Siro textile fabrics feel soft, shiny, have clear lines, good air permeability and drape, good dyeing performance and high heat conductivity. They are suitable for making wool shirts, men’s and women’s spring and summer fashion and suit fabrics and other high-end fabrics. Relying on its unique yarn quality, Siro yarn has been widely used in the cotton spinning industry. However, there are many differences between the quality control of Siro spinning and ordinary ring spinning. Some new problems that arise during the spinning process require us to carefully analyze, constantly summarize, and gradually improve the quality of this special spinning.
01 The principle of siro spinning
After slight modification on the ordinary ring spinning machine, Two parallel rovings are fed into the drafting area and output through the front roller to form a triangle area and converge to a point. They are combined, twisted and wound onto the yarn tube. The rotation of the spindle and the traveler adds twist to the yarn. Pass from bottom up to the front roller grip. The two single yarns above the convergence point have the same twist direction as the strands below, but the twist is less at the top and more at the bottom.
02 Structural characteristics of Siro yarn
Siro yarn is composed of two low-twisted whiskers It is made up of twisted strips, and its structure is somewhat different from that of single yarns and strands.
(1) The two fiber bundles of siro yarn are twisted together in a spiral shape, with distinct layers and not mixing with each other. When it is untwisted until the twist is almost exhausted, it can be clearly seen that there are two undivided fiber bundles in the yarn body. This state is different from both single yarn and strands.
(2) The direction of twisting on the two strands of Siro yarn is consistent with the twist direction of the yarn. The angle between the surface fiber and the yarn axis is the largest, while the strand The angle between the fiber and yarn axes in the thread is minimal, and the twist directions of single yarns and strands are usually opposite.
(3) From the cross-section of the yarn, the single yarn is approximately round. The twist on the two strands of the siro yarn is very small, and the fibers are easy to redistribute. When twisting They are squeezed together and have an approximately circular cross-section. The single yarn in the strand has a large twist and the fibers are dense. After twisting, the fibers are difficult to move fully and have two distribution centers. Compared with stranded fabrics, Siro spinning fabrics are smoother and softer.
03 Analysis of factors affecting yarn quality
The wear resistance of siro yarn is better than Single yarn is also better than ply yarn. The number of hairiness is doubled compared with single yarn. Siro yarn has more details. Other performance indicators are basically close to or slightly lower than single yarn or ply yarn. The reason for these results lies in the yarn forming mechanism. difference.
3.1 Yarn strength
The strength of Siro yarn is obviously better than that of ordinary double rovings fed without spacing. Similar double-spun yarn, but similar in strength to real ply yarn. From the analysis of the special process of Siro spinning, there are mainly three factors.
(1) For Siro yarn, the mutual entanglement of yarns effectively binds the surface fibers to the yarn body, and the surface fibers also contribute to the strength of the yarn, so Siro yarn The strength is slightly affected by fiber transfer, and the strength is higher than ordinary yarn with the same linear density.
(2) Due to the twist on the single yarn of Siro spinning, the fiber changes from the inner layer to the outer layer and from the outer layer to the inner layer before the single yarn is twisted at the convergence point. The transfer on the layer is only half of that of ordinary single yarn. The inclination angle between the fiber and the yarn axis is small. When the yarn is stretched, the fiber strength utilization rate is relatively high.
(3) Compared with ordinary strands, Siro yarn undergoes 2 or 3 less processes, resulting in less wear and less strength loss.
Although Siro yarn has unique advantages in strength, people’s requirements for it are endless. In order to improve the strength of Siro yarn, in addition to choosing a larger twist coefficient, use a smaller In addition to fiber raw materials with longer lengths, this can also be achieved by feeding finer rovings and selecting a smaller draft ratio in the back area.
(1) Feeding thinner rovings Roving. Siro yarn does not gain strength through twisting and fiber transfer like ring yarn, but the tightness obtained through the mutual entanglement of single yarns is also affected by the tightness of the single yarns output by the front roller nip. Influence. When feeding finer rovings, the required drafting multiple is smaller, so that the rovings spread to a smaller extent during the drafting process. Therefore, narrower fiber slivers can be produced, allowing the fibers to spread between the front roller nip and It is easier for the yarn to be twisted between the travellers. Of course, the selection of the roving quantity needs to be matched with the appropriate roving twist coefficient to ensure the quality of the semi-finished product and the smooth progress of spinning.
(2) Use a smaller draft ratio in the back zone. The unevenness of yarn strength usually decreases as the draft ratio decreases, both for ordinary yarns and siro yarns. There is diffusion in the roving during the drafting process trend, when the roving basis weight and twist coefficient are constant, when a lower draft multiple is used, the slivers will be tighter, and the single yarn slivers above the convergence point will be entangled with each other due to the effect of tension. , only tighter whiskers are likely to withstand smaller local stretching, thus reducing the strength unevenness.
3.2 Hairiness
The factors that affect the surface hairiness of Siro yarn are: roving spacing, twist, and spindle speed. Except for low twist and high spindle speed, increasing the yarn spacing will reduce the yarn hairiness. Compared with ordinary Compared with yarns, the hairiness of Siro yarn increases with the increase of twist coefficient within a specific twist range. This specific twist coefficient range varies with fiber type and spindle speed. Outside this range, The twist increases and the hairiness decreases.
The influence of spindle speed on hairiness is through the centrifugal force affecting the winding process and the influence of the traveler on the yarn.The shearing effect of the thread and the spinning tension affect the hairiness of the yarn.
(1) Centrifugal force. Proportional to the square of the spindle speed, the fiber will be thrown out of the yarn surface, the centrifugal force will increase, and the yarn hairiness will increase.
(2) The shearing effect of the traveler. When the spindle speed is high, it can grind up the fibers on the yarn surface or cut off the protruding fiber tail ends, which is related to the shape and cross-section of the traveler. When the shearing effect of the traveler is strong, yarn hairiness increases.
(3) The spinning tension is proportional to the square of the spindle speed. When the spinning tension is high, yarn hairiness increases. Generally speaking, for cotton yarn, when the spindle speed is lower than 10 200 r/min, the hairiness increases with the increase of the spindle speed.
04 Problems that easily occur in the spinning process
4.1 Siro spinning methods to prevent yarn defects Measures
(1) Ensure that the card clothing of the carding machine is in good condition and has no holes to prevent the formation of slubs, resulting in yarn details or single yarns.
(2) The machine must be kept clean, especially the surfaces of the spinning channel parts such as yarn guide rods, bell mouths, rollers, rubber rollers, and aprons. Carding 2. The draw coiler should be cleaned regularly to prevent damage, and the air suction of each machine should be kept normal.
(3) Prevent tops from being caused by human factors. Observing from the front of the roving machine, we found that every hairy point of the cooked sliver that is fed to people will produce a yarn defect. Such yarn defects are often caused by the operator’s body touching the sliver during operation, and the high sliver fluffing the sliver.
(4) Reduce splice yarn defects. The joints of fine yarns produce short slubs, while the joints of roving and drawn yarns tend to produce long slugs or long details. Reducing the breakage rate of fine yarns and reducing thick splices are the keys to reducing splice yarn defects.
4.2 Measures to prevent siro yarn from running out of single yarns
(1) Taking into account the quality of the finished yarn Indicators and spinnability, choose the appropriate spacing between bell mouths.
(2) Optimize the pre-spinning process. Ensure the evenness of the roving, increase the twist coefficient of the roving appropriately, and select the appropriate roving basis weight.
(3) Reduce the spinning speed appropriately and choose a traveler with a low center of gravity and one size lighter to stabilize the spinning tension and reduce end breakage.
(4) Properly adjust the braking amount of the compression spring in the hanging spindle to ensure flexible unwinding of the roving and prevent the roving from accidentally elongating or even breaking the roving, causing single yarn to run out.
(5) Appropriately increase the yarn twist coefficient. Experiments have shown that when the twist coefficient is about 420, the breaking strength of the yarn reaches the highest value, and as it continues to increase, the breaking strength decreases. The elongation at break increases with the increase of twist coefficient.
(6) The fixed length of roving must be unified, and the fine yarn must be replaced by roving collectively.
(7) The fine yarn stopper reduces the number of viewing surfaces and conducts frequent inspections. If a single roving yarn is found to be spinning, the bobbin must be picked out, and another empty bobbin must be inserted for spinning, and the order will be run. The yarn bobbins are handled by specialized personnel.
(8) The last bobbin after the roving is spun on the spinning frame must be manually inspected before it can go to the winding process.
(9) The upper pin and front rubber roller should be pushed forward appropriately to reduce fiber loss, improve evenness and reduce breakage.
4.3 Control of bellows cotton in Siro spinning
The two rovings fed into Siro spinning have At a certain distance, the length of single yarn strips on the upper side of the convergence point is longer, and the number of slip fibers increases, resulting in increased weaknesses, reduced yarn strength in single yarn segments, increased end breaks, increased single yarn running, and increased bellows cotton. In addition to reducing yarn details and reducing end breaks, controlling the amount of cotton in the bellows also requires controlling the air volume of the fan, the angle of the suction tube, and the distance between the suction tube and the roller.
4.4 Adjustment of lower apron lifting and yarn guide stroke
In general, when spinning extra-fine yarns below 6 tex, apron hanging is easy to occur. The first reason is that the extra-fine yarn has a large draft multiple, the middle roller speed is low, and the lower apron speed is also low. Second, the extra fine yarn uses long-staple cotton or medium-length chemical fiber. The fiber is long and the drafting force is large. It is easy for the apron to be blocked due to fluctuations in the drafting force during operation. It is difficult to pass through the jaws. When the apron enters the Hanging appears between the philtral roller and the lower pin. Although the basis weight of a single roving of Siro spinning is light, the twist coefficient of a single roving exceeds that of ordinary rovings. Therefore, the drafting force of Siro spinning with two rovings is much greater than that of ordinary spinning. A slight change in the drafting force is more likely to cause the rubber ring to hang. The gap between the jaws is enlarged by 0.5 mm to reduce the resistance of the rubber ring passing through the jaws and make it easier to pass, thus solving the problem of hanging the rubber ring.
The yarn guide stroke should not be too large to prevent the slivers from running out of the jaws and causing uneven slivers. The width of the two roving slivers of Siro spinning reaches 5 mm. As long as the yarn guide stroke is slightly larger and the bell mouth position accuracy is worse, deviation will easily occur. Therefore, you must first ensure that the double-eye speakers on the equipment are aligned with the center of the rear rubber roller. Then make a special eccentric wheel for the yarn guide stroke to reduce the yarn guide traverse distance by 2mm, which can solve the problem of yarn guide stroke deviation.
05 Conclusion
Using siro spinning on cotton spinning equipment can improve yarn quality, Can meet the needs of high-end fabrics. Because Siro yarn has less hairiness, higher strength, good wear resistance and pilling resistance, its structure is more similar to single yarn. For spun yarns, the winding joints are the same as for single yarns. It can replace strands within a certain range.
However, there are still problems in operation management, process configuration, quality control and other aspects of Sirotex production. We should analyze, test and study them in a timely manner and take corresponding measures. Technical measures have improved the quality of Siro spinning to meet the needs of high-end fabrics in the market.
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