The effects of a number of process parameters, including the nozzle angle, nozzle pressure, spindle diameter, yarn delivery speed, and distance between the front roller and the spindle, on the structure and properties of vortex spun yarns were investigated. A modified version of the tracer fiber technique (J. Text. Inst., 43, T60-T66, 1952) combined with the Image Analysis Application Version 3.0 (B.A.R.N. Engineering) was utilized to explore yarn structure. The migration behavior of fibers was characterized using the migration parameters introduced by Hearle et al. (Text. Res. J., 35, 329-334, 788-795, 1965). The results showed that the short front roller to the spindle distance caused better evenness, low imperfections, and less hairiness. High nozzle angle, high nozzle pressure, low yarn delivery speed and small spindle diameter reduced hairiness as well. High nozzle angle, high nozzle pressure and low speed also led to higher fiber migration. Surprisingly nozzle angle, nozzle pressure or delivery speed did not have any significant effects on yarn tensile properties. This is believed to be caused by the relatively small differences between the levels of these parameters used in the trials. The present study provides a window into the vortex spinning technology, but further research needs to be conducted to establish a "process-structure-property model" for vortex yarns.

The Murata Vortex Spinner is the world's first spinning frame to produce yarns from 100% carded cotton at very high spinning speeds, up to 400 m/min in mill operating conditions [1-3]. There are several claimed advantages of this system such as "ring-like" structure, low hairiness, reduced fabric pilling, better abrasion resistance, higher moisture absorption, better color-fastness and fast drying characteristics [2]. However, most of these claims have been made by the machinery makers. Currently there is no comprehensive study available on this relatively new technology, particularly the influence of machine parameters on the structure and properties of vortex spun yarn. Apart from this, in the very competitive business of textiles, further improvements in terms of yarn quality and productivity are always welcome. The main purpose of this research was thus to increase the possible areas of application of vortex spun yarns by systematically investigating the roles played by various processing parameters on the yarn structure and, in turn, the yarn properties. This goal was achieved by employing an experimental approach to examine the structure of vortex spun yarns, and determine the correlation between process parameters, yarn structure and yarn properties. It is hoped that results of this study will provide the first step to establish a "process-structure-property model" for vortex yarn, which can be used to optimize and improve the vortex spinning technology.

Experimental Procedure

Yarns Studied

Cotton fibers with an upper half mean length value of 1.44 and micronaire value of 3.4 were used for the investigation. A very low percentage (around 0.5%) of black fibers of the same type was blended with raw cotton fibers at the opening stage. These fibers served as tracer fibers during the analysis of vortex yarn structure. After opening and carding, the materials were subjected to three passages of drawing, and then taken to the Murata Vortex Spinning frame for spinning.

Five different process parameters, which were thought to influence the properties and structure of vortex yarns, were chosen for investigation. These were: the nozzle angle, the nozzle pressure, the spindle diameter, the yarn speed, and the distance between the front roller and the spindle. Some of these parameters can be seen in Figure 1. Vortex yarn samples (28's Ne) were spun on No. 851 Murata Vortex Spinner using the values of spinning parameters shown in Table 1. The experiment was conducted as a 25 factorial split plot design with the yarn speed and the nozzle pressure as main plots and the nozzle angle, the spindle diameter, and the distance between the front roller and the spindle as subplots.

An obvious feature is that the magnitude of change in the parameters is relatively small but these were the greatest ranges that could be achieved on the machine due to the availability of machine parts and it is not possible to spin yarns outside certain limits.

It was impossible to spin yarns with acceptable break rates in the combination of low air pressure, high delivery speed, short front roller to spindle distance, large spindle diameter and small nozzle angle. One possible reason is that the high speed along with the low air pressure might worsen the spinning stability since yarn receives fewer twists in those conditions.

Observation of Migration

A modified version of the tracer fiber technique originally introduced by Morton and Yen [4] combined with the Image Analysis Application Version 3.0 [5] was used to investigate the yarn structure. Fourteen tracer fibers from each of 31 different yarns (434 fibers) were used for this investigation (Seven fibers were randomly selected from each of the two packages). The experimental arrangement is shown in Figure 2. The yarn sample was first sent into a container containing a suitable immersion liquid and left there until the wetting out was complete. (Initial trials clearly demonstrated that the analysis of the tracer fiber could not be achieved unless the yarn was thoroughly wetted out by the immersion liquid.) Then it was pulled through a glass trough also containing the immersion liquid, which was, in turn placed on a microscope stage. Yarn guides were used to maintain the yarn sample on a set path through the trough. Images of the tracer fibers were captured via a half-inch black and white charged coupled device (CCD) camera mounted to the objective of a Zeiss compound polarized light microscope. These images were transferred to a computer and stored. The computer used for this work was a Dell Dimension XPS R400. In order to process the analogue video signals from the CCD camera and digitize them into pixels for subsequent transfer to computer memory, the Matrox Meteor II PCI frame grabber was installed on the computer. The captured images were digitized into 450 640 pixels with 8 bit per pixel.

Image Processing

To observe one whole tracer fiber it was necessary to capture several consecutive images (approximately 11-13 images). Due to the high magnification employed for this process each captured picture covered only a part of the tracer fiber. Later these images were processed through Spin Panorama 2.1 (PictureWorks Technology, Inc.) to create composite images (Figure 3). This software creates panoramic images utilizing a four-step process: getting images from a panoramic series; stitching images together; cropping the stitched images; and creating (saving) the final panorama. Although the authors final image was not a panoramic image Spin Panorama 2.1 software produced fairly good results in joining individual images.

Migration was quantified using migration parameters introduced by Hearle et al. [6, 7] Due to the complexity of images and presence of optical noise caused by poor resolution associated with the optical anisotropy of cotton fibers, along with the presence of convolution in the fiber and the twist in the yarn, it was difficult to separate the paths of individual fibers and yarn boundaries by using an automatic subroutine. Thus, a manual technique was employed. Yarn boundaries, and peaks and troughs of tracer fiber were marked manually utilizing Adobe PhotoShop 6.0. Subsequently all images were transferred to Matlab; the co-ordinates of yarn boundaries, peaks and troughs were extracted from these images and stored in matrix form. The quantities of yarn and migration parameters were estimated through a specially designed Matlab processing routine. The same program was also used to generate the plots for the corrected helix envelope profiles, distribution of helix angle along the yarn length, and the frequency distribution of the helix angle.

Yarn Properties

Evenness, imperfection, and the hairiness properties of resulting yarns were measured on the Uster Evenness Tester and yarn tensile properties were tested on the Uster Tensorapid tester. All these tests were performed under standard conditions (70F and 65% relative humidity). The results from these tests are given in Table 3 below.

Statistical Treatment

The analysis of variance was performed on test results from the Uster Evenness and Uster Tensorapid tester as well as the calculated values of fiber migration and yarn parameters using SAS PROC GLM. As the trials were not replicated, high-order interactions were pooled to obtain an error term. The significance of independent variables and their interactions on the yarn structure parameters and physical properties were tested at a 0.05 probability level. A probability value (p) that was smaller than 0.05 led to the conclusion that the independent variable had a significant effect on the dependent variable. The results of the analysis of variance test are reported in Tables 5 and 6 below. The values of the correlation coefficients between the yarn structural parameters and physical properties were also calculated.

Results and Discussion

Classification of Vortex Yarn Structure

A typical fiber configuration in vortex yarns is given in Figure 3. As seen from the figure, the vortex yarn structure varies along the yarn length. The configuration of each tracer fiber was studied and grouped according to the classification illustrated in Table 2. The results of fiber configuration classification showed that the percentage of straight, hooked (trailing) and hooked(both ends) was similar.

Migration in Vortex Yarn

The images captured during the analysis of yarn structure suggest that the fiber migration in vortex yarns differs from that in both air-jet and ring yarns. In vortex spinning fibers emerging from the front rollers are sucked into the spiral orifice at the inlet of the air jet nozzle and move towards the tip of the needle protruding from the orifice (Figure 1). In the meantime, these fibers are subjected to a whirling air flow and receive twist. Twist tends to move upwards, but the needle prevents this upward twist penetration. Therefore, the upper parts of some fibers are kept open as they depart from the nip line of the front rollers. After these fibers have passed through the orifice, the upper parts of the fibers spread out due to the whirling air flow. They then wind over the hollow spindle. Subsequently these fibers are wrapped around the fiber core and turned into yarn, as the already formed yarn part is pulled through the spindle [8-10].

The main difference between the air jet and vortex yarn is the number of wrapper fibers which is much higher in vortex yarns [11]. In air jet spinning, only the edge fibers become wrapper fibers. In vortex spinning, on the other hand, the fiber separation from the bundle occurs everywhere in the entire outer periphery of the bundle. It is very likely that during yarn formation the leading part of the fibers will not be able to escape from the false twist penetrating upwards and eventually become located in the core. The trailing parts, on the other hand, will not receive twist and become wrapper. The images captured during analysis of yarn structure confirmed this assumption. Most of tracer fibers first showed core fiber characteristics, lying parallel to the yarn axis and then wrapper fiber characteristics, being helically wound onto the core.

Structure and Properties of Vortex Yarns

Yarn Properties

The short front roller to the spindle distance produced more even yarns with fewer imperfections and less hair (Table 3). The nozzle angle had a significant effect on evenness and hairiness values. A high nozzle angle caused more even and less hairy yarns. The interaction of a high nozzle angle and short front roller to spindle distance led to better irregularity. Nozzle pressure and spindle diameter only affected hairiness. Hairiness was low at the high nozzle pressure and the small spindle diameter. The yarn speed had a significant effect on the number of thick places and hairiness. A low yarn delivery speed caused a smaller number of thick places and low hairiness. The interaction of the yarn speed and nozzle angle had a significant effect on hairiness as well.

Yarn Structure-Property Relationships

There was no correlation between the yarn structural parameters and physical properties (Tables 5 and 6). One might anticipate that a high mean migration intensity value should result in a higher tenacity. Probably, this is due to the relatively small differences between the levels tested for each process parameters.


The current work investigated the effects of five different process parameters: the distance between front roller to spindle, nozzle angle, nozzle pressure, spindle diameter, and yarn speed on yarn properties. Attempts were made to subsequently relate these properties to the changes in the yarn structure, which in turn are caused by process parameters. Among these parameters, the distance between the front roller and the spindle affects mainly yarn evenness, imperfection and hairiness values, which are all better if this distance is short. The high nozzle angle, the high nozzle pressure, the low yarn delivery speed and the small spindle diameter reduce hairiness. The high nozzle angle improves yarn evenness as well. The mean migration intensity and equivalent migration frequency are greater at the high nozzle angle and the low speed. The high nozzle pressure also increases the mean migration intensity. The low yarn speed causes the smaller yarn diameter and it is likely that the yarn receives more twist at these conditions.


The authors wish to thank the National Textile Center (NTC) for their financial support (NTC Project: F99-NS06), and Cotton Incorporated for providing their facilities.
Literature Cited
1. Artzt, P., Yarn Structures in Vortex Spinning, Melliand International, 6, 107 (2000).

2. Leary, R. H., OTEMAS'97 Survey 1: Yarn Formation, Textile Asia, 28, 11-23 (1997).

3. Morton, W. E., and Yen, K. C. The Arrangement of Fibers in Fihro Yarns, J. Text, Inst., 43, T60-T66 (1952).

4. Image Analysis Application Version 3.0, B.A.R.N. Engineering 108 Trapez Lane Gary, NC 27511, U.S.A.

5. Hearle, J. W. S., Gupta, B. S., and Merchant, V. B., Migration of Fibers in Yarns. Part I: Characterization and Idealization of Migration Behavior, Text. Res. J., 35,329-334 (1965).

6. Hearle, J. W. S., and Gupta, B. S., Migration of Fibers in Yarns. Part III: A Study of Migration in Staple Fiber Rayon Yarn, Text. Res. J., 35, 788-795 (1965).

7. Gray, W. M., How MVS Makes Yarns. 12th Annual Engineer Fiber Selection System Conference Papers, (May 17-19, 1999).

8. Murata Machinery Limited, No. 851 Murata Vortex Spinner, Service Manual.

9. Deno, K., Spinning apparatus with twisting guide surface, United States Patent 5,528,895, June 25, 1996.

10. Basal, G., and Oxenham, W., Vortex Yarn vs. Air-Jet Yarn, AUTEX Res. J., 3(3), 96-101 (2003).

About the author:
Basal, Guldemet, Oxenham, William, Textile Research Journal,

Guldemet Basal, Department Of Textile Engineering, Ege University, Bornova, Izmir, 35100 Turkey

William Oxenham1, College of Textiles, North Carolina State University, Raleigh, North Carolina, 27695 U.S.A.

E-mail: william_oxenham@ncsu.edu
Copyright Textile Research Institute Jun 2006

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