End-break in air-end spinning is one of the common phenomena in air-end spinning production. End-breakage will have a certain impact on the output, quality and manufacturing rate of cotton yarn. The higher the end-breakage rate, the greater the harm. The increase in the end-break rate and the number of joints will inevitably result in thick joints and screw heads, thus affecting the quality of the yarn. At the same time, end-breaks are a concrete reflection of the level of management in the spinning production process. Therefore, minimizing the occurrence of broken ends during production is an important way to achieve high productivity, efficiency, and high quality.
Reasons for end breakage in air-jet spinning
The main cause of end-breakage in open-end spinning is caused by the strong weak loops in the yarn during the fiber cohesion and merging process. The rotor speed of the air-jet spinning machine is very high, the centrifugal force is large, and the negative pressure in the rotor is very high, so the fibers in the rotor experience large air resistance during the twisting process. When the fiber bundle is still in the sliver stage and is peeled off from the cohesion tank, its ability to resist flexing is very poor because it has less twist. If the strength of the fiber bundle is less than the tension formed by the friction resistance, air resistance and centrifugal force in the rotor, the yarn will break.
Practice has proved that the majority of rotor yarn breakage occurs in the sliver section between the peeling point and the false twist end. Specifically, it can be divided into two types: decapitation before twisting and decapitation after twisting. The main reason for end breakage before twisting is that when the fibers are transported to the cohesion tank, the fiber arrangement is damaged by different forces during the cohesion and merging process, resulting in advanced or lagging movement. The focus is on the sliver. Impurities, dust, dead cotton bundles, and unstable operation and negative pressure. End breakage after twisting is mainly caused by the large loss of twist and changes in the volume and twist of the yarn during the twist transfer process.
Analysis of the causes of end-breakage caused by air-jet spinning
01 Causes of temperature and humidity
If the relative temperature and humidity are too high, the cotton sliver will be difficult to loosen and remove impurities, resulting in end breakage; if the relative humidity is too low, the fibers will have poor fluffy cohesion, resulting in end breakage. The moisture regain of the cotton sliver is controlled between 6.1% and 7.2%, which is beneficial to the opening and fiber transfer of the cotton sliver by the opening roller, and is beneficial to the twisting of the spinning rotor. The high moisture regain increases the difficulty of carding and transferring cotton fibers by the carding roller. It is easy to hang flowers on the tooth ends of the carding roller to form fiber bundles and cause breakage.
02 Reasons for operation
Flying flowers attached to the sliver, excessive accumulation of dust in the rotor condensation groove, false twisting of the sliver, etc. are all factors that cause end breakage. The working status of the rotor condensing tank has an important impact on the evenness level and end breakage of the yarn. If there are many impurities and small dust clusters in the condensing tank, the distribution of fibers entering the condensing tank will be uneven. It also affects the transmission of twist, so the strength of the sliver with less cotton fiber distribution will also be lower when peeled off. Another situation is that the frosted surface in the condensation tank peels off due to extended use or improper use of the spinning rotor, making it difficult to peel off the fibers and causing end breakage. Empty cans, bumped tops and other reasons will also cause a certain amount of broken ends.
03 Equipment reasons
The tooth ring of the combing roller should be smooth and sharp, so as to facilitate the combing, removal and transfer of fibers. However, the opening roller will inevitably produce inverted teeth and curved teeth during the production process. These curved teeth are very detrimental to the transfer of cotton fibers, and will gather cotton fibers to form cotton bundles, causing yarn breakage. The false twisting disc plays a false twisting role in the spinning and twisting process. It is required that the arc surface and hole in contact between the false twisting disc and the yarn sliver should be very smooth to facilitate the formation and transmission of twist and reduce yarn interference. The friction resistance of the strip reduces the occurrence of breakage.
04 Process reasons
Unreasonable design and configuration of rotor speed and yarn take-up speed will cause end breakage. Too much or too little pressure on the rubber roller and improper selection of tension coefficient will cause end breakage. The twist is too small, resulting in insufficient cohesion between fibers, which is also a major factor causing breakage.
05 Raw material factors
The raw materials used in open-end spinning are mostly low-grade cotton and some reused cotton. These raw materials contain more impurities and dust, and have a higher short staple rate. Moreover, the main length of the fiber is short and the strength is low, which increases the spinning time. The difficulty also increases the probability of yarn breakage. Therefore, if other conditions remain unchanged, increasing the cotton level can significantly reduce the occurrence of yarn breakage.
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