Drafting and Twisting Processes in Open-end Spinning Machine MS-400 By TeiryoKojima, Kozo Susamiand Masaaki Tabata, Members,TMSJ Basedon the Journal of the Textile Machinery Society of Japan, Proceedings, Vol. 21, No. 11, p. 737(1968); Vol. 25, No. 9, p. 623(1972) Abstract The most characteristic features of the open-end spinning compared to the ring spinning are in the drafting and twisting mechanism. In the present paper, some discussion will be made on the analysis of the drafting and twisting processes in MS-400 open-end spinning and their relation to the properties of its spun yarn. The mechanical characteristics of MS-400 are; (1) Roller drafting device (2) Ejector for fiber separation (3) Special eyelet, a yarn guide attached to the axis of the drum. These mechanisms make MS-400 a suitable spinning machine for man-made fibers. In the first part of this paper, the behaviour of fibers in the ejector separated into individ uals from a fiber bundle by the air stream will be considered. The discussion will be extended on the degree of fiber separation and the state of fibers, such as straightness at the outlet of the ejector. The second part deals with some mathematical analysis of the process of fiber collection in the drum and its self-doubling effect on the yarn irregularity. It is shown that the self-doubling effect is extremely useful for decreasing the yarn irregularity of short wave length and for improving the blend uniformity of fibers in the yarn. In the third part, the effect of the eyelet equipped in the drum is considered. The eyelet is shown to have a great influence on the yarn strength and on the end down in spinning. In the last part, a brief mention will be made on the spinning features obtained by the practical production in MS-400. KEY WORDS: DRAFTING,TWISTING, OPEN END SPINNING 1. Introduction Principal processes of spinning machines consist of draft ing, twisting and winding. If fiber properties are being fixed, yarn qualities are mostly governed by fiber motion in drafting and twisting processes, although these processes are quite different in open-end spinning from those in ring spinning; this characterizes the yarn property produced by open-end spinning. In this report, discussion will be made on drafting and twisting processes in the open-end spinning machine MS-400 and their relation to the yarn properties. Also the characteristics of the open-end spun yarn will be considered. Toray Industries Inc. carried on the study of open-end spinning in cooperation with 1-iowa Machinery Ltd. for several years, and developed MS-400; it belongs to a drum type spinning machine, as schematically shown in Fig. 1, A sliver is fed to 4-line double apron drafting system (1), and passes through an ejector (2) into which compressed air (6) is fed through a valve (10). A fiber bundle is separated to single fibers, and they are sent to a drum (3) rotating in Fig. 1 Main constitution of MS-400 8 Journal of The Textile Machinery Society of Japar high speed, and then twisted by the rotation of the drum (3) where relative to delivery rollers (4), forming a yarn which is F0=C(Va-V0)2 wound in a cheese (14) on a winding drum (5). F=C(Va-V)2 The most characteristic processes of yarn formation in Vd=V0/Va MS-400 are the separation of a fiber bundle in the ejector and the fiber motion in the drum; these characteristics will be discussed in the following chapters. 2. Separation of Fiber Bundle by Ejector-Air Draft Fig. 3 Relation between distance and flying speed V of a fiber Fig. 3 shows the variation of the fiber speed calculated by Fig. 2 Constitiuton of the ejector the above equation, indicating that a fiber in the ejector gets nearly the same velocity as air at few centi-meters Fig. 2 shows a schematic diagram of an ejector, which distant from the nip point of front rollers. This distance is consists of two parts; nozzle and diffuser. Fibers sent from extremely shorter than that anticipated. However, the front rollers of the drafting device are fed into the ejector friction between neighboring fibers in the bundle acts on through the nozzle. Compressed air is fed into an air the fiber in the ejector, adding to air force, causing a slightly chamber and is gushed out through the alley between the longer distance until the fiber gets the same velocity as air. nozzle and the diffuser, causing a sucking air stream in the Nevertheless, an ejector 1.5 times longer than the fiber nozzle. The fiber bundle is separated by the air-friction be length would be enough to separate a fiber bundle. tween fibers and air stream in the nozzle. Now, considering the state of fibers separated with the We shall consider the variation of the flying speed of a ejector, the performance of fiber esparation is very im single fiber supplied in the ejector from front rollers of the portant not only in MS-400 but also in any other open-end drafting device, in order to guess the process of the fiber machines: it directly influences upon both the evenness of bundle separation. The following symbols are adopted[1]: and the breakage of yarns. It is desirable to get uniform x= Distance from the nip point of front rollers to separation of fibers in the ejector. But the degree of fiber the trailing end of a fiber at time t. separation is dependent on the properties of raw materials, m= Mass of a fiber. quality of fiber bundles, ability of the ejector and air V= Flying speed of a fiber at time t. pressure supplied to it, etc. The relation among them is too Va=Air speed in the ejector. complicated to make a theoretical analysis, and experi When a fiber was placed in air stream and its one end was mental observation would be reasonable. connected to a strain meter, the air resistance of the fiber Figs. 4 and 5 show photographs of fibers flowing from was proportional to (air speed)2. This suggests that the air the ejector to the drum in spinning condition. They are resistance acting on a moving fiber should be proportional taken with a camera equipped with 75mm telescope lens, to (relative speed between the fiber and air)2. So, the fiber 20mm ring, film of ASA 400 (Kodak), and flash time of motion after the release from the nip point of front rollers 12 micro-second. In Fig. 4, four fibers are shown supplied is: simultaneously to the drum. In Fig. 5, a single fiber is presented. By this way, the behavior of fibers moving from the ejector to the drum was observed to estimate the uni where C=const. formity of fiber separation from 1,000 frames of photo When the initial speed of the fiber is Vo (equal to the sur graphs. face speed of front rollers of the drafting device), the fiber Fig. 6 shows an example of the relation between the speed Vat an arbitrary position x is given by: number of fibers in a frame of the photographs (horizontal axis) and its frequency (vertical-axis). No fibers in a frame means the occurrence of "open-end" there. The distri Vol. 20 No. 1 (1974) 9 Fig. 6 Relation between number of fibers per frame of photos and its frequency celerated in the air stream and supplied to the drum at the velocity equal to air velocity. So the degree of fiber sepa ration can be estimated by the average number of fibers Fig. 4, Fig. 5 Photograph of hbers flowing trom the supplied to the drum, which could be calculated from ejector to the drum in spinning bution in Fig. 6 almost follows Poisson distribution. As suming the number of fibers be n and its frequency be f, an Table 1 shows the average fiber speed V and the average average number of fibers n can be expressed by number n•Œ of fibers with different kinds of fibers having the staple length of 51 mm. It can be seen that the higher the air pressure, the better the fiber separation. But the air which n can be considered the average fiber density in the air flow blowing from the ejector to the drum. When the Table 1. Degree of Fiber Separation yarn take-up speed is Vy and the number of fibers in the yarn cross-section is ny which is determined by both the yarn count and the fiber denier, the average fiber speed V supplied from the ejector to the drum is calculated by The calculated speed is almost equal to the air speed blow ing from the ejector to the drum which can be experi mentally measured. This shows that fibers are fully ac Table 2. Content of Hook Fibers after Separation (%) 10 Journal of The Textile Machinery Society of Japan pressure supplied to the ejector should not be raised ex cessively, because if the fiber speed exceeds the surface speed of the drum, the fiber arrangement and its straight ness are disturbed. Comparing the materials of fibers used, the degrees of fiber separation of polyester or polyester rayon blended are worse than those of polypropylene or polyacrylonitrile. Table 2 shows the fiber-hook observed on photographs mentioned above. Fibers used are polyester, polyacrylo Fig. 8 Relative motion of the peeling point A and nitrile, nylon and polyester-rayon blended of 51mm staple the supplying point B length.