Modern Yarn Production: Rotor Spinning
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
Cell: +91 9662020909
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
Cell: +91 9662020909
- Rotor spinning has been characterized from the outset by incomparably higher production potential than ring-spinning.
- This potential has been steadily increased by the continuous rise in rotor and winding speeds. Rotor-spun yarns have therefore always been successful where they could be manufactured more cheaply than ring-spun yarns and proved suitable for the range of application in question. Rotor spinning combines two process stages → spinning & → winding in a single machine.
- Open-End Spinning is also known as Rotor Spinning, Free Fibre Spinning & Break Spinning. The principle behind open end spinning is similar to that of a cloth dryer spinning full of sheets. If you could open the door and pull out a sheet, it would spin together as you pulled it out.
- Sliver from the card goes into the rotor, is spun into yarn and comes out, wrapped up on a bobbin, all ready to go to the next step. There is no roving stage or re-packaging on an auto-coner. This system is much less labour intensive and faster than ring spinning with rotor speeds up to 140,000rpm.
- The Rotor design is the key to the operation of the open-ended spinners. Each type of fibre may require a different rotor design for optimum product quality and processing speed.
- The first open-end machines in the United Kingdom were placed, under great secrecy, by courtaulds into maple mill, Oldham in 1967.
- One disadvantage of open-end spinning is that it is limited to coarser counts, another is the structure of the yarn itself with fibres less in parallel compared to ring spun yarns for example, consequently cloth made from open-end yarn has a 'fuzzier' feel and poorer wear resistance.
- Rotor spinning is more cost-effective than ring spinning in the manufacture of yarns with coarse to medium counts. In recent years, there have been many attempts to develop rotor spinning further into the area of fine counts, i.e.yarn counts finer than 40s cotton count
- The global demand for spun fibre is huge. Converting raw fibre to yarn is a complicated process. Many manufacturers compete to provide the spinning machines that are essential to meeting the demand by delivering increases in spinning productivity and additional improvements in yarn quality.
- Over the past three centuries spinning technology has been continuously improved through thousands of minor innovations, and occasional major advances that have collectively increased the quality and lowered the cost of producing yarn dramatically.
- The industrial revolution which began in the eighteenth century produced many important innovations in the textile industry. Those related to the spinning of fibers are listed below:-
- 1764: James Hargreaves invented the ‘spinning jenny’.
- 1769: Richard Arkwright invented the water-powered spinning frame.
- 1779: Samuel Crompton combined the two systems in his ‘spinning mule’.
- 1828: Thorpe, Jenk and Mason created the prototype ‘ring frame’.
- 1937: Berthelsen developed a relatively perfect open end.
- 1965: Czech KS200 rotor spinning machine was introduced at 30000 rotor rpm.
- 1967: Improved BD200 with G5/1 Rieter were presented with first mill of OE coming under production
- 1971–1975: There was a considerable increase in machine manufacturer and newer and improved version of machines were launched with increased speed at 100000 rpm.
- 1975: Also witnessed first automated machine from Suessen equipped with Spincat and Cleancat which opened up the industrial rotor spinning breakthrough.
- 1977: Witnessed Schlafhorst with Autocoro machines which made a mark in open end market.
|Passage of material in different spinning systems|
The rotor spinning machine is unlike any other machine in the short staple spinning mill in the range of tasks it has to perform, namely all the basic operations:
- Sliver feed: A card or drawframe sliver is fed through a sliver guide via a feed roller and feed table to a rapidly rotating opening roller.
- 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.
- Fiber transport to the rotor: Centrifugal forces and a vacuum in the rotor housing cause 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.
- Fiber 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: When a spun yarn end emerges from the draw-off nozzle into the rotor groove, it receives twist from the rotation of the rotor outside the nozzle, which then continues in the yarn into the interior of the rotor. The yarn end rotates around its axis and continuously twists-in the fibers deposited in the rotor groove, assisted by the nozzle, which acts as a twist retaining element.
- Yarn take-off, winding: The yarn formed in the rotor is continuously taken off by the delivery shaft and the pressure roller through the nozzle and the draw-off tube and wound onto a cross-wound package. Between takeoff and package, several sensors control yarn movement as well as the quality of the yarn and initiate yarn clearing if any pre-selected values are exceeded.
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- The general principle of open end rotor spinning is shown in Fig.
|Principle of open end rotor spinning|
- The input sliver is first opened and drafted by the opening roller. The fibres are transported via a tube to the rotor where the fibre strand is subjected to twist insertion.
- After twisting, the output yarn is then wound into ‘cheese’or ‘cone’ packages of the required size. The input sliver can be a carded or drawn sliver. Generally a drawn sliver is used. The sliver is pulled through a condenser by a feed roller, operating in conjunction with a spring-loaded feed pedal. The nip point between feed roller and feed pedal determines the position of fibre bundles moving into the opening roller.
- A sliver may have more than 20,000 fibres in its cross-section. This means that a yarn of 100 fibres in a cross-section will require a total draft of 200.
- This amount of draft is substantially higher than that in ring spinning. Drafting in rotor spinning is accomplished first using an opening roller (mechanical draft) which opens the input sliver, followed by an air stream (air draft).
- The rapidly rotating opening roller combs out the leading ends of fibres. The separated trash is collected in a central chamber from where it can be removed. The fibre from the opening roller is sucked through a transport tube and deposited into the inner grooved surface of the rotor.
- The transport tube is tapered so as to create an accelerating air stream, which straightens the fibres. These two operations produce an amount of draft that is high enough to reduce the 20,000 fibres entering the opening roll down to few fibres (2–10 fibres) at the exit of the transport tube.
- Consolidation in rotor spinning is achieved by mechanical twisting. The torque generating the twist in the yarn is applied by the rotation of the rotor.
- The amount of twist (turns per metre) is determined by the ratio between the rotor speed (rpm) and the take-up speed (metres/min). Every turn of the rotor produces a turn of twist. The winding operation in the rotor spinning is completely separate from the drafting and the twisting operations.
FIBER PROCESSING IN ROTOR SPINNING
- The extent of the opening action imposed by the combing roll will depend on the fibre length. As the fibre length increases, the force acting on the fibre beard increases significantly.
- This can result in fibre damage and wastage. Careful control of fibre length is therefore required for rotor spinning. As the fibre flows around the combing roll, friction between the fibres and the metal chamber results in a lower fibre speed than the surface speed of the opening roll.
- Alternatively, an external pump can be used as is the case for most modern machines. Another approach to minimize fibre disorientation in the air duct is by designing it in a shape that is tapered towards the rotor to allow acceleration of the fibres as they approach the rotor inside surface. This action may also straighten the trailing fibre hooks.
- As successive layers of fibres are laid into the inside surface of the rotor, a doubling action occurs. This action tends to even out minor irregularities in the yarn.
- This doubling action contributes significantly to the low irregularity and greater uniformity of rotor spun yarn. The elimination of the roving process also contributes greatly to the uniform quality of rotor yarn. These fibres have a free end that wraps itself around the yarn periphery.
- This is a characteristic that is peculiar to rotor spun yarns. These fibres are commonly called ‘fibre belts’ or ‘wrapper fibres’ The proportion of wrapper fibres is often estimated using the ratio between the staple fibre length and the rotor circumference. Other fibre attributes that may contribute to wrapper fibres within a yarn include fibre stiffness and fineness. Stiffer and coarser fibres are more likely to become wrapper fibres.
- The feed roller and feed plate
- A saw-tooth or pin-covered roller called an opening roller
- A tapered tube termed the transport channel
- A shallow cup called a rotor (a groove is cut into the internal peripheral surface, termed the rotor groove)
- A flanged tube (called the doffing tube) which faces the rotor base, coaxial to the rotor spindle
- A pair of delivery rollers that feed the spun yarn to the winding unit.
|Parts of rotor|
DIFFERENT DESIGNS OF NEVEL:-
- 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.
- Open end yarns produce different characteristics in the end product. These yarns may be used to advantage in fabrics where uniformity and a smoother surface are of prime importance.
- Open end yarns are used in pile fabrics, apparel, household, industrial and technical applications. Uses include heavyweight satin and poplins, corduroy, velveteen, rainwear, denims, drills, sheets, pillow cases, bed spreads, printed fabrics, curtains, window blinds, upholstery, cleaning cloths, dress goods, underwear, rugs, carpets, blankets, terry towels and diapers.