OPEN END SPINNING UNIT

Open end spinning is an excellent short-term blending process. The presence of short fibers in the material fed does not seriously affect the efficiency of Open end spinning and it may be that process will have a bright future in the spinning of waste. Whenever the final judgment on open end spinning may be, it is a process that is here to say.

Few innovations in the field of textiles have created such interest as open-end spinning. Despite the tremendous efforts that have been made over the years to further the development of ring spinning, it now seems to be generally accepted that, owing to mechanical, technological and above all economic limitations, the potential of that well established process has been virtually exhausted and that further advancement will only be achieved through an entirely new approach; it may be that Open-end spinning will be the answer.

Spinning may be defined as the process of converting fibres and/or filaments(s) into yarn. In the production of manmade fibres, the extrusion of the fibre forming liquid through the spinners followed by hardening of this liquid jet in to solid filaments is called as the process of spinning.

The meaning of the spinning in this case may be completely different from that used for natural fibres. Generally, we can define spinning as a process that produces a yarn as its final product. The spinning of manmade fibres can be carried out by three different processes:-

• Wet Spinning
• Dry Spinning
• Melt Spinning

These different types of spinning methods are used based on the properties of the fibre forming substance can be spun by using more than one type of the above mentioned spinning techniques.

In today’s technology, many spinning systems are used commercially to produce spun yarns with a wide range of values of characteristics. Among these systems, ring spinning enjoys the greatest diversity and the highest quality levels. Ring spinning has been able to supplant almost all other conventional spinning methods and has proved very resistant to inroads by the newcomers. This can be attributed mainly to its flexibility, universal applicability, and yarn quality.

In ring spinning drafting, twisting and winding of the yarn is carried out simultaneously. By the end of 19th century process of ring spinning was fairly well perfected. Its output rate was much than that of self-acting mule which was an intermittent process. Consequently, the world textile industry made a major shift from mule to ring spinning in the first quarter of the 20th century. The developments of ring frame were accelerated after its adoption as a major system of yarn manufacturing. However, during mid of the twentieth century it was realized that output rate of ring spinning frame cannot be increased because of inherent limitations. It was concluded that it has reached a pinnacle of achievement! The textile institutes, universities and machinery manufacturers accelerated research work for development of new technologies, which did not suffer from the limitations of ring spinning frame. The research work led to the development of some new technologies based on the concept of performance of the processes of drafting, twisting and winding separately and independently of each other so that following objects can be achieved:

• Full speed of twisting mechanism is utilized for twist insertion.

• Full speed of the winding mechanism is utilized for winding of the yarn for substantial enhancement of output rates.

The open-end rotor spinning system is one of the new technologies and has penetrated world-wide the spinning industry.

Open end spinning is not a new concept, although it has only recently become a commercial proposition; Samuel Williams mentioned the basic idea as long ago as 1807! Several patents was filled about the turn of the century and the others between 1925 & 1950. Since then, over 100 patents relating to free-fibre-spinning devices and associated mechanisms have been filled. Although the first full-sized machine, the KS200, was only demonstrated publically at Brno in 1965 & the first really commercial machine, the BD200, appeared in 1967, by 1971 no fewer than thirteen free-fibre spinning machines, made by various manufacturers, were on show at the Paris exhibition, and further models hav been introduced since then.

Several attempts have been made to catalogue and classify the many embodiments of the open-end principle that have materialized over the years. This is from simple, since there are so many variables involved and certain features are common to several of the various systems, whereas others are not. The variables involved include the state of the material as fed; the method of the feed; the means of opening, separating, and conveying the fibres; and the techniques of reassembling the fibres and of imparting twist of them.

Perhaps the best classification is that devised by the Shirley Institute which is based on the methods of fibre assembly, namely;-

• Vortex assembly
• Axial assembly
• Discontinuous assembly
• Rotor assembly

Open End Spinning is a technology for creating yarn without using a spindle. It is also known as break spinning or rotor spinning. It was invented and developed in Czechoslovakia. Open End spinning is also known as breaks spinning or free fibre spinning. In this process the fibrous material is highly drafted to separate out the individual fibres. The individual fibres are subsequently collected onto the open end of the yarn.

In this process the fibre silver is separated in to single fibres and in which the separated fibre material is brought by an air stream to a collecting surface from which it is drawn off while being twisted. This I s wound on to a bobbin to form the yarn package.

A typical OE-rotor spinning system as shown in this figure essentially consists of a feed roller which feeds the sliver to an opening roller to open the sliver. Fibres are pneumatically delivered to the rotor groove through a conically shaped feed duct. During pneumatic transport, the fibres lose their orientation which is partially corrected by the conical cross-section of the feed duct For yarn formation a seed yarn is sucked in by the rotor.

Transition of the untwisted fibres into twisted yarn takes place in the rotor groove. As the fibres are deposited in the rotor groove continuously, the yarn is formed and wound by a separate winding mechanism continuously. The processes of drafting fibres, twisting into yarn and winding of yarn take place independently of each other. Due to the utilization of the entire rotational speed of the rotor for twist insertion, output is about 7 times higher than that of ring spinning frame. However, the twist generated by the rotor and transmitted by the open yarn end entails a considerable twist loss at the yarn formation point and is reported to be about 20%, as the Torque developed is very small.

This places a critical limit to the number of fibres at the yarn formation point below which spinning cannot take place. Consequently, OE rotor spinning is limited to the production of coarse and medium categories of yarn counts. Furthermore, the flow of fibre feed intersects the yarn withdrawal vector once per rotor revolution. Wrapper fibres which receive alternating directions of twist form an integral part of the OE-Yarn Structure. Twist in OE-Yarn is therefore indeterminable. The wrappers fibres either do not or only partially share in load bearing, when stress is applied to the yarn.