))Target: Familiarize yourself with the production of fabrics and their structure. Learn to determine the direction of the grain thread and the right side of the fabric.
Visual aids: “Cotton” and “Linen” collections; fibers (wadding), yarn (threads from fabrics), illustrations of spinning production; fabric samples with selvedges.
Equipment and materials: cotton wool, magnifying glasses, fabric samples, paper, scissors, glue, workbook, textbook, computer (presentation)
During the classes
I. Organizational moment
Checking students' readiness for the lesson
II. Repetition of covered material.
Oral survey.
Review questions.
- What does sewing materials science study?
- What is fiber called?
- What are the two types of textile fibers?
- What is hygroscopicity called?
III. Explanation of new material with practical reinforcement.
(slide 3) Even in ancient times, man learned to combine individual short and thin fibers into long threads - yarn and make fabrics from it. At home, great-grandmothers spun yarn by hand (using a spindle and a spinning wheel). Later, weaving machines appeared. The width of the fabric depended on the width of the loom, which determined the cut in folk clothing.
In Western Europe, the manufacturing period (industrial production of fabrics) began at the end of the 16th century. and continued until the last third of the 18th century. In Russia it began a little later.
To make yarn, people used fibers that they could obtain from the natural conditions that surrounded them.
(slide 4) At first it was fibers of wild plants, then animal wool, and then fibers of cultivated plants - flax and hemp. With the development of agriculture, cotton began to be cultivated, which produces very good and durable fiber. Later, fabrics began to be made from a wide variety of fibers.
(slide 5) Yarn is made from fibers, which is used to make fabrics, knitwear, braid, lace, and sewing threads.
(slide 6) First, the fiber is loosened - divided into small pieces using needles and teeth of a loosening machine. Then, in a scutching machine, using a special drum with pegs, weeds are separated from it and loosened again.
(slide 7) Then the mass of fibers is processed on carding machines to separate them into individual fibers and partially straighten them, placing them parallel to each other.
(slide 8) On the same machines they turn into a thick, loose rope - a tape, which is leveled in thickness on tape machines.
(slide 9) After this, on roving machines, the sliver is gradually pulled out with special drawing devices and slightly twisted until a roving is obtained.
(slide 10) Roving machines operate on draw and roving machines.
(slide 11) On spinning machines, yarn is obtained from roving: the roving is pulled out, twisted using spindles and wound onto bobbins. The spindles rotate very quickly - they make from 8 to 14 thousand revolutions per minute. Each spindle spins 8-18 m of yarn per minute, and each machine has 200-500 spindles.
High-performance spindleless spinning machines are installed in the workshops of modern spinning factories. In these machines, a stream of combed fibers is blown by a stream of air into a rapidly rotating chamber, in which the resulting sliver is spun into yarn.
People of various professions work at the spinning mill. The main profession in the spinning industry is a spinner. He services several spinning machines at the same time, eliminates roving and yarn breaks, changes reels or bobbins, and performs equipment maintenance work.
Fabric making stages
(slide 12) Yarn arrives at the weaving factory in huge bobbins. From this yarn, fabric is made on looms by interlacing yarn and thread. Fabric removed from the loom is called gray, because. it has impurities. It needs finishing. It is given a beautiful appearance, quality is improved, and a design is applied. Fabric that has undergone finishing is called ready.
They work on looms weavers.It serves several machines at the same time. Weavers replace empty bobbins with full ones, eliminate thread breaks, and remove the finished fabric from the loom. On automatic machines, the spool is changed automatically. The weaver must know the requirements for the fabric, its defects, and the reason for thread breakage.
Now there are modern shuttleless, more productive weaving looms in which the weft thread is laid with a jet of compressed air or water.
(slide 13) Fabric is produced on weaving looms.
Fabric removed from the loom contains impurities and contaminants. This fabric is called harsh. It is not intended for making clothes and needs finishing The purpose of finishing is to give the fabric a beautiful appearance and improve its quality. This fabric is called ready-made.
(slide 14) The threads running along the fabric are called basis. Cross threads in fabric are called duck Non-fraying edges are formed on both sides of the fabric along the grain thread - edges. The process of obtaining fabric is called weaving. There are several types of weaving threads in fabrics. The easiest - linen, where the threads intertwine through one.
The warp thread is determined by the following signs: along the edge, according to the degree of stretching - the warp thread stretches less, the warp thread is straight, and the weft thread is crimped.
(slide 15) The fabric has a front and back side. The front side of the fabric can be determined by the following features:
- on the front side of the fabric the printed pattern is brighter than on the back side;
- on the front side of the fabric the weave pattern is clearer.
- the front side is smoother, because weaving defects are displayed on the reverse side.
Physical education minute
Exercises
Lean back in your chair, straighten your legs forward, arms down. Lower your head, close your eyes, relax (15-20 seconds).
Starting position (ip.) – sitting on a chair, arms down, head down. 1-2 – hands behind the head, fingers intertwined, bend over, throwing your head back, – 3-4 – i.p. (The pace is slow, repeat 3-4 times).
I.P. – sitting on a chair, hands on your belt. 1 – hands to shoulders, hand into fist; 2 – arms up, stretch, hands straight; 3 – arms to shoulders, hands into fists; 4 – “drop” your hands down (the pace is slow, repeat 3-4 times).
I.P. – sitting on a chair, arms down. 1-2 – raise your shoulders, trying to touch your earlobes; 3-4 – lower. (Medium tempo, repeat 4-6 times).
I.P. – sitting on a chair, hands on your belt. 1-2 – two springy tilts to the left, touch the field with your hand; 3-4 – i.p. The same to the right (medium pace, repeat 3-4 times).
I.P. – sitting on a chair, arms down, legs bent at the knees, place on the floor. 1-2 – raise your heels, lower them; 3-4 – raise your socks, lower them (medium tempo, repeat 3-4 times).
(slide16) IV. Practical work No. 2. Making a plain weave design from paper. Determining the front and back sides of the fabric. Safety precautions (work according to the textbook).
The threads in the fabric are intertwined in a certain order. Let's consider the most common type of weave - plain. In a plain weave, the warp and weft threads alternate. Cotton fabrics - calico, calico, cambric, as well as some linen and silk fabrics - have a plain weave.
V. Target bypass. Monitoring correct work practices, compliance with technology and safety regulations.
(slide1 7 )VI. Consolidation of the studied material. Crossword.
VII. Evaluation of completed work.
VIII. Homework. Compile your own collection of samples of cotton and linen fabrics.
Bibliography
- Technology: Textbook for 5th grade students of secondary schools. Edited by V.D. Simonenko. M.: “Ventana-Graf”, 2003.
- Didactic material on labor training “Cooking and textile processing” Book for teachers. Edited by E.V. Starikov and G.A. Korchagin. M.: “Enlightenment”, 1996.
- Lesson plans for the textbook “Technology 5th grade” by V.D. Simonenko. Edited by O.V. Pavlova, G.P. Popova. Volgograd. “Teacher”, 2008
Fabric is made from yarn in weaving factories. The raw material for yarn production is fiber. The properties of fabrics and their quality depend on the fibers from which they are made, i.e. from the original type of raw material.
All fibers can be divided into two large groups: natural or chemical. and animals - exist in nature, chemical fibers (synthetic and artificial) - are obtained artificially.
Types of weaving threads in fabrics:
- simple: main - linen, twill, satin, satin; finely patterned - matting, rep, reinforced twill, diagonal, crepe;
- complex: double, pile, loop, openwork, pique;
— large-patterned: jacquard.
The technology for manufacturing fabrics of different weavings is produced on various looms: main and finely patterned weaves - on single-shuttle automatic looms; variegated and complex weaves - on multi-shuttle; large-patterned - on Jacquard machines.
In a plain weave, the warp and weft threads are woven through a single thread. This gives greater fabric strength and wear resistance. Most cotton fabrics are produced using plain weave.
In a twill weave, the warp threads overlap two weft threads through one thread. On the front side of the fabric a pattern is formed in the form of a rib running in the oblique direction of the fabric. Twill weave fabrics are soft, have great extensibility in the oblique direction, drape well, and sections have high fraying. Compared to plain weave fabrics, fabrics are denser, thicker, heavier, and less durable. Some cotton, silk and woolen fabrics are produced using twill weave.
Satin weave has a higher weft density, since in this weave one weft thread is covered by four warp threads. In a satin weave, on the other hand, the warp thread passes over four weft threads. Fabrics with such weaves are soft, less durable than plain weave fabrics, they have greater fraying and slip when cutting, and stretch strongly along an oblique cut. Satin and satin weaves are used to produce cotton fabrics.
It is worth mentioning that in Russian cotton was originally called cotton paper. In many classic literary works you can find the expression “paper cap”. And this is not at all a headdress made of the paper we are now familiar with, but just a wardrobe item made of cotton fabric. Therefore, the concepts “cotton” and “cotton” are identical.
Where does cotton come from?
It comes from cotton. It is a shrub reaching from 0.5 to 3 meters in height depending on the species. It has a spiral arrangement of leaves and a tap root system. About 40 species of cotton are known, but only a few of them are cultivated.
The bud blooms into a flower, then self-pollination occurs, the flower turns into a box, which begins to ripen and opens (Hlopok tsvetok and Hlopok korobochka). Fibers sprouted from seeds (Odin hlopchatnik) are exposed to light.
Each fiber is a dead tubular cell. Its length is several thousand times greater than its width. It consists mainly of cellulose, but in its raw form also contains some resins and waxes.
Cotton is thermophilic. The ideal temperature for it is around 30°C. Loves sun and moisture. Does not grow well in cool or hot weather. The leading countries in cotton exports are China, India and the USA.
Cotton collection and processing
Cotton plantations are so vast (Cotton pole) that cotton is harvested by mechanization. However, this method has the disadvantage of introducing unnecessary parts of the plant into the harvest. Manual assembly is much more accurate, but ten times less productive.
The collected cotton is cleaned. It happens like this. Cotton bales arrive from collection points to the manufacturing plant. There they are opened and kept for a day for the so-called “blooming”. After that, the cotton is loaded onto special machines, where it is loosened and cleaned of unnecessary impurities and seeds. The cotton then goes through a final cleaning process.
The resulting cotton fibers are twisted and pressed. The seeds are not thrown away: some of them will be sown again, some will be used for oil, and the remaining cake will become feed for livestock.
Production of cotton fabric
Cotton fibers are spun into threads. They are glued with solutions based on resins, fats and starch in order to successfully withstand mechanical stress during further processing.
Next comes bleaching. Previously, the sun's rays served as bleach, but now more modern technologies are used - solutions that contain substances based on chlorine or hydrogen peroxide.
At the next stage, the previously used glue is washed off.
Sometimes the fabric is made from already dyed threads. In other cases, bleached fabric, which during processing becomes completely hydrophilic (absorbs water with appetite), is dyed with special synthetic substances, of which there are thousands in the industry.
During the production process, cotton can also be subjected to so-called finishing, which is worth talking about in more detail.
Finishing is a series of operations that give the fabric the necessary consumer properties. There are mechanical varieties like shaving and napping, but most are done using chemicals.
Blueing, for example, enhances the effect of whiteness. The name of the anti-crease finish, which uses formaldehyde resins, speaks for itself. And, of course, mercerization - soaking fibers, threads or finished fabric in caustic sodium at zero temperature. This operation gives cotton silkiness, strength and the ability to retain its shape.
Cotton or cotton fabric, the fabric is durable, attractive in appearance and durable. Products made from it are pleasant to the touch, wash well and have excellent hygroscopic properties (cotton can absorb up to 15-20% of its own weight without feeling wet). Cotton is the most popular material in the textile industry, and that probably says it all.
Basic Spinning Processes
FABRIC PRODUCTION TECHNOLOGY
First, textile threads are produced from raw materials - fibers or filaments - yarn or filament threads. Yarn is obtained by spinning fibers. Complex threads are twisted from several elementary threads.
The resulting yarns or filament threads are then produced into fabric through the weaving process. In this case, a raw fabric is obtained, which is subjected to finishing, giving it a beautiful presentation.
The fibrous mass of natural fibers, after collection and primary processing, enters the spinning mill. Here, a continuous strong thread - yarn - is produced from fibers of limited length. This process is called spinning. Along with natural fibers, staple chemical fibers are also processed in spinning mills.
The raw materials for spinning are textile fibers: cotton, flax, wool, waste from silk weaving and sericulture, and various chemical fibers.
The spinning process can be divided into three stages:
Preparation of the fibrous mass and the formation of a tape from it;
Preparation of sliver for spinning and pre-spinning;
Spinning.
The stage of preparing the fibrous mass and forming a tape from it includes the processes of loosening, mixing, scuffing, and carding.
When loosening, the tightly compressed mass of fibers is divided into small shreds for better mixing and cleaning the fibrous mass from impurities. Loosening is carried out on feeder-rippers.
Individual lots of cotton, wool and other fibers vary in length, thickness, moisture content and other properties. Loosened fibers from different batches are mixed together in order to obtain large batches of raw materials that are homogeneous in their properties. Therefore, several batches of fibers are usually mixed. Fibers of different natures are also mixed to obtain yarn with certain properties. The main mixing takes place on the mixing grid. After mixing, the fibrous mass is sent to scutching.
Scuffing provides further loosening and intensive cleaning of the fiber mass from impurities. The loosened and purified fibers are converted into canvas, which is wound into a roll. The process is carried out on scattering machines.
In order to separate small shreds and tufts of fibrous mass into individual fibers, the canvas is carded. Remove small, tenacious impurities remaining after the processes of loosening and scuffing. When carding, a fly or roving is formed from a thin layer of combed fibers. Carding is carried out on carding machines, in which the fibrous web passes between the surfaces of the card belts, covered with thin sharp metal needles. When leaving the carding machine, a thin combed layer of fibers - a carded card - is passed through a funnel and converted into a tape of non-uniform thickness, which is a bundle of fibers oriented in the longitudinal direction.
To obtain roving, the batt fleece is not formed into a tape, but is divided into narrow strips, which, after compaction, are converted into roving.
The second stage of spinning production consists of preparing the sliver for spinning and pre-spinning.
Preparing the sliver for spinning consists of straightening and stretching the sliver. First, fold 6-8 tapes together, aligning them in thickness. To obtain mixed yarn, ribbons of different fiber compositions are combined. The folded tapes are pulled out evenly, while the tape becomes thinner and the fibers are straightened and oriented.
The tapes are aligned and drawn on draw machines, which are equipped with several pairs of rollers rotating at increasing speed. Passing between the rollers, the tape gradually becomes thinner and the fibers in the tape are oriented in the direction of movement. Processing can be carried out sequentially on several machines to obtain increasingly thinner strips. High-drawing draw frames are widely used, replacing several draw frames.
Pre-spinning is the gradual pulling of the sliver into the roving. It is carried out on roving machines, where the strips are finally drawn into a roving of the required thickness, slightly twisted to strengthen it, and also wound onto a package of a given shape and size.
The third stage is spinning, during which the final thinning of the roving and its twisting occur, i.e., turning the roving into yarn, as well as winding the yarn onto a package of a given shape and size. Spinning is performed on spinning machines.
The raw materials entering the spinning production have different qualities: length, thickness, fiber crimp. From thin, long-fiber raw materials, thin, smooth, dense yarn is obtained, and from shorter and thicker fibers - thick, fluffy and loose. The yarn production steps presented above remain the same for both fine and thick yarns. However, when spinning thin long or thick short fibers, each of the listed production stages has differences in technological processes and equipment. There are differences in processes and equipment when producing yarn of different fiber compositions.
The set of processes and machines by which the fibrous mass is processed into yarn is called a spinning system. Known spinning systems differ from each other mainly in the way they carry out two main processes: carding the fiber mass and thinning the product (Fig. 10).
Card spinning system- the most common. Carding of fibers here is carried out on carding machines. The thin layer of fibers removed from these machines is formed into a tape. The sliver is then successively thinned into roving and yarn by drawing in the drafting devices of subsequent machines. This system produces yarn with a linear density of 15-84 tex from medium-fiber cotton, as well as from chemical and short flax fibers.
Yarn spun using this system from fibers dyed in one or different colors (with the exception of linen) is called melange.
Carded yarn is quite uniform, has medium purity, but lacks smoothness.
Carded yarn is used in the production of fabrics, knitted fabrics, stitched nonwovens, some types of ribbons, braid, cords, and lace.
The comb spinning system after carding operations provides for additional combing of the fibers on combing machines. At the same time, short fibers and small debris are removed, long fibers are straightened and oriented parallel to each other. Further thinning of the resulting tape is carried out, as in the card system, by stretching on subsequent machines. This system spins yarn that is stronger, smoother, cleaner and finer. For spinning, fine-fiber cotton, flax, fine long wool, and waste from silk-winding and silk-weaving industries are used. The highest quality products are made from combed yarn. However, the use of a combed spinning system increases the cost of yarn.
Like the previous two, the hardware spinning system includes carding, but unlike the above systems there is no sliver formation.
Monofilament is a single thread that does not divide in the longitudinal direction without destruction, suitable for direct use in the production of textile materials.
Further processing of primary threads can significantly change their appearance and properties. The result is twisted and textured threads, which are called secondary.
Twisted threads consist of several primary threads folded together longitudinally and twisted into one. They have greater strength than primary threads and greater stability of other properties.
Twisted threads include twisted yarn and twisted filament threads.
Twisted yarn can be single-twisted, obtained by twisting two, three or more yarns of the same length in one step, and multi-twisted, obtained as a result of two or more successive twisting processes. So, to obtain double-twisted yarn, first some of the threads are twisted, and then, putting them together, they are twisted a second time.
In any of these cases you can get:
a) simple twisted yarn, when individual folded threads fed with the same tension form a homogeneous twisted thread structure along its entire length;
b) reinforced, having a core (single yarn, twisted yarn, complex threads, etc.), enveloped in different fibers (cotton, wool, flax, various chemical fibers) or threads tightly connected to the core by twisting;
c) shaped twisted yarn, consisting of a core thread, wrapped around a surge or effect yarn, having a greater length than the core. The surge thread forms spirals, knots of various shapes and lengths, ring-shaped loops, etc. on the core thread. Loops, knots and other effects are fixed on the core thread by a third securing thread fed into the torsion zone at the speed of the core thread. The use of shaped twist threads makes it possible to obtain fabrics with a beautiful external effect.
Twisted filament threads, similar to twisted yarn, can be single- or multi-twist. In this case, it is possible to obtain simple complex twisted, combined and shaped threads.
According to the degree of twist, twisted threads of different degrees of twist are distinguished. Threads with weak or flat twist have up to 230 twists per 1 m of length. They are used in weaving as weft threads. Medium twist threads, or muslin, have 230-900 twists per 1 m of length and are used as warp threads in the production of fabrics. High twist threads, or crepe, have up to 2500 twists per 1 m of length. Such threads are most often produced from raw silk or chemical filament threads. Fabrics made from crepe threads have a beautiful fine-grained, matte surface, i.e. they have a crepe effect. In addition, they are more rigid and elastic, which reduces their wrinkling.
According to the direction of twist, which characterizes the direction of the turns of the twisted thread, right-hand twist threads (Z) and left-hand twist threads (S) are distinguished (Fig. 12).
The properties of twisted yarns and filament yarns are greatly influenced by the combination of the twist direction of the primary yarn and the direction of subsequent twists. The best properties are found in twisted threads in which the directions of the primary and subsequent twists do not coincide (Z/S or S/Z). During the final twist in the direction opposite to the primary one, the component threads unwind until they are secured by turns of repeated twist. Thanks to this they
form a dense thread of round shape, uniform in thickness. As a result, the twisted thread gains greater strength, and products made from it gain greater wear resistance. Textured are called threads, the appearance, structure and properties of which are changed by additional physical-mechanical, physical-chemical and other treatments. The threads have increased volume, loose structure, increased porosity and extensibility. These features are a consequence of the increased tortuosity of the elements of their structure. These include textured (high bulk) yarns and textured filament yarns.
High-volume yarn with increased elongation (30% or more) is obtained from synthetic multi-shrink staple fibers. High-shrinkage fibers, highly stretched during the manufacturing process, are shortened by steaming and, due to friction, impart a wave-like crimp to the low-shrinkage fibers, increasing the porosity, thickness and volume of the yarn.
However, textured filament yarns are more widely used in industry. There are three main methods for producing textured yarns.
The first method - thermomechanical - consists of imparting crimp to smooth complex synthetic threads by intensive twisting, fixing the twist using heat treatment, followed by unwinding. In this way, highly extensible threads are obtained. Threads obtained in this way from nylon complex threads are called elastic. The high reversible stretchability of the elastic makes it possible to produce products that should fit the human body well (socks, swimsuits, etc.). Textured threads made from polyamide filament yarns are called meron, and those made from polyester are called melan.
The second method is physical modification - imparting zigzag crimp and looseness to smooth thermoplastic filament threads by pressing (corrugating) them into special chambers followed by heat treatment. The resulting threads are classified as high-tensile threads. Textured thread obtained by corrugation is called corrugation. It is used to produce knitted fabrics for a range of outerwear, various dress and suit fabrics.
The third method is aerodynamic - imparting looseness and looseness to chemical threads of any kind by exposing them to a turbulent air flow in a loose state. This is how threads of normal extensibility are obtained. Using this method, it is possible to obtain combined and shaped textured threads from primary threads of different types. Such looped threads obtained from polyamide are called aeron. They are used for the production of high-quality dress, suit, and shirt fabrics.
Based on their fibrous composition, threads are classified into homogeneous, mixed, heterogeneous, mixed-heterogeneous and combined.
Yarn is homogeneous if it consists of fibers of the same type (cotton, flax, wool, silk, chemical fibers); complex threads consisting of elementary threads of the same type; monofilament; twisted threads (twisted cotton yarn, twisted viscose thread, etc.); textured threads (elastic from nylon thread, melan from lavsan thread).
Mixed yarn is a yarn consisting of a mixture of fibers of different origins, evenly distributed over the entire cross-section along the yarn (for example, from a mixture of cotton and lavsan fiber, wool and nylon fiber, etc.).
Twisted threads can be heterogeneous, containing homogeneous threads of different types (for example, wool yarn twisted with nylon filament thread), and mixed-heterogeneous (for example, half-woolen yarn made from a mixture of cotton and wool, twisted with nylon filament thread).
Textured threads are combined, containing different types of textured threads and ordinary chemical filament threads (for example, a combined textured tacon thread consists of a textured acetate thread twisted with a regular nylon filament thread).
In terms of finishing and coloring, textile threads can be harsh - without finishing; bleached; plain painted; sour; boiled; melange - from a mixture of colored fibers; highlighted - from two or more multi-colored fibers; shiny, matte. The finishing and coloring of textile threads depend on their fibrous composition and structure.
Control questions
1. What is yarn?
2. What is a filament thread?
3. What is monofilament?
4. What is twisted thread? What types of twisted threads do you know?
5. What is single-twist, double-twist thread?
6. How does a simple twisted thread differ from a shaped twisted thread?
7. What is reinforced twisted thread? How does it differ from plain and shaped twisted threads?
8. How do twisted threads differ in the degree of twist?
9. How do twisted threads differ in the direction of twist?
10. What is textured spun thread? What are the features of textured threads?
11. What types of textured twisted threads do you know? What are the characteristics of these threads?
12. How are different types of textured threads produced?
13. How are threads distinguished by their fibrous composition?
14. What are homogeneous, mixed, heterogeneous, combined threads?
15. What types of thread finishing do you know?
Basic properties of textile threads
The main properties characterizing textile threads include: thickness, twist, strength, elongation, unevenness.
The thickness of textile threads, as well as fibers, is characterized by linear density T (tex), which is determined by the already known formula
where m is the mass of the fiber, g; L - fiber length, km.
The linear density of a textile thread is determined by weighing a skein, i.e. a skein of yarn 100 or 50 m long, followed by recalculating the total length of the threads into kilometers and calculating the indicator using the above formula. The linear density of the thread can be calculated using the length of the thread in meters, using the formula
T = (1000t)/1,
where m is the mass of the fiber, g; / - fiber length, m.
The thickness of fabrics, knitted and non-woven fabrics depends on the thickness of the threads. The use of thinner threads makes it possible to obtain thinner fabrics and textile materials.
The twist of the threads is determined by the number of twists or turns per 1 m of thread length. This indicator is determined on a device - a torque meter. The twist of the thread depends on its thickness. The thicker the thread, the lower the number of twists per 1 m of thread length.
In order to be able to compare the degree of twist of threads of different thicknesses, an indicator has been introduced, which is called the twist coefficient b. It is calculated using the formula
where K is the number of twists per m of thread length; T-linear thread density, tex.
A low twist coefficient indicates that the thread is soft, not dense or elastic. High - because the thread is elastic, dense, thin, tough.
An increase in the number of twists leads to an increase in the strength of the thread, but increasing the strength of the thread has limits. “If you continue to twist the thread, then its strength will begin to fall. The number of twists of the thread, after which the strength of the thread begins to fall, is called critical twist .
Soft voluminous fabrics are obtained from soft threads with a gentle (small) twist. The use of high twist threads allows us to produce dry, dense, elastic fabrics.
The strength and elongation of the thread is characterized by the following indicators: breaking load and breaking elongation, which are determined when testing the skein, i.e. skein of yarn 100 or 50 m long, on a breaking machine. The force at which the skein breaks shows the breaking load in centinewtons (cN), which characterizes the strength of the threads. At the moment of rupture, the elongation at break is also recorded, measured in millimeters.
Threads with reduced strength are less processed in weaving. Their frequent breakage is observed, which leads to a decrease in the quality of the fabrics. A small elongation of the thread at break indicates the rigidity of the thread, its intractability to stretching.
The unevenness or unevenness of the thread in linear density is a significant indicator of the quality of the thread. Unevenness may result from uneven fiber length, thickness, crimp and strength. It can occur at any stage of spinning production. Unevenness in linear density is determined visually or using special instruments. In the visual method, threads are wound onto screens of a contrasting color, and then the wound samples are compared with standards of varying degrees of unevenness.
The smoother the threads, the fewer deviations are observed in thickness, strength, and twist throughout their entire length.
Weaving production
Fabric is a textile fabric formed by interlacing two mutually perpendicular systems of threads on a loom. The process of creating fabric is called weaving.
The system of threads located along the fabric is called the warp, the system of threads located across the fabric is called the weft.
Fabric production is carried out in three stages:
Preparation of warp and weft;
Making fabric on a loom;
Sorting of manufactured fabrics.
At the first stage, the warp and weft threads are prepared for the weaving process. The threads received from the spinning plant are rewound into packages convenient for threading into a weaving machine.
Preparation of the warp consists of the following operations: rewinding, warping, sizing and threading of individual threads into the parts of the loom.
Rewinding of warp threads from spinning cobs or skeins onto large bobbins of cylindrical or conical shape is carried out using winding machines. In this case, packages of great length are obtained, the threads are cleaned of foreign impurities and their weak points are eliminated. Since rewinding is carried out with a certain tension of the threads, weak points are revealed by breaks. The broken ends of the threads are tied with a special weaving knot. On modern winding machines, where the rewinding speed reaches 1200 m/min, the tying of broken ends is performed automatically. The warp threads, wound on large bobbins, go to the warping.
The warping is that warp threads from a large number of bobbins (from 200 to 600 or more) are wound parallel to each other with the same tension on one large spool with flanges. Such a coil is called a warping shaft. All warp threads wound on the warping shaft must be the same length. The warping operation is carried out on a special warping machine. Warping speed - 800 m/min. The warp threads are fed from the warping shaft for sizing.
Sizing is the gluing of warp threads with a special adhesive - sizing. Sizing gives the warp threads smoothness and strength. This is extremely important in order to prevent the warp threads from breaking during the weaving process due to abrasion on the loom parts.
The size is cooked separately and then fed into the sizing machine. The size formulation includes adhesive, softening, antiseptic substances, wetting agents - substances that make the threads hygroscopic. The size recipe may vary depending on the type of fabric.
The warp threads, passing under tension through a sizing machine, are treated with sizing, pressed out, dried, separated one at a time and, located parallel and at an equal distance from each other, are wound on a shaft, which is called a weaving beam. The speed of movement of the base in the sizing machine is from 12 to 75 m/min. Weaving machines for producing fabrics for different purposes and fiber composition have different widths. Therefore, a weaving beam of appropriate width is installed on the sizing machine.
Before the weaving beam is installed on the loom, the warp is threaded and tied. Threading, or threading the warp, is an operation in which each thread of the warp must be threaded in a certain order through the parts of the loom: lamellas, eyes of the healds and teeth of the reed.
The lamella is a thin metal plate with a round hole into which the warp thread is threaded. The lamellas serve to automatically stop the weaving machine when the warp thread breaks. The number of lamellas is equal to the number of warp threads in the warp and, accordingly, the number of threads in the warp of the fabric.
The heald frame, or heald, is located across the entire width of the loom. It consists of two horizontal strips placed one below the other. A heddle with a peephole in the middle of each heddle is fixed vertically between the slats. Warp threads are threaded through the eyes of the heddles - one through each eye. The heald frames provide the formation of a shed for laying the weft thread. The number of heald frames depends on the type of fabric weave and ranges from 2 to 32. The number of heddles corresponds to the number of warp threads in the beam, but the order of threading into the eyes of the heddles depends on the weave of the fabric.
The reed also runs the full width of the loom and consists of flat metal plates mounted vertically on two slats. The metal plates are called reed teeth. The reed serves to nail the newly laid weft thread to the previous one, as well as to maintain a uniform, parallel arrangement of the warp threads during weaving. Each warp thread is sequentially passed between the teeth of the reed.
The work of threading the warp threads into the holes of the lamellas, the eyes of the healds and between the teeth of the reed is carried out on a special parting machine. The sorting is done manually by two workers. The feeder feeds the warp threads sequentially, one after another, and the threader, with a special hook, pulls all the threads from the first to the last through the parts of the loom. With this organization, 1000-2000 threads are threaded per hour.
Threading is carried out when rethreading a loom to produce a new type of fabric or when replacing worn parts of a loom. If the same fabric is produced on a loom, then in this case weaving is not carried out, but the ends of the corresponding threads of the new warp from the new warp are tied (attached) to the ends of the old warp. When tying the ends of the warp, knotting machines are used with a knitting speed of 5000 knots per hour or more. To start the loom, the connected units are carefully pulled through the holes of the lamellas, the eyes of the healds, and the teeth of the reed.
There are and are used automatic machines for threading warp threads.
Preparing the weft for weaving is a simpler process, which consists of rewinding the threads onto special wooden shuttle bobbins and moistening the threads.
Rewinding on shuttle bobbins is necessary if weaving will be done on shuttle looms. This operation is performed on weft-winding machines at a speed of 300 m/min.
The threads are moistened so that when laying the weft thread from the shuttle bobbin, several turns of the thread do not unwind at the same time, which leads to the formation of defects on the fabric. Moistening of threads of different fibrous composition is carried out in different ways. Cotton and linen yarn are kept in rooms with high air humidity, wool yarn is steamed, and silk and chemical threads are emulsified.
At the second stage, fabric is produced on a loom (Fig. 13). From the weaving beam (1), the warp threads (2) go around the rock (3), pass the lamellas (4), the eyes of the healds (5) and the teeth of the reed (6). When the heald frames with heddles (5) are alternately raised and lowered, the warp threads form a shed into which the weft thread (7) is inserted. The reed (6), thanks to the rocking movement of the batt mechanism (8), when moving to the right, nails the weft thread to the edge of the fabric (9) and moves to the left position. The resulting fabric, bending around the chest (10) and the felt (11), is moved by the product regulator and wound onto the product roller (12). The warp, unwinding from the weaving beam, is thus always in a tense state.
We have already talked about materials for sewing products, and today we will look at the technology of fabric production, how fabrics differ from other sewing materials.
Fabric production. Process.
The fabric is produced by weaving two systems of threads: warp and weft. The warp, consisting of many threads, is stretched along the loom (it is also called a grain thread) and moves slowly, unwinding from a large reel - the warp. At the center of the loom is a shed-forming mechanism (we see the heddle in the video) that separates the warp threads to form a diamond-shaped space called the shed. Weft threads (transverse) are inserted into the shed using a shuttle, intertwined with the warp threads and compacted using a comb-shaped reed, which makes a back-and-forth motion.
Weaving looms can be shuttle or shuttleless, having instead of shuttles moving tubes - “rapiers”, through which the weft thread is thrown with the help of compressed air. There are carriage looms that produce complex (jacquard) weave fabric. Modern machines are created with program control. But, despite all the complexity of the equipment, it is based on the same old loom, the same principle of interlacing threads: warp and weft.
But in order to obtain fabric, threads are needed, which means that weaving is preceded by the process of producing yarn - one of the initial stages of the weaving process. We already talked about this in the lessons on linen and cotton fabrics. The yarn is spun into threads (thread is stronger than yarn) and then woven into fabric. After preparation, the fiber passes through carding machines, where additional quality sorting (long, medium and short fiber) and alignment are performed. In this case, the fiber is transformed into a tape that is not strong enough, which is pulled into a thick, loose thread - roving (video “Cotton Fabrics”), wound onto spools. This thread is then passed through roving machines, where it is compacted, twisted, and becomes thinner and stronger. But this is not yarn yet.
The spinning shop receives roving, the raw material for yarn production. On spinning machines, the roving, unwinding from the bobbins, is stretched and twisted, coming out as a thin thread, which is wound on bobbins attached to spindles. In this way, cotton, wool, linen and staple yarn are produced.
Before actual weaving, another preparatory weaving operation is carried out - the creation of warp and weft packages (longitudinal and transverse threads of the future fabric). Yarn is rewinded from spinning cobs to larger bobbins, convenient for weaving, as well as for lengthening the thread. The bobbin holds 8-9 times more yarn than the cob. (Removal of products on a weaving loom is rare, sometimes not every day - such a long whole fabric is produced on the loom).
At the same time, the winder checks each thread for strength, eliminates flaws and defects (bumps, loops, thick and thin places), for which, during rewinding, the thread is pulled between two washers, pressed against each other by a spring and through a thin hole that eliminates thickenings. The main thread is impregnated with a special solution for strength. The prepared yarn is sent to the weaving shop.
Fabric finishing.
Depending on the fiber composition of the fabric, the finishing varies. This general description applies to fabrics made from natural fibers: cotton, linen, wool, staple fabric. Although the finishing may be different in these groups of fabrics, we are considering a general algorithm.
The finished fabric is called harsh, it is hard and ugly, therefore it is moved to finishing shops, where the process of bleaching, dyeing, drawing, finishing, mercerization takes place - depending on the specified quality of the fabric, on the type and properties of sewing materials, on the purpose of the fabric. Technical fabrics remain harsh.
Finishing – giving the fabric improved properties: treatment with special solutions, thanks to which the fabric becomes wear-resistant, low- or non-shrink, water- and oil-dirt-repellent, wrinkle-resistant, easily smoothed, uniform in width, elastic, etc. Finishing appeared in the textile industry with the development of chemistry. After finishing, a starching effect appears on the fabric; it becomes stiffer and holds its shape better.
The mercerization process, on the contrary, makes fabrics silky and soft.
Finishing is carried out on different machines, but, in general, the process can be represented as follows: the fabric is tucked into the machine, spreading mechanisms are installed - they are stretched along the weft thread (widthwise), as a result of which you can see small punctures along the edge. The fabric is moved from one roller to the other, passing the fabric through a reservoir of solution.
Fabrics can be bleached and plain dyed. But there may be a pattern woven using multi-colored threads - a stripe, a checkered pattern, for example, and this fabric is called multicolored.
The pattern can be created by weaving the threads (roses in the photo), but we will talk about weaving in the next lesson.
And there are fabrics on which a design is printed using paint - printed fabrics. In this case, the fabric passes through a system of reservoirs with various dyes and between rollers with different design elements: flowers - red, for example, color, leaves - green, etc.
Previously, the design was cut out by hand on boards. How many elements of different colors - so many stencils. The boards were painted in the appropriate color, turned over onto fabric and beaten on them so that the design was imprinted - hence the name “printed” - the design was stamped.
Fabric quality.
The quality of fabric is its reliability, durability, beautiful appearance, meeting fashion trends. Fabric produced by textile enterprises must meet the technical requirements established by the standards. In the USSR there were GOSTs - state standards as a guarantee of quality. Nowadays, technical specifications are more specified - compliance with technical conditions that can be changed.
The quality of the fabric is checked at all stages of production: from the receipt of raw materials to the finished products of spinning, weaving, textile and haberdashery, knitting industries. Taking into account the nature and number of defects, the grade of products is determined. Requirements for fabric quality: cleanliness, integrity, quality of pattern, colors. Materials may have weaving defects: holes, dressings, twists, slacks; and finishing defects: unpainted, blurred drawing, creases, etc. Fabric defects must be taken into account when cutting.
During the finishing process, the fabric is in a wet state, under high tension. It is dried in a stretched form. This is not a natural state for it, therefore, as soon as the fabric gets into a damp environment (rain, washing, etc.), it shrinks and returns to its original state. The degree of shrinkage depends on the quality and nature of the fiber: the softer the fiber, the looser its structure, the higher the degree of shrinkage (cotton and wool, for example). Also depends on the finish of the fabric. If the fabric is impregnated with a special solution, for example in tarpaulin fabrics with water-repellent impregnation, then there will be no shrinkage in the fabric.
Plainly dyed fabric, as with a printed design, can “fade” - the paint, when wet, can run off and stain nearby fabrics. Fabric with a printed pattern can also dye itself, thus smearing the pattern across the field of the canvas. Plain-dyed fabrics shed less often than printed fabrics, but it is better to check before use: wet a piece of fabric or a corner, put a white fabric on top and iron it with a hot iron. Multi-colored fabrics, as experience shows, practically do not fade.
All these nuances must be taken into account when sewing a product.
I told you about the fabric production process, and in the video lesson I showed weaving on a loom. I will say that in my lessons I do not intend to give scientific knowledge on materials science using special terms and listing with thorough accuracy all types of equipment. Chemicals used, etc. There are specialized sites for this. I also don’t consider it necessary to reprint technical textbooks, as some of my colleagues do. Our task is to have a general understanding of the production of fabric and how this process can affect the sewing and operation of the product.
In the following lessons we will talk to you about the types of weaving, how to learn to identify the grain thread and cross thread, determine the front and back sides.
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With love, Olga Zlobina.
