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Makhkamova Shoira Fahritdinovna, senior teacher,
Tashkent Institute of Textile and Light Industry E-mail: [email protected]
RESEARCH OF THE WORK OF THE IMPROVED STRUCTURAL DESIGN OF THE DRAFTING SYSTEM ON THE RING SPINNING MACHINE
Abstract: The article presents the research results of setting parameters influence of draft system (rear exhaust draft and the load on the roller) to quadratic unevenness of yarn over the cross section, breaking tenacity and quadratic unevenness on breaking force.
Keywords: ring spinning machine, drawing, drafting system, improved drafting system, yarn quality, factorial design.
Introduction. Today, Uzbekistan is carrying out large-scale work aimed at developing an important strategic industry - the textile industry. For ensuriy the release of high-
quality competitive products, technical re-equipment and modernization of textile enterprises, introduction of new innovative technological processes and means of production automation are carried out. A powerful impulse that opened up new opportunities for improving the industry was the Decree of the President of the Republic of Uzbekistan Shavkat Mirziyoyev "On the Program of Measures for the Further Development of the Textile and Clothing and Knitting Industries for 2017-2019" [1].
Technical progress in the field of spinning production has led to the creation of new spinning methods and new types of spindleless spinning machines that are being intensively introduced into the textile industry. However, the features of the yarn of the pneumomechanical spinning method in the near future do not yet completely replace the yarn of the ring spinning method. At the present time, foreign machine-building firms, paying much attention to new ways of forming yarn, continue to perfect ring spinning machines. These improvements are aimed to increase the productivity of equipment, the level of automation and computerization of machine maintenance operations, to improve the working units of the machine both by improving their design, and making them from more durable materials, as well as improving the accuracy of manufacturing.
Drafting system is one of the critical nodes of ring spinning machines. Most firms recommend a simple three-cylinder two-strap drafting system with a degree of draft up to 60. From the quality of the details of the drafting system and the parameters of its adjustment depends the quality of the produced yarn, the stability of the technological process of spinning, the productivity and use of raw materials. Solving issues related to ensuring the normal flow of the technological process of drawing is a complex task. In recent years, domestic and foreign scientists have done a lot ofwork aimed at solving this problem [2], but a number of issues remain unresolved.
Unsatisfactory work of the drafting system of spinning machines leads to the formation of internal irregularity of the yarn. Therefore, studies aimed at improving the drafting system and optimizing the parameters of its adjustment are certainly actual.
Theoretical part. Drawing is one of the most important processes in spinning technology. Drawing is carried out in drafting system, the construction of which implements the basic provisions of the theory of drawing.
One of the reasons that increases the irregularity of the yarn when drawing the product in the drafting system is the unsatisfactory straightening of the fibers, leading to a decrease in the proportion of controlled fibers during the stretching process, increasing their irregular shifts, creating fiber grouping that reduces the strength and irregularity in the strength of the yarn. Straightening of the fibers occurs mainly during the drawing process between the draft pairs. The efficiency of the straightening of the fibers also depends on the magnitude of the stresses of the forces of friction. Consequently, increasing the load on the rollers and improving the quality of their coating will lead to an increase in the straightness of the fibers and a decrease in the irregularity of the outgoing product.
To create the necessary frictional forces in the drawing field and ensure a reliable clamping of the fibers, the surface of the cylinders is made grooved. The rollers of the drafting system, pressed to the grooved cylinders, rotate under the action of frictional forces. The stratification of the drawn product and the appearance of irregularities are observed due to the lag of the roller from the cylinder and the uneven rotation of the roller. The elastic coating of the rollers when worn with the flutes wears out, and with a small width of the flutes, even a partial damage of the fibers occurs.
To eliminate these drawbacks, it was suggested to improve the drafting system by replacing the grooved part ofthe draft cylinders with bushings with an elastic coating [3]. In this case, the contact strip of the draft pair is doubled, which ensures a reliable clamping ofthe fibers, the frictional field force remains constant
along the length of the top roller, thereby stretching the process with high stability. The use of bushings with an elastic coating allows the processing of a twisted roving with increased load on the rollers and at high speed without damaging the fibers.
The purpose of this work is to choose the optimum settings for an improved drafting system that ensure a high quality of the yarn.
Figure 1. General view of the improved drafting system of the ring spinning machine
Experimental part. The research was carried out in the production environment ofJV LLC "Uztex Shovot". The influence of the tuning parameters of the improved drafting system, mounted on the ring spinning machine G35 by Rieter, on the physical and mechanical properties of a 20-tex yarn of linear density were studied.
For the production of semi-finished products and yarn, a factory sorting consisting of cotton fiber oftype 4 (Mehnat selection) of grade I, Oliy class - 55%, Yakhshi class - 45% was used.
On six spindles of the spinning machine G35, the corrugated part of the draft cylinder was replaced with bush-
ings with an elastic coating. The hardness of the coating is 55 ± 5 Shore A, the nominal tensile strength is not less than 16.7 mPa (170 kgf /sm2), the elongation at break is not less than 550%. For a greater uniformity of the clamping of the fiber in the discharge pair, the coating thickness was 4.5 mm.
Two factors varied in studying the influence of the parameters of the improved drafting system on the yarn quality parameters: break draft between II-III cylinders (X1) and load on the discharge roller (X2). Levels and intervals of variation of factors are given in (Table 1).
Table 1. - Levels and intervals of variation of factors
Factors Variation levels Variation interval
-1 0 + 1
X( - break draft between II - III cylinders 1.15 1.25 1.35 0.10
X2 - load on the I line, H 150 160 170 10
To solve the problem of optimizing the tuning parameters of the improved drafting system, a 32 full factorial design - 9 experiments, i.e. a complete search of all possible combinations, all levels of factors, as in textile research the usual search is the most effective method of searching for an optimum [4].
As response variables were chosen:
- quadratic irregularity of yarn in section,% - Y1
- breaking tenacity of yarn, cN/tex - Y2
- quadratic irregularity of yarn of breaking force,% - Y3. The planning matrix and the results of the experiment are
shown in (Table 2).
Table 2. - The planning matrix and the results of the experiment
Experiment Coded value of factors Factors Optimization options
No. X2 Y2
1 2 3 4 5 6 7 8
1 1 -1 1.35 150 14.92 11.60 10.1
2 1 0 1.35 160 14.45 11.86 9.6
3 1 1 1.35 170 14.14 12.09 9.1
4 0 -1 1.25 150 14.36 11.66 9.7
5 0 0 1.25 160 13.95 12.3 8.9
6 0 1 1.25 170 13.90 12.54 8.6
1 2 3 4 5 6 7 8
7 -1 -1 1.15 150 14.21 11.88 9.4
8 -1 0 1.15 160 13.78 12.65 8.3
9 -1 1 1.15 170 13.40 12.72 8.0
The physical and mechanical properties of the yarn were determined by testing on Uster laboratory equipment. Test results are shown in (Tables 3 and 4).
Table 3. - Irregularity, defects and hairiness of the yarn
№ Indicator name (index name) X, = 1.35 X, = 1.25 X, = 1.15
150Н 160Н 170Н 150Н 160Н 170Н 150Н 160Н 170Н
1. Irregularity of section,%
- linear, U 11.75 11.41 11.19 11.33 11.13 11.05 11.24 10.95 10.68
- quadratic, Cm 14.92 14.45 14.14 14.36 13.95 13.93 14.21 13.78 13.40
2. The Us st level for C ,% 30 26 25 26 22 22 25 21 20
3. The ratio C / U 1.27 1.266 1.264 1.267 1.253 1.261 1.265 1.258 1.255
4. Thick places (-40%), units/km 140 130.8 123 136 114 113.7 123.8 110.5 96.5
Us st,% 25 24 21 24 20 20 21 18 18
Thin places (-50%), units/km 3.5 3.3 3.0 3.3 2.7 2.6 3.4 2.1 1.5
Us st,% 8 7 5 7 6 6 7 < 5 < 5
5. Thick places (+50%), units/km 93.5 90.2 82.2 92.5 81.5 77.3 79.9 73.8 72.1
Us st,% 19 16
6. Neps (+200%) 275.0 205.0 222.5 220.0 257.5 225.0 280.0 225.0 210.0
Neps (+280%) 42.5 30.0 32.5 50.0 27.5 37.5 50.0 45.0 35.0
7. Hairiness, H 6.72 6.65 6.81 6.69 6.62 6.65 6.53 6.87 6.64
237 224.3 208.2 231.8 198.2 193.6 207.1 186.4 170.1
Table 4. - Indicators of physical and mechanical properties and breakage of yarn
№ Indicator name (index name) X, = 1.35 X, = 1.25 X, = 1.15
150Н 160Н 170Н 150Н 160Н 170Н 150Н 160Н 170Н
1. Linear density of yarn, tex 19.9 20.1 20.0 19.8 20.2 20.0 20.1 20.2 19.9
2. Metric number 50.25 49.8 50.0 50.5 49.5 50.0 49.8 49.5 50.25
3. Coefficient of variation of linear density,% 0.86 0.9 0.9 0.97 1.0 0.89 1.01 0.92 0.94
4. Breaking force, cN 230.8 238.4 241.8 230.8 248.5 250.8 238.8 255.5 253.1
5. Coefficient of variation of breaking force,% 10.1 9.6 9.1 9.7 8.9 8.6 9.4 8.3 8.0
6. Breaking tenacity, cN/tex 11.6 11.86 12.09 11.66 12.3 12.54 11.88 12.65 12.72
7. Level of quality 1.15 1.23 1.33 1.2 1.38 1.45 14.26 1.52 1.59
8. Coefficient of using fiber strength in yarn strength 0.448 0.458 0.467 0.45 0.475 0.484 0.459 0.488 0.491
9. Elongation,% 3.9 4.2 4.1 4.2 3.8 3.9 4.27 4.10 4.1
10. Work to break, cN-Cm 450 500 496 485 472 489 510 524 519
11. Relative work break for 1 meter of yarn, N 45.2 49.8 49.6 49.0 46.7 48.9 50.7 51.9 52.2
12. Discontinuity: per 1000 spindles/hour 52 50 48 48 48 46 45 45 43
For each optimization parameter, regression equations were constructed.
Evaluation of the significance of regression coefficients was carried out by the Student's criterion, and the assessment
Table 5. - Values of coefficients,
of the adequacy of the equations is based on the Fisher's criterion.
The values of the regression coefficients, dispersion and confidence intervals Ab are shown in (Table 5).
persion and confidence intervals
Optimization parameters bo bn b2 b2 52 s2 sk Sb, Ab.
Y1 14.12 0.353 0.342 0.0075 0.03 0.035 0.0039 0.000144 0.012 0.0516
Y2 12.14 0.283 0.368 0.0875 0.0067 0.0584 0.0052 0.0001926 0.01388 0.0597
Y3 9.077 0.517 0.583 0.1 0.0063 0.073 0.0196 0.000726 0.02694 0.116
As is well known, when b. < Ab, the influence of i factor should be considered insignificant. After discarding minor terms, the regression equations acquire the corresponding form: quadratic irregularity of yarn of section,%
y1 = 14,12 + 0,353x1 - 0,342x2 (l)
breaking tenacity of yarn, cN/tex
y2 = 12,14 -0,283x1 + 0,368x2 -0,0875x1x2 (2) quadratic irregularity of yarn of breaking force,%
y3 = 9,077 + 0,5173xj -0,583x2 (3)
Convinced of the adequacy of equations (1-3), we can conclude that the amount of drawing in the back of the im-
proved drafting system and the amount of load on the rollers affect the internal irregularity of the yarn, its breaking force and the irregularity of the breaking force.
It can be seen from formula (l) that the quadratic irregularity along the section increases with the increase of the rear draft and with the decrease of the load, and the wiring effect is 3.2% higher than the load. For illustration, (Fig. 2) shows spectrograms of the mass of yarns of two variants: optimal (a) (E = 1.15, load 170N) and variant (b) with E = 1.35 and load 150N.
a) b)
Figure 2. Spectrograms of yarn mass in cross section at: a) E = 1.15, load 170H; b) E = 1.35, load 150 N
12,§5____ 12,3__ --• 12,54 E=1,15 E=1,25
11,88 <" "__—-—"il 86 . _ « 12,09 E=1,35
P0, sN/teks 1,66 11,6 --"I- - — ■ _ "
10,1
Cv, % 9,7 9,4^ 9,6 __ " -•. _ _ ^ 8,9 9,1
vs -- ^ 8,3 ____ --- 8,6 ----8 E=1,35 E=1,25 E=1,15
Load of the rollers, H
Figure 3. Dependence of the breaking tenacity of the yarn and the coefficient of variation of breaking force on the load of the rollers and the rear break draft
14
13
12
11
10
9
8
150
160
170
180
In (Fig. 2), one can see individual peaks on the spectrograms ofvariant (b) of elevations and more obvious irregularities (impulse deviations) in comparison with variant (a) in the wavelength region X = 4-10 cm, which is typical for waves of irregularity from drawing and is explained by insufficient control over the movement of fibers in the drafting system at the values of the factors E = 1.35 and the load of 150N. Therefore, variant a) can be taken as optimal values.
From formulas (2) and (3) it can be seen that the breaking force of the yarn decreases with the increase of the draft in the rear zone, but increases with increased loads on the roller, and the effect of the load is 1.3 times higher. The coefficient of variation of breaking force increases with increasing drawing and decreases with loads, as is clearly seen in (Fig. 3). Figure 3 shows:
1) with increasing load on the rollers, the yarn has a higher breaking force and a higher uniformity of breaking force with any break draft in the rear zone
2) an increase in the rear break draft at any load leads to a decrease in the breaking tenacity and an increase in the coefficient of variation of breaking force
References:
1. On the program of measures for the further development of the textile and clothing and knitwear industry for - 2017-2019: Decree of the President of the Republic of Uzbekistan of December 21,- 2016.- No. PP-2687 // Collection of Legislation of the Republic of Uzbekistan - 2016.- No. 51.- 584 p.
2. Ke-Zhang Chen, Cun-Zhu Huang, Shang-Xian Chen, Ning Pan. Developing a New Drafting System for Ring Spinning Machines. Textile Research Journal,- 2000.- Vol. 70. - Issue No. 2.- P. 154-160.
3. Makhkamova Sh. F., Zhumaniyazov K. Zh. Influence of the design of the draft cylinder of the drafting system on the uniformity of the contact strip // Textile Problems,- 2009.- No. 4.- P. 18-20.
4. Sevostyanov A. G. Methods and means of studying the mechanical and technological processes of the textile industry. Textbook.- M.; MSTU - 2007.- 648 p.
3) the highest breaking tenacity is 12.72 cN/tex with the smallest coefficient of variation of breaking force - 8.0% in the version with a break rear draft of1.15 and the load on the front roller 170N.
Conclusions:
As a result of an experimental study using an improved drafting system, the following conclusions can be drawn:
1) With a decrease in the break rear draft and with an increase in the load on the rollers, the internal irregularity of the yarn is reduced, and the breaking force of the yarn is increased, the coefficient of variation of breaking force is reduced
2) The most optimal settings for the improved drafting system are the break draft in the range 1.15-1.25, and the load on the front roller in the range 160-170 N.
3) The constructed mathematical models in the form of regression equations allow to determine the degree of influence of each factor and to predict the parameters of the investigated physical and mechanical properties of yarn with varying values of the influence of factors on them.
