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Rotor spinning working principle

The document summarizes rotor spinning, which is a technology for creating yarn without using a spindle. It describes how in rotor spinning, a sliver is fed into an opening unit where individual fibers are separated and then reassembled, twisted, and wound onto a package. The key aspects of rotor spinning covered include the fiber collection process in the rotor groove, how twist is inserted as the rotor rotates, and factors that influence fiber placement and yarn quality.

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ROTOR SPINNING PRESENTED TO: SIR Dr. Rafique Ahmed Jhatial PRESENTED BY: HAMMAMA SOHAIL (11TE47)
CONTENTS: OPEN-END SPINNING ROTOR MACHINE PRINCIPLE OF ROTOR SPINNING FIBER COLLEDTION ON ROTOR GROOVE TWIST INSERTION IN ROTOR SPINNING MACHINE
OPEN-END SPINNING: • open-end spinning is a technology for creating yarn without using a spindle. •It was invented and developed in Czechoslovakia. •Open End spinning is also known as break 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. •This is rotated to twist the fibre into the yarn structure to form a continuous strand of yarn. •This is wound onto a bobbin to form the yarn package.
Advantages of Open End Spinning •Lower power consumption per unit quantity of yarn produced •Higher speed of twist insertion resulting in very high yarn delivery speed • A significant resulting increase in productivity. • Larger delivered package size • Elimination of some processes such as roving and winding • More uniform yarns.
•The first functioning of rotor spinning ,machine was presented at the ITMA in 1967. •Yarn spinning according to the rotor spinning principle predominates for all non conventional spinning methods. It omits the step of forming a roving. After drafting, the sliver is fed into a rotary beater. •This device ensures that the fibers are beaten into a thin supply which enters a duct and gets deposited on the sides of the disc(rotor). •The transportation of the fibers is achieved through air currents. The fibres are twisted together by the spinning action of the rotor, and the yarn is continuously drawn from the centre of the rotor. •The resultant yarn is cleared of any defects and wound onto packages. ROTOR SPINNING:
•Rotor spinning is a stable spinning process, i.e. it functions trouble-free under normal spinning conditions, without variations in running behavior or yarn quality. •As a rule rotor spinning operates with normal draw frame sliver of a quality customary in spinning mills. Special preparatory passages, such as are sometimes necessary for other spinning processes (e.g. air-jet spinning), are not required here. •Rotor spinning is appropriate for mill operations in that its technology can be implemented with relatively simple and robust spinning elements. •The process imposes no special requirements on the atmosphere in the spinning mill as regards temperature, humidity and air conditioning and in many cases is actually less critical in this respect that ring or air-jet spinning.
PRINCIPLE OF ROTOR SPINNING MACHINE:
Sliver feed: A card or draw frame sliver is fed through a sliver guide via a feed roller(f) and feed plate (B) to a rapidly rotating opening roller(o). In rotor spinning, a sliver is fed into the opening unit. The fed sliver is opened into individual fibres and then the individualised fibres are reassembled, twisted and wound on a package. o Sliver opening: The rotating teeth of the opening roller comb out the individual fibers from the sliver clamped between feed table and feed roller. After leaving the rotating opening roller, the fibers are fed to the fiber channel
 Fibre transport to the rotor: Centrifugal forces and a vacuum in the rotor housing causes the fibers to disengage at a certain point from the opening roller and to move via the fiber channel to the inside wall of the rotor. R  Fibre collection in the rotor groove: The centrifugal forces in the rapidly rotating rotor cause the fibers to move from the conical rotor wall toward the rotor groove and be collected there to form a fiber ring.
Yarn formation: The rotor rotates at high speed creating a centrifugal force. To start spinning, a length of yarn already wound onto the package of the take-up mechanism is threaded through the nip line of the delivery rollers and into the draw-off tube . Because of the vacuum, the tail end of this yarn is sucked into the rotor. The rotation of the rotor pulls the yarn end onto the part collected ribbon of fibres through the air drag and the centrifugal forces, and simultaneously inserts twist into the yarn tail. A little of this twist propagates into that part of the ribbon in contact with the yarn tail, binding it to the yarn end.
If a yarn breaks, the spinning process is interrupted at the particular spinning position. Re-starting the spinning process is called "piecing". The robot "pieces" the newly spun yarn onto the yarn-end to be found on the package.  Robot locks onto the spinning position with an end down.  The feed roller starts. Fibers are fed into the rotor where they form a fiber ring.  The yarn end, prepared by the Robot is "dropped" into the rotor and connects itself with the fiber ring.  The yarn is withdrawn from the rotor. The fiber ring is broken and the spinning process starts. Piecing process:
Yarn Take-up and Winding: Once the yarn tail enters the rotor, the delivery rollers (K) are set in motion to pull the tail out of the rotor. The pulling action on the tail results in a peeling of the fibre ribbon from the rotor groove. The newly formed yarn (Y) is wound up on a cheese (P) by a winding drum. A yarn stop motion interrupts material supply to the opening roller (O) when an end breaks. Capacitive or optical sensors incorporated in the yarn path record yarn faults (thick and thin places), enabling them to be cleared in limits are exceeded.
BY PASS: •Releasing the fibers from the wire of the opening roller and transporting the fibers through the fiber channel requires a rather fast air speed. •Extracting a high amount of dirt requires a rather slow air speed in the trash-chute. •The bypass provides an adjustable air opening, next to trash chute, which allows for adjusting the air speed inside the trash chute. •A certain amount of air, required to release the fibers from the wire of the opening roller and for drafting the fiber flow in the fiber channel, is lead away by the bypass. •. According to the adjustment of the bypass, the amount of spinning air entering the trash chute can be reduced. More trash will be extracted. The amount of trash extracted can be predicted accurately.
Position (1) Bypass open: Position (2): Bypass open to 50%: Position (3): Bypass closed:  High amount of trash extracted  Recommended for Carded cotton with high trash content  Normal setting of trash extraction  Recommended for Carded cotton with low amount of trash, and blends of synthetic fibers and cotton  Low amount of trash extracted  Recommended for very clean sliver, for blends of synthetic fibers and cotton, Synthetic fibers
FIBER COLLECTION IN THE ROTOR GROOVE (BACK- DOUBLING) • The process of yarn formation in rotor spinning involves the separation by an opening roller of a fiber bundle fed in into individual fibers or small groups of fibers. •Which are then transported by the air current into the rotor, where they slide down the rotor wall. They are only combined again into fine layers of fibers in the rotor groove.
• A layer of these individual fibers is deposited in the rotor groove with each revolution of the rotor until the yarn reaches the required thickness. This buildup of fiber layers to the final yarn thickness is described as back- doubling, with the number of fiber layers resulting from the (genuine) yarn twist set and the diameter/circumference of the rotor used. •The fibres are finally pressed into the rotor groove with considerable force due to the high centrifugal acceleration on the rotor wall and on adjacent fibres, and are held in this position up to the twist imparting point. The way in which this fibre sliding phase takes place from striking the rotor wall to organized fibre deposition in the rotor groove has a considerable effect on yarn quality and also spinning stability.
Many parameters affect optimum fibre placement in the rotor groove, and that all parameters affect each other mutually. The most important factors exerting influence in this respect are:  Fibre feed height and direction on the rotor wall  Fibre arrival speed relative to the peripheral speed of the rotor wall  Fibre and rotor wall coefficient of friction  Rotor wall fibre slip angle (inclination angle)  Rotor speed, rotor diameter. Fibre placement in the rotor groove
TWIST INSERTION IN ROTOR SPINNING •The twisting process in rotor spinning is different from that in ring spinning system. In ring spinning, fibres are translated from a thin ribbon to a roughly circular shape. To spindle Yarn Delivery rollers •Fibres are gripped at the nip of the front rollers as well as in the twisted structure. The outermost fibres are strained in tension and, unless there is excessive yarn tension, the core is subjected to compression. As the fibres on the outside edges are under the greatest stress, they are pulled towards the centre, causing a radial migration in the yarn. The fibres in the central region are subjected to much lower levels of stress and some may be slack, allowing migration outward towards the edges. As a result, the fibres depart from a purely helical conformation to give an interlocking structure.
•In order to begin spinning, one end of an existing yarn (Y), is introduced into the rotor through the yarn withdrawal tube. The free end of the seed yarn is thrown to the peripheral surface of the rotor by the centrifugal force produced. The high speed of the rotor causes the yarn end to rotate in the same direction as the rotor itself. When the rotating end of the yarn touches the fibres assembled in the rotor groove, it acts like a crank and twists the yarn section following the draw-off nozzle outside the rotor. In this way, twist is produced primarily outside the rotor, between the draw-off nozzle and the subsequent yarn deflection or yarn nip point. •In rotor spinning, the fibre collecting surface, (rotor groove), is v-shaped and therefore fibres are usually translated from a triangular to a circular shape. The fibre assembly, being formed in the rotor groove. Direction of Yarn Rotation Draw-off Nozzle Yarn in Rotor Groove Yarn Rolling Movement on Nozzle Yarn P O
TWIST STRUCTURE •The rotor groove enter as a thin stream of fibres and it takes many layers to make up sufficient linear density to make a yarn. there are many doublings, which tend to even out any short-term irregularities in the yarn. Thus, rotor yarns tend to be more even. •On the other hand, these doublings have an adverse influence on the twist structure of the yarn. The first few layers make the core of the yarn and the other layers twist without any firm link being established between the layers. Due to the lack of interlinking, these layers form concentric sleeves. These sleeves easily slip when the yarn is subjected to a tensile load. •Apart from the layers, which form the body of the yarn, the fibres caught by the rotating yarn arm also form a layer. •These fibres are irregularly distributed throughout the length of the yarn and wrapped around the yarn with a non-uniform winding angle and hardness. Thus, the twist in the core is not the same as in the outer layers.
Rotor spinning working principle