Evaluation of false-twist textured yarns by image processing

Transcription

1 Indian Journal of Fibre & Textile Research Vol. 40, December 2015, pp Evaluation of false-twist textured yarns by imae processin P Ghaderpanah, F Mokhtari a & M atifi Textile Enineerin Department, Textile Excellence & Research Centers, Amirkabir University of Technoloy, Tehran, Iran Received 12 April 2014; revised received and accepted 3 Auust 2014 A new method has been introduced to determine the crimp features of false twist textured yarns by applyin computer vision and imae processin method. Hence, the test results, with accuracy, are achieved more quickly than by the other excitin method. The mean anle of filament orientation in false twist textured yarns with different texturizin variables (heater temperature, texturizin speed and twist) is determined. Similarly, the direct trackin alorithms to achieve a ood correlation with crimp contraction are also used. The results show that by this new method a correlation coefficient of more than 95% is achieved between mean orientation anle and crimp contraction. Keywords: Direct trackin alorithms, Filaments orientation anle, False twist, Imae processin, Nylon 6, Textured yarn 1 Introduction Durin 1950, a new branch was created in the textile industry astexturizin of continuous filament yarn 1. Texturizin meant to create a permanent deformation of the filament yarns, which creates different properties. In eneral texturizin is done by one of these three methods, viz. mechanical, thermal-mechanical and chemical-mechanical. Texturizin by the false twist method is the most important and practical method to produce these yarns. Various factors affect the shape and crimp properties of textured yarn. Important factors are filaments chemical structure, yarn count, of filaments, shape of surface area and factors related to system such as yarn motion systems, yarn time passes in each step, type of heater and its lenth and temperature. The computer vision in research and quality control procedures is applicable. Millman et al. 2. have introduced a system that allows further investiation of the samples tested at hih speed and accuracy without any contact with the samples. This system was able to detecttanle and sensitive to the diameter chanes. A roup of researchers used methods such as the measurement of yarn packae density, thickness of the fabric production and the amount of water carried by the texture yarn in order to evaluate bucklin and stitch density. The main purpose of texturizin the air jet is to produce bulky yarns. Bulk and density of loops is important factors for the quality control of texture yarns 3. a Correspondin author. mokhtari.fatemeh2@mail.com In recent years, many research projects have been carried out to present new methods for determination of crimp, especially crimp concentration in texture yarns. With the advent of modern computers and new prorammin tools, the use of computer vision for quality control and test products is increasin 4. The structure of false twisted yarn is similar to the fractal shape. Therefore, some researchers evaluate thecrimp of textured yarn based on their work on the use of fractal eometry. In this study, a new method to quantify the crimp amount of sinle filaments has been developed. Also the effect of the filaments in the false twist texture yarn in this new method is studied. 2 Materials and Methods 2.1 Materials The Nylon 6 with yarn count 98 (dtex) and density (/cm 3 ) for this research was provided by the ealea Company of Thailand. Modulus and elonation at rupture of samples were cn/tex and 49.16% respectively. Texturizin of semi orientation yarn was done by texture devise model Minibulk cs (Ernest Scar and Sons Company of Enland), and the samples shrinkae was 0.69% with double refraction Evaluated variables were temperature, speed and twist; effect of each variable was studied, keepin the other variables constant. Table 1 shows the texturizin conditions of all samples in 1.2 draw ratio. Crimp properties of texturized yarns were measured as per the DIN standards. In this method, one hank with linear density of 2500dtex was

2 400 INDIAN J. FIBRE TEXT. RES., DECEMBER 2015 kept under tension of 0.01cN/tex at 120 C for 10 min, and after coolin it was aain kept under a tension of 2cN/tex for 10 s. Immediately its lenth ( ) was measured. Then the yarn was kept under tension of 0.01 cn/tex for 10 min and its lenth ( z ) was measured. After that samples were kept under tension of 0.1cN/tex for 10s and its lenth ( f ) was measured. In the final stae, after attainin tension of 10cN/tex for 10 s, it was decreased to 0.01cN/tex in 10 min, and the sample lenth ( b ) was measured. Crimp concentration, hardness and stability were determined usin the followin equations: Crimp concentration (CC%)= Crimp hardness (CM%)= Crimp stability (CS%)= Table 1 Texturizin condition of samples Draw ratio Heater Twists per temperature, C meter b z f z (1) (2) (3) Texturizin speed, m/min Methods Preparation To take photos of texturized yarn, diital microscopic Dino (AU-351) was used with a resolution of VGA, which was connected to a PC. Diital microscopy was equipped with a lens ( 10), ( ), and ( ). For lihtin, ED can be used to set front lihtin and behind lihtin. The best imae was obtained by a lens of ( ). The sample lenth in these imaes was 1.54 mm. To et imaes of texture yarn with false twist, the yarn without any additional twist was opened, and then fixed from one side; from another side it was placed under appropriate weiht so that it did not cause its crimp to open. Also no more stretch was applied on it, bein straiht under enz to photoraphy. To reach this oal, 50 m clamps were used. In this study, from every yarn packae, 30 samples with a lenth of 11 cm were prepared and from each sample 5 photos were taken Imae Processin In the imae processin tool of Matlab Software, by im2bw method all imaes in black and white format were obtained and by Otsu method the threshold to separate filaments from the backround was defined. In evaluated imaes, the lihtin point in white indicatesthe existence of the filament and the black lihtin point is representin the backround 5. After obtainin binary imaes, it is time to make them thinner. Thinnin is an importantstep in preprocessin in detectin the pattern. In some cases, it is necessary to have a simple candidate of the imae that has numeral properties of the initial imae.falsetwist texture yarn and its imae skeleton are illustrated in Fi Corrective Methods In the imae skeleton, hair branches occur at the end of the fibres that should be omitted before the Fi. 1 Schematic diaram of false-twist texture yarn (a), and its skeleton (b)

3 GHADERPANAH et al.: EVAUATION OF FASE-TWIST TEXTURED YARNS BY IMAGE PROCESSING 401 Fi. 2 Schematic diaram of false-twist texture yarn (a) before, and (b) after corrective procedure next operation. Thus, corrective alorithm should be used. It is supposed that branches must not exceed a certain. Hence, the branches lenths that exceed from a certain are omitted by the spur operation. Multifilament false-twist texture yarns are shown before and after corrective procedures (Fi.2) Assined Connection Points P-point in coordinate (x,y) has two horizontal neihbors and two vertical neihbors that are called the four neihborin. If four diaonal neihbors are also considered, it is called eiht neihborin. The coordinate of these neihbors is shown in Fi.3. White points indicate the fibre existence. So, at first find these points and then points with more than 3 neihbors are introduced as connection points. To determine the anles of the filaments alined in multifilament texture yarn, the improved alorithm was used, considerin the direct trackin method. Direct trackin alorithm is lon and for intersection points, should be sinle definition based on minimum deviations from the initial direction, that itself makes the complexity, hih computational volume and low speed of alorithm. So, in improved alorithm, at first, filaments connections points are evaluated and then omitted from imae Remove Connections Removin the connection points reduces the complexity of the alorithm without affectin the result.as a result, the connection points are removed from the imae and then all filaments can be directly traced. In fact, the filaments are considered as separated pieces in the connection points (Fi. 4) Determination of Orientation Anle By removin the connection points of the imae, the filaments will not have continuity and can be labeled as sinle piece of filament. In the imaes of false twist texture, filaments yarns are not straiht. Fi.3 Neihborin points coordinates of the main point (x,y) Thus, after labelin each piece, the lenth is considered as a tracin piece. For example, if 10 points of filament are considered as a tracin lenth, the anle between the first and the eleventh point, and the anle between the eleventh and the twenty first points are determined with the x axis. The averae filament position anle is determined as the index to crimp concentration Orientation Index Orientation index (F) is definedas the ratio of double refraction of filament to ideal double refraction that shows the position of macromolecules completely parallel to the fibre axis. This index is related to averae slope anle Ø, as shown below: F = (n 1 n 2 )/(n " n " (4) 1 2 ) F = 1 ( 3 2 )sin 2 Ø (5) For a fibre in ideal conditions of which macromolecules are oriented, alin its axis to F=1 and Ø = 0 and for homoeneous fibre, F=0 and Ø = 55, where Ø is the anle of filament with yarn axis Performance Evaluation of Alorithms In order to measure the accuracy of the proposed methods before runnin the proram on the texture

4 402 INDIAN J. FIBRE TEXT. RES., DECEMBER 2015 sample yarn, at first accurate performance on simulated samples iscontrolled. Anles from the X axis are measured and compared with the results of the alorithm. Some simulated imaes are shown in Table 2. The relative error rate in calculation of the anle in the axis with defined alorithm is 1.15%, which is calculated usin the followin equation: Table 2 Calculated mean anle from samples and by imae processin method for simulated samples Imae of simulated model Measured anle from sample de Measured anle by alorithm de ar ai e = a i (6) where e is relative error;, the mean anle obtained from the sample; and, the mean anle obtained from the imae processin method. ow relative error obtained from this method show hih accuracy. After ensurin the correctness of the proram, an investiation is also initiated on the false twist texture yarn (Table 2) Results and Discussion 3.1 Effect of Twist on Mean Anle of Alined Filaments After preparation by imae processin, the orientation anle of the filament alined index is evaluated. The mean of the orientation index and the alined filament anles in texture yarn are presented in Table 3. By increasin twist, mean anle increases and orientation index decreases. In other words, deviation from straiht of filament increases. Hence, bendin and torsional moments are applied to the yarn. Filament bendin and torsion caused their deviation from yarn axis and orientation parallel with yarn axis decreases. The statistical tests with 95% confidence show that these five samples have different Mean of twist per meter Table 3 Alorithm results for samples with different mean twist per meter Density % Mean anle of orientation, de CV of filament alinment anles Orientation factor Crimp concentration, % Fi.4 (a) Simulated imae with connection points, and (b) omittin connection points

5 GHADERPANAH et al.: EVAUATION OF FASE-TWIST TEXTURED YARNS BY IMAGE PROCESSING 403 meanins in their level. Fiure 5 shows the relationship between crimp contraction percentae and orientation anle for yarn. Considerin that the explanation of linear relations are easier than polynomial, and linear fittins have the correlation coefficient (CC) of more than 95%. Yarn concentration is calculated usin the followin relationship: CC%=a a m +b (7) where a m is the crimp contraction; b, the oreintation anle when crimp contraction is zero; and a, the ratio of orientation anle to crimp contraction. 3.2 Effect of Heater Temperature on Mean Anle of Alined Filaments Table 4 shows the variation in filaments placement in texture yarn for different heater temperature. After imae evaluation by imae processin, the mean Fi.5 Relationship between crimp concentration and mean anle of orientation anle of filaments and the mean index orientation are calculated (Table 4). In Fi. 6, the variation in mean anle of alined filaments and index orientation with chanes of heater temperature are illustrated. The results show that by increasin heater temperature, mean anle increases and the orientation index decreases. The deviation from the straiht position of filaments in comparison with yarn axis increases. It is caused by better fixin of crimp at hiher temperatures. Based on the Duncan test, althouh increasin heater temperature from 160 C to 170 C or from 180 C to 190 C causes a decrease in mean anle orientation, the difference between mean anle of orientation and orientation index does not have meanin from a statistical view. 3.3 Effect of Texturizin Speed on Mean Anle of Alined Filaments To evaluate the effect of texturizin on filament placement, samples in different texturizin speed are presented in Table 5. With the texturizin speed, the mean anle of alined filaments decreases and the orientation index increases. At hih speed, the stayin duration of yarn in the heater decreases and hence there is no chance for the yarn to move and filament deviation from the straiht line decreased. ikewise, the Duncan test (Table 6) shows that there is a sinificant difference between the sample roups. The relationship between crimp concentration and mean anle of orientation has a linear correlation coefficient of more than 95%. Fi.6 Variation in (a) mean anle of alined filaments, and (b) orientation factor versus heater temperature Heater temperature, C Table 4 Alorithm results for samples effect of heater temperature Fiure density, % Mean anle orientation CV of alin filament anle Orientation index Crimp concentration, %

6 404 INDIAN J. FIBRE TEXT. RES., DECEMBER 2015 Table 5 Alorithm results for samples effect of texturizin speed Texturizin speed, m/min Density % Mean anle of orientation CV of alined filament anle Orientation index Crimp concentration, % Table 6 Duncan test for evaluation of texturizin speed on variation of mean orientation anle Velocity N Subset for alpha = Si Conclusion This study is a novel approach usin computer vision to determine the percentae of crimp concentration in false twist texture yarn so that the test results with accuracy are achieved more quickly than other existin methods. Also, the study of placin the filaments in the false twist texture yarn is considered as the aim of this research. Experiments performed on imaes on false twist texture yarn includes determination of orientation index and mean anle filament alinment index. In the mean anle of orientation, with a correlation coefficient of more than 95%, the yarn is found to have a linear relationship with the amount of crimp concentration. The effect of production variables (twistin, temperature and speed of texturizin) on the arranement of the filaments in the false twist texture yarn in this new method is also studied. It is observed that (i) increasin texturizin twist causes a decrease in orientation alon the yarn axis, (ii) increasin heater temperature results in deviation of filaments from the yarn axis and (iii)increment of texturizin speed has hih orientation as a result. References 1 Hearl J & Hollick, Yarn Texturin Technoloy (The Textile Institute, Woodhead Publishin td), Millman M P, Ascar M & Jackson M R, Mechatronics, 11 (2001) Senupta A K, Kothari V K & Renasamy R S, Chemifasern/Text-ind (CTI), 40 (1990) Yousefzadeh M, Amani-Tehran M, atifi M & Mohaddes- Mojtahedi M R, Amirkabir J, 16 (2005) Wan Shiton, Chun Fu-lai & Xion Fuson, Pattern Reconition, 41 (1) (2008) Maleki M, atifi M & Amani M, Int J Nanotechnol, 6 (12) (2009) 1131.