Abstract
The causes of rotor yarn defects are analyzed from the aspects of cotton distribution, workshop temperature and humidity, operation, key components of equipment and technology; production should be based on different The spinning varieties should be comprehensively considered and corresponding technical measures should be taken to reduce the occurrence of scattered defects such as slubs, slubs, hairiness, and evenness in the rotor yarn, and improve the quality of the yarn.
01 The impact of raw cotton on yarn quality
The quality of cotton plays a decisive role in yarn quality. When selecting raw materials, in addition to considering the user’s special requirements for the product, yarn quality and production efficiency must also be considered. Comparison of quality indicators of yarns with different cotton blends
See Table 1.
With different cotton blends, the yarn quality is obviously different. Our company’s rotor spinning machine mainly produces medium and coarse yarns, and the cotton content is composed of low-grade raw cotton and reused cotton. Low-grade raw cotton contains high impurities and poor maturity, which puts forward special requirements for blowroom and carding processes. Reused cotton has a greater impact on the strength of the finished yarn. Among them, small impurities and defects in reused cotton have a greater impact on the quality of yarn and cloth. In the blowroom and carding processes, coarse impurities are easier to combine with cotton fibers because they are heavier than cotton fibers. The fibers are separated and eliminated. Small impurities, especially defects with fibers, such as soft seed skin, stiff cotton, fibrous seed scraps, neps, and yellow roots, are difficult to remove in blowroom cotton. Residual impurities and defects are wrapped around or attached to the yarn sliver, which worsens the evenness, increases breakage, and increases the number of neps and impurities in the cotton yarn, thereby affecting the appearance quality of the finished yarn. Therefore, it is very important to understand the relationship between yarn quality and raw cotton properties. According to the quality requirements of the product, the proportion of recycled cotton, reused cotton and raw cotton should be reasonably selected to achieve the requirements of reducing product cost and improving product quality.
02 Effect of temperature and humidity on yarn quality
Production practice It shows that the stability of temperature and humidity in the rotor spinning workshop has a great influence on rotor spinning defects. If the temperature and humidity in the rotor spinning workshop are unstable, it will cause the spinning condition to be good and bad, end-breaks to be high and low, rollers to be entangled, and yarn defects to be high and low. When the temperature in the workshop is high and the relative humidity is high, the roller winding, the licker-in roller and the rotor embedment are very serious. If this continues, the licker-in roller will be seriously damaged, and the saw tooth working surface of the opening roller will appear wear marks, grooves, and missing teeth. and bent teeth, etc., so that the fibers on the needle teeth of the opening roller cannot be transferred smoothly, resulting in fiber hanging and winding, which seriously affects the carding degree of the fed sliver, and even produces a large amount of whitening, resulting in long thick places and short places in the yarn. Thickness increases suddenly. In order to stabilize the temperature and humidity in the workshop and stabilize the yarn quality, we have taken the following measures:
(1) A set of special air-conditioning equipment has been installed in the rotor spinning process;
(2) The doors and windows of the rotor spinning workshop should be sealed as much as possible to reduce the entry of outside airflow and stabilize the temperature and humidity inside the workshop;
(3) In summer, the rotor spinning process The dust return air is discharged to the outside. In winter, 80% of the dust return air in the rotor spinning process is reused to stabilize the temperature and humidity in the workshop.
The impact of operation on yarn quality
Yarn defects caused by improper operation mainly include slub yarn and yarn containing trash. . Thick yarns are generally divided into two categories: untwisted and twisted. Untwisted yarns generally have flying flower attachment bamboos, while twisted thick yarns are divided into two types: regular and irregular. It is mainly formed during the twisting process of cotton fibers.
03 Untwisted thick parts (floating thick parts)
None Twisted slubs are produced when the yarn leaves the spinning device after it is spun. It is caused by flying flowers high in the air in the workshop or during cleaning and then falls on the yarn. This type of defect is small in number and has little impact on the quality of the yarn. big.
04 Twisted thick places
For regular thick places , the distance between thick places is exactly the circumference of the condensation groove of the spinning rotor, and the length and shape of the thick places are basically the same. It is caused by the following reasons: there is a large amount of dust or impurities in the condensation groove; there is a crack at the mouth end of the spinning rotor Or burrs, the cotton fibers transferred from the cotton conveying channel will cause burrs at the mouth of the spinning rotor. When the burrs enter the spinning rotor and are twisted in the yarn, thick spots will be formed. Irregular thick spots are caused by hanging in the carding channel, hanging in the licker-in, or poor lathe joints.
05 Trash yarn
Trash on the opening roller There is a cleaning device in the area, which should be cleaned regularly or irregularly as required, otherwise there will be more and more impurities. When the impurities reach a certain height, they will be sucked into the opening roller and enter the spinning rotor to form impurities. Or slub yarn.
06 Effect of equipment status on yarn quality
Spinning rotor
The spinning rotor is one of the important components of the rotor spinning machine. Its quality directly affects the level of yarn production. In order to optimize the spinning rotor, aluminum spinning rotors and The steel spinning rotor was tested on the C 36 tex variety. The results are shown in Table 2.
As can be seen from Table 2, the various spinning indicators of the steel spinning rotor are better than those of the aluminum spinning rotor. Rotor material: Rotor quality: Steel rotor: Evenness CV/% 16. O 15. O Hairiness index/clrl 7.06 6’26 Strength/eN·tex” 10.3 12.4 Note: Hairiness index refers to the sum of the total length of all hairiness within the 1 em detection length of the yarn.
Twist-resistant discs
At present, the twist-resistant discs include smooth, four-slot, eight-slot and spiral type. Effectively prevent yarn breakage. Use suitable twist-stop discs during production.Whether it is smooth or not is related to the smoothness of spinning and the quality of the yarn. It should be selected according to the requirements of raw materials and yarn quality during production. When our company produces C 58.3 tex weakly twisted yarn, we initially use smooth twist-resistance discs, which results in a large amount of hairiness, many broken ends, and difficult spinning. After switching to the spiral twist-stop disc, the yarn is smooth, even, and has less breakages. The spinning quality of different twist-stop discs is shown in Table 3.
Opening roller
The rack of the opening roller should be smooth and Sharp, which is conducive to carding, removing impurities and transferring fibers. Our company has always used randomly configured Graf OB20 card clothing, which has good sharpness and good carding effect. However, due to the influence of temperature, humidity and raw materials during the spinning process, the fibers are wrapped around the feed roller and squeeze the entrance of the opening roller cavity, causing the opening roller and the opening roller cavity to rub against each other, damaging the lick-in roller and the cavity. This causes the licker-in to produce inverted teeth and curved teeth, which affects fiber transfer, and will gather cotton fibers to form cotton bundles, resulting in end breakage or slub yarn formation.
07 Effect of process conditions on yarn quality
Spinning rotor The angle of the condensation groove of the spinning rotor directly affects the bulkiness, strength and spinning end breakage of the yarn. For the c 58.3 tex special spinning variety, a steel spinning rotor with a diameter of 48 mm is used, and condensation grooves at different angles are used. The spinning conditions of code 03 (32.) and code 05 (500) are shown in Table 4.
It can be seen from Table 4: The yarn strength and evenness of the spinning rotor code 03 (32) are better, and the thick places and neps are better. Less, that is, the spinning quality index of the rotor coded 03(50) is better than that of the rotor coded 05(32). If the angle of the rotor condensation groove is small, larger impurities in the cotton sliver may be embedded in it to form yarn defects. Therefore, for raw cotton with different properties, comprehensive considerations should be taken when selecting the angle of the rotor condensation groove.
Opening roller speed
The main function of the opening roller is When carding and removing impurities from the cotton layer, the speed of the carding roller is too fast, which may not significantly improve the carding degree, and can easily damage the fibers and increase waste. The yarn quality of c 58.3 tex special spinning yarn varieties at different opening roller speeds is shown in Table 5.
It can be seen from Table 5 that when the speed of the opening roller is 8000 r/min, the rotor yarn strength, evenness CV and thick place indicators are relatively low. good. </p
