Open-End Spinning PDF

Open-end or Rotor Spinning History of Open-End/Rotor spinning Rotor Spinning is a more recent method of yarn formation compared to Ring Spinning. There are three distinctive features of rotor spinning compared with ring spinning: (i) Twists are introduced without a spindle (without package rotation...

Open-end or Rotor Spinning History of Open-End/Rotor spinning Rotor Spinning is a more recent method of yarn formation compared to Ring Spinning. There are three distinctive features of rotor spinning compared with ring spinning: (i) Twists are introduced without a spindle (without package rotation) but with the help of a rotor. (ii) A carded or carded and drafted sliver is fed directly to the machine; there is no combing and roving operations; (iii) The yarn is wound directly onto a package. The package diameter is less restricted and thus bigger and can hold much more yarn. This method of spinning was widely adopted by the denim industry in the 1970s due to its efficiency (low energy & shorter route) and cost- effectiveness (high production speed). Working Principles of Rotor/O-E Spinning Sliver is fed into the machine and combed and individualized by the opening roller. The fibers are then deposited into the rotor where air current and centrifugal force deposits them along the groove of the rotor where they are evenly distributed. The fibres are twisted together by the spinning action of the rotor, and the yarn is continuously drawn from the center of the rotor. The resultant yarn is then cleared of any defects and wound onto a package.  Show different key aspects of the machine X-check?? Yarn Package Rotor-spun Yarn Sliver Opening Roller Rotor Yarn Clearing Device Working Principles of Rotor/O-E Spinning The working principle of open-end spinning is analogous to that of a domestic washing machine full of sheets. If you could open the door and pull out a sheet, it would spin together as you pulled it out. With each rotation of the rotor, a twist is inserted, converting the fibre bundle into a yarn as it is pulled out of the rotor through a navel. Short Video on Rotor Spinning Implications of the 3 Distinctive Features (i) Twists are introduced without a spindle (without package rotation) but with the help of a rotor. What does this imply? Rotor spinning allows for faster rotor speeds up to 160,000 rpm; i.e. faster rate of twist insertion and thus faster delivery speed for similar twist levels of ring- spun yarns. Twist insertion is not limited by spindle or package speed as is the case for ring spinning. Therefore, the production rates of rotor spinning are 6-8 times higher than that of ring spinning and as the machines are fed directly by sliver and yarn is wound onto packages ready for use for fabric manufacture, the yarn is cheaper to produce. Production-related Setting Parameters for Rotor Yarn Fibre Length Natural and man-made fibres up to 60 mm Rotor Speed 35,000-160,000 rpm Yarn Deliver Speed 70-350 m/min Tpm/Tpi 200-1500 / 5-40 Package Weight Up to 6 kg or 270-350 mm diameter o Rotor spun yarns are commonly used for cotton in the medium count (50 Ne, 12 tex) to coarse count (6 Ne, 100 tex) range. o It can also be effectively used for polyester-cotton blends, as well as other short and medium staple systems. o Synthetic staple fibres such as polyester alone cannot be effectively open-end spun due to a dusting of oligomer from the fibres that interfere with the spinning action of the rotor. https://www.slideshare.net/slideshow/rotor-spinning-process/81735802 (ii) A carded or carded & drafted sliver is fed directly to the machine; there is no combing & roving operations; What does this imply? There is no need for roving and combing machines. This makes the process quite cost effective as there are less capital, labour, and energy costs. Less amount of power needed during rotor yarn manufacturing. Energy consumption with productivity is lower in case of rotor yarn production. (iii) The yarn is wound directly onto a package. The package diameter is less restricted and thus bigger and can hold much more yarn. What does this imply? There is no need for a separate yarn winding machine. The operation of winding from spindles to cones is eliminated. Stopping the spinning frame to remove the packages, as on ring spinning machines because the diameter of the bobbin is limited by the diameter of the ring, does not occur in rotor spinning. Thus, the productivity is higher. Winding machine: ring spun yarn from spindles to yarn cones Both of the above add to the cost effectiveness of rotor over ring spinning. Ring bobbins/cops ~ 180-250g each converted into yarn package of 2-5 kg Properties of Rotor Yarn Open-end spinning produces a different type of yarn to ring spinning: Open-end yarns tend to be more uniform, lower in strength, Ring v Rotor Spun Yarn more extensible, bulkier, more abrasion resistant and more absorbent (less compact). Open-end spun yarns are complimentary products to ring- spun yarns. In ring-spun yarns, the fibres have more parallel arrangements of fibres and denser packing. In rotor spun yarns, there are higher numbers of disoriented folded fibres, less packing and the presence of non-load bearing wrappers fibres. Open-end yarns tend to be more uniform than ring-spun yarns. Why? Because of the short-term mass leveling action that occurs inside the rotor. There is more mass regularity as the fibres are deposited at an almost constant feed arte inside the rotor. In ring-spinning, the fibres in the yarn cross-section is dictated by the drafting action of the drafting rollers and fibre friction. These mechanical actions lack precision. So imperfection index is higher in ring-spun than in rotor yarns. Open-end yarns tend to have lower tensile strength than ring- spun yarns. Why? Because of the way the fibres are aligned in the yarn. At the core, the fibres are relatively straight, and are held together in a ‘sheath-core’ structure by twisted and wrapper fibres. Randomly twisted and wrapper fibres do not contribute greatly to the tensile strength of the yarn. Besides, the rotor-spun yarn is more rigid/stiff in terms of bending properties and less hairy. Other Properties of OE Spun Yarns Aesthetic Properties of Rotor Spun Yarn: o Surface rougher than ring spun yarn because of wrapper fibres o Less hairiness than carded ring-spun yarn o Less lustrous than ring-spun yarn Applications of Rotor Spun Yarns Generally, medium to low quality yarns are produced from rotor spinning. The yarns are used for making heavy weight fabrics such as dungaree, denim, chino, towels, blankets, sheets, and curtains. Rotor spun yarns are also used for making socks, t-shirts, shirts, and pants.  Ring vs. Open-end Spinning Ring Spinning Open-end Spinning Carded & Combed yarns (finer & Carded yarns (coarser) softer) Yarns for varied applications Yarns for heavier fabrics such as denim, towels, and poplins Stronger 20% more twisted but still 15-20% weaker, for similar yarn count Suitable for all staple fibers Not suitable for 100% man-made staple fiber spinning  Rotor-spun yarn in Denim (Case-study) The case-study is meant to allow the reader to understand the importance of choosing the right yarn in order to obtain the desired effect in manufacture of denim fabric. When designing jeans from denim fabric, it’s not only the fit and details of the jeans that are designed, the yarn is designed too! Yarn designers work with three characteristics to design the look, feel and fade of the fabric: o the thickness or count of the yarn o the texture or ‘slubs’, and o how twisted it is or level of twist. YARN COUNT FOR DENIM: The yarn used for denim usually has a yarn count between Ne 4 and Ne 20. In denim fabric, both the warp and weft yarns can be made from rotor yarns. However, it is more common for the weft 13/1 yarns to be made from rotor yarns due to their cost-effectiveness and good abrasion resistance. The warp yarns, which are typically more visible and subject to more stress, are often made from ring-spun yarns for their superior strength and appearance. SLUBS IN YARN: Slubbiness is a measurement of the irregularity of the yarn, and affects yarn appearance and texture. These slubs or irregularity in the cotton yarn are ‘desired imperfections’ that give the denim an uneven appearance. Once the yarn has been dyed, woven, and after some wear and/or wash, the slubs present themselves as vertical streaks that are brighter than the rest of the fabric. If denim is slubby, it has a lot of slubs and thus a lot of character. Without slubs, denim from more regular OE-spun warps is flat, and it fades more evenly. This does not make the denim attractive. SLUBS IN YARN: In ring spinning, due to specificities of the roving frame and the drafting system, slubs are ‘naturally’ created. When the denim industry turned to open-end spinning in the 1970s, few saw the uniformity of the rotor yarn as a problem! But when vintage denim or new denim that was designed to look old resurfaced in the 1980s, makers started incorporated methods that create slubs in open-end yarns. The slubs give denim its distinctive character. It’s done electronically with small changes in the speed of the rotor and the velocity of the air stream. The yarns, thus produced, are less regular in diameter than conventionally produced rotor-spun yarns. YARN TWIST: The level of twist affects the absorption level of dyestuff. The higher the level of twist in the yarn, the less dye/indigo it absorbs. Denim made from ring-spun yarn with a high yarn twist fades faster. Another bonus of high yarn twist is that it makes the denim stronger. In open-end spinning, the fibres are not spun in a parallel direction. This means they’re less twisted. The yarn is more open or less compact compared to ring-spun yarn, which makes the dye penetrate deeper into its core. That’s why it’s harder to get high-contrast fades from open-end denim. Other Pros of ring spinning for warps in DENIM Ring spinning enables multi-core yarns where polyesters or other materials provide strength and/or elasticity to the yarn without affecting how it looks and feels on the outside; esp for denim with stretch. The corespun elastic yarns cannot be produced by rotor spinning method. So, ring-spun yarns have made a comeback in recent years, especially with stretch and “authentic” denim, due to their special characteristics and texture.  End of Lecture on Open-End/Rotor Spinning Spinning Machine Parameters for change of Yarn count and Twist This part is not examinable In Ring spinning, machine and material parameters play a crucial role in controlling the yarn count: 1.Drafting System: The draft ratio, which is the ratio of the surface speed of the front roller to the back roller, determines how much the roving is stretched. Higher draft ratios produce finer yarns (higher yarn count) and vice versa. 2. Roving count: The thickness of the roving fed into the ring frame also impacts the final Ring cop ~ 180-250g yarn count. Finer rovings are used to produce finer yarns. Roving Hank =1.5 Ne Yarn Count = Roving Hank x Ring Draft = 1.5 x 25 Ring Draft = 25 = 37.5 ≈ 38 (Ne) Twist in Ring Spinning: The ratio of the spindle speed to that of the front roller delivery speed affects the twist insertion rate. (machine parameters) Higher spindle speeds at constant front roller delivery speed produce yarns of higher twist levels. Twist (tpm) = [Spindle Speed (rpm)/Front Roller Delivery Speed (m/min)] Spindle speed = 12,500 rpm Front roller delivery speed = 7.5m/min Twist (tpm) = [12,500 rpm/7.5m/min] = 1667tpm = 41tpi In Rotor spinning, machine and material parameters influence the yarn count: 1. Feed Roller Surface Speed: Higher the feed roller speeds generally produce coarser yarns due to more materials being fed into the groove of the rotor. 2. Feed Sliver Count: The linear density and uniformity of the feed sliver directly impact the final yarn count. Finer and more uniform slivers are used to produce finer yarns. 3. Yarn Delivery Speed: as YDS increases, finer the yarn gets Feed Sliver Count = 4000tex Yarn Count = [FRS Speed x Feed Sliver Count/ YD speed] Feed Roller Surface Speed = 0.4m/min Yarn Delivery Speed = 50m/min Yarn count = [0.4 x 4000/50] = 32 tex or 18 Ne Twist in Rotor Spinning: The twist is determined by the ratio of the rotor speed to the yarn delivery speed. (machine parameters) Higher rotor speeds at constant yarn delivery speed produce yarns of higher twist levels. Twist (tpm) = [Rotor Speed (rpm)/Yarn Delivery Speed (m/min)] Rotor speed = 40,000 rpm Front roller delivery speed = 50m/min Twist (tpm) = [40,000 rpm/50m/min] = 800tpm = 20tpi End of Lecture