Where is the thread thickness measured? Thickness characteristics of fibers, threads and sewing threads. Work methodology

The thickness of fibers, threads and sewing threads is usually estimated by indirect characteristics: linear density, trade number (symbolic designation) and diameter.

Linear density (thickness, T), tex is characterized by the ratio of the mass of fibers or filaments m, 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 is the length of the threads, km;

1000 - coefficient for converting meters to kilometers;

L is the length of the threads, m.

For flax fiber, which is complex, linear density is sometimes determined from cleavage. Linear density by cleavage characterizes the fiber's ability to further cleave. To determine it, it is necessary to count one fiber in a 10 mm long clipping with a tendril more than 5 mm for 2 fibers, a fiber with two antennae more than 5 mm for 3 fibers, etc.

The unit for measuring linear density in g / km is called tex from the word "textile". According to GOST 10878-70 “Textile materials. Linear density in tex units and the main series of nominal linear densities ”provides for the use of multiples and sub-multiples of linear density units. Thus, the linear density of fibers, which is usually less than 1 tex, is recommended to be expressed in militex - mtex (mg / km), and the thickness of intermediate products of spinning production (canvas, ribbon, roving, etc.), thick threads and twisted products (thread, cord , rope-rope and others), which usually amounts to more than 1000 tex, - in kilotexes - ktex (kg / km). In this case, 1000 mtex \u003d 1 tex \u003d 0.001 ctex.

For brevity, the term “thickness in tex” may be used instead of the term “linear density”. However, you cannot replace the name of the characteristic “linear density” with the name of its unit of measurement “tex”. Therefore, you cannot write “fiber tex T \u003d 0.2”, but write “linear density (or thickness) of the fiber T \u003d 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 thread).

Until January 1, 1971, the transverse dimensions of the fibers and threads were estimated through a 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, d:

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

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

or

Fiber number iV, m / g, mm / mg, km / kg characterizes its fineness. The numerical values \u200b\u200bof the number of fibers do not change when using the same multiples or sub-multiples of length and mass units indicated in formula (1.7).

The value of the thickness (fineness) of the fibers. The thinner the fibers, the thinner and more uniform in strength the yarn produced from them. In this case, the value of fineness, i.e., small thickness of the fibers, is more noticeable for thinner yarns.

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

Conditional and estimated diameters. When comparing the thickness of fibers or threads, it should be borne in mind 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 densities of fibers in the cross-section of yarn or filaments in a complex cross-section. If you need 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 by formula (1.11) derived from equality (1.10) under the assumption that S \u003d 7rd yc 2/4, i.e., that the fiber or filament is not hollow and has a cylindrical shape:

where t is the thickness index determined by the formula

y is the density of the substance, mg / mm 3 (for the values \u200b\u200bof y, see Table 1.4).

Table 1.4

Density of different textile materials

Fiber type	Density, mg / mm 3
Asbestos
Cotton
Silk
Woolen
Triacetate
Ceramic
Glass
Viscose
Copper-ammonia
Acetate
Polyester (lavsan)
Polyacrylonitrile
Polyamide (nylon)
Polyamide (anid)
Polyethylene
Polypropylene
Chlorinic

For round filaments and filaments without a channel, d yc is close to the actual dimensions of the diameter. The size of the cross section for hollow fibers and threads is more consistent with the calculated diameter (d p). When calculating its value, it is necessary to know the average density, that is, the mass per unit volume of fibers or filaments, 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 (for values \u200b\u200bof 8, see Table 1.5).

Table 1.5

Average density of various textile materials

Material	Average density, mg / mm 3
Yarn
Cotton
Viscose
Woolen
Silk
Complex thread
Glass
Raw silk
Viscose
Acetate
Nylon
Jersey
Combed
Felt
Technical
Insulating
Fabrics
Combed

The calculated and nominal thread diameters are used to determine some characteristics of the structure and filling of fabrics and knitted fabrics.

To determine the estimated diameter of the sewing thread, the following formula is also used:

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

Coefficient values A for some types of thread (yarn) used in the garment industry

Table 1.6

Linear density of threads. Distinguish between nominal T 0, actual T f, conditional T to, calculated T p and the resulting T R linear thread densities.

Nominal called the linear density of a single-strand yarn or thread planned for production in production (GOST 10878-70, GOST 11970. (0-4) GOST 21750-76). Nominal linear density is calculated when threading spinning machines based on the linear density of roving and drawing.

The nominal linear density of a single-strand yarn is denoted 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 thickness 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 the cabled yarn is indicated, and in the last two examples, the double-twisted). The linear density of complex chemical threads is denoted by two numbers. The first number indicates the linear density of the filament, and the second in parentheses - the number of filaments in it (for example, T () (120)).

The actual is called the linear density of a single yarn or filament yarn, determined by an experimental laboratory way 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; adjustment and wear of the working bodies of spinning and twisting machines; carelessness of service personnel and other reasons. Therefore, the standards for threads and threads set the tolerances for deviations of the actual linear density from the nominal, the excess of which is unacceptable.

Tolerances in standards are set within certain limits of the numerical value of linear density, according to uneven linear density (%) and according to the deviation of the actual linear density from the nominal (%). 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 unevenness in the actual linear density is determined according to the formulas of mathematical statistics and compared with the standard;

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

Conditioned linear density calculated by the formula

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

Tf is the actual linear density of the threads, tex;

W K - normalized (conditioned) moisture content of the threads,%; TUF is the actual moisture content of the threads,%.

The normalized (conditioned) humidity for mixed and heterogeneous threads is determined by the formula

where a. is the fractional content of the i-th component of the mixture, La. \u003d 1.0; W. is the conditioned humidity of the i-th component, %. Conditioned linear density of threads is used in calculations if, when accepting 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 - conditional weight of threads, g;

T k - conditional linear density of the thread, tex. Calculated Linear Density counted for woven threads, in which the individual components are not subjected to joint twisting:

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

A number of articles of fabrics and knitted fabrics are produced from spun yarns, the linear density of which is necessary to calculate and assess 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 garment industry.

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

The resulting linear density of a twisted multiple twist yarn (s) of the same thickness (in particular sewing threads) is calculated by the formula

In formulas (1.21) and (1.22), the following notation is adopted:

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

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

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

To calculate the linear density of the threads, it is necessary to determine their length and weight. According to GOST 6611.1-73 “Textile threads. Method for determining linear density "a certain number of skeins of yarn is unwound from the samples of packages - heap lengths of 5, 10, 25, 50, 100 or 200 m and pieces of yarn 0.5 or 1 m long. To unwind the yarns into skeins of the required length, a device called reel. The coils obtained on reels are usually used to establish the strength of the threads, and then their weight 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 the formula (1.6) (GOST 6611.1-73).

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

Sewing thread diameter. This characteristic of thread thickness is always taken into account in the sewing industry when sewing clothes. The width of the eyelet of the sewing needle should be 1.45-1.65 times the diameter of the thread, and the thread itself must sink into the groove of the eyelet of the needle, otherwise, increased penetration of fabrics, knitted and non-woven fabrics may be observed when making clothes from them. The thread diameter can be determined by calculation and experiment. Roughly the estimated diameter of the threads d p (mm), is determined by the 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 a TsNIHBI device.

• GOST 11970.0-2003. Textile materials. Threads. Range of nominal linear densities of a single cotton yarn. GOST11970.1-70. Textile threads. A range of nominal linear densities for single pure wool and semi-wool yarns. GOST 11970.2-76 Textile yarns. A range of nominal linear densities of a single bast yarn. GOST 11970.3-70. Textile threads. A range of nominal linear densities of man-made filaments, monofilaments and single yarns from man-made and silk fibers. GOST11970.4-70. System tex. Nominal thicknesses of glass filaments and glass fiber single yarns.
• GOST 21750-76. Chemical fiber and tow. A number of nominal linear densities.

Purpose and objectives of the work:

Purpose of the work - To study various methods for determining the linear density of threads and sewing threads.

The task of the work - To get acquainted with the device and the principle of operation of the equipment used.

Theoretical substantiation of the work:

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

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 thread) and is defined as the ratio of the weight of the threads, g, to their length, km

T \u003d m / I g / km (1)

Linear density of threads. Distinguish between nominal 1 o, actual Tf, conditioned G, with the calculated Gy and the resulting Tk linear density of the threads.

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

The actual is called the linear density of a single yarn or filament yarn, determined experimentally.

The calculated linear density is calculated for spun threads, in which its individual components are not subjected to joint twisting.

The resulting linear density is called the linear density of the twisted yarn or threads from threads of the same or different thickness, calculated taking into account their twisting. For a single twist twisted yarn consisting of yarns (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 weight. According to GOST 6611.0-93, a certain number of skeins of threads is unwound from samples of packages - a roll of length 5, 10, 25, 50, 100 or 200 m.To unwind the threads into skeins of the required length, a device called a chain saw is used. The skeins obtained on reels are usually used to establish 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 the formula (1)

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

Krona 4 consists of six blades, one of which has two spokes on hinges, closed by couplings.

When the couplings are shifted to the crown blade, the upper parts of the spokes can bend in the hinges, thus reducing the reel perimeter, which facilitates the removal of skeins of threads. With a straight spokes of this blade, the perimeter of the reel is 1 m.

A block 5 is planted on the bushing 6, connected by a belt drive with an electric motor unit. The threads from the packages put on the pins 9 are threaded into the eyes of the thread guides 1, into the thread guides 2 and are secured by springs on one of the blades of the reel crown. The yarn guides, fixed on the rods of the yarns 2, during the operation of the reel, make a slow reciprocating movement in a plane perpendicular to the passage of the threads. The back-and-forth movement and the folding device receives from the spring located at one end of its rod in the sleeve, and the roller fixed to the other bent end (not shown in the figure).

The counting mechanism 3 consists of a cogwheel, on which there is a reading scale, where 100 divisions are applied. For one revolution of the crown 4, the scale moves one division relative to the stationary arrow. Since the perimeter of the reel 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.

On the crown, you can wind five heaps at the same time. The crown rotation frequency is 200 rpm. For the automatic stop of 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 based on the balance of a three-arm lever. The mass of the material is indicated on a graduated scale and is determined by the value of the angle of deflection of the lever with the arrow from the initial equilibrium position.

The general view of the weight textile quadrant is shown in Fig. 25. A three-arm lever is attached to the axle 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 counterbalance weight is attached to the third arm 4. On a scale of 12, use the arrow // to determine the weight of the thread. The stand 6 is mounted on a support 9 with set screws 7, 8 and level 10. Before determining the weight of the threads, the quadrant is level. In this case, the arrow 11 should be at the zero mark of the scale.

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

Work methodology

Determine the actual linear density of the single strand cotton yarn using the reel and the textile weights 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 a cotton sewing thread.

Objective:Study of methods for determining linear density, indicators of twisting and twisting of threads and sewing threads.

Devices and materials:thickness gauge , sewing thread samples, ruler, textile magnifier, electronic scales, twist gauge, preparation needles.

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

2. To 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 linear density, twist direction, number of folds, calculated and actual diameters of threads and sewing threads.

Basic information

Types of textile threads.In modern textile production, a wide range of yarns of various structures is used: classic types of yarn, complex, combined yarns and monofilaments, film yarns and yarn-like knitted, woven, braided 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 yarnis the presence of protruding fiber tips on its surface. When untwisted, the yarn eventually breaks down into individual fibers of limited length. Combed, carded, rotor and hardware yarns differ in the degree of surface hairiness: as a rule, combed yarns have a smoother and less hairy surface, while hardware and high-volume yarns have the greatest fluffiness and bulk.

Unlike yarn surface complex threads,consisting of filaments, smooth, even, and there are no protruding ends on it, unless the filaments are damaged. Surface voluminous and fluffy textured yarns,the elementary threads of which have a stable crimp, are covered with separate loop-sucrutins. Their number and sizes depend on the texturing method. Shaped yarnshave in their structure periodically repeating local changes. The local structure effects found in fancy yarns are very numerous and varied (loops, knots, thickenings, curls, roving sections, lumps of fibers, etc.).

When untwisted, the twisted threads are separated into constituent 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 located along helical lines and therefore their turns are noticeable on the surface. The density and inclination of the turns relative to the longitudinal axis increase as the degree of twist increases from the minimum values \u200b\u200bin the shallow twist yarns to the maximum in the crepe twist yarns. Crepes have significant rigidity, elasticity and twist unbalance. This makes them wriggle and twist in a free state, forming curls.

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

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

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

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

Linear density T, tex, an indirect unit for measuring the thickness of fibers or filaments, 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 the thread mass t,g, to its length L, m

T \u003d 1000 m / L(2.1)

Measurement units of linear density, except for tex according to GOST 10878-70, are militex (mtex) 1 mtex \u003d 10 -3 tex; decitex (dtex) 1 dtex \u003d 10 -1 tex; kilotex (ktex) \u003d 10 3 tex.

The linear density of twisted and spun threads is called the resulting linear density T. R.

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

Conditioned linear density T to Is the actual linear density of a single or twisted (spun) yarn, reduced to normalized moisture content. These indicators are calculated by the formula

, (2.2)

where Wн - normalized moisture content of threads,%;

Wf -actual moisture content of the threads,%.

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

Nominal (T o)called the linear density of a single thread, planned for production in production; it is usually indicated in the technical characteristics of the thread and material (GOST 10878-71, GOST 11970.0-5-70, GOST 21750-76).

Calculated Linear Density (T p) is calculated for spliced \u200b\u200bthreads, 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 nIs the nominal linear density of the individual stitched threads.

Actual Linear Density textile thread ( T f) determined experimentally and calculated by the formula (2.4)

T f \u003d 1000 × S m / L × n,(2.4)

where S m - total mass of elementary samples, g;

L - length of a thread in an elementary sample, m;

p - the number of elementary samples.

To characterize the thickness of sewing threads, use the symbol - trade number N, which is indicated on the labels of each product unit. The higher the trade number, the thinner the sewing thread.

The trade number shows the number of meters of yarn with a weight of 1 g

N \u003d l / m , (2.5)

where l - thread length, m;

m - thread weight, g.

The thickness of the twisted threads (yarn) is designated 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 \u003d 1000 / N(2.6)

An important indicator when choosing sewing threads for sewing products is the thread diameter. 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 twisting 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) - from right to top to left.

Figure 2.1 - Arrangement of turns in the yarn:

a - right twist; b - left twist

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

The twisted yarn structure is characterized by number of additions - the number of threads that make it up.

Twist of threads characterized by number of torsions К, 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 the device of the twist meter. 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 twists): and double torsion(GOST 6611.3-73). In the first method direct unwinding the thread on the twist gauge is untwisted until the constituent threads are completely parallel. The number of twists is recorded on the counter. The readings are converted to 1 m of thread length - this is the actual twist.

Figure 2.2 shows universal steepness meter KU-500... The device consists of a body 12, a tensioner and an eyepiece, fixed on the guide 22 by brackets 4 and 18, respectively. The body 12 is a box inside which an electric motor is mounted, a clutch with a set of gear wheels for rotating the right clamp 10 and a mechanism for changing the direction of rotation of the counting device 11. The tensioning device consists of a bracket 4 with an extension scale 5 fixed on it and an oscillating system with an arrow 6, a left clamp 7, a load scale 2 with a weight 3 and a counterweight 20. To fix the arrow 6 in the zero position, a lock 21 is provided. The eyepiece consists of magnifiers 8 and screen 9 with black and white background.

Figure 2.2 - Universal steepness meter

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

After determining the test parameters (distance between clamps, pretensioning values), set the required distance between clamps 7 and 10. Then, by moving the weight 3 along the load scale 2, create a corresponding pretensioning force. If the required tension force must be more than 50 cN, an additional replaceable weight is installed on the weight 3, and a counterweight 19 is screwed into the right end of the load scale. The clutch switch 13 is placed in the Z or S position corresponding to the twist direction of the test thread. The package with the test 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 swinging clamp 7, and then in the right clamp 10 so that the arrow 6 points to the zero division of the elongation scale 5. When determining the number twisting method by direct untwisting, the arrow 6 is fixed in the zero position by the latch 21. The toggle switch 15 is set to the Z or S position similar to the switch 13. The rotation speed of the right clamp 10 is controlled by variable resistance using the handle 16. While rotating, the right clamp unwinds the thread. The parallelism of the constituent threads is checked with a preparation needle, passing it between the threads from the left clamp to the right. If the constituent threads are close to parallelization, unwinding is completed by rotating the handle 14. Then, the readings of the counter 11 are recorded and the number of twists per meter is calculated.

When determining the number of twists of the thread double twisting method arrow stop 6 is set so that the arrow can 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 opposite direction to the twist direction, will first untwist the thread and then twist. When untwisted, the thread is lengthened and the arrow 6 is deflected to the left to the limiter, and when twisted, the thread is shortened and the arrow moves to the zero mark of the scale. When the pointer 6 returns to the zero position, the motor is turned off. The counter reading is twice the number of twists for a given clamping length. The calculation of the number of twists per 1 m is carried out according to the formula (2.8), taking into account that the number of twists recorded by the counter should be divided in half before being substituted into the formula.

The number of twists is calculated by the formula

, (2.8)

where n - number of tests;

L 0 - clamping length, m;

Ki -number of torsions in individual tests.

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

(2.9)

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

The amount of twist,%, determined by the formula

(2.10)

where L 1 -untwisted thread length, mm;

L o -twisted thread length, mm.

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

Work methodology

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 from textile materials, and consists in unwinding and examining the samples under a magnifying glass and under a microscope at low magnification. Samples of filaments taken from materials have additional crimp, therefore, before examining under a magnifying glass or microscope, it is advisable to fix them (glue the ends) in a straightened state on a paper backing or place them between two glass slides. The prepared sample is placed on a microscope stage and viewed in reflected light.

When studying the samples, the main distinctive features of the structure of the thread are revealed: the appearance of its surface, the number of folds, the type and shape of the constituent fibers and threads, the nature of their arrangement in the structure, the direction of twisting, etc. To determine the direction of twist, the thread is slightly untwisted by hand over 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 heaps.

The type of elementary samples (frame or segment), their length and quality are established for each type of thread in the corresponding regulatory and technical documentation GOST 6611.0-73. When performing the work, 10 m of threads are unwound (5 samples). After that, determine the mass of the yarn thread and calculate the linear density by the formula (2.1) and the trade number by the formula (2.5). Electronic scales are used to weigh the lengths of threads.

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

Scales (Figure 2.3) are intended for weighing small weighed amounts of fibers, threads, materials with a mass of no more than 150g. accurate to 0.005g. Accuracy class (GOST 241044) - 4. Type of measurements - strain gauge. The device is equipped with automatic zero setting and gain control. Laboratory balance with liquid crystal display (1), number of indicator digits -6. Working platform with a diameter of 125mm (2) made of stainless steel.

To work on electronic scales you need:

Align the device to the level (3), which is to the left of the electronic board;

Place the transparent plastic cover on the surface of the device;

Connect the power supply unit of the scale to the electrical network;

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

Wait until the end of the automatic testing of the device (until the electronic display shows "0.000");

Open the cap lid;

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

Close the hood lid and wait until the specific weight of the material has been reached.

The balance should not be located near heating devices, as well as not be exposed to air currents.

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

Determination of the diameter of the threads and sewing threads.By calculation, its diameter is determined by the 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 coils in one layer. To maintain a constant tension, one end of the thread is glued to a glass slide, and a load is suspended from the other. Turning the slide evenly, a thread is wound around it.

To measure the thickness of materials, as a rule, thickness gages of the TP (manual thickness gauge) and TH (desktop thickness gauge) are used (Figure 2.4), which may differ in the measurement range, the arc of the body, and the presence or absence of a mechanism for normalized measurement of forces. 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 transferred to the sample.

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

Check the zero setting before working on the device. If, when the measuring surfaces touch, 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 (while loosening the screw clamp on the housing)

Figure 2.4 - General view of the tabletop thickness gauge

1 - lever, 2 - indicator, 3 - small scale, 4 - upper table, 5 - lower table, 6 - bezel, 7 - measuring rod.

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

The spot sample is placed between the lower fixed and upper movable tables. The movement of the upper stage 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. Thread the threads between the teeth of the combs and the discs of the device. After lowering the upper disc onto the threads, the arrow on the thickness gauge scale shows the value of the thread diameter. The most accurate result is obtained after the simultaneous threading of six or more threads. In this case, the threads are less flattened under the pressure of the discs. Conduct 10 such tests, then derive the average value, compare the actual and calculated values \u200b\u200bof the thread diameter, draw conclusions.

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

The number of folds is determined by securing both ends of the sewing threads, and untwisted 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 balance of the twisted yarns.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 unwinding of the thread and the formation of loops - sucrutin. Such a thread is called non-equilibrium. The imbalance is especially important for sewing threads and twisted yarns. Non-equilibrium thread twists get stuck in the needle holes of sewing machines and thread guides and cause threads to break. In addition, if the thread is unbalanced in twist, then during sewing, the loop formed can deviate from its normal position so much that it will be outside the range of the shuttle nose, as a result of this, the shuttle can pass without catching the loop. The imbalance of threads is most often determined as follows. The thread 1 m long is folded in half (Figure 2.5). A 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 balance of the 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 threads

Control questions:

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

Laboratory work No. 3

Analysis of weaving weaves

Objective:Get acquainted with the methods of analysis of weaving weaves. Acquire the skills of sketching weaving weaves.

Devices and materials:tissue samples, textile magnifying glass, preparation needle, colored paper.

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

2. Analyze the weaves of different types of fabric.

3. Make a model of weaving

Basic information

the cloth Is a textile fabric formed as a result of the interweaving of 2 or more mutually perpendicular yarn systems. The threads along the canvases are called basic; the threads lying across the canvases are weft. The different sequence of alternation of the main and weft overlaps creates a huge number of weaving weaves, which are one of the main structural characteristics of fabrics. Weavedetermines the order of mutual arrangement and connection of warp and weft threads.

The meeting point of the warp and weft is called overlap... Distinguish: the main overlap, when on the right side of the fabric, the warp thread is located on top of the weft thread, and weft overlap, when the weft thread is above the warp thread. Shift (z)shows how many threads have shifted in the weave vertically overlapping one thread relative to the overlap of another.

Finished weave pattern , called rapport.It defines the smallest number of warp threads (R 0) and weft threads (R y) forming it. The section in which the thread passes from the front side to the wrong side and vice versa is called communication field.The area where the weft and warp threads, in contact, intersect, is called contact field... Areas where the threads do not touch - free field... The through pores formed between the threads are called lumen fields... Communication, contact and free fields can be basic and weft.

The weave pattern is presented in the form of a graph (Figure 3.1). In the graph, each horizontal row corresponds to the weft thread, each vertical column corresponds to the warp 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 wefts are left unhatched.

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

The rapport can be expressed as a fraction, the numerator of which shows the number of basic overlaps, and the denominator the number of weft overlaps in the rapport.

Weave fabrics are divided into 4 classes (Figure 3.2):

1. Simple (main) weaves

2. Small-patterned weaves

3. Complex weaves

4. Large-patterned (jacquard) weaves.

Figure 3.2 - Classification of weaving weaves

Plain weaves fabrics have the following features: warp rapport is always equal to weft rapport; each warp thread is interwoven with each weft thread only once. Plain, twill and satin (satin) weaves are considered simple weaves.

Plain weave has the smallest rapport: Rо \u003d Rу \u003d 2. Plain weave fabrics are bilateral, with a uniform smooth surface on the front and back sides (Figure 3.3). Since the threads form only the fields of connection and contact, the structure of the plain weave fabric has the greatest cohesion and, other things being equal, greater strength and rigidity. This weave is the thinnest, lightest and least dense fabrics.

Twill weave has a rapport R ≥ 3, S \u003d 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.

Twill are distinguished: weft 1/2,1/3, 1/4, on the front side of which weft overlaps prevail, and the main 1 / 2,1 / 3, 1/4, on the front side of which the main floors prevail. A characteristic feature of twill weave fabrics is the presence on the surface of noticeably 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 ribs depends on the ratio of the thickness of the warp and weft threads and the density of their location. The fabrics of this weave are distinguished by greater softness, elasticity, extensibility, drape. The main twill weave is used to produce semi-silk fabrics. Weft twill weave produces semi-woolen fabrics, cotton warp and woolen weft.

Satin (satin) the weave is characterized by a rapport R≥5 and a shift z ≥ 2. The front side of the satin weave is formed by long main overlaps, and the satin weave - weft. The fabrics formed by these weaves have a smooth, even surface with increased sheen. Silk fabrics (atlases) are most often produced with satin weave (Figure 3.5), satin - cotton sateen (Figure 3.6).

Figure 3.6 - Scheme and graph of satin weave

Small-patterned weaves are divided into two subclasses: derived main weaves and combined.

Derivatives weaves are formed by a modification of the main ones. These include derivatives of plain weave, such as matting, reps (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 graph of the rep weave

Figure 3.8 - Scheme and graph of weaving reinforced twill

Figure 3.9 - Scheme and graph of interlacing complex twill

Derived weaves are obtained by reinforcing single main or weft overlaps. Matting weave 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 graph of weaving reverse twill

Matting weave 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 - Scheme and graph of weaving matting

TO combined weaves include crepe (Figure 3.12), embossed, etc. They are formed by combining different weaves.

Complexweaves include double, multi-layer, pile. At least three systems of threads are involved in their formation.

Figure 3.12 - Scheme and graph of crepe weave

IN double the weaves of 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-layer. D vuhface (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 cut of a two-layer weave fabric with different ways of connecting the fabrics

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

Figure 3.14 - Scheme of the incision of the weft nap weave

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

Figure 3.15 - Diagram of the incision of the fabric of the warp weave

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

Work methodology

Determining the type of weave... When 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. The warp threads always run along the edge. If there is no hem in the swatch, pull the fabric in both directions - usually the fabric pulls more along the weft. If several threads of both directions are removed from the sample with a preparation needle, the weft threads will be bent more than the warp threads (the exception is rep-type fabrics with a thin base and thick weft). The warp threads are usually more twisted than the weft threads; they are smoother and harder, the weft threads are looser and softer. More often, the warp threads have the Z twist direction, the weft ones - S. If twisted threads are located in one direction of the fabric, and single threads in the other, then the warp threads will be twisted. The main threads are located more evenly, parallel to each other, sometimes two or three threads from the teeth of the reed remain in the fabric. The density of the fabric along the weft is less uniform: there may be threads located in an arched shape or superimposed one on top of the other, there are often distortions of the fabric along the weft.

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 warp and weft threads in the compared sides should be located in the same direction. In some tissues, the difference between the front and seamy sides is more pronounced, in others it is hardly distinguishable. The weave pattern is more prominent on the front surface. The front-side finish is more elaborate, with less visible fiber tips. In pile fabrics, the split pile is always located on the front side. In brushed fabrics, the pile on the front side is thicker, better rolled up, shorter cut than on the wrong side. In printed fabrics, the pattern is on the front side.