The thickness of the thread in what is measured. Characteristics of the thickness of fibers, threads and sewing threads. Work methodology

It is customary to evaluate the thickness of fibers, threads and sewing threads by indirect characteristics: linear density, trade number (symbol) and diameter.

Linear density (thickness, T), tex is characterized by the ratio of the mass of fibers or threads t, g to their length L v km:

where T is the linear density of threads, tex (g/km);

t- weight of threads, g;

L 1 - thread length, km;

1000 - coefficient for converting meters to kilometers;

L - thread length, m.

For flax fiber, which is complex, it is sometimes determined linear density by splitting. Linear density by splitting characterizes the ability of fibers to further splitting. To determine it, it is necessary to count one fiber in a cut 10 mm long with a antennae greater than 5 mm as 2 fibers, a fiber with two antennae greater than 5 mm as 3 fibers, etc.

The unit of measurement of linear density in g/km is named tex from the word "textile". According to GOST 10878-70 “Textile materials. Linear density in units of tex and the main series of nominal linear densities” provides for the use of multiple and submultiple units of linear density. Thus, the linear density of the fibers, which is usually less than 1 tex, is recommended to be expressed in millitex - mtex (mg / km), and the thickness of the semi-products of spinning production (canvas, tape, roving and others), thick threads and twisted products (thread, lace , rope-rope and others), which usually amounts to more than 1000 tex, - in kilo-tex - ktex (kg / km). In this case, 1000 mtex \u003d 1 tex \u003d 0.001 ktex.

For brevity, instead of the term “linear density”, it is allowed to use the term “thickness in tex”. However, you cannot replace the name of the characteristic “linear density” with the name of its unit of measurement “tex”. Therefore, one cannot write “tex of the fiber T = 0.2”, but one should write “linear density (or thickness) of the fiber T = 0.2 tex”.

The linear density of the threads is directly proportional to their cross-sectional area (i.e., the greater the numerical value of the linear density, the thicker the threads).

Until January 1, 1971, the transverse dimensions of the fibers and threads were evaluated through the metric number. The metric number was an indirect characteristic of the fineness of fibers and threads, inversely proportional to their cross-sectional area, and was determined as the ratio of the length of the fibers and threads L, m to their mass t, G:

where N- metric number, mm/mg, m/g, km/kg.

Between linear density T and metric number N there is the following dependency:

or

Fiber number iV, m/g, mm/mg, km/kg characterizes its fineness. The numerical values ​​of the number of fibers do not change when using the same multiple or submultiple units of length and mass indicated in formula (1.7).

The value of the thickness (thinness) of the fibers. The finer the fibers, the finer and more uniform in strength the yarn produced from them. At the same time, the value of fineness, i.e., the small thickness of the fibers, is more noticeable for thinner yarn.

The possibility of obtaining the thinnest yarn is determined by the minimum possible number of fibers in its cross section. For each spinning method, this number is constant, so the highest spinnable number of yarn, equal to the ratio of the number of fibers to their number in cross section, is proportional to the number of fibers processed.

Conditional and calculated diameters. When comparing the thickness of fibers or threads, it should be taken into account that, with the same thickness index, they have the same cross-sectional area filled with a substance, but the dimensions of their apparent diameter may be different due to the presence of channels or different packing density of fibers in the yarn cross section or elementary filaments in the complex cross section. If it is necessary to know the transverse dimensions of the threads and fibers, they are measured using a microscope or the conditional (d yc) and calculated (d p) diameters are calculated.

The nominal diameter is calculated according to the formula (1.11), derived from equality (1.10) under the assumption that S= 7rd yc 2/4, i.e., that the fiber or filament is not hollow and has a cylindrical shape:

where m is the thickness index, determined by the formula

y is the density of the substance, mg / mm 3 (for the y values, see Table 1.4).

Table 1.4

Density of different textile materials

Type of fiber	Density, mg / mm 3
asbestos
Cotton
Silk
Woolen
Triacetate
ceramic
Glass
Viscose
Copper-ammonia
Acetate
Polyester (lavsan)
Polyacrylonitrile
Polyamide (kapron)
Polyamide (anid)
Polyethylene
Polypropylene
Chlorine

For rounded elementary fibers and filaments without a channel, d yc is close to the actual dimensions of the diameter. The diameter dimension for hollow fibers and filaments is more in line with the calculated diameter (d p). When calculating its value, it is necessary to know the average density, i.e., the mass of a unit volume of fibers or threads, measured along the outer contour, 8, mg / mm 3. So, for a hollow fiber with a length L, mm, and a mass t, mg

where 8 is the average density of fibers and threads, mg / mm 3 (see the values ​​\u200b\u200bof 8 in Table 1.5).

Table 1.5

Average density of different textile materials

Material	Average density, mg / mm 3
Yarn
Cotton
Viscose
Woolen
silk
complex thread
glass
Raw silk
Viscose
Acetate
Nylon
Knitwear
Combed
Felt
Technical
insulating
fabrics
Combed

The values ​​of the calculated and conditional diameters of the threads are used to determine some characteristics of the structure and filling of fabrics and knitted fabrics.

The following formula is also used to determine the estimated diameter of sewing threads:

where BUT- coefficient depending on the density of the substance, (values BUT see table. 1.6).

Coefficient values BUT for some types of thread (yarn) used in the clothing industry

Table 1.6

Linear thread density. There are nominal T 0, actual T f, standard T to, calculated T p and resulting T R linear densities of threads.

Rated call the linear density of single-filament yarn or thread planned for production in production (GOST 10878-70, GOST 11970. (0-4) GOST 21750-76). The nominal linear density is calculated when threading spinning machines based on the linear density of the roving and draft.

The nominal linear density of single-thread yarn is indicated by an integer, the nominal linear density of twisted threads from single threads of the same thickness - adjacent numbers separated by multiplication signs (for example, T 0 x 2; T 0 x 5 x 3, etc. The first number is this is the nominal linear density of single twisted threads, the second is the number of folds in the first twist, the third is the number of folds in the second twist, etc.). The nominal linear density of twisted threads from single threads of different thicknesses is indicated by their sum (for example, + T 2 + T 3 +

T p, or T g x 2 + T 2, or (T: + T 2) + (T 3 + T 4), etc.

In the first example, the nominal linear density of a single-twisted thread is indicated, and in the last two examples - a double-twisted thread). The linear density of complex chemical threads is denoted by two numbers. The first number indicates the linear density of the complex thread, and the second in brackets - the number of elementary threads in it (for example, T () (120)).

Actual they call the linear density of a single-filament yarn or a complex yarn, determined experimentally and calculated by the formula (1.6).

The actual linear density often does not coincide with the nominal due to the uneven structure of the fibers or filaments; inconsistency in time of the technological process in production; changes in atmospheric conditions; disorder and wear of the working bodies of spinning and twisting machines; inattention of service personnel and other reasons. Therefore, in the standards for threads and threads, tolerances for deviations of the actual linear density from the nominal are established, the excess of which is unacceptable.

Tolerances in the standards are set within certain limits of the numerical value of the linear density, according to the unevenness of the linear density (%) and according to the deviation of the actual linear density from the nominal one (%). In the first case, the limits of deviations of the actual linear density from the nominal are indicated in the standards for each linear density separately; in the second, the non-uniformity in terms of the actual linear density is determined according to the formulas of mathematical statistics and compared with the standard standard;

in the third, the deviation of AT (%), the actual linear density Tf from the nominal T 0 is determined by the formula

Conditional linear density calculated by the formula

where T to - conditional linear density of threads, tex;

Tf - actual linear density of threads, tex;

W K - normalized (conditional) moisture content of threads, %; TUf - the actual moisture content of the threads,%.

Normalized (conditional) humidity for mixed and heterogeneous threads is determined by the formula

where a. - fractional content of the i-th component of the mixture, La. = 1.0; W. - standard humidity of the i-th component, %. The standard linear density of the threads is used in the calculations, if, when accepting the threads, the standard provides for the determination of their length on the packages. The calculation is carried out according to the formula

where L is the length of the thread on the package, km;

t to- standard weight of threads, g;

T to - conditional linear density of the thread, tex. Estimated linear density calculated for warped threads in which the individual components are not subjected to co-twisting:

where Tf T 2 ,..., T p- nominal linear density of individual striated threads, tex.

A number of articles of fabrics and knitted fabrics are produced from warped yarns, the linear density of which is necessary to calculate and evaluate the structure and some physical and mechanical properties of these materials, as well as to correctly substantiate the technological modes of processing these materials in the clothing industry.

The resultant is the linear density of twisted yarn or threads of the same or different thickness threads, calculated taking into account their wrapping. For a single-twist twisted yarn, consisting of yarn(s) of the same thickness, the resulting linear density is determined by the formula

The resulting linear density of a multi-twisted twisted thread, consisting of yarn(s) of the same thickness (in particular, sewing threads), is calculated by the formula

Formulas (1.21) and (1.22) use the following notation:

T 0 - nominal linear density of a single thread, tex;

p p p 2 ,..., P.- the number of additions of the thread, respectively, at the first, second, j- m twisting;

y v 2 ,..., y.- twisting of the thread, respectively, from the first, second, j-something twisting, % (see wrapping definition below).

To calculate the linear density of the threads, it is necessary to determine their length and mass. According to GOST 6611.1-73 “Textile threads. Method for determining the linear density ”from the samples of the packages, a certain number of skeins of threads are unwound - skeins 5, 10, 25, 50, 100 or 200 m long and pieces of threads 0.5 or 1 m long. To unwind the threads into coils of the desired length, a device called reel. The skeins obtained on reels are usually used to determine the strength of the threads, and then their mass is determined on a technical or analytical balance or on a weight textile quadrant, and the actual linear density of the threads is calculated using formula (1.6) (GOST 6611.1-73).

Trade number of sewing threads. This concept is used to characterize the fineness of sewing threads in the trade. The trade number has a conventional numerical designation. The larger it is, the thinner the sewing threads. The trade number is not determined, it is indicated on the labels pasted on the thread package.

Sewing thread diameter. This characteristic of the thickness of the threads is always taken into account in the clothing industry when tailoring. The width of the eye of the sewing needle should be 1.45-1.65 of the thread diameter, and the thread itself should sink into the groove of the eye of the needle, otherwise there may be an increased penetration of fabrics, knitted and non-woven fabrics when making clothes from them. The thread diameter can be determined by calculation and experiment. Approximately calculated thread diameter d p (mm) is determined by formulas (1.14) or (1.15).

Experimentally, the diameter of sewing threads is determined by measuring them under a microscope, micrometer (thickness gauge) or on the TsNIHBI device.

• GOST 11970.0-2003. Textile materials. threads. A range of nominal linear densities of a single cotton yarn. GOST 11970.1-70. Textile threads. A range of nominal linear densities of single pure wool and wool blend yarns. GOST 11970.2-76. Textile threads. A series of nominal linear densities of a single bast yarn. GOST 11970.3-70. Textile threads. A range of nominal linear densities of complex man-made yarns, monofilaments and single yarns from man-made and silk fibers. GOST 11970.4-70. tex system. Nominal thicknesses of multifilament glass filaments and single strands of glass fiber.
• GOST 21750-76. Fiber and tow chemical. A number of nominal linear densities.

Purpose and tasks of the work:

The purpose of the work is to study various methods determination of the linear density of threads and sewing threads.

The task of the work is to get acquainted with the device and the principle of operation of the equipment used.

Theoretical justification of the work:

It is customary to evaluate the thickness of threads and sewing threads by indirect and characteristics: linear density, trade number (symbol) and diameter.

The linear density of the threads is directly proportional to their cross-sectional area (i.e., the larger the numerical value of the linear density, the thicker the threads) and is defined as the ratio of the mass of the threads, g, to their length, km

T = m/I g/km (1)

Linear thread density. There are nominal 1 o, actual Tf, standard G, with calculated Gr and the resulting Tk are the linear densities of the threads.

The nominal density is the linear density of a single-thread yarn or thread planned for production in production.

The actual one is the linear density of a single-filament yarn or a complex yarn, determined experimentally and laboratory.

Estimated linear density is calculated for warped threads, in which its individual components are not subjected to co-twisting.

The resultant is the linear density of twisted yarn or threads of the same or different thickness threads, calculated taking into account their wrapping. For twisted single-twisted yarn, consisting of yarn(s) of the same thickness.

Description of the laboratory setup:

To calculate the linear density of the threads, it is necessary to determine their length and mass. According to GOST 6611.0--93, a certain number of skeins of threads are unwound from the samples of packages - skeins 5, 10, 25, 50, 100 or 200 m long. To unwind the threads into skeins of the desired length, a device called a chainsaw is used. The skeins obtained on reels are usually used to determine the strength of the threads, and then their mass is determined on a technical or analytical balance or on a weight textile quadrant and, using formula (1), the actual linear density of the threads is calculated

One of the most common devices for winding threads into coils of the required length is the MPA-1M automated reel, manufactured by the Ivmashpribor plant. The device consists of a crown 4 (Fig. 24), an electric motor 7 with a drive to a counting mechanism 3, thread spreaders 2 and thread guides /. Thread spreaders and thread guides are mounted on metal racks 8, fixed on the table 10 of the reel; pins 9 are also installed on the racks (on the left) for putting packages with threads on them.

Crown 4 consists of six blades, one of which has two hinged spokes closed by couplings.

When the couplings are shifted to the crown blade, the upper parts of the spokes can be bent at the hinges, while reducing the perimeter of the reel, which makes it easier to remove the coils of threads. At direct location spokes of this blade reel perimeter is 1 m.

On the sleeve 6, a block 5 is mounted, connected by a belt drive to the electric motor block. The threads from the packages put on the pins 9 are threaded into the eyes of the thread guides 1, into the thread spreaders 2 and are fixed with springs on one of the blades of the reel crown. The thread guides mounted on the rods of the thread spreaders 2, during the operation of the reel, perform a slow reciprocating motion in a plane perpendicular to the passage of the threads. The spreader receives reciprocating motion from a spring located at one end of its rod in the sleeve, and a roller attached to the other, bent end (not shown in the figure).

The counting mechanism 3 consists of a gear wheel, on which there is a reference scale, where 100 divisions are applied. For one revolution of the crown 4, the scale moves relative to the fixed arrow by one division. Since the perimeter of the winding crown is 1 m, the number of divisions shown on the scale by the arrow corresponds to the number of meters of threads wound on the crown.

Five skeins can be wound on the crown at the same time. Crown rotation frequency - 200 rpm. To automatically stop the reel after winding threads of a given length (25, 50 and 100 m) on its crown, there is a special mechanism.

Weighing textile quadrants are dial scales that work on the principle of equilibrium of a three-arm lever. The mass of the material is indicated on a graduated scale and is determined by the angle of deviation of the lever with the index arrow from the initial equilibrium position.

A general view of the weight textile quadrant is shown in fig. 25. A three-arm lever is attached to the axis 3 of the rack 6. A hook 2 is suspended on the first arm / lever, an arrow 11 (mass indicator) is fixed on the second arm 13, and a balancing weight is fixed on the third arm 4. On a scale of 12, using the arrow //, the mass of the thread is determined. Rack 6 is mounted on a stand 9 with set screws 7, 8 and level 10. Before determining the mass of threads, the quadrant is set according to the level. In this case, arrow 11 should be at the zero mark of the scale.

To determine the mass of a skein of threads (skein) is hung on hook 2 and, putting a finger on the edge of the scale, open the fork lock 15, which serves to hold the lever in its original position when hanging a skein of threads on the hook.

Work methodology

Determine the actual linear density of a single-ply cotton yarn using the reel and textile weight quadrant.

From the combined test results, calculate the average linear density of the threads and the unevenness along it.

Determine the diameters of the tested threads by calculation.

Using one of the known experimental ways, determine the diameter of cotton sewing threads.

Objective: The study of methods for determining the linear density, indicators of twisting and twisting of threads and sewing threads.

Devices and materials: thickness gauge , samples of sewing threads, a ruler, a textile magnifier, electronic scales, a twist gauge, dissecting needles.

Tasks: 1. To study the classification of textile threads used in the production of clothing materials.

2. Study the characteristics of the structure of threads and sewing threads.

3. Determine the indicators of the structural characteristics of 3 types of threads.

4. Prepare samples and conduct tests to determine the linear density, twist direction, number of additions, calculated and actual diameter of threads and sewing threads.

Basic information

Types of textile threads. In modern textile production, a wide range of threads of various structure is used: classic types of yarn, complex, combined threads and monofilaments, film threads and thread-like knitted, woven, woven textile products (chains, cords, ribbons, braids, etc.). Knowing their structural features, it is relatively easy to predict the properties of materials made from these threads and products.

Distinctive feature yarn is the presence on its surface of the protruding tips of the fibers. When untwisted, the yarn eventually disintegrates into individual fibers of limited length. Combed, carded, pneumo-mechanical and apparatus yarns differ in the degree of surface hairiness: as a rule, combed yarn has a smoother and less hairy surface, and apparatus and high-volume yarn has the greatest fluffiness and volume.

Unlike yarn surface complex threads, consisting of filaments, smooth, even and free from protruding ends, unless the filaments are damaged. Surface voluminous and fluffy textured threads, the elementary filaments of which have a stable crimp, are covered with separate twisting loops. Their number and size depend on the texturing method. Fancy threads have in their structure periodically repeating local changes. The local effects of the structure found in shaped threads are very numerous and varied (loops, knots, thickenings, twists, sections of the roving, lumps of fibers, etc.).

Twisted threads, when untwisted, are separated into component threads: yarn - into single yarns, complex threads - into single threads, combined - into threads of various types. The constituent threads in the structure of twisted threads are arranged along helical lines and therefore their turns are visible on the surface. The density of the arrangement and the inclination of the turns relative to the longitudinal axis increase as the degree of twist increases from the minimum values ​​in the threads of a gentle twist to the maximum in the threads of a crepe twist. Crepes have significant rigidity, elasticity and unbalance in twist. This causes them to squirm and twist in a free state, forming twists.

Structural characteristics of textile threads. The structure of a single-filament yarn is characterized by the thickness, length, shape of the fibers, as well as their number and uniformity of distribution in individual sections, the relative position and twist intensity. The main structural characteristics of twisted yarn are the thickness, magnitude and direction of twist of a single thread; number of additions, i.e. the number of threads forming the twisted yarn, the intensity and direction of twist in the twisted yarn.

Thus, the structural characteristics of textile threads and sewing threads are the thickness (linear density of the threads), the number of folds, the direction and magnitude of the twist, and the twist.

The use of the linear dimensions of the diameter to characterize the thickness of the threads is inconvenient for a number of reasons: its measurement is difficult irregular shape the cross section of the threads, the presence of voids and air gaps between the fibers in the yarn, the dependence of the thickness on the degree of twist and the density of the fibers in the cross section of the threads, the possibility of flattening the threads when used to determine the thickness of devices.

In this regard, the thickness of threads and sewing threads is evaluated by indirect units of measurement: linear density, trade (conditional) number.

Line density T, tex, an indirect unit for measuring the thickness of fibers or threads, is directly proportional to their cross-sectional area, i.e. the larger the numerical value of the tex, the thicker the thread. Defined as the ratio of thread mass t, g, to its length L m

T=1000m/L(2.1)

Linear density units, except for tex according to GOST 10878-70, are millitex (mtex) 1 mtex = 10 -3 tex; decitex (dtex) 1 dtex = 10 -1 tex; kilotex (ktex) = 10 3 tex.

The linear density of twisted and twisted threads is called resulting linear densityT R.

Linear density is distinguished by nominal, actual, calculated and standard.

Conditional linear densityT to- this is the actual linear density of a single or twisted (gusseted) thread, reduced to a normalized moisture content. These indicators are calculated by the formula

, (2.2)

where Wн– normalized moisture content of threads, %;

Wph - actual moisture content of threads, %.

In terms of linear density, only the thickness of threads of the same fibrous composition and structure can be compared.

Rated (That) call the linear density of a single thread, planned to be produced in production; it is usually indicated in technical specification thread and material (GOST 10878-71, GOST 11970.0-5-70, GOST 21750-76).

Estimated linear density (T p) is calculated for warped threads in which its individual components are not subjected to joint twisting

T p \u003d T 1 + T 2 + ... + T n, (2.3)

where T 1 ,T 2,T n is the nominal linear density of the individual stranded threads.

Actual line density textile thread ( T f) determined by experimental laboratory and calculated by the formula (2.4)

T f \u003d 1000 × S m / L × p,(2.4)

where S m is the total mass of elementary samples, g;

L is the length of the thread in the elementary sample, m;

P is the number of elementary samples.

To characterize the thickness of sewing threads, a symbol is used - trade number N, which is indicated on the labels of each unit of production. The higher the numeric value of the trade number, the finer the sewing threads.

The trade number indicates the number of meters of yarn having a weight of 1 g.

N=l/m , (2.5)

where l– thread length, m;

m is the weight of the thread, g.

The thickness of the twisted threads (yarn) is indicated by a fraction, the numerator of which is equal to the number of threads that make up the twisted yarn, and the denominator is the number of threads included in it. The relationship between the linear density of sewing threads and their trade number is expressed by the expression:

T= 1000/N(2.6)

An important indicator when choosing sewing threads for sewing products is the diameter of the threads. It is determined by calculation and experiment.

Estimated thread diameter, mm, determined by the formula

, (2.7)

where d is the average density of the thread, mg / mm 3, the values ​​\u200b\u200bof which are given below.

Experimentally, the diameter of the threads is measured using projection devices or microscopes.

The direction of twist characterizes the location of the turns of the peripheral layer of the thread: at right twist(Z) the constituent threads are directed from left to top to right, with left twist(S) - right up to left.

Figure 2.1 - The location of the turns in the yarn:

a - right twist; b - left twist

For silk threads, on the contrary, the right twist is denoted by S, and the left by Z. The direction of twist of the sewing threads affects the looping process and the loss of strength of the threads during sewing.

The structure of twisted threads is characterized the number of additions- the number of its constituent threads.

Thread twist characterized number of twists K, which indicates the number of turns around the axis of the thread, calculated per unit length of the thread (1 m) before unwinding, and is determined on a twist gauge. The actual number of twists characterizes the degree of twisting of threads of the same linear density. In standard tests, two methods are used to determine the actual number of twists (actual twist): and double twist(GOST 6611.3-73). With the first method direct unwinding the thread on the twist gauge is untwisted until the component threads are completely parallel. The number of twists is marked on the counter. The readings are recalculated for 1 m of the length of the thread - this is the actual twist.

Figure 2.2 shows universal krutkomer KU-500. The device consists of a housing 12, a tensioner and an eyepiece, fixed on the guide 22 by brackets 4 and 18, respectively. 11. The tensioning device consists of a bracket 4 with an elongation scale 5 fixed on it and a rocking system with an arrow 6, a left clamp 7, a load scale 2 with a weight 3 and a counterweight 20. A latch 21 is provided to fix the arrow 6 in the zero position. The eyepiece consists of magnifier 8 and screen 9 with black and white background.

Figure 2.2 - Universal twist gauge

Before threading the thread into the clamps of the twistmeter, the method for determining the number of twists, the direction of twist of the thread and the test parameters are set: the number of point samples, clamping distance, preload.

After determining the test parameters (distance between the clamps, pre-tension values), the required distance between the clamps 7 and 10 is set. Then, by moving the weight 3 along the load scale 2, an appropriate pre-tension force is created. If the required tension force should be more than 50 cN, an additional replaceable weight is installed on weight 3, and a counterweight 19 is screwed into the right end of the load scale. The clutch switch 13 is set to position Z or S, corresponding to the direction of twist of the tested thread. The package with the tested thread is put on the rod 17, the end of the thread is pulled through the eyes of the thread guides 1 and 23 and fixed first in the left rocking clamp 7, and then in the right clamp 10 so that the arrow pointer 6 points to the zero division of the elongation scale 5. When determining the number torsion by the method of direct unwinding, the arrow 6 is fixed in the zero position with the latch 21. The toggle switch 15 is placed in the Z or S position similarly to the switch 13. The speed of the right clamp 10 is controlled by variable resistance using the handle 16. Rotating, the right clamp unwinds the thread. The parallelism of the constituent threads is checked with a dissecting needle, passing it between the threads from the left to the right clamp. If the components of the thread are close to parallelization, the unwinding is completed by rotating the handle 14. Then the readings of the counter 11 are recorded and the number of twists per 1m is calculated.

When determining the number of thread twists double twist method pointer limiter 6 is set in such a way that the pointer could deviate to the left of the zero mark of the scale by no more than two divisions. Turn on the device. The right clamp, rotating in the direction opposite to the direction of twist, will first unwind the thread and then twist. When unwinding, the thread lengthens and arrow 6 deviates to the left to the limiter, and when twisting, the thread shortens and the arrow moves to the zero mark of the scale. When the arrow pointer 6 returns to the zero position, the electric motor is switched off. The counter reading is equal to twice the number of twists in a given clamping length. The calculation of the number of twists per 1 m is carried out according to the formula (2.8), given that the number of twists recorded by the counter should be divided in half before substitution into the formula.

The number of twists is calculated by the formula

, (2.8)

where n– number of tests;

L0– clamping length, m;

Ki- number of twists in individual tests.

twist coefficient, characterizing the intensity of twisting threads of different linear density, calculated by the formula

(2.9)

Since the constituent threads are arranged in spiral turns during twisting, their length is shortened, or wrapping.

The amount of twist,%, determined by the formula

(2.10)

where L1- length of untwisted thread, mm;

L o - twisted thread length, mm.

In addition to the characteristics discussed above, the structure of the yarn is evaluated hairiness or fluffiness - the presence of fiber tips on the surface. Most often, the following characteristics are used to assess hairiness: the number of fibers per unit length (usually 1 m) and the average length of the fibers in millimeters.

Methodology for performing work

Analysis of the structure of textile threads. The study of the structure of various textile threads is carried out on samples obtained from packages or taken out of textile materials, and consists in unwinding and examining samples under a magnifying glass and under a microscope at low magnification. Samples of threads taken out of materials have additional crimp, therefore, before examination under a magnifying glass or microscope, it is advisable to fix them (glue the ends) in a straightened state on a paper substrate or place them between two glass slides. The prepared sample is placed on the microscope stage and examined in reflected light.

When examining samples, the main distinctive features the structure of the thread: the appearance of its surface, the number of additions, the type and shape of the constituent fibers and threads, the nature of their location in the structure, the direction of twist, etc. To determine the direction of twist, the thread is slightly untwisted by hand in a small area. If the top end of the thread is untwisted clockwise, the thread has a right twist (Z), if counterclockwise it has a left twist (S).

Determination of the linear density of threads. The linear density of textile threads is determined according to GOST 6611.1-73 “Textile threads. Thickness determination method”. The test is carried out by weighing elementary samples in the form of a skein.

The type of elementary samples (skein or cut), their length and quality are established for each type of thread in the relevant regulatory and technical documentation GOST 6611.0-73. When performing work, 10 m of threads are unwound (5 samples). After that, the mass of the threads is determined and the linear density is calculated according to the formula (2.1) and the trade number according to the formula (2.5). Electronic scales are used to weigh thread segments.

The device and principle of operation of electronic laboratory scalesCAS MW-150T.

Scales (Figure 2.3) are designed for weighing small portions of fibers, threads, materials weighing no more than 150g. with an accuracy of 0.005 g. Accuracy class (GOST 241044) - 4. Measurement type - tensometric. The device is equipped automatic installation zero and gain adjustment. Laboratory scales with a liquid crystal display (1), the number of digits of the indicator -6. Working platform with a diameter of 125mm (2) made of stainless steel.

To work on electronic scales, you must:

Set the device according to the level (3), which is located to the left of the electronic display;

Install a plastic transparent cap on the surface of the device;

Turn on the power supply of the scales in electrical network;

Switch on the device using the ON/OFF button (4).

Wait for the end of automatic testing of the device (until “0.000” is set on the electronic display);

Open the cap cover;

Place the material to be weighed on the center of the weighing pan with tweezers;

Close the lid of the hood and wait for the specific weight of the material to be established.

The balance must not be placed near heating devices, nor be exposed to air currents.

Figure 2.3 - General view of electronic laboratory scales CAS MW-150T

Determining the diameter of threads and sewing threads. By calculation, its diameter is determined by formula (2.7). Experimentally, the diameter of sewing threads is determined by measuring them under a microscope or thickness gauge. To determine the diameter of the threads under a microscope, they are usually wound on a glass slide in spiral turns in one layer. To maintain a constant tension, one end of the thread is glued to a glass slide, and a weight is suspended from the other. Rotate the slide evenly and wind the thread around it.

To measure the thickness of materials, as a rule, thickness gauges of the TR type (hand-held thickness gauge) and TN (desktop thickness gauge) (Figure 2.4) are used, which may differ in the measurement range, the arch extension of the body, as well as the presence or absence of a normalized force measurement mechanism. The principle of operation of the thickness gauge is reduced to measuring the vertical distance between the supporting platform, on which the material sample is located, and the measuring platform parallel to it, through which pressure is transmitted to the sample.

The device and principle of operation of the thickness gauge. The standard requirements (GOST 12023–93) are met by a thickness gauge TN 40-160 of indicator type with a normalized measuring force. The division price is 0.1 mm. Measurement range 0-40mm.

Before working with the device, check the zero setting. If, when the measuring surfaces come into contact, the pointer of the reading device does not align with the zero stroke of the scale, then turn the rim to align the zero stroke with the arrow (at the same time, loosen the screw clamp on the body).

Figure 2.4 - General view of the desktop thickness gauge

1 - lever, 2 - indicator, 3 - small scale, 4 - top table, 5 - bottom table, 6 - rim, 7 - measuring rod.

It is also necessary to check the consistency of the readings. To do this, raise the measuring rod by 2-4 mm and lower it two or three times. If, with closed measuring surfaces, the pointer takes any other position, then by turning the rim, combine the zero stroke of the scale with it.

An incremental sample is placed between the lower fixed and upper movable tables. The movement of the upper table is transmitted to the indicator, which has two scales.

To measure the diameter of sewing threads to the thickness gauge, you need a special comb device. The threads are threaded between the teeth of the combs and the disks of the device. After lowering the upper disk onto the threads, the arrow on the thickness gauge scale shows the value of the diameter of the threads. The most accurate result is obtained after threading six or more threads at the same time. At the same time, the threads are less flattened under the pressure of the discs. Carry out 10 such tests, then derive the average value, compare the obtained actual and calculated values ​​of the diameter of the threads, and draw conclusions.

Determining the direction of twist, the number of additions. To determine the direction of twist, a short piece of thread is clamped with fingers and, holding it vertically, is slightly untwisted. If the upper end of the thread is untwisted in a clockwise direction, located in a horizontal plane, it has a Z twist (silk - S twist); when unwinding the upper end counterclockwise, the thread has an S twist (silk - Z twist).

The number of additions is determined by fixing both ends of the sewing thread, and unwind it until the strands are completely parallel, which is checked with a needle. After that, one of the strands is also untwisted and the needle is divided into threads, the number of which is recorded. The total number of additions is equal to the sum of the threads included in the strands.

Determination of the equilibrium of twisted threads. When the thread is twisted, due to reversible elastic and elastic deformation, a torque occurs, usually directed in the direction opposite to twisting. This leads to the unwinding of the thread and the formation of loops - sukrutin. Such a thread is called non-equilibrium. Disequilibrium is especially important for sewing thread and twisted yarn. The twists of unbalanced threads get stuck in the holes of the needles of sewing machines and thread guides and cause the threads to break. In addition, if the thread is unbalanced in twist, then when sewing, the resulting loop may deviate so much from its normal position that it will be outside the range of the hook nose, as a result of which the hook may pass without catching the loop. The disequilibrium of threads is most often defined as follows. A thread 1 m long is folded in half (Figure 2.5). The thread is considered to be in equilibrium if no more than six turns are formed on its hanging part.

Figure 2.5 - Determination of the equilibrium of threads during twisting

a - balanced thread, b - unbalanced thread

The results of tests and calculations are entered in table 2.1.

Table 2.1 - Linear density and indicators of the structure of the threads

Test questions:

1. Define the concepts of linear density: actual, resulting, nominal, standard, normalized, calculated?
2. How to determine the actual linear density of the threads, and why is this necessary?
3. How to determine the actual diameter of sewing threads, and why is this necessary?
4. Method for determining twist, twist, balance and the number of additions of threads?
5. What is twist, twist coefficient, twist?
6. What sewing thread is called non-equilibrium? Influence of disequilibrium of sewing threads on production processes.
7. How to determine the direction of twisting of sewing threads, and why is this necessary?
8. List the types of textile threads.

Lab #3

Analysis of weaving

Objective: Familiarize yourself with the methods of analysis of weaving weaves. Acquire the skills of sketching weaving weaves.

Devices and materials: tissue samples, textile magnifier, dissecting needle, colored paper.

Tasks: 1. To study the classification of weaving weaves, the principles of their mathematical designation and methods of weaving analysis.

2. Conduct an analysis of weaves various kinds fabrics.

3. Make a layout of weaving

Basic information

Textile- this is a textile fabric formed as a result of the mutual interweaving of 2 or more mutually perpendicular systems of threads. The threads located along the canvases are called the main ones; threads lying across the canvases - weft. A huge number of weaving weaves, which are one of the main structural characteristics of fabrics, are created by a different sequence of alternating main and weft overlaps. weave determines the order of the relative position and connection of the warp and weft threads.

The place where the warp and weft threads meet is called overlap. There are: main overlap, when the warp thread is located on top of the weft thread on the front side of the fabric, and weft overlap, when the weft thread is above the warp thread. Offset (z) shows how many threads have shifted in the weave along the vertical overlap of one thread relative to the overlap of another.

Finished weave pattern , called rapport. It determines the smallest number of warp threads (R 0) and weft threads (R y) that form it. The area where the thread passes from the right side to the wrong side and vice versa is called communication field. The area where the weft and warp threads intersect when touching is called contact field. Areas where the threads do not touch - free field. Through pores formed between the threads are called lumen fields. Link, contact and free fields can be basic and weft.

The weave pattern is presented in the form of a graph (Figure 3.1). On the graph, each horizontal row corresponds to a weft thread, each vertical column corresponds to the main thread; warp and weft threads are conventionally assumed to be of the same thickness, there are no gaps between them. The main overlaps on the graph are shaded, the weft ones are left unshaded.

Figure 3.1 - Scheme (a) and graph (b) of weaving

Rapport can be expressed as a fraction, the numerator of which indicates the number of main overlaps, and the denominator is the number of weft overlaps in the rapport.

Weaves of fabrics are divided into 4 classes (Figure 3.2):

1. Simple (main) weaves

2. Finely patterned weaves

3. Complex weaves

4. Large-patterned (jacquard) weaves.

Figure 3.2 - Classification of weaving

Plain weaves fabrics have the following features: warp rapport is always equal to weft rapport; each warp thread is intertwined with each weft thread only once. Simple weaves include plain, twill, and satin (satin) weaves.

plain weave has the smallest rapport: Ro=Ru=2. Plain weave fabrics are double-sided, with a uniform smooth surface on the front and back sides (Figure 3.3). Since the threads form only fields of connection and contact, the structure of the plain weave fabric has the greatest unity and, other things being equal, greater strength and rigidity. This weave is the thinnest, lightest and least dense fabric.

Twill weave has rapport R ≥ 3, S=1. It is denoted by a fraction: its numerator shows the number of main overlaps within the rapport, and the denominator shows the number of weft overlaps.

Twills are distinguished: weft 1/2,1/3, 1/4, on the front side of which weft overlaps predominate, and main 1/2,1/3, 1/4, on the front side of which the main overlaps predominate. characteristic feature fabrics of twill weaves is the presence on the surface of markedly pronounced diagonal stripes formed by longer overlaps (Figure 3.4).

Figure 3.3 - Scheme and graph of plain weave

Figure 3.4 - Scheme and graph of twill weave

Most often the direction of the diagonal is positive - to the right, less often negative - to the left. The angle of inclination of the diagonal scars depends on the ratio of the thickness of the warp and weft threads and the density of their arrangement. Fabrics of this weave are distinguished by greater softness, elasticity, extensibility, drape. The main twill weave produces semi-silk fabrics. Weft twill weave produces wool blend fabrics, cotton warps and wool wefts.

Satin (satin) the weave is characterized by a repeat R≥5 and a shift z ≥ 2. The front side of the satin weave is formed by long main overlaps, and the satin weave is formed by the weft. The fabrics formed by these weaves have a smooth, even surface with increased luster. Satin weave (Figure 3.5) most often produces silk fabrics (satins), satin - cotton satin (Figure 3.6).

Figure 3.6 - Scheme and graph of satin weave

Finely patterned weaves are divided into two subclasses: derivatives of the main weaves and combined.

Derivatives weaves are formed by modifying the main ones. These include derivatives of plain weave, such as gunny, rep (Figure 3.7), twill - for example, reinforced twill (Figure 3.8), complex twill (Figure 3.9), reverse twill (Figure 3.10), as well as derivatives of satin (satin) - reinforced satin, reinforced satin.

Figure 3.7 - Scheme and schedule of rep weave

Figure 3.8 - Scheme and schedule of weaving reinforced twill

Figure 3.9 - Scheme and schedule of weaving a complex twill

Derivative weaves are obtained by reinforcing single warp or weft laps. Weave matting fabrics are obtained by increasing the main and weft overlaps at the same time. In the fabrics of this weave, a checkerboard pattern is more noticeable (Figure 3.11) .

Figure 3.10 - Scheme and schedule of weaving reverse twill

Weave matting fabrics are obtained by increasing the main and weft overlaps at the same time. In the fabrics of this weave, a chess pattern is more noticeable. .

Figure 3.11 - Scheme and schedule of weaving matting

To combined weaves include crepe (Figure 3.12), embossed, etc. They are formed by a combination of different weaves.

Complex weaves include double, multilayer, pile. At least three systems of threads are involved in their formation.

Figure 3.12 - Scheme and schedule of crepe weave

AT double weaves, the front and back sides are most often formed from threads of different quality or color and may have different weaves. Since the threads of the upper and lower weaves are located one above the other, double-weave fabrics have a significant thickness.

Double weaves can be double-faced and double-layered. D double-faced(one and a half layer) are formed from one warp and two wefts or two warps and one weft.

Figure 3.13 - Scheme of a section of a two-layer weave fabric with different ways canvas connections

Double layer weaves are formed by two systems of warp threads and two weft threads. The connection of the canvases is carried out over the entire area of ​​\u200b\u200bthe fabric with the help of the lower warp, with the help of the top warp or with the help of a special pressing base (Figure 3.13).

Figure 3.14 - Scheme of the section of the weft-pile weave fabric

Pile weaves can be weft-pile (Figure 3.14) and warp-pile (Figure 3.15). The surface of pile weave fabrics is covered with trimmed or terry pile. In fabrics of openwork weave, the warp threads lie in zigzags, passing from one row to another and making up a transparent pattern resembling a hemstitch.

Figure 3.15 - Scheme of the section of the warp weave fabric

Large-patterned (jacquard) weaves have a large rapport (more than 24). Such weaves are produced on special jacquard machines.

Methodology for performing work

Determining the type of weave. Starting to analyze the weave, first determine the direction of the warp and weft, the front and back sides of the fabric, after which they begin to sketch the weave.

Definition of warp and weft threads. The warp threads are always located along the edge. If there is no hem in the sample, the fabric should be pulled in both directions - usually the weft pulls the fabric more. If several threads in both directions are removed from the analyzed sample with a dissecting needle, then the weft threads will be bent more than the warp threads (with the exception of rep-type fabrics, which have a thin warp and a thick weft). The warp threads are usually more twisted than the weft threads; they are smoother and stiffer, the weft threads are looser and softer. More often, the main threads have a twist direction Z, weft - S. If the fabrics are located in one direction twisted threads, and in the other single, then the warp threads will be twisted. The main threads are arranged more evenly, parallel to each other, sometimes cuts of two or three threads from the teeth of the reed are preserved in the fabric. The weft density of the fabric is less uniform: there may be threads arranged in an arcuate manner or superimposed one on top of the other, fabric distortions along the weft are not uncommon.

Determination of the front and back sides of the fabric. To recognize the front and back sides, the fabric should be laid so that both sides can be compared at the same time. In this case, the main and weft threads in the compared sides should be located in the same direction. In some fabrics, the difference between the front and back sides is more pronounced, in others it is barely distinguishable. The weave pattern protrudes more prominently on the front surface. The finishing of the front side is more thorough, the tips of the fibers are less visible on it. In pile fabrics, the cut pile is always located on the front side. In fabrics with a fleece, the pile on the front side is thicker, better rolled up, cut shorter than on the wrong side. In printed fabrics, the design is on the front side.