Spinning principle, structural characteristics and quality control of Siro Spinning

Siro fabrics have soft handle, luster, clear lines, good air permeability and drape, good dyeing performance and high heat conduction. They are suitable for making wool shirts, men's and women's spring and summer fashion and suit fabrics. Siro yarn has been widely applied in cotton spinning industry for its unique yarn quality. However, the quality control of siro spinning is different from that of ring spinning. Some new problems in the spinning process need to be carefully analyzed and summarized to gradually improve the quality of this special spinning.
1. Principle of Siro Spinning
After a slight modification on the ordinary ring spinning frame, two parallel rovings are fed into the drafting area and output by the front roller to form a triangle area, which is combined and twisted to winding the yarn tube. The rotation of spindle and traveller adds twist to the yarn, and the twist is transmitted from bottom to top to the front roller grip. The two single yarn twists and downward strands above the gathering point twist the same direction, but the twist is much less.
2, the structural characteristics of Siro yarn
Siro yarn is twisted by two strands of low twist yarn. Its structure is different from that of single yarn and ply yarn.
(1) the two strand bundles of Siro yarns are twisted together in a helical manner, distinct from each other and intermingled with each other. When it is twisted back to the end of the twist, it can be clearly seen that there are two fibers in the yarn. This state is different from the single yarn and the strands.
(2) The twisting direction of Siro yarn is the same as that of yarn. The angle between surface fiber and yarn axis is the largest, while that between fiber and yarn axis is the smallest in ply yarn. The twist direction of single yarn and ply yarn is usually opposite.
(3) From the cross-section of the yarn, the single yarn is approximately circular, the twist on the two strands of Siro yarn is very small, the fibers are easy to redistribute, and the cross-section is also approximately circular when twisting. The twist of single yarn in ply yarn is bigger and the fibers are compact. After twisting, the fibers are difficult to move sufficiently and have two distribution centers. Compared with strands, the fabric of siro spinning is smooth and soft.
3. Analysis of factors affecting yarn quality
The wear resistance of Siro yarn is better than that of single yarn and ply yarn. The hairiness of Siro yarn is twice less than that of single yarn. The details of Siro yarn are more. The other performance indexes are close to or slightly lower than that of single yarn or ply yarn. The reason for these results lies in the difference of yarn forming mechanism.
3.1  yarn strength
The strength of Siro yarn is obviously superior to that of the same kind of double-spinning yarn fed by ordinary double-roving without spacing, but similar to that of real-ply yarn. There are three main factors in siro spinning special process analysis.
(1) For Siro yarns, the intertwining of yarns effectively binds the surface fibers to the yarn body, and the surface fibers also contribute to the yarn strength. Therefore, the strength of Siro yarns is less affected by the transfer of fibers, and the strength is higher than that of ordinary yarns with the same yarn density.
(2) Because of twist on Siro spinning single yarn, the fibers transfer from inner layer to outer layer and from outer layer to inner layer before twisting at convergence point. Only half of the ordinary single yarn, the tilt angle between fibers and yarn axis is small. When the yarn is stretched, the utilization ratio of fiber strength is relatively high.
(3) Compared with ordinary ply yarn, Siro yarn passes through less than two processes-ldquo; wear and tear in the three processes is smaller and strength loss is less.
Although Siro yarn has unique advantages in strength, people's demands on it are endless. In order to improve the strength of Siro yarn, besides choosing bigger twist coefficient and using longer and better fibre material, it can also be realized by feeding finer roving and choosing smaller draft multiple of back zone.
(1) feeding on finer roving. Siro yarn does not acquire strength through twisting and fiber transfer as ring spinning yarn does, but the tightness obtained through intertwining of single yarns is influenced by the tightness of single yarn output from front roller nippers. When the finer roving is fed, the drafting multiple is smaller, which makes the roving diffuse less in the drafting process. Therefore, narrower fibers can be produced, which makes the fibers easier to be twisted into the yarn between the front roller nipper and the traveler ring. Of course, the selection of roving quantity needs to be matched with appropriate roving twist coefficient to ensure the quality of semi-finished products and the smooth spinning process.
(2) use smaller draft drafting times. The yarn strength irregularity usually decreases with the decrease of drafting ratio, as is the case for ordinary yarns and Siro yarns. Roving tends to diffuse in drafting process. When the roving quantity and twist coefficient are fixed, the sliver will be tighter when the lower drafting ratio is adopted. Because of the effect of tension on the single yarn above the convergence point in the process of interwinding, the tighter sliver will be able to withstand smaller local tension. Reduce strength irregularity.
3.2  Mao Yu
The factors affecting the surface hairiness of Siro yarn are: yarn spacing, twist and spindle speed. In addition to low twist and high spindle speed, increasing yarn spacing will reduce yarn hairiness. Compared with ordinary yarns, the hairiness of Siro yarns increases with the increase of twist coefficient in a specific twist range, which varies with the type of fibers and spindle speed. Outside this range, the twist increases and the hairiness decreases.
The influence of spindle speed on hairiness is determined by the size of three factors: centrifugal force in winding process, shearing effect of traveller on yarn and spinning tension.
(1) centrifugal force. It is directly proportional to the square of spindle speed, and the fiber will be thrown out of the yarn surface and the centrifugal force will increase.The yarn hairiness increased.
(2) shear action of travellers. When the spindle speed is high, the yarn surface fibers can be ground or the protruding end of the fibers can be cut off, which is related to the shape and cross section of the traveller. When the shearing force of the traveller is strong, the yarn hairiness increases.
(3) spinning tension is directly proportional to the square of spindle speed, and yarn hairiness increases when spinning tension is large. Generally speaking, for cotton yarn, hairiness increases with the increase of spindle speed when spindle speed is less than 10 200 r/min.
4. Easy problems in spinning process
4.  1  siro spinning preventive measures for yarn defects
(1) To ensure that the card clothing is in good condition and without holes, to prevent the formation of slubs, resulting in yarn details or running single yarn.
(2) The machine platform should be kept clean, especially the spinning passage parts such as guide rod, bell mouth, roller, cot and apron surface should be inspected at all times, carding and drawing coiler should be cleaned regularly to prevent hanging flowers, and the suction of each machine platform should be kept normal.
(3) prevent human caused wool tops. From the observation in front of the roving frame, it is found that every hairy spot of the feed sliver will produce a yarn defect. This kind of yarn defect is often caused by the body touching the sliver during the operation of the lathe blocker, and the sliver will be haired by the top sliver.
(4) reduce the yarn defects. The joint of the spun yarn is short and thick, and the joint of roving and drawing is easy to produce long thick or long details. Reducing the breakage rate and reducing the rough joint is the key to reduce the yarn defects.
4.2 measures to prevent running yarn from Siro yarn
(1) taking into account the quality index and spinnability of the finished yarn, choose the appropriate distance between the mouths.
(2) optimize the pre spinning process. Ensure evenness of roving yarn, increase roving twist coefficient appropriately, and select proper roving quantity.
(3) Reduce the spinning speed properly, select the travelling ring with low gravity center and light size, stabilize the spinning tension and reduce broken ends.
(4) Appropriately adjust the braking amount of the medium pressure spring in the hanging ingot to ensure the flexible unwinding of the roving, prevent the unexpected elongation of the roving, or even break the roving, resulting in single yarn running.
(5) appropriately increase yarn twist factor. Experiments show that when the twist coefficient is about 420, the breaking strength of the yarn reaches the maximum value, and decreases with the increase of the twist coefficient. The elongation at break increases with the increase of twist factor.
(6) roving length should be unified and roving group should be roving.
(7) Spinning block lathe workers reduce the stand, frequent inspection, found that single roving yarn spinning, must pick out the tube yarn, another insert tube spinning, running single yarn tube to be handled by a specialist.
(8) the last tube must be checked manually before spinning to the winding process.
(9) the upper and the front cots are suitable for the current flush, reducing the fiber loss, improving the evenness and reducing the broken ends.
4.3 control of siro spinning bellows
Siro spinning feeds two rovings with a certain distance. The length of single yarn at the top of the convergence point is longer and the number of slip fibers increases, which results in the increase of weaknesses, the decrease of yarn strength, the increase of broken ends, the increase of running single yarn and the increase of bellows cotton. In addition to reducing yarn details and broken ends, the control of cotton volume in bellows should also control the air flow of fans, the angle of cotton suction tubes and the distance between cotton suction tubes and rollers.
4.4 adjustment of the lifting and guiding movement of the apron.
In general, when spinning extra-fine count yarn below 6 tex, apron hanging is easy to occur. The reason is that the draft multiple of extra-fine count yarn is large, the speed of middle roller is low, and the speed of lower apron is also low. The second reason is that extra-fine count yarn uses long staple cotton or medium-long chemical fibers with long fibers and high drafting force, which is prone to be induced by fluctuation of drafting force in operation. As a result, the operation of the apron is blocked, and it is difficult to pass through the pliers. When the apron enters the man, the upper hanging occurs between the roller and the lower pin. Siro spun yarn is even lighter than single roving, but the twist coefficient of single roving has exceeded that of ordinary roving. Therefore, the roving strength of siro spinning with two roving is far greater than that of ordinary spinning. Slight changes in draft force are more likely to appear on aprons. Take the jaw gauge to enlarge 0.The resistance of the apron is reduced and easy to pass through the jaw. It solves the problem of lifting the apron.
The yarn guide should not be too large to prevent the bar from running out of the jaw to cause uneven evenness. The width of two roving slivers in siro spinning is up to 5 mm. As long as the guide motion is slightly larger and the position accuracy of the bell mouth is slightly worse, it is easy to run off. So first of all, ensure that the binocular horn on the equipment is aligned with the center position of the cots. The special eccentric wheel for yarn guide can reduce the yarn guide transverse distance and solve the problem of yarn guide deviation.
5, concluding remarks
The use of siro spinning on cotton spinning equipment can improve yarn quality and meet the needs of high-grade fabrics. Because Siro yarn has fewer hairiness, higher strength, good wear resistance and pilling resistance, its structure is more similar to single yarn. Spinning and winding joints are the same as single yarn. It can replace the stock line within a certain range.
However, there are still some problems in the specific production of Siro spinning, such as operation management, process configuration, quality control and so on. We should analyze, test and study them in time and take corresponding technical measures to improve the quality of siro spinning to meet the needs of high-grade fabrics in the market.