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Promotional Toolkit. Engineering Data Module Beta. Go back to Home page Go back to Textile Technology page. This Reference is not available in your current subscription. Notify your administrator of your interest. Textile Technology Details This book, ideal for students studying textile technology, provides an overview of the complete process of textile manufacturing. The various raw materials, the different methods of yarn and fabric manufacturing, and an introduction to knitting technology, nonwovens, finishing, and ready-made garment production are described in detail.
The book includes a discussion of current recycling processes. Thomas Gries is a member of the Academy of Science NRW and an internationally recognized reviewer of numerous journals.
In addition, he has authored and co-authored numerous books and book chapters on topics of textile technology. He has received numerous prizes and awards for his scientific work in the fields of textile engineering, chemistry fiber production and processing, technical textiles, fiber composite materials, medical textiles, and smart textiles.
He is a recognized expert in the field of chemical fiber engineering and simulation of textile processes and machines. Dieter Veit is reviewer of several international journals and author and co-author of several books on subjects of textile engineering. For his scientific and educational services within the scope of its activities at the RWTH Aachen, he received a number of awards. One of them is based on polyacrylnitrile with the processing steps polymerization, wet- spinning, drawing, oxidation, carbonization, and graphite annealing.
The other method is based on meso phases pitch with the processing steps thermal treatment, melt spinning and oxidation, carbonization and graphitization annealing. The carbonization and graphitization annealing serve as surface treatments. The main objective of both production methods is to arrange graphite layers in the fiber direction. Among the exceptional properties of carbon fibers are their high tenacity, high modulus of elasticity, the high brittleness, the low creeping tendency, the chemically inert behavior, the low heat-expansion, and the good electrical conductivity.
For various applications, carbon fiber staple yarns are processed into building components and used as prepregs. Textile structures of carbon filaments are used in composite plastics and with fiber reinforced concrete.
Furthermore, short fibers of down to 6 mm length are used . To increase the fiber tenacity, they have to be parallelized. Therefore, chemical fibers are drawn. The fiber diameter decreases, while the macromolecules become oriented in the fiber direction. Between the chain molecules, semi-valence bonds such as hydrogen bridges and other interactive bonds, for example, van der Waals forces, develop, which lead to a higher fiber tenacity.
The drawing process is shown schematically in Figure Figure depicts the various drawing principles. Depending on their draw ratio, filament yarns are distinguished according to Table Filaments are often only partially drawn during the spinning process Table Of importance are so-called POY yarns which are spun with an unheated godet takeup device. The desired final draw ratio of the partially oriented yarn is achieved during a subsequent process.
This is done by draw twisting, stretch winding, warp drawing, or draw texturing Figure A low or partially oriented filament yarn is being drawn completely directly after spinning in the same process between two godets. Winding speeds exceed -1 5, m min. For some years, PET-uncrimped yarns have been spun commercially without any additional drawing devices. It remains to be seen how popular this godet-less spinning method will become.
The drawing is a two-step process with subsequent thermal fixation four pairs of godets. For most technical applications, the uncrimped yarns obtain their final, application-dependent yarn construction with an additional processing step such as twisting, combining to cables, covering by spinning or braiding. On the other hand, they can be produced from the POY material with an additional drawing process such as draw winding and draw-twisting Table Draw-twisting and draw-winding are especially suitable for small lots and specialty yarns. So far, mostly producers of chemical fibers have invested in these processes.
However, draw-twisting and draw-winding machines may become more popular for textile processing companies, as POY material is offered in large quantities at relatively low prices, and the processing principle allows one to adjust the degree of drawing and twisting individually.
Draw-twist cops are also processible on double-thread twisting machines. Texturing Texturing is one of the most important steps of the processing of filament yarns to textile products. The uncrimped filament yarns are texturized using their thermoplastic properties and are transformed into crimped yarns Figure Crimp gives a handle more similar to that of natural staple fiber yarns and also 2 Raw Materials 57 better heat insulation properties and higher elasticity than flat filament yarns.
Owing to these properties, textured filaments are used, for example, in apparel, for fine stockings and panty hose, and as carpet tuft materials. The heated yarn is twisted by the twister 5. The twist is fixed into the yarn by a subsequent cooling zone 4. A yarn crimped this way is called HE-yarn, as it is highly elastic and has a large crimp contraction.
Sometimes, high yarn elasticity is not desired. In this case, the texturing process can be altered with a so-called SET zone. For the reduction of the crimp, the yarn is reheated in a second heater 7 located after the twister. The second heating partially breaks up again the hydrogen bridges that fixed the twist in the yarn. This causes the yarn to relax, and elasticity as well as crimp are reduced. This less elastic yarn is called SET yarn. The process ends with the winding of the textured yarn on bobbins at speeds of — -1 m min.
This resulted in high machines with restricted accessibility. This disadvantageous trend has been opposed with the introduction of short high-temperature heaters HT heater. An automated bobbin stripper at each single winding head is standard equipment offered by all machine manufacturers today. These developments have led to new machine cross sections. HT heaters in the primary zone are less than 1 m long, in contrast to the 2.
Heater length, heater temperature, and filament speed have to be coordinated in such a way that the fixation temperature of the yarn is exactly reached at the heater exit. Figure Draw-texturing machine: arrangement 1 Figure Draw-texturing machine: arrangement 2 In arrangement 1 Figure , there is a walkway for the operator on each side of the machine.
A second walkway on each side is provided for bobbin loading and unloading. Because machines of this type require more space, some manufacturers stick with the traditional one-walkway-only per machine side. In arrangement 2 Figure , a middle walkway is constructed to unload the bobbins of both machine sides. Arrangement 2 is more advantageous than arrangement 1 in terms of space requirements. With this method, the yarn is produced in a single process starting with the pellets via extrusion spinning, drawing, texturing, tangling, and winding Figure The crimped structure is achieved by reducing the filament speed in a heated chamber stuffer box.
The yarns produced are in the titer range of to 4, dtex and the maximum -1 production speeds reach up to 5, m min. Therefore, filaments are often converted into staple fibers either by cutting prevalent or tearing. The processing steps for the staple fiber production after spinning depend on the fiber material. The drawing is done in several steps. There may be a thermofixation step, particularly with polyester.
Further steps are stuffer box texturing and consecutive thermosetting and cutting or tearing. The staple fibers are not produced until the very last step. The fibers are also coated at a suitable point within the process. For fibers produced by wet spinning, additional baths and drying steps are integrated.
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Figure shows schematically the processing steps for staple fiber production. Staple fibers may be produced according to the conventional twostep process or the one-step compact process. The spinning speed is 10 to 20 times higher compared to compact spinning. In the first step, the filament cable is produced. The second step consists of drawing, crimping, and cutting. The disadvantage of this process is the large space required for the spinning machine, can coiler, and can creel. The spinning shaft is 1. The advantage of the two-step process is that each step can be run at optimum speed and processing parameters.
To increase the flexibility, the cutting process can be split off as a separate, individual process, the so-called converting. Like the cutting of the filament cables within the processing line, the cut converter as well as the tear converter produces a band of single staple fibers as feed material for the next processing steps in the secondary spin-processing. In the tear converter, the cables are drawn stepwise to ensure the cohesion of the rope Figure With the cut converter, the actual process of separating the filaments into pieces is a pinching between the cutting edges of the converter and the opposed edge.
New developments include spiral-shaped cutting edges with various distances. Another option is a changeant knife. Cut converters are used for polyester, polypropylene and polyamide fibers. However, it remains to be seen whether cut-converters prevail over tear converters owing to quality restrictions.
Tear converters are standard in the processing of polyacrylnitrile fibers. The staple length is adjusted according to the spinning process. Compact spinning is characterized by low machine height, low spinning speed, and large number of capillaries. The fineness is limited by the harsh cooling of the spun filaments during spinning. This limits the maximum draw ratio. The cooling and the integration into the processing line limit the production speed. The compact spinning is used primarily for polypropylene staple fibers and for the flexible production of speciality fiber types.
Table shows three kinds of cotton for a denim mixture. Carpet Yarns used in carpets require different fiber properties than yarns for use in apparel and home textiles. The titer range of the filament yarns for the carpet production is to dtex. The titer of the single fiber is similar to that of coarse wool fibers. For the production of carpet, mostly chemical fibers are used, but natural fibers can also be used. Figure gives a list of the most popular carpet fibers. Most staple fibers for the carpet production have a staple length of 80 to mm, a round, elliptical, or trilobal cross section, and are heavily crimped.
The parameters for drawing, texturing, and setting are set to obtain strong crimp and crimp stability at a low extensional modulus and tenacity wool type . With fiber blends, special effects and a higher usage value of carpets may be achieved. Especially for the tufting process, titer blends with certain amounts of coarse, medium, and fine fibers are used.
Another important principle of blending fibers is the combination of staple or filament fibers of different colors or dyeing properties multicolor yarns or differential dyeing yarns. Furthermore, blends of fibers with different shrinkage properties are used. With defined heat treatment, the high-shrinking component will cause a strong contraction of the yarn, resulting in increased bulk, high filling capacity, and a pleasant touch of the pile surface .
This special effect is obtained by heat setting and fixating twisted yarns. The resulting permanent twist structure gives the desired surface effect. Airbags In , John W. Hetrick submitted US patent no. This invention included the idea of an airbag to protect passengers in an automobile in the event of an accident. Between and cars with airbags were first produced in the United States.
The number of systems increases constantly. Additional elements are necessary to attach the airbag in the car. The materials or material alternatives mainly used for the production of airbags are listed in Table If certain limits are exceeded, first the safety belt lower limit value and then the airbag upper limit value are activated. The whole process including activation, inflation, and discharge of the airbag caused by the impact of the passengers is completed in 70 to 80 ms.
During activation, inflation and deflation of the airbag is subjected to extreme thermal caused by high temperatures of the gas from the generator and the accompanying particles and dynamic stress. Therefore, the material for airbags has to have a high melting point and high melt enthalpy safety against burnout. To withstand the large explosion energy, the material must also have a high tenacity at a decent elongation and a low initial extensional modulus.
This ensures that locally occurring stress peaks can be distributed over a larger area, and tear caused by too much stress can be avoided. Table Properties of yarns used for airbags  PET 1. Finer yarns used at present are mostly dtex yarns of PA 6 or PA 6. Furthermore, aramide and polyethylentherephthalate PET are used. The tendency to make airbag yarn finer and finer continues, the percentage of uncoated airbags has increased . Even modified polyester has been used as material for airbag fabrics. Experiments showed that airbags made from this fiber do not need to be coated.
Properties of yarns used for airbags are listed in Table In Europe, PA 6. Their most important properties are summarized in Table Yarns of PA 6.
Furthermore, PA 6. The longterm experience in using these yarns also plays an important role. For the spinning process, the yarn is coated with a low molecular weight oil or a water based lubricant to be able to sustain the mechanical strains during spinning without any damage. Among passengers, children are mostly at risk. This is especially relevant in the case of child seats facing backwards and for children who are not wearing safety belts . Therefore, safety belts need to be worn and children need to sit in the back of cars.
Also, a reduction of the mass of airbags may decrease the risk of injury for driver and passenger. Attempts have been made to reduce the area-specific weight by using finer filament yarn titers and also finer filament titers Table A decrease of the filament titer increases the air permeability. Experiences have already been made with PA 6.
Begriffe Zahlen Handelsnamen, TextilRundschau 19 , - Afzal, I. Beschaffenheit und Eigenschaften. Springer Verlag, Berlin Wulfhorst, B. Melliand Textilberichte 39 , - Satlow, G. Grundlagen der Chemie und Technologie. Georg Thieme Verlag, 9. Deutscher Fachverlag GmbH, Lenzinger Berichte 76 , 76 - 80  Falbe, H. Thieme Verlag, 9. Konferenz-Einzelbericht: 7. Textil-Industrie 72 , 21 - 29  Wulfhorst, B.
Chemical Fibers International 47 , -  Bending, U. Vortrag Occupant crash protection. March  Bachinger, J. Vortrag auf der Betriebsleitertagung, Lenzing Woodhead Publ. Terms - figures — trademarks.
Business Publishers, Frankfurt a. In contrast to the chemical fibers, which can be manufactured industrially in almost every desirable length and shape the various natural fibers are available only in specific lengths, titers, and cross-sections, and with certain crimp and stress— strain behavior depending on their type and origin. The development of spinning processes was based on these characteristics. This is another reason that the properties of chemical fibers are often adjusted to those of natural fibers so that they can be mixed or blended and also processed on conventional spinning machines.
The functions of the spinning machines are the preparation of the fibers for the actual spinning process, the organization of the fibers in a coherent, continuous structure, and the production of packages or units suitable for further processing. The basic principle of producing a yarn by organizing, parallelizing, drawing, and twisting of the fibers has not changed since the very beginning of spinning thousands of years ago. German technical terms used in spinning are explained in the German standards DIN . For further explanations about spinning, see also [2 — 12].
The name three-roller spinning comes from the arrangement of the rollers in the drafting zone at the most commonly used spinning machine, the ring spinning frame. This spinning principle is suitable for all fiber types with lengths up to 40 mm. It is very flexible with regard to the properties and applications of the produced yarns. Yarns manufactured by ring spinning are processed into wovens, hosiery, knits, and braidings in the areas of apparel, home textiles, and technical textiles.
Figure gives an overview of the various processing steps from the bale of raw cotton or cut synthetic fibers to the final yarn. Depending on the desired yarn properties and the fiber material, various different machine sequences and spinning principles are applied to reach a compromise between optimum yarn properties and cost-saving manufacture.
Table shows the main function of each machine during processing. The generic term mixing means a thorough blending of nonhomogeneous fibers of the same type as well as a quantitatively defined combining of different fiber types. Opening is the disentanglement of compressed fiber packages into single fibers. Cleaning is the removal of particles such as wood, leaf, or seed coat fragments cotton or fiber knots and neps that cannot be opened. Parallelizing leads to an orientation of the fibers in one direction.
Drawing is the drafting of an oriented fiber web in a drafting field. The purpose of drawing is to provide an optimally straightened, parallel, and uniform fiber orientation. Figure schematically depicts two typical setups for the spinning preparation of cotton [2, 11 — 17]. The type and intensity of the individualization of the fibers critically influence the further processing steps. The more intensively the cotton fibers have been individualized, the more contamination particles appear on the surface of the fiber bulk and may be removed.
Target weights for the individualized flocks are about 0. Figure Working elements of a bale breaker  3 Principles and Machinery for Yarn Production 79 With modern bale reducing systems, up to 80 bales are lined up on the floor and reduced by a programmable bale breaker in layers from top to bottom. Fiber flocks are removed mechanically with the help of beaters Figure The fiber flocks are then transported by air streams through pipelines.
Opening and Cleaning The main functions of the opening and cleaning machines are the further separation of the fiber flocks and the removal of contamination particles and dust from the cotton. High fiber throughput with as little fiber damage as possible is desired. With the working principle free beat the flocks are caught in free fall and accelerated by the cleaning elements. The opening is created by the interaction of forces of acceleration and inertia.
Contaminating particles resulting from the effect of centrifugal and gravity forces can be separated by grids. There are machines with one roller single-roller cleaner or with two rollers double-roller cleaner. Depending on the degree of opening, the beaters are nose beater, pins, or saw teeth Figure Because of the squeezed position of the fibers, the effect of opening with the restricted beat is more intense, but also more aggressive compared to the free beat.
This may lead to fiber damage if the flocks have not been sufficiently preopened. While fibers stay in the air stream rotating with the roller owing to their small mass and high air resistance, dirt particles are carried to the outside due to their high mass and small air resistance and can then be removed at the knife.
The cleaning effect depends on the machine model and the fiber material. The degree of cleaning may refer to single machines as well as to groups of machines, for example, to all preparatory machines. The objective of mixing is to optimize the homogeneity of the material mixture by combining several bales. The expression mixing is divided into the two functions: dosage blending and mixing thoroughly mixing.
Blending is the adjustment of defined mass percentages of several raw material components. Blending by manual layup or with automated bale reduction systems is less precise. The machines most often used for this task are the mixing chamber and the multiple mixer. With the mixing 3 chamber principle a very large volume e. This may be done continuously or noncontinuously. The largest mixers are used in mock-worsted spinning Section 3. There are two working principles: either flocks that had been fed at the same time are processed at different times, or flocks fed at different times are processed at the same time.
The separation and parallelization of the fibers is caused by the carding action. The regions where carding action takes place are called carding fields. Carding is caused by the mutual action of the sharp-pointed teeth of the card clothing that are oriented in the same direction and move relatively to each other Figure If v2 Carding action Stripping action Figure Carding action and stripping action Figure depicts a high-speed revolving flat card used for cotton and chemical fiber processing. The fiber material is continuously delivered to the card via a pneumatic feeder system.
The feeding cylinder and feeding plate present the fibers to the licker-in which is a roller covered with saw teeth. Caused by the difference in peripheral speeds, the tufts are separated. The main working element of the card is the tambour. The doffer 3 Principles and Machinery for Yarn Production 83 and the tambour provide a carding action, which causes a further separation of the fibers.
The major part of the carding action is accomplished between the tambour and the flats whose teeth are positioned toward each other for carding action. This causes separation into single fibers and the parallelization of the fibers. At the same time, contaminants and short fibers are removed.
Modern cards often provide additional rigid carding segments and dirt separation elements before and after the revolving flats. Even though carding action takes place between tambour and doffer, fibers are transferred from the tambour to the slower moving doffer because of the particular angles of the teeth. The transfer behavior is described by the transfer ratio, which quantifies the percentage of the fibers present on the tambour that are transferred to the doffer during one revolution of the tambour. Below the card, contaminants and dust are removed from the fiber material on the tambour with help of grids or, for modern cards, adjustable knives.
F chute feed S seeding area V licker-in T tambour A doffer D flats W stripping brush roller K can coiler Figure High-speed revolving flat card  Figure Card A brushing roller picks the condensed card web up from the doffer. Two nip rollers squeeze remainders of contaminants before the web is combined to a sliver. The sliver formation is accomplished with crossover draw-off or with a 84 3 Principles and Machinery for Yarn Production trough-shaped cone. The card sliver is deposited in cycloids in a rotating can.
This method ensures a gentle deposition and a high degree of filling of the cans. To compensate mass irregularities, cards are equipped with short-term and long-term control devices. The latest developments in microfiber carding can be found in . New developments in online measurement technology of cards are given in .
Draw frames consist of a can creel, a frame that holds the drive and control devices, the drawing field, and a can coiler with automated changer Figure The continuous sliver is drafted between the nip lines, as the surface speeds of the roller pairs increase in machine direction. The appropriate setting for the nip line distances as well as the roller geometry and the roller surfaces significantly determine the result of the drafting process.
The total drafting action usually consists of a low preliminary draft of about 1. The multiplication of the drafts of the single zones equals the overall draft ratio. The drafted sliver is deposited in cycloids into cans. Most spinning processes include two subsequent drafting passages to increase fiber homogenization and parallelization of the card slivers. The closed-loop control is used at the card to keep the sliver weight constant. In this mechanism, a sensor scans the sliver mass at the card exit.
The feed roller is adjusted according to the measured value. The advantage of this system is that the corrected value input at the feed roller is checked again at the measuring point. However, short-term fluctuations cannot be detected. The open-loop control is standard with draw frames Figure At the entrance of the draw frame, the measuring point, a system of tracer and grooved roller, detects the mass of the incoming slivers. According to the relative sliver mass, the speed of the two roller pairs at the entrance of the drafting field is increased or decreased.
In this mechanism, short-term fluctuations e. However, the modified value cannot be checked again, as the regulating point is behind the measuring point. Because of this deficiency, the sliver mass is independently measured again at the exit of 86 3 Principles and Machinery for Yarn Production the draw frame e. There are two different principles of combing preparation. The card slivers can either be drafted first and then wound up as combing rolls sliver doubling principle , or they can be wound up first and then be drafted together on a ribbon lap machine ribbon lap principle.
In modern combing preparation, the sliver doubling principle is preferred. With the combing itself, the fiber web rolled off the lap is pinched between tongs and mechanically combed out with combs. The removed short fibers and dirt particles are called noil or comber waste. The combed cotton is deposited as 3 Principles and Machinery for Yarn Production 87 sliver into cans.
The last stage in the combing room is an autoleveller draw frame that homogenizes the combed slivers. Combing provides multiple advantages in subsequent processing steps. Modern cotton combing machines work intermittently with moving clamps. The web rolled off from the lap 1 is pinched between the lower 4 and the upper clamp 5. The circular comber covered with combing segments 7 combs out the fiber beard that is protruding from the clamps.
The short fibers that are now sticking in the circular comber are removed from the combing segments with a brush 8. Figure Working elements of the combing machine  88 3 Principles and Machinery for Yarn Production After the combing action depicted in Figure , the upper clamp rotates upwards. The clamps are now open. Upper and lower clamp swing around the pivotal point of the clamps 6 toward the detaching rollers The detaching rollers grab the fiber beard and attach them to the previously combed fibers as a continuous fiber web.
This action is called soldering. After soldering, the top comb 9 moves down into the fiber beard, so that the detaching rollers do not pull out the web from the clamps during the detachment. With the transporting movement of the detaching rollers, the web is separated; this is called detachment. The detachment is supported by the clamps swinging backwards. Prior to the next combing sequence, the delivery rollers 10 transport the web forward through the open clamps at an adjustable feed rate.
On closing of the clamps, the next combing sequence starts. The first ring spinning frame was built in in the United States. Ring spinning soon dominated because of its high production speed and is practiced worldwide with about million spindles estimated in In recent years other nonconventional spinning methods have gained importance.
Ring spinning consists of three subsequent processing steps: slubbing, ring spinning, and winding. With nonconventional spinning methods, these three steps are combined in one processing step Figure This safety twist has to be small enough to still allow drafting of the flyer yarn to the final yarn titer in the drafting field of the ring spinning machine. The sliver is first drafted in the flyer drafting field which is often designed as a three-roller—two-aprondrafting unit. From the drafting field the drawn sliver is transported over the flyer top into the flyer leg which it exits at the bottom.
A finger guide leads the sliver to the bobbin surface.
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With this mechanism the sliver obtains one twist with each revolution of the flyer. The winding itself is caused by a lead of the bobbin against the flyer top. The vertical movement necessary for the winding is accomplished by the bobbin. Because the flyer operates at a constant feed speed, the vertical movement and the revolutions per minute have to be adjusted continuously according to the bobbin diameter. The limit of revolutions per minute for the flyer is about to rpm and depends on the maximum feed speed. For a bobbin change, the flyer legs have to be removed which makes automation difficult.
Several more disadvantages associated with the flyer spinning principle include that the stopping of the entire machine is necessary if a sliver breaks. For decades, people have been working on eliminating the flyer process and spinning drawn slivers directly on the ring spinning frame so-called direct spinning. First, the sliver is drafted to the final yarn titre via a double-apron drafting unit draw ratios about 10 to The essentially untwisted yarn exits the drafting field and is twisted by the rotation of the traveller on the ring Figure The rotation of the cop drags the ring traveller with it.
The yarn is twisted once with each revolution of the ring traveller. The twist formation moves up to the spinning triangle whose geometry is determined by the equilibrium of the 90 3 Principles and Machinery for Yarn Production torsional moment of the yarn and the opposing moment of the loose fiber sliver.
Owing to the trailing of the traveller, the twist of the yarn is a little lower than the twist that would be produced by the rotating cops only. To produce a cop winding that allows unwinding in further processing at high speed and without breaks, the ring rails follow a defined pattern of vertical movement. A pattern of vertical movement used often is depicted schematically in Figure At higher traveller temperatures the heat produced by friction cannot dissipate sufficiently, which will result in the destruction of the traveller or the yarn.
Because this value is substantially higher than with other spinning methods such as OE rotor spinning, ring spinning produces the finest, the most uniform, and strongest yarns. Modern automation systems also contain combined systems of flyer spinning machine, ring spinning machine, and winding machine. The cop and bobbin transport and change, as well as the yarn splicing, are automated in this system.
Figure Diagram of vertical movement for the elements ring C , rings to restrict the thread balloon B and thread guide A  For the production of woollen yarns, ring spinning can also economical owing to their relatively low twist which reduces the economic advantage of nonconventional spinning machines. This is achieved through a condensing of the fibers after the main draft by using a perforated roller in combination with a suction unit. The hairyness of the yarn is thus reduced and the tenacity is higher when compared to ring-spun yarns.
The yarn evenness is also improved. Ring spinning  Compact spinning  Figure Principles of ring and compact spinning Currently, there are three different systems on the market Figure In contrast to ring spinning, in which a continuous thread of fibers is rotated at one end and wound on a package, with OE spinning the fiber thread is interrupted and the single fibers are reattached to a rotating, open yarn end.
The advantage is that not the whole yarn stock, but only the very end of the yarn has to rotate energy consumption! Yarn formation according to the rotor spinning principle predominates for all nonconventional spinning methods. Worldwide, more than 7 million spindles are in operation. In recent years about , spindles were installed each year . The feed for rotor spinning is card, drawn, or combed sliver. Below the opening cylinder contamination particles are segregated.
The fibers are detached from the clothing with an air stream and accelerated in a conical guiding channel. This channel ends in a rotor rotating with up to , rpm. Because of their centrifugal force, the fibers slide along the outside of the rotor wall and form a ringlike structure in the rotor groove.
Because the fibers are continuously accelerated during this process, their position in the rotor groove is mostly straightened. The yarn rotates in the rotor groove, which causes fibers lying in the groove to attach to its end. With the pull-off of the yarn through the nozzle and the uptake pipe, a continuous spinning process takes place. Yarn can be produced in a wide titer range from 12 to tex [26 — 45]. The fibers are twisted without stress between the pull-off nozzle and the rotor groove. The yarn twist is produced by the rotation of the rotor and the pull-off from the rotor and by a false twist at the pull-off nozzle.
This false twist contributes significantly to the spinning stability and is removed again later Equations 3. When fibers are attached to the end of the twisted yarn in the rotor groove, they wind around the yarn end with one fiber end in the direction of yarn twist, and with the other fiber end opposite to the direction of yarn twist.
The resulting yarn appearance is attractive in some products, for example, blue jeans. In other products, these wrapper fibers are unwanted. In yarns for cut-pile carpets, wrapper fibers are disadvantageous, as they prevent the pile from opening uniformly.
Figure Formation of wrapper fibers  For OE rotor spinning, a minimum of 70 to fibers in the yarn cross section is necessary. Because of this process-inherent restriction, rotor yarns cannot be spun as fine as ring yarns minimum of 50 to 70 fibers per cross section. The tenacity of rotor yarns is lower than that of comparable ring yarns. Rotor spinning is much more economical than ring spinning, however, as the flyer spinning process is omitted. Rotor spinning is fully automated and delivers cross-wound bobbins ready for further processing without any additional winding step.
With OE rotor spinning, multiple different raw materials can be processed cotton, wool under special conditions, flax as additive, chemical fibers, for example, viscose, polyacrylnitrile, polyester , and very different yarns can be produced. For different material and different yarn characteristics, the spinning elements such as opening cylinder, rotor, pull-off nozzle Figure , have to be adjusted in shape and material.
In spinning practice, a large number of spinning components is available on the market. Multiple slivers are fed to the opening unit and separated into single fibers.
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