From the different forms of decapitation: general decapitation, repeated decapitation, partial decapitation, large-scale decapitation analysis operation, equipment, process, temperature and humidity, raw materials, etc., analyze the reasons and take corresponding measures to effectively reduce the decapitation. head.
End spinning is one of the common phenomena in air spinning production. After the end breaks, it will have a certain impact on the output, quality and production rate of the cotton yarn. The higher the end breaks, the greater the harm. Increasing the breakage rate and the number of splices will inevitably cause the thickness of the splice and the screw head, which will affect the yarn quality. At the same time, the breakage is a specific embodiment of the management level in the spinning production process. Therefore, the occurrence of decapitation should be minimized in production, which is an important way to achieve high yield, high efficiency and high quality.
01
Causes of jet spinning breaks
The main reason for the breakage of air-jet spinning is caused by the weak loop of the fiber formed during the process of agglomeration and merging. The rotor speed of the rotor is high, the centrifugal force is large, and the negative pressure in the rotor is high. Therefore, the air resistance of the fibers in the rotor during twisting is also large. When the fiber bundle is still peeled off the condensing tank at the sliver stage, it has poor twist resistance at this time because of its low twist. If the strength of the fiber bundle is less than the tension formed by the frictional resistance, air resistance and centrifugal force in the rotor, the sliver will break.
Practice has proved that most of the breaks in the spinning sliver occur in the sliver section between the stripping point and the false twist. It can be divided into two types: break before twisting and break after twisting. The main reason for the break before twisting is that when conveying the fibers to the agglomeration tank, the fiber arrangement was damaged by different forces during the agglomeration and merging process, and caused by leading or lagging motion. The focus is on the sliver. Foreign matter, fine dust, dead cotton tufts as well as unstable operation and negative pressure. The breakage after twisting is mainly the breakage caused by the large loss of twist and the change in the volume and twist of the sliver during twist transfer.
02
Analysis of the causes of end breaks caused by air spinning
▎2.1 Reasons for temperature and humidity
The relative temperature and humidity are too large, the sliver is not easy to loosen and the impurities are not excluded to cause the broken ends; if the relative humidity is too low, the fiber has poor fluffy cohesion and forms broken ends. The moisture regain of the sliver is controlled between 6.1% and 7.2%, which is beneficial to the carding and fiber transfer of the sliver by the carding roller, and is beneficial to the twisting of the spinning cup. The high moisture regain rate increases the difficulty of carding and transferring the cotton fibers of the carding roller, and it is easy to hang flowers on the tooth end of the carding roller to form fiber bundles, resulting in broken ends.
▎2.2 Reason for operation
Flying flowers attached to the sliver, the accumulation of spinning cup condensation grooves and excessive dust, false twisted heads around the flowers, etc. are all factors that cause broken ends. The working state of the spinning cup condensing tank has an important influence on the level of yarn formation and breakage of the yarn. If there are many impurities and small dust particles in the condensing tank, the fiber distribution into the condensing tank is uneven at this time. It also affects the transfer of twist, so the strength of the sliver with less cotton fiber distribution will be lower when peeled. Another situation is that the matte surface in the condensation tank is peeled off due to the extended use or improper use of the spinning cup, which makes it difficult for the fiber to peel off, resulting in broken ends. Empty cans, touching tops, etc. can also cause a certain amount of head breaks.
▎2.3 Equipment reasons
The ring gear of the carding roller should be smooth, sharp and sharp, so as to facilitate the carding, impurity removal and transfer of fibers. However, during the production process of the carding roller, it is unavoidable to produce back teeth and bent teeth. These bent teeth are very unfavorable to the transfer of cotton fibers, and they will gather cotton fibers to form cotton bundles, which will cause the yarn ends to break. The false twisting disk plays a false twisting function during the spinning twisting process. It is required that the arc surface and the hole of the false twisting disk in contact with the sliver be very smooth to facilitate the formation and transmission of the twist and reduce the yarn twist. The frictional resistance of the strip reduces the occurrence of broken ends.
▎2.4 Process reasons
The design of the spinning cup speed and the yarn take-off speed is not reasonable, which will cause end breaks. The pressure of the rubber roller is too large or too small. Improper selection of the tension coefficient will cause head breakage. If the twist is too small, the cohesion between the fibers is insufficient, which is also a major factor that causes breakage.
▎2.5 Raw material factors
The raw materials used in air-jet spinning are mostly low-grade cotton and a part of reused cotton. These materials contain impurities and dust, and have a high lint rate, and the main fiber length is short and the strength is low. The difficulty of the yarn also increases the chance of yarn breakage. Therefore, under the condition that other conditions remain unchanged, increasing the level of cotton distribution can significantly reduce the occurrence of yarn breakage.
03
Control measures of air-jet spinning break
Air-jet spinning breaks are divided into: general breaks, repeated breaks, partial breaks, and large-area breaks.
▎3.1 Control measures for general decapitation
The cause of the general decapitation is accidental. It has little to do with the process, temperature and humidity, and most of them are caused by random factors. Pay particular attention to the control of operating equipment. Operational control measures: pay attention to the quality of local cleaning, yarn flying, unscheduled empty can change, and sliver breaks caused by factors such as sliver defects. Equipment control measures: It is mainly due to occasional factors such as machine vibration that the fiber is condensed and weak when it is condensed. When controlling, pay attention to its contingency, such as the broken ends caused by cotton roller accumulation of flowers.
▎3.2 Repeated decapitation control measures
Repeated decapitation refers to two or more consecutive decapitations of the same single spindle. The impact of this decapitation is the most harmful. The control focuses on process reasons and equipment reasons. When repeated end-breaks in large areas, the operation reasons, temperature and humidity reasons, raw material factors, spinning cup cleaning effects, etc. are considered.
▎ 3.2.1 Control measures for operating reasons
Catch the regular defects in the sliver in time, and the internal cleaning effect of the spinner is required to be good, and there is no accumulation of dust and dust in the carding cavity.
▎3.2.2 Equipment cause control measures
Focus on the timely repair and maintenance of deformation and damage to the cotton board, cotton roller, carding roller, and fiber channel.
▎ 3.2.3 Control measures for raw material factors
After repeated head breaks occur, when the accumulated dust in the spinning cup continues to increase after cleaning, pay attention to the impurities in the raw cotton and adjust the mixing ratio of reused cotton.
▎ 3.2.4 Control measures for process reasons
Too small winding tension is likely to cause repeated head breaks. The negative pressure of the spinning cup remains stable, and the pressure of the rubber roller and the yarn take-off roller is unified. Too small or too large will cause repeated head breaks. The speed of the rotor and the diameter of the rotor must be matched, otherwise the negative pressure will be insufficient and large-scale repeated end breaks will occur.
▎3.3 Control measures for partial decapitation
Local decapitation has increased significantly, and comprehensive factors are considered for different varieties; local machines focus on the control of mechanical and technological factors. Raw material factors: The control of local decapitation of different varieties focuses on raw material factors and reasonable selection of processes. The adjustment of the raw materials should be based on the number of yarns spun. Control of operating reasons: Reasonably grasp the accumulated time of the spinning cups, and clean the air spinning device according to different types.
Partial machine breakage focuses on process control, pay attention to whether the negative pressure of the draw yarn and the negative pressure of the process exhaust are reasonable, the winding tension, the pressure of the top roller, and the speed of the spinning cup meet the process requirements. According to the number of spinning yarns, cotton distribution, equipment operation status, and quality of accessories, a reasonable design of the rotor speed and yarn introduction speed should be selected during production. The yarn number is thinner, and the cotton distribution is relatively good. The important parts such as the spinning cup, carding roller, and false twist head also work well. At this time, you can choose a higher spinning cup speed and the yarn drawing speed. In terms of equipment, attention is paid to maintenance intervals, mechanical conditions and effects.
▎3.4 Control measures for large-scale decapitation
Large area decapitation refers to the decapitation phenomenon of some types and machines. The main reasons for this phenomenon are due to the negative pressure of the process, temperature and humidity and the provision of raw materials.
▎3.4.1 Temperature and humidity control measures
The relative humidity is too high, the fiber is not easy to open, the impurities are difficult to remove, and the fiber agglomerates and fiber bundles are likely to cause breakage. When the relative humidity is too low, the fiber is fluffy and the fiber has poor cohesion. It is easy to cause strong loops during twisting and cause large area breaks. Selection range: summer temperature 32 ℃ ～ 33 ℃, relative humidity 67% ～ 70%; winter temperature 26 ℃ ～ 28 ℃, relative humidity 63% ～ 65%, meanwhile, reasonably control the temperature and humidity of the front spinning, and reduce entanglement in production. Winding phenomenon.
▎3.4.2 Control measures for negative pressure process
Negative pressure is one of the important factors affecting the end break, and it is also an important factor affecting the quality of the yarn. The effect of process negative pressure on large-scale breakage is mainly related to the operation status of the machine exhaust and dust removal unit. In actual production, the miscellaneous box should be cleaned in time to prevent small wind and poor exhaust.
▎3.4.3 Control measures for raw material factors
Under the condition that other conditions remain unchanged, increasing the level of cotton can obviously reduce the occurrence of yarn breakage.
▎ 3.4.5 Control measures for process reasons
The cotton grabbing machine minimizes the depth of cotton grabbing to ensure uniform mixing; the carding principle is to reduce fiber damage and control the growth of short fluff, taking into account the effect of carding and removing impurities, unified nozzle, and uniform spacing to reduce bench difference; drawing process to prevent looping The disc scratches the sliver.
▎ 3.4.6 Control measures for operating reasons
Intensify the cleaning and reduce the attachment of flying flowers and accumulate flowers; increase the capture of sliver defects. The stopper should do the cleaning work according to the prescribed time and requirements to keep the air supply openings and channels of the spinner open. Do not over-press the sliver when changing the sliver barrel to prevent sticking. On the other hand, tampons should not be left for too long.
▎3.4.7 Equipment reason control measures
The parts in contact with the cotton fiber must be smooth and clean, and no hanging flower phenomenon should occur. It is necessary to ensure the sharpness of the ring gear of the carding roller, and there must be no back teeth. Rework and replace the spinning cup, carding roller, false twist head, and cotton conveying channel on a periodic basis. Lubricate and change the spinning cup and carding roller regularly.
04
Concluding remarks
Rotor spinning is a comprehensive reflection of various factors such as process, equipment, operation, raw materials, temperature and humidity in the rotor spinning process. When reducing the break, it is used for general breaking, repeated breaking, local breaking, and large area breaking. Different control measures and strengthened management can effectively reduce guillotines
