correct, then the mechanical draft selected is correct. Otherwise, the gears should be changed so that the sliver is weight is as per the requirement without autolevller.
· Intensity of levelling and timing of correction are two important parameters in autolevellers.
· Intensity of levelling indicates the amount of correction. i.e If 12% variation is fed to the drawframe the draft should vary 12% , so that the sliver weight is constant.
· Timing of correction indicates that if a thick place is sensed at scanning roller, the correction should take place exactly when this thick place reaches the correction point(levelling point)
· Higher the feed variation, higher the correction length. e.g. if feed variation is 1 %, and if the correction length is 8 mm, if feed variation is 5% the correction length will be between 10 to 40 mm depending upon the speed and type of the autoleveller.
· Higher the speed, higher the correction length
· Whenever the back roller setting, guide rails setting, delivery speed,break draft etc are changed, the timing of correction should also be changed. · U% of sliver will be high, if timing of correction is set wrongly
· If intensity of levelling selected is wrong , then 1 meter C.V % of sliver will be high.
· Most of the modern autolevellers can correct 25% feed variation. It is a general practice to feed 12% varition both in plus and minus side to check A%. This is called as Sliver test. The A% should not be more than 0.75%.
A% is calculated as follows
If no of sliver fed to drawframe is N, Check the output sliver weight with “N”, “N+1”, “N-1” slivers. then
A% = ((gms/mt(N-1) – gms/mt(N))/ gms/mt(N) ) x 100
A% = ((gms/mt(N+1) – gms/mt(N))/ gms/mt(N)) x 100
· Life of servo motor and servo amplifier will be good, if
1. it is used for carded material
2. feed variation is less
3. motor is checked for carbon brush damages, bearing damages etc periodicall
4. if the delivery speed is less

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RING FRAME


Ring spinning machine (year of constr. 1988) i...
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The ring spinning will continue to be the most widely used form of spinning machine in the near future,because it exhibits significant advantages in comparison with the new spinning processes.

· Following are the advantages of ring spinning frame

  • It is universally applicable, i.e.any material can be spun to any required count
  • It delivers a material with optimum characteristics, especially with regard to structure and strength.
  • it is simple and easy to master
  • the know-how is well established and accessible for everyone

· Functions of  ring frame

  • to draft the roving until the required fineness is achieved
  • to impart strength to the fibre, by inserting twist
  • to wind up the twisted strand (yarn) in a form suitable for storage, transportation and further processing.

DRAFTING

· Drafting arrangement is the most important part of the machine. It influences mainly evenness and strength The following points are therefore very important

  • drafting type
  • design of drafting system
  • drafting settings
  • selection of drafting elements like cots, apron, traveller etc
  • choice of appropriate draft
  • service and maintenance

· Drafting arrangement influence the economics of the machine – directly by affecting the end break rate and indirectly by the maximum draft possible.

· If higher drafts can be used with a drafting arrangement, then coarser roving can be used as a feeding material. This results in higher production rate at the roving frame and thus reducing the number roving machines required, space, personnel and so on.

· In fact increase in draft affects the yarn quality beyond certain limit. Within the limit some studies show that increase in draft improves yarn quality. The following draft limits have been established for
practical operation:

  • carded cotton- upto 35
  • carded blends – upto 40
  • combed cotton and blends(medium counts) – upto 40
  • combed cotton and blends(fine counts) – upto 45
  • synthetic fibres – upto 50

· The break draft must be adapted to the total draft in each case since the main draft should not exceed 25 to 30. It should be noted that higher the break draft, more critical is the break draft setting

· The front top roller is set slightly forward by a distance of 2 to 4mm relative to the front bottom roller, while the middle top roller is arranged a short distance of 2mm behind the middle bottom roller.

· Overhang of the front top roller gives smooth running of the top rollers and shortens the spinning triangle. This has a correspondingly favourable influence on the end break rate.

· Rubber cots with hardness less than 60 degrees shore are normally unsuitable because they can not recover from the deformation caused by the pressure on the top roller while running.

· Soft rubbercots for top rollers have a greater area of contact, enclose the fibre strand more completely and therefore provide better guidance for the fibres.However softer cots wear out significantly faster
and tend to form more laps.

· Normally harder rubbercots are used for back top rollers, because the roving which enters the back roller is compact , little twisted and it does not require any additional guidance for better fibre control.

· In the front top roller, only few fibres remain in the strand and these exhibit a tendency to slide apart. Additional fibre guidance is therefore necessary.Therefore rubbercots with hardness levels of the order 80 degrees to 85 degrees shore are mostly used at the back roller and 63 degrees and 65 degrees at the front roller.

· If coarse yarns and synthetic yarns are being spun, harder rubbercots are used at the front roller because of increased wear and in the case of synthetic yarns to reduce lapups.

· Three kinds of top roller weighting(loading) are presently in use

  • spring loading
  • pneumatic loading
  • magnetic weighting

· With pneumatic loading system, the total pressure applied to all top rollers is obtained by simple adjustment
of the pressure in the hose using pressure reducing valve. Moreover the rubbercots will not get deformed if
the machine is stopped for a longer duration, because the pressure on top rollers can be released to the
minimum level.

· The fibre strand in the main drafting field consists of only a few remaining fibres. There is hardly any friction field and fibre guidance provided by the rollers alone is inadequate. Special fibre guiding devices are therefore needed to carry out a satisfactory drafting operation. Double apron drafting arrangements with longer bottom aprons is the most widely used guiding system in all the modern ringframes.

· In doube apron drafting system two revolving aprons driven by the middle rollers form a fibre guiding  assembly. In order to be able to guide the fibres, the upper apron must be pressed with controlled force against the lower apron. For this purpose, a controlled spacing (exit opening), precisely adapted to the fibre volume is needed between the two aprons at the delivery. This spacing is set by “spacer” or “distance clips”. Long bottom aprons have the advantage in comparison wiht short ones, that they can be easily replaced in the event of damage and there is less danger of choking with fluff.

· Spindles and their drive have a great influence on power consumption and noise level in the machine The running characteristics of a spindle, especially imbalance and eccentricity relative to the ring flange, also affect yarn quality and of course the number of end breakage. Almost all yarn parameters are affected by poorly running spindles. Hence it should be ensured that the centering of the spindles relative to the rings is as accurate as possible. Since the ring and spindle form independent units and are able to shift relative to each other in operation, these two parts must be re-centered from time to time. Previously, this was done
by shifting the spindle relative to the ring, but now it is usually carried out by adjusting the ring.

· In comparison with Tangential belt drive, the 4-spindle drive has the advantages of lower noise level and energy consumption, and tapes are easier to replace.

· Lappet guide performs the same sequence of movements as the ringrail, but with a shorter stroke, this movement of the guide ensures that differences in the balloon height caused by changes in the ring rail
positions do not become too large. This helps to control the yarn tension variation with in control, so that ends down rate and yarn charactersitics are under control.

· Spindles used today are relatively long. The spacing between the ring and the thread guide is correspondigly long, thus giving a high balloon. This has two negative influence

  • A high balloon results in large bobbin diameter leading to space problems
  • Larger the balloon diameter , higher the air drag on the yarn.This inturn causes increased deformation of the balloon curve out of hte plane intersecting the spindle axis.This deformation can lead to balloon stability, there is increase danger of collapse.

Both these disadvantages result in higher yarn tension, thereby higher endbreaks.In order to avoid this, balloon control rings are used. It divides the balloon into two smaller sub-balloons. Inspite of its large overall
height, the double-balloon created in this way is thoroughly stable even at relatively low yarn tension.

· Balloon control rings therefore help to run the mahcine with long spindles(longer lift) and at high spindle speed, but with lower yarn tension. Since the yarn rubs against the control ring, it may cause roughening
of the yarn.

· Most ends down arise from breaks in the spinning triangle, because very high forces are exerted on a strand consisting of fibres which have not yet been fully bound together in the spinning triangle.

RING and TRAVELLER COMBINATION:

· The following factors should be considered

  • materials of the ring traveller
  • surface charecteristics
  • the forms of both elements
  • wear resistance
  • smoothness of running
  • running-in conditions
  • fibre lubrication

· For the rings two dimensions are of primariy importance. 1.internal diameter 2. flange width.

· Antiwedge rings exhibit an enlarged flange inner side and is markedly flattened on it upper surface. This type of profile permitted to use travellers with a lower centre of gravity and precisely adapted bow(elliptical travellers), which in turn helped to run the machine with higher spindle speeds. Antiwedge rings and elliptical travellers belong together and can be used in combination.

· Low crown profle has the following advantage. Low crown ring has a flattened surface top and this gives space for the passage of the yarn so that the curvature of the traveller can also be reduced  and the centre of gravity is lowered.In comparison with antiwedge ring, the low crown ring has the advantage that the space provided for passage of the yarn is somewhat larger and that all current traveller shapes can be applied, with the exception of the elliptical traveller. The low crown ring is the most widely
used ring form now.

· The ring should be tough and hard on its exterior. The running surface must have high and even hardeness in the range 800-850 vikcers. The traveller hardness should be lower (650-700 vickers), so that wear occurs
mainly on the traveller, which is cheaper and easier to replace. Surface smoothness should be high, but not too high, because lubricating film can not build up if it too smooth.

· A good ring in operation should have the following features:

  • best quality raw material
  • good, but not too high, surface smoothness
  • an even surface
  • exact roundness
  • good, even surface hardness, higher than that of the traveller
  • should have been run in as per ring manufacturers requirement
  • long operating life
  • correct relationship between ring and bobbin tube diameters
  • perfectly horizontal position
  • it should be exactly centered relative to the spindle

· In reality, the traveller moves on a lubricating film which builds up itself and which consists primarily of cellulose and wax. This material arises from material abraded from the fibres.If fibre particles are caught
between the ring and traveller, then at high traveller speeds and with correspondingly high centrifugal forces, the particles are partially ground to a paste of small, colourless, transparent and extremely thin platelets. The platelets are continually being replaced during working. The traveller smoothes these out to form a continuous running surface.The position, form and structure of lubricating film depends on

  • yarn fineness
  • yarn structure
  • fibre raw material
  • traveller mass
  • traveller speed
  • height  of traveller bow

Modern ring and traveller combination with good fibre lubrication enable traveller speeds upto 40m/sec.

· Traveller imparts twist to the yarn. Traveller and spindle together help to wind the yarn on the bobbin. Length wound up on the bobbin corresponds to the difference in peripheral speeds of the spindle and traveller. The difference in speed should correspond to length delivered at the front rollers. Since traveller does not have a drive on its own but is dragged along behing by the spindle.

· High contact pressure (upto 35 N/square mm)is generated between the ring and the traveller during winding, mainly due to centrifugal force. This pressure leads to generation of heat. Low mass of  the traveller does not permit dissipation of the generated heat in the short time available. As a result the operating speed of the traveller is limited.

· When the spindle speed is increased, the friction work between ring and traveller (hence the build up) increases as the 3rd power of the spindle rpm. Consequently if the spindle speed is too high, the traveller sustains thermal damage and fails. This speed restriction is felt particularly when spinning cotton yarns of relatively high strength.

· If the traveller speed is raised beyond normal levels , the thermal stress limit of the traveller is exceeded, a drastic change in the wear behaviour of the ring and traveller ensues. Owing to the strongly increased adhesion forces between ring and traveller, welding takes place between the two. These seizures inflict  massive damage not only to the traveller but to the ring as well.Due to this unstable behaviour of the ring and traveller system the wear is at least an order of magnitude higher than during the stable phase. The traveller temperature reaches 400 to 500 degrees celsius and the danger of the traveller annealing and failing is very great.

· The spinning tension is proportional

  • to the friction coefficient between ring and traveller
  • to the traveller mass
  • to the square of the traveler speed

and inversely proportional

  • to the ring diameter
  • and the angle between the connecting line from the traveller-spindle axis to the piece of yarn between the traveller and cop.

· The yarn strength is affected only little by the spinning tension. On the other hand the elongation diminishes with increasing tension, for every tensile load of the fibres lessens the residual elongation in the fibres and hence in the yarn. Increasing tension leads also to poorer Uster regularity and IPI values.

· If the spinning tension is more, the spinning triangle becomes smaller . As the spinning triangle gets smaller, there is less hairiness.

SHAPE OF THE TRAVELLER:

· The traveller must be shaped to match exactly with the ring in the contact zone, so that a single contact surface, with the maximum surface area is created between ring and traveller. The bow of the traveller should be as flat as possible, in order to keep the centre of gravity low and thereby improve smoothness of running. However the flat bow must still leave adequate space for passage of the yarn. If the yarn clearance opening is too small, rubbing of the yarn on the ring leads to roughening of the yarn, a high level of fibre loss as fly, deterioration of yarn quality and formation of melt spots in spinning
of synthetic fibre yarns.

WIRE PROFILE OF THE TRAVELLER:

· Wire profile influences both the behaviour of the traveller and certain yarn characteristics, they are

  • contact surface of the ring
  • smooth running
  • thermal transfer
  • yarn clearance opening
  • roughening effect
  • hairiness

MATERIAL OF THE TRAVELLER

· The traveller should

  • generate as little heat as possible
  • quickly distribute the generated heat from the area where it develops over the whole volume of the traveller
  • transfer this heat rapidly to the ring and the air
  • be elastic, so that the traveller will not break as it is pushed on to the ring
  • exhibit high wear resistance
  • be less hard than the ring, because the traveller must wear out in use in preference to the ring

· In view of the above said requirements, traveller manufacturers have made efforts to improve the running properties by surface treatment. “Braecker” has developed a new process in which certain finishing components diffuse into the traveller surface and are fixed in place there. The resulting layer reduces temperature rise and increases wear resistance.

· Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. Mass of the traveller depends upon

  • yarn count
  • yarn strength
  • spindle speed
  • material being spun

If traveller weight is too low, the bobbin becomes too soft and the cop content will be low. If it is unduly high, yarn tension will go up and will result in end breaks. If a choice is available between two traveller weights, then the heavier is normally selected, since it will give greater cop weight, smoother running of the traveller and better transfer of heat out of traveller.

· When the yarn runs through the traveller, some fibres are liberated. Most of these fibres float away as dust in to the atmosphere, but some remain caught on the traveller and they can accumulate and form a tuft. This will increase the mass of traveller and will result in end break because of higher yarn tension. To avoid this accumulation , traveller clearers are fixed close to the ring, so that the
accumulation is prevented. They should be set as close as possible to the traveller, but without affecting its movement. Exact setting is very important.

· Specific shape of the cop is achieved by placing the layers of yarn in a conical arrangement. In the ending of a layer, the ring rail is moved slowly but with increasing speed in the upward direction and quickly but with decreasing speed downwards. This gives a ratio between the length of yarn in the main up) and cross(down) windings about 2:1.

· The total length of a complete layer (main and cross windings together) should not be greater han 5m (preferably 4 m) to facilitate unwinding. The traverse stroke of the ring rail is ideal when it
is about 15 to 18% greater than the ring diameter.

· End break suction system has a variety of functions.

  • It removes fibres delivered by the drafting arrangement after an end break and thus prevents multiple  end breaks on neighbouring spindles.
  • It enables better environmental control, since a large part of the return air-flow of the air-conditioned system is led past the drafting system, especially the region of the spinning triangle.
  • In modern installations, approx. 40 to 50 % of the return air-flow passes back into the duct system of the air-conditioning plant via the suction tubes of pneumafil suction system.
  • A relatively high vacuum must be generated to ensure suction of waste fibres
    • for cotton – around 800 pascals
    • for synthetic – around 1200 pascals
  • A significant pressure difference arises between the fan and the last spindle. This pressure difference ill be greater , the longer the machine and greater the volume of air to be transported. The air flow rate is normally between 5 and 10 cubic meter/ hour.
  • Remember that the power needed to generate an air-flow of 10 cubic meter/ hour , is about 4.5 times he power needed for an air-flow of 6 cubic meter/ hour, because of the significantly higher vacuum
    level developed at the fan.

SPINNING GEOMETRY:

· From Roving bobbin to cop, the fibre strand passes through drafting arrangement, thread guide, balloon control rings and traveller. These parts are arranged at various angles and distances relative to each other.
The distances and angles together are referred to as the spinning geometry,has a significant influence n the spinning operation and the resulting yarn. They are

  • yarn tension
  • number of end breaks
  • yarn irregularity
  • binding-in of the fibres
  • yarn hairiness
  • generation of fly etc.

· Spinning Triangle:
Twist in a yarn is generated at the traveller and travel against the direction of yarn movement to the ront roller. Twist must run back as close as possible to the nip of the rollers, but it never penetrates completely to the nip because, after leaving the rollers, the fibres first have to be diverted inwards and wrapped around each other. There is always a triangular bundle of fibres without twist at the exit of the rollers, this is called as SPINNING TRIANGLE. Most of the end breaks originate at this point. The length of the spinning triangle depends upon the spinning geometry and upon the twist level in the yarn.

· The top roller is always shifted 3 to 6 mm forward compared to bottom roller. This is called top rolleroverhang.This gives smoother running and smaller spinning triangle. The overhang must not be made too large,
as the distance from the opening of the aprons to the roller nip line becomes too long resulting in poorer fibre control and increased yarn irregularity.

· Continuous variation of the operating conditions arises during winding of a cop.The result is that the tensile force exerted on yarn must be much higher during winding on the bare tube than during winding on
the full cop, because of the difference in the angle of attack of the yarn on the traveller. When the ring rail is at the upper end of its stroke, in spinning onto the tube, the yarn tension is substantially higher
than when the ring rail is at its lowermost position. This can be observed easily in the balloon on any ring spinning machine.

· The tube and ring diameters must have a minimum ratio, between approx. 1:2 and 1:2.2, in order to ensure that the yarn tension oscillations do not become too great.

· Yarn tension in the balloon is the tension which finally penetrates almost to the spinning triangle and which is responsible for the greater part of the thread breaks. It is reduced to a very small degree by
the deviation of the yarn at the thread guide. An equilibrium of forces must be obtained between the yarn tension and balloon tension.

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RINGS & TRAVELLERS :


Ringspinnen
Image via Wikipedia

In most cases, the limit to productivity of the ring spinning machine is defined by the traveller in interdependence with the ring, and yarn. It is very important for the technologist to understand  this and act on them to optimise the yarn production.

  • The following factors should be considered
    • materials of the ring traveller
    • surface characteristics
    • the forms of both elements( ring and traveller)
    • wear resistance
    • smoothness of running
    • running-in conditions
    • fibre lubrication

TRAVELLER:

Traveller imparts twist to the yarn. Traveller and spindle together help to wind the yarn on the bobbin. Length wound up on the bobbin corresponds to the difference in peripheral speeds of the spindle and traveller. The difference in speed should correspond to length delivered at the front rollers. Since traveller does not have a drive on its own but is dragged along behind by the spindle.

High contact pressure (upto 35 N/square mm)is generated between the ring and the traveller during winding, mainly due to centrifugal force. This pressure leads to generation of heat. Low mass of the traveller does not permit dissipation of the generated heat in the short time available. As a result the operating speed of the traveller is limited.

Heat produced when by the  ring traveller  is around 300 degree Celsius. This has to be dissipated in milliseconds by traveller into the air.

Parts of a traveller:

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Height of bow:  It should be as low as possible for stable running of traveller. It should also have sufficient yarn passage.

Yarn passage: According to count spun the traveller profile to be selected with required yarn passage.

Toe gap : This will vary according to traveller number and flange width of the ring

Wire section: It plays an important role for yarn quality, life of traveller.

Ring contact area: This area should be more, uniform, smooth and continuous for best performance.

Inner width: This varies according to traveller profile and ring flange.

SALIENT FEATURES OF A TRAVELLER:

  • Generate less heat
  • dissipate heat fastly
  • have sufficient elasticity for easy insertion and to retain its original shape after insertion
  • friction between ring and traveller should be minimal
  • it should have excellent wear resistance for longer life
  • hardness of the traveller should be less than the ring

When the spindle speed is increased, the friction work between ring and traveller (hence the build up) increases as the 3rd power of the spindle rpm. Consequently if the spindle speed is too high, the traveller sustains thermal damage and fails. This speed restriction is felt particularly when spinning cotton yarns of relatively high strength.

If the traveller speed is raised beyond normal levels , the thermal stress limit of the traveller is exceeded, a drastic change in the wear behaviour of the ring and traveller ensues. Owing to the strongly increased adhesion forces between ring and traveller, welding takes place between the two. These seizures inflict massive damage not only to the traveller but to the ring as well.Due to this unstable behaviour of the ring
and traveller system the wear is atleast an order of magnitude higher than during the stable phase. The traveller temperature reaches 400 to 500 degrees celcius and the danger of the traveller annealing and failing is very great.

The spinning tension is proportional

  • to the friction coefficient between ring and traveller
  • to the traveller mass
  • to the square of the traveller speed

and inversely proportional

  • to the ring diameter
  • and the angle between the connecting line from the traveller-spindle axis to the piece of yarn between the traveller and cop.
  • In order to maintain the same friction or spinning tension with different coefficients of friction, different traveller weights must be used. The coefficient of friction is determined by the fiber lubrication and is subject to fluctuation. Dry cotton means higher coefficient of friction. For manmade fibres depending upon the manufacturer, lower to medium coefficient of friction.

The coefficient of friction with fiber lubrication can vary from 0.03 and 0.15.

R = Coefficient of friction  x N

where

R – traveller friction in mN

N = Normal force >= (Fc x ML x V xV)/(R)

Fc – centrifugal force

ML – mass of the traveller in mg

V – traveller speed in m/s

R – radius of the ring (inside)

  • The yarn strength is affected only little by the spinning tension. On the other hand the elongation diminishes with increasing tension, for every tensile load of the fibres lessens the residual elongation in the fibres and hence in the yarn. Increasing tension leads also to poorer Uster regularity and IPI values.
  • If the spinning tension is more, the spinning triangle becomes smaller . As the spinning triangle gets smaller, there is less hairiness.

SHAPE OF THE TRAVELLER:

  • The traveller must be shaped to match exactly with the ring in the contact zone, so that a single contact surface, with the maximum surface area is created between ring and traveller. The bow of the traveller should be as flat as possible, in order to keep the centre of gravity low and thereby improve smoothness of running. However the flat bow must still leave adequate space for passage of the yarn. If the yarn clearance opening is too small, rubbing of the yarn on the ring leads to roughening of the yarn,
    a high level of fibre loss as fly, deterioration of yarn quality and formation of melt spots in spinning of synthetic fibre yarns.

WIRE PROFILE OF THE TRAVELLER: 

  • Wire profile influences both the behaviour of the traveller and certain yarn characteristics, they are
    • contact surface of the ring
    • smooth running
    • thermal transfer
    • yarn clearance opening
    • roughening effect
    • hairiness

MATERIAL OF THE TRAVELLER

  • The traveller should
    • generate as little heat as possible
    • quickly distribute the generated heat from the area where it develops over the whole volume of the traveller
    • transfer this heat rapidly to the ring and the air
    • be elastic, so that the traveller will not break as it is pushed on to the ring
    • exhibit high wear resistance
    • be less hard than the ring, because the traveller must wear out in use in preference to the ring
  • In view of the above said requirements, traveller manufacturers have made efforts to improve the running properties by surface treatment. “Braecker” has developed a new process in which certain finishing components diffuse into the traveller surface and are fixed in place there. The resulting layer reduces temperature rise and increases wear resistance.
  • Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. Mass of the traveller depends upon
    • yarn count
    • yarn strength
    • spindle speed
    • material being spun

If traveller weight is too low, the bobbin becomes too soft and the cop content will be low. If it is unduly high, yarn tension will go up and will result in end breaks. If a choice is available between two traveller weights, then the heavier is normally selected, since it will give greater cop weight, smoother running of the traveller and better transfer of heat out of traveller.

  • When the yarn runs through the traveller, some fibres are liberated. Most of these fibres float away as dust in to the atmosphere, but some remain caught on the traveller and they can accumulate and form a tuft. This will increase the mass of traveller and will result in end break because of higher yarn tension. To avoid this accumulation , traveller clearers are fixed close to the ring, so that the accumulation is prevented. They should be set as close as possible to the traveller, but without affecting its movement. Exact setting is very important.
  • For the rings two dimensions are of primarily importance. 1.internal diameter 2. flange width.
  • Antiwedge rings exhibit an enlarged flange inner side and is markedly flattened on it upper surface. This type of profile permitted to use travellers with a lower centre of gravity and precisely adapted bow(elliptical travellers), which in turn helped to run the machine with higher spindle speeds. Antiwedge rings and elliptical travellers belong together and can be used in combination.
  • Low crown profile has the following advantage. Low crown ring has a flattened surface top and this gives space for the passage of the yarn so that the curvature of the traveller can also be reduced and the centre of gravity is lowered.In comparison with antiwedge ring, the low crown ring has the advantage that the space provided for passage of the yarn is somewhat larger and that all current traveller shapes can be applied, with the exception of the elliptical traveller. The low crown ring is the most widely used ring form now.
  • The ring should be tough and hard on its exterior. The running surface must have high and even hardeness in the range 800-850 vikcers. The traveller hardness should be lower (650-700 vickers), so that wear occurs mainly on the traveller, which is cheaper and easier to replace. Surface smoothness should be high, but not too high, because lubricating film can not build up if it too smooth.
  • A good ring in operation should have the following features:
    • best quality raw material
    • good, but not too high, surface smoothness
    • an even surface
    • exact roundness
    • good, even surface hardness, higher than that of the traveller
    • should have been run in as per ring manufacturers requirement
    • long operating life
    • correct relationship between ring and bobbin tube diameters
    • perfectly horizontal position
    • it should be exactly centred relative to the spindle
  • In reality, the traveller moves on a lubricating film which builds up itself and which consists primarily of cellulose and wax. This material arises from material abraded from the fibres.If fibre particles are caught between the ring and traveller, then at high traveller speeds and with correspondingly high centrifugal forces, the particles are partially ground to a paste of small, colourless, transparent and extremely thin platelets.
    The platelets are continually being replaced during working. The traveller smoothed these out to form a continuous running surface.The position, form and structure of lubricating film depends on
  • yarn fineness
  • yarn structure
  • fibre raw material
  • traveller mass
  • traveller speed
  • high of traveller bow

Modern ring and traveller combination with good fibre lubrication enable traveller speeds upto 40m/sec.

TECHNOLOGICAL GUIDELINES:

  • When the ring diameter is less,  balloon diameter will be small. This leads to more yarn tension. Hence use lighter travellers.
  • When the ring diameter is bigger, balloon diameter will  be more. This  leads to less yarn tension and the balloon touches the separator. Hence use heavier travellers
  • When the tube length  is short, the yarn tension will be more. Hence use lighter travellers
  • When the tube length is long, the yarn tension will be less, hence use heavier travellers
  • When the yarn contact area and ring contact area in traveller is closer, fibre lubrication is better especially in cotton. For this use heavier travellers
  • When spindle speed is increased use lighter traveller with low bow height. At higher speeds, lighter travellers give lesser yarn tension. When low bow height travellers are used centre of gravity will be closest to the ring which aids in running of traveller.
  • Use lighter travellers on new rings. This is done to reduce end breakages by reducing the yarn tension.
  • Use heavier travellers on old rings. This is done to avoid bigger balloons
  • Heavier travellers reduce hairiness
  • When using lighter travellers, yarn stretch will be less. It helps for better yarn elongation
  • During running-in the end breakage rate  should be kept minimum, hence use lighter travellers.
  • The shorter the  balloon, the lighter the traveller to be used, the higher traveller speeds can be achieved.
  • The ring traveller, together with the  yarn as a pull element, is set into motion on the ring by the rotation of the spindle. If the direction of pull deviates too much from the running direction of the traveller (spinning angle less than 30 degrees) the tension load will be too high.

Preconditions for good operating results

The maximum ability of the ring/traveller system to withstand occurring stress situation during operation determines the performance limit of the ring spinning and twisting machine. Traveller wear does not only depend on traveller material; problems of heat dissipation are of crucial importance, too. The heat generated between ring and traveller must be reduced as quickly as possible to avoid local temperature in the traveller wear zones. The ability of the traveller to resist to stress is determined by several factors. Investigations regarding improvements of rings and travellers aimed at a further increase of performance should above all make sure that all other conditions with a certain influence on the spinning process are optimal.

Therefore make sure that:

¥ the rings are correctly centered with regard to the spindles

¥ the yarn guide eyelet is well centered with regard to the spindle

¥ the spindle bearing is in good condition, thus preventing spindle vibrations

¥ the ratio between bobbin diameter and ring diameter  is correct

¥ the concentricity of the ballon control ring  with regard to the

spindle is correct

¥ the fibre tufts which accumulate on flange travellers are removed by

means of suitable traveller cleaners

¥ the climatic conditions (temperature and relative air humidity) are favourable

for the spinning process

¥ the air in the mill is free from disturbing particles that influence efficient

performance of the traveller

It has to be stressed that a smooth and well run-in track is of most importance.

Concentricity of spindle, ring, yarn guide and balloon control ring

Especially at high spindle speeds concentric positioning of ring, spindle, yarn  eyelet and balloon control ring is required for keeping the ends down rate at low level. Spindles and rings must be aligned and centered absolutely parallel. Ring rails or ring holders should, therefore, be installed absolutely horizontally compared to the vertically fitted spindles. Ring and traveller form the main elements in ring spinning and twisting. They determine to a large extent performance and operating conditions of the machine.

The traveller accomplishes two main tasks while running on the ring at high speeds:

a) It gives the roving  supplied by the feed rollers the necessary twist.

b) It assists in winding the yarn onto the bobbin in the form of a cop with ã correct  tension.

During this operation the ring guides the traveller, which is essential for the perfect positioning of the yarn and the formation of the cop. The traveller is pressed against the ring track by centrifugal forces. The resulting frictional forces reduce traveller speed, which is dragged along by the passing-through yarn, and provide the yarn with the tensile forces necessary for assembling the individual fibres into the spun yarn as well as for limiting the yarn balloon.

Steel travellers are hardened to a certain degree and polished to a mirror finish. They can be adapted in shape, weight and surface finish to the ring, yarn type and yarn count. Nylon travellers of standard quality (for HZ and J rings) are made of highly wear-resistant polyamide. Extremely aggressive yarns are processed with glass-fibre-reinforced a Super Nylon  travellers. Twisting and winding carried out by the traveller must be performed with appropriate yarn tension. The ratio between spindle speed and the speed at which the yarn is supplied determines yarn twist. Any change of this ratio is easily compensated by the traveller without having an influence on twisting, winding and tensioning.

On flange rings, the gliding speed of travellers having a suitable shape can be as rapid as 130 ft/s (88 MPH) or 40 m/s (140 km/h); on DIA-DUR coated rings the speed can to some extent reach 147 ft/s (100 MPH) or 45 m/s (160 km/h) . Having an average life span of 200-300 operating hours the traveller covers a distance of more than 18.000 miles (30.000 km) – a tremendous task for a small part of wire weighing only a few milligrams. These standards can even be surpassed by nylon travellers used on HZ rings, if operating conditions are favourable.

These high traveller speeds involve pressures of up to 35 N/mm 2 . But even if high-quality materials with an optimum of hardness and resistance to wear are used, these standards can only be reached if

¥ in the case of flange rings, a film of lubricating fibres is produced continuously,

¥ in the case of HZ and J rings, a sufficient amount of lubricant is consistently

provided.

d 1 = spinning ring diameter

d 2 = fitting diameter

h 1 = ring height

h 2 = ring height above ring rail

b = flange width

flange 1 = 3.2 mm

flange 2 = 4.1 mm

Spindles operating without vibrations contribute a great deal to a smooth operation of the traveller. Non-concentric spindles and spindles not running smoothly cause constant changes in yarn tension , because the traveller cannot run around the ring without being shaken.

Vibration-free movements of ring rail and ring holder

The ring rail should move smoothly without jerking. Vibrations and hard jolts at the reversing points of the ring rail disturb the operation of the traveller. Repeated changes in yarn tension cause the traveller to flutter. This results in increasing yarn breaks and in accelerated wear of ring and traveller.

Correct ratio between bobbin diameter, bobbin length, ring diameter and spindle gauge

Ratio bobbin length (H) : Inside ring diameter (D)

Thread tension increases with growing bobbin length. In view of the limited thread tension, the total bobbin length should not exceed 5 times the ring diameter. Only when using balloon control rings or similar devices this value can be exceeded.

H : D = 5 : 1

Ratio bobbin diameter (d) : Inside ring diameter (D)

The bobbin diameter d is equivalent to the mean outer bobbin diameter d 1 + d 2

The following values are recommended:

for spinning: d : D = 0.48 – 0.5 (a = 29°-30°), (minimum value a = 26°)

for twisting d : D = 0.44 – 0.5 (a = 27°-30°), (minimum value a = 22°)

For light and heavy bobbins, the values for light bobbin types are decisive for calculating d : D. If the ratio d : D is reduced thread tension increases.

Correct surface smoothness, i.e. optimum peak-to-valley height and evenness of the ring track

The traveller contact surfaces must be smooth and even. Only then a smooth operation of the traveller will be possible. The contacted surfaces should be clean and preferably without traces of wear. In addition, they should be designed in such a way that they offer sufficient adherence for potential lubricants (e.g. fibres, oil, grease).

Once the sliding surfaces have lost their original quality, even the best ring traveller will not be able to run smoothly. For maintaining the surface of the running track in a good condition, it is very important – besides a certain degree of maintenance – to run the ring well in.

Balloon control rings and separators

The influence of balloon control rings is quite considerable, especially at long cops. A reduction of the yarn balloon is advantageous or may even be the prerequisite for optimum performance. If balloon control rings are mounted at correct distance (the yarn balloon should be restricted as long as possible during one lift of the ring rail) then a marked performance increase is possible. The balloon control rings are removed when sensitive materials are processed and sufficiently long separators are installed to avoid many yarn breaks and to prevent fibre fly from accumulating on the adjacent spindles.

Traveller cleaners

Traveller cleaners are an excellent method for removing all fibre fly that  accumulates on the outer part of C and El travellers. The traveller cleaner should have the right distance to the outside ring flange. A distance of about 0.5 mm between cleaner and traveller (in operating position) is recommended. When adjusting the distance between outside ring flange and cleaner, the size of the traveller should be taken into consideration.

Room climate

Constant temperature and air humidity have positive effects on the operation of the traveller. Changes of the room climate, such as raised air humidity will increase wear by friction. Besides the regular exchange of air, the purity of the air is of great importance for the traveller. Any dust (also dust from unsuitable floors) or other impurities may impair traveller operation and lead to more ring/traveller wear.

Flange width and ring height

Optimal operating results are reached when the ideal flange width is chosen for flange rings and the ideal ring height is obtained for self-lubricating HZ and J rings, dependent on yarn count range, yarn quality and traveller type.

Ring profile and traveller shape

Determining the most favourable ring and traveller shapes is a precondition for obtaining the optimal individual performance. If ring profile and traveller shape match well, the traveller will adopt a stable position in the ring. It should have sufficient tolerance of movement, so that any obstacles which may occur especially when the machine is started are avoided. A satisfactory large yarn clearance counteracts yarn breaks and yarn damage.

Running-in of rings

Normally the running-in procedure is decisive for the future positive/nega tive behaviour of the ring and the length of its service life. Every ring requires a certain degree of running-in time if it is to maintain high traveller speeds with as little ring and traveller wear as possible.  During running-in the use of steel travellers without surface treatment is recommended. After the termination of the running-in process, steel travellers with surface treatment or nylon as well as bronze travellers can be used.

The running-in process, beginning with the starting phase, consists of improving the initial running properties of the metallic running surface up to the  optimal values by smoothing and passivation(oxidation) as soon as possible. In this way, together with fibre lubrication, constant minimum mixed friction conditions and minimum thermal stressing can be attained for the ring traveller. A careful running-in process will improve the lifetime of the rings.

In order to keep the stress on the traveller as low as possible during the starting phase, it is advisable to always change the traveller in the upper third part of the cops. Further advantages are brought with the use of a traveller running-in program(reduction of the speed by about 10% for 10 to 20 minutes, only available on modern spinning machines).

Spindle speed should be reduced at least for the first 10 traveller changes. If final speed is higher than 32m/sec, reduce by atleast 20%.   If final speed is lower than 32m/sec, reduce by at least 10%.

New rings  should not be degreased, but only rubbed over with a dry cloth.

In general, the running in should be done with the same traveller type which is used for normal operation with the 10 to 20% less than normal speed. It is not advisable to do running with the same speed but with  1to 2 numbers lighter travellers than usual.

The first traveller change should be carried out after 15 min

The second traveller change should take place after 30 min

The third traveller change should be made after 1 to 1.5 hours.

The fourth traveller change should be made after the first doff.

Further traveller changes are to be made  according to the manufacturers recommendations

HAIRINESS: Following are the reasons for higher yarn hairiness due to  ring and travellers

  • Poorly cantered spindles, anti balloon rings and yarn guides lead to inconsistent yarn tension.
  • Rough surfaces roughen the yarn(due to damaged parts)
  • Open anti balloon ring
  • The clearance between ring and cop should not be too small. Traveller will cut the fibres protruding from the cop.
  • the fibres get electrostatically charged
  • poor twist propagation to the spinning triangle due to lighter travellers
  • Heavy friction of the balloon on the anti-balloon ring respectively impact on the balloon separator( due to lighter traveller)
  • Poor ring cantering
  • crooked  tubes
  • yarn getting roughened in narrow yarn passage in the traveller
  • scratched up yarn passages catch the yarn and roughen it (due to very high traveller running time)
  • friction of the yarn due to very high traveller weight
  • rough gliding surface of the ring ( due to worn out rings)
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COM-4 AND ELITE YARNS


COM-4 CONCEPT:

With the ComforSpin   technology a new yarn with perfect yarn structure – the COM4  yarn – has been established in the market. With the help of a microscope the structure of the yarns can easily be compared: The conventional ring yarn shows to be far less perfect than commonly assumed. The long, protruding fibres cause a number of problems in downstream processing. COM4  yarn shows a very compact structure with highly parallel fibres and much less disturbing hairiness.

The air current created by the vacuum generated in the perforated drum condenses the fibres after the main draft. The fibres are fully controlled all the way from the nipping line after the drafting zone to the pinning triangle.clip_image002

An additional nip roller prevents the twist from being propagated into the condensing zone. The compacting efficiency in the condensing zone is enhanced by a specially designed and patented air guide element.

Optimal interaction of the compacting elements ensures complete condensation of all fibres. This results in the typical COM4 ® yarn characteristics.

The ComforSpin ® technology allows aero-dynamic parallelization and condensation of the fibres after the main draft. The spinning triangle is thus reduced to a minimum. The heart of  ComforSpin   machine is the compacting zone, consisting of the following elements:

• perforated drum

suction insert

• air guide element

The directly driven perforated drum is hard to wear  and resistant to fibre clinging. Inside each drum there is an exchangeable stationary suction insert with a specially shaped slot. It is connected to the machine’s suction system.

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THE ELITE YARN:

The operating method of the SUESSEN EliTe  Spinning System is well-known.After the fibres leave the drafting system they are condensed  by an air-permeable lattice apron,which slides over an inclined suction slot.The fibres follow the outer edge of this suction slot and at the same time  they perform a lateral rolling motion.

Above the front bottom roller of the drafting system,the fibre band  influenced by high draft  is spreading.In the area of the suction slot,which is covered by the lattice apron,the fibre band is condensed.Commencing from the semi-dotted clamping line of the EliTe Q Top Roller,twist is being inserted.There is no spinning triangle.

The improvement achieved is shown in Fig .The left side displays the fibre triangle at the exit of a conventional ring frame drafting system.The twist imparted by the spindle cannot flow up to the clamping line.The outer fibres spread out and are thus more highly tensioned than those on the inside. The right side of the picture does not show a spinning triangle.The yarn twist flows right up to the clamping line.The yarn is round and smooth.

Since the spinning triangle is very very small, the end breaks will be very less and therefore the fly liberation will also be less.

Condensing of the fibre bundle,which follows the drafting process,can already be seen as a significant  development of the ring spinning technology.Condensed ring yarn is more  than a speciality.In view of its manifold advantages.

It is of technological importance that the suction level relevant for the condensing operation is exactly the same for all spinning positions. To fulfil this criteria,individual motors combined with suction units for  6 spinning positions,have  been arranged accordingly.This provides short air-flow distances with identical negative pressures at all spinning points .

During yarn formation all fibres are perfectly condensed and gathered parallel to each other in the compacting zone. Consequently all fibres are twisted in and contributing to the superior fibre utilisation rate compared to conventional ring yarn. The result is exceptionally low hairiness combined with higher yarn tenacity and elongation. These are the unique characteristics of these yarns.

ADVANTAGES OF COMPACT YARN:

• higher fibre utilisation clip_image005

• higher tenacity with same twist factor, or

• same tenacity with reduced twist factor for higher production

• lowest hairiness (highest reduction in hairs longer than 3 mm)

• fewer weak points

• better imperfections (IPI) values

• higher abrasion resistance

• greater brilliance of colour

• intensive dye penetration

• no singeing before printing

  • Due to better utilization of fibre substance it is possible to reduce yarn twist of  these Yarns,particularly of knitting yarns,by up to 20%,maintaining the yarn strength of conventional ring yarns.This increases yarn production. The ends-down rate in spinning these Yarns is reduced by 30 to 60%,which improves machine efficiency.
  • Applying the same winding speed as with conventional ring yarns,there are less raised points in these Yarns and the increase in yarn imperfections is reduced because they have a better resistance to shifting. Higher winding speeds are therefore possible with  compact yarns Yar ns .
  • In accordance with up to 20%twist reduction in spinning compact yarns ,the twisting turns can be reduced for certain types of yarn.As a result,production of twisting frame is increased and twisting costs are reduced.
  • Owing to the lower hairiness and higher tenacity of compact Yarns,the ends-down rate in beaming is reduced by up to 30%.Higher beamer efficiency,higher produc tion and fewer personnel for repair of ends-down in beaming are the consequence.
  • Compact  Warp yarns help to save up to 50%of sizing agent,while the running behaviour of weaving machi-nes is the same or even better. Cost can be saved  in sizing and desizing  processes.
  • Owing to the better work capacity of  compact Yarns ,ends down can decreased  by up to 50% in the warp and by up to 30%in the weft. Efficiency is consequently increased by 2 to 3%, production is increased and weaving costs are reduced.  In practice,the average ends-down rate is reduced by 33% per 100,000 weft insertions of  compact Yarns on rapier weaving  machines and by 45% on air-jet weaving machines.  Instead of a weft insertion of 500 –600 m/min with conventional ring yarn,700-800 m/min is possible with compact  Yarns on air-jet weaving machines.
  • Due to reduced Yarn hairiness,singeing can sometimes be dispensed with,or it can be carried out at a higher cloth advance speed.As a result,production costs are considerably reduced.
  • fibres upto 7% can be saved because singing can be avoided
  • Dyeing and Printing Improved structure of compact  Yarns and their reduced twist favours the absorption of colour pigments and chemical finishing agents.Saving of dyestuff is possible.
  • Owing to the  improved yarn strength, compact  Yarns are well suited for non-iron treatment of woven fabrics. In the course of such treatment,the strength of fabrics made from conventional ring yarns can decrease by up to 25%,with frequent problems in the manufacture of clothes. compcat Yarns make up for this loss in strength.
  • Knitting :Compact Yarns with their increased yarn strength and reduced formation of fluff permit to achieve higher machine efficiency and therefore production on knitting machines at a reduced ends-down rate,less interruptions and less fabric faults. Production costs therefore decrease. The enormously low hairiness of compact  Yarns often permits to dispense with usual waxing. Considerable cost saving is achieved because of this.
  • In knitting fibre abrasion reduced by 40% due to low hairiness. Fewer defects/ yarn breaks and  better quality. Less contamination on all machines by foreign fibres . Less wear of needles, guide elements and sinkers due to less dust in the compact Yarn . Low hairiness has positive impact on loop structure .  L Low pilling values get more and more important . In many cases single compact  Yarns substitute conventional ply yarns. Waxing can be reduced or completely dispensed with .
  • Compact  Yarns are much more suitable for warp knitting than conventional ring yarns,because of  their higher work capacity and lower hairiness. They are predestined to bear the high load due to numerous deflecting points with high friction in the warp knitting machine.
  • Due to better embedding of fibres (including short ones)in  compact  Yarn,approx.6%fewer combing noils are possible.
  • Cheaper carded qualities instead of combed qualities can be spun with the Compact  Spinning ystem.
  • in many cases single EliTe ® Yarns can substitute conventional ply yarns
  • new qualities can be developed, opening up a new creative scope for products

Hairiness Testing of Yarns

Hairiness 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:

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RING YARN                                                                  COMPACT YARN

There are two major manufacturers of hairiness testing equipment on the market,and both have their advantages and disadvantages. Some detail is given below.

USTER

USTER is the leading manufacturer of textile testing equipment. The USTER hairiness H is defined as follows .

H =total length (measured in centimetres) of all the hairs within one centimetre 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.ZWEIGLE

Zweigle 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.

Ten Fundamental Rules for Successful Operation of EliTe  Ring Spinning Machines:

  • EliTe Q Spinning Machines produce yarn of supreme quality and come up to the expectations.  Installation of the machine in the spinning  mill EliTe Q Spinning Machines have a considerable air flow rate –a machine with .1008 spindles sucks in about 60 cubic meter  of air per minute,i.e. it has the effect of a vacuum cleaner. The ambient air is sucked into machine and most of the fly and dirt contained in it is deposited on the EliTe Q Machine. Although EliTe Spinning Machines generate considerably less fly than standard ring spinning machines, they are soon covered with dust and fly if they are installed in the same room as conventional spinning machines. The fly has a negative effect on the yarn in the condensing zone and the smooth running of the lattice apron. As a result,the yarn is of substandard quality.

Rule .:EliTe Q Spinning Machines must be separated from conventional spinning machines.

  • Spinning room conditions: The fibres in the condensing zone are exposed to the room conditions without any protection. Our recommendations on the room conditions suitable for processing cotton and man-made fibres should be followed, therefore. If the air humidity is too high, there will be a higher tendency towards roller laps. If the air is too dry,t here will be more fly. If the room temperature is too high, there will be higher friction values and premature wear.

Rule 2:maximum room temperature:33 .C

humidity should be

  • max…,5 g water/kg air for cotton
  • min.9,0 g water/kg air for cotton
  • max..0,0 g water/kg air for synthetics
  • min.9,0 g water/kg air for synthetics
  • Position of the Eli Top in relation to the front bottom roller of the drafting system:  If the setting is correct, the top edge of the suction slot in the Eli Tube is precisely set at the nip line of the delivery top roller. If the nip line cuts the slot, condensation is impaired. The hairiness of the yarn increases and the tearing strength is reduced. If the nip line is behind the slot, part of the spinning torsion may get into the condensation zone, resulting in an increased ends-down rate and damaged lattice aprons.

Rule 3:The front top roller is precisely 3.5 mm offset towards the operator in relation to the front bottom roller of the drafting system.

  • Traverse mechanism:  The roving must run over the slot in such a way, that, from the operator ’s view, the  fibres move from the top right to the bottom left. If the fibres run over the slot top from the L.H. side,they make an S-shaped movement causing a certain unsteadiness in the condensing zone. This has a negative effect on the yarn values.

Rule 4:The traverse mechanism for the sliver should be adjusted in such a way that the traverse motion at the front of the drafting system does not exceed 4 mm,and that the l.h.limit position of the sliver is level with the L.H..edge of the top of the slot.

  • Cleaning the Eli Tubes and lattice aprons :Eli Tubes and lattice aprons are the most important components of the EliTe Q Condensing System. Careful maintenance is an important prerequisite for optimum yarn values. In the centre area, where the suction is active, a permanent air flow keeps the lattice aprons clean. To the left and right of this area, the lattice apron can be clogged by fine dust. With the time, this results in a considerable increase of the friction between the lattice aprons and the EliTube.  If this friction is too high, erratic running of the lattice apron and substandard yarn quality is the result. Therefore,lattice aprons and Eli Tubes should be removed from the machine from time to time and cleaned. This can be done when the machine is running. The time needed per box length is 5 min. The expenditure of time necessary for changing the EliTubes with lattice aprons is about  90 minutes for a machine with .1008 spindles, which corresponds to a loss of production of  90 minutes. For yarn count Ne 40, the production loss involved is less than 370 g. The cleaning frequency varies depending on the portion of fine dust of the cotton. As an average value, 500 operating hours may be taken into account. The aprons are cleaned in a washing machine or in an ultrasonic cleaning device.The EliTubes are cleaned using a damp piece of cloth. Damaged lattice aprons must be replaced. On EliTubes with considerable traces of wear, the inserts must be replaced.

Rule 5:Lattice aprons and Eli Tubes must be cleaned from time to time.

  • Measures to be taken in the case of laps at the front top roller Laps may occur in the case of unsuitable room conditions or damaged or inappropriately buffed cuts, or if the fibre material used is prone to the formation of laps. Large laps may block the delivery and front rollers and damage the cot of the blocked roller. If spinning is continued with damaged cots,periodic yarn faults will be the result. Consequently, a blocked Eli Top must be replaced by a new Eli Top and repaired in the service room. For this purpose,all operators should carry a spare Eli Top with them.

Rule 6:EliTops with blocked top rollers must be replaced by new top rollers.

  • Buffing the EliTe Q Top Rollers : The cots of the EliTe Q Top Rollers are subject to wear and should be buffed from time to time.The tension draft in the condensing zone –6 %as a general rule depends on the difference in diameter between the front top roller and the delivery top roller. Changed tension drafts may result in changed yarn parameters.

Rule 7:Make sure that the difference in diameter of the front top roller and the delivery roller corresponds precisely to the desired tension draft.

  • Checking the partial vacuum As a general rule,continuous control of the vacuum pressure is not necessary. When the whole machine is cleaned, we recommend, however,to remove also the connecting hoses between the suction tubes and the fans and to clean them.

Rule 8:Clean the connecting hoses with regular frequency.

  • Maintenance of the fans:  Fans may be clogged after a time,which has a negative effect on the suction.

Rule 9:The fans should be removed from the machine and cleaned once a year.

  • Spinning speed:  In the case of EliTe Q Spinning Machines, return on investment is not based on higher production, but on the production of yarn of supreme quality.  The Suessen recommendations concerning traveller speeds and running-in speeds for rings and travellers should be followed, therefore. Not the ultimate increase in speed, but the yarn quality leads to success.

Rule 10:Yarn quality is more important than quantity.

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