The purpose, principles, requirements and methods of cotton blending in cotton spinning process
1. The purpose of cotton distribution:
a. In order to maintain the stability of production and yarn quality.
Producing with high quality and low consumption requires that the production process and yarn quality remain relatively stable. Keeping the properties of raw cotton relatively stable is an important condition for stable production and quality. If single-mark spinning is used, when one batch of raw cotton is used up, another batch of raw cotton must be replaced to replace the batch. Such frequent and large-scale replacement of raw materials will inevitably cause fluctuations in production and yarn quality; if using The use of a variety of raw materials, as long as they are properly matched, can keep the properties of the mixed cotton relatively stable, thus keeping the production process and yarn quality relatively stable.
Use raw cotton rationally and try to meet the requirements of yarn quality and yarn count. Because yarn quality and characteristic requirements are not the same, and the spinning process has its own characteristics, therefore, various yarns have different requirements for yarn quality and yarn count. The quality requirements for using raw cotton are also different. In addition, the quantity of raw cotton stored in cotton spinning mills varies, and the quality varies. If one kind of raw cotton or one batch of raw cotton is used to spin a kind of yarn, it will be difficult to meet the requirements in terms of quantity and quality. Therefore, mixed cotton spinning should be used to make full use of the characteristics of various raw cottons, learn from each other’s strengths, and meet yarn quality requirements.
b. In order to save cotton and reduce costs
Raw cotton is priced according to quality. The prices of raw cotton with different fiber lengths and different grades vary greatly. Investment in raw cotton accounts for 50% of the cost of cotton yarn. %–85% (depending on the variety). If the raw cotton grade is higher, although the yarn quality can be guaranteed, the production cost will increase, which means the profit per ton of yarn will be reduced. Therefore, the cotton allocation should be based on economic benefits. , control the unit price of cotton blending and the amount of cotton used per ton of yarn, and strive to save the cost of raw cotton. For example, in cotton blending with shorter fiber length, appropriately mixing a certain proportion of low-grade raw cotton with longer length will not reduce the quality of the yarn. , on the contrary, it can improve the strength of the yarn. Raw cotton scraps, waste, combed waste, reused cotton and other components can be reused in the cotton mix in a certain proportion, which can also reduce the cost of cotton and save cotton. Effect.
2. Principles of cotton allocation
The principles of cotton allocation pay attention to quality, make comprehensive arrangements, make overall plans, ensure key points, look forward and backward, keep a steady stream of water, understand both ends, and make reasonable allocations. .
Quality requires overall consideration and comprehensive arrangement. The key point of ensuring is to properly handle the relationship between quality and saving cotton. On the basis of many varieties of production, according to different quality requirements, it can not only ensure the use of cotton in key varieties, but also ensure the use of cotton in key varieties. And can make overall arrangements.
To look forward and backward is to fully consider all aspects of raw cotton in stock, semi-finished products in the workshop, and raw cotton procurement to ensure supply.
The long-term goal is to extend the service life of each batch of raw cotton as much as possible and strive to produce multiple marks, at least 6-8 marks.
Understanding both ends, reasonable allocation means to find out the cotton consumption trend and raw cotton quality in a timely manner, grasp product quality feedback information at any time, and be flexible and budget-conscious in deploying raw cotton.
3. Cotton matching requirements
Cotton spinning mills produce multiple varieties, with yarns of different counts, yarns with different technological processes and processing methods. There are yarns with different uses, such as:
1. Yarn count
High-count yarn generally refers to yarn with a count of 50 or more. It is generally used in high-end products and requires strong yarn strength. High, with few appearance defects and even evenness. The thread diameter of high-count yarn is smaller, and the number of fibers contained in the cross-section is less. Defects are easily exposed, and the number of fibers in the cross-section is unevenly distributed, which affects the evenness level of cotton yarn. Larger, therefore, when matching cotton, raw cotton of different grades and qualities should be selected according to different counts.
2. Combed yarn and carded yarn
Combed yarn is generally a high-end product that requires good appearance, uniform evenness, and few neps and impurities. The combing process can remove a large number of short fibers and some impurity defects, but it is more difficult to remove neps. Therefore, the cotton used for combing requires the raw cotton linters and neps to be as low as possible. If the maturity is too poor, the tax rate will be too high. If neps are produced, use as little as possible. Because combed products are used to make high-end fabrics, they have higher requirements for the dyeing effect of the cloth. Therefore, raw cotton with good color and good uniformity is selected, and sometimes long-staple cotton is required.
3. Single yarn and stranded yarn
Generally single yarn adopts backhand twisting direction, and stranded yarn adopts forward twisting direction. The angle between the fiber in the strand and the strand axis is small, so The fiber utilization rate is high, the strength is greatly enhanced, and the evenness is improved. Generally, the evenness level can be increased by 2-3%. Most of the hairiness and defects are wrapped inside the yarn, thus reducing the chance of being exposed to the outside of the yarn. Therefore, The number of hairiness and defects is also greatly improved. Strands are generally used with warp yarns, so the cotton grade and quality may be reduced.
4. Warp yarns and weft yarns
The warp yarns bear more tension and friction opportunities during use, so the warp yarn strength requirements are higher. When matching cotton, you should choose slender fibers and strong single fibers. Raw cotton with high, moderate maturity and good uniformity has more opportunities to remove neps and impurities on the yarn during the preparation and weaving process, and it also needs to go through the sizing process.�The phenomenon of double peaks taking over batches will appear.
②The number of teams and the mixing percentage
The number of teams and the mixing ratio are directly related. If the number of teams is large, the mixing ratio will be small. If the number of teams is small, the mixing ratio will be large. When there are too many teams, the mixing ratio will be large. Production management is difficult, and it is easy to cause uneven cotton mixing. When the number of teams is too small, the mixing is relatively large, and it is easy to cause large differences in the performance of raw cotton when batches are received.
Therefore, when determining the number of teams, you must first know the cotton mixing processing method. If manual small-batch production is used, the number of teams should be small, no more than 4 teams. When mixing cotton with the cotton picking machine, it can be increased to 6-9 Team, if drawing and strip mixing are used in the post-process, the matching ratio of cotton slivers must also be considered.
Secondly, when determining the number of teams, we must also consider the total amount of raw cotton input. When cotton yarn is produced in small batches, the number of teams will not be too large.
Furthermore, when determining the number of teams, factors such as the origin, variety, and quality indicators of raw cotton must also be considered. There are many ginners and varieties in raw cotton production areas. When the quality difference is large, the number of teams is likely to increase.
When determining the number of teams, the variety and requirements of the product should also be considered. For example, when the color requirements of the product are higher, the number of teams is likely to be larger. When the quality of the yarn fluctuates greatly, the number of teams should also be larger.
When the number of teams is determined, the blending percentage of various raw cottons can be determined according to the quality of raw cotton and yarn quality requirements. In order to reduce fluctuations in yarn quality, the maximum blending ratio is generally about 25%.
Factory raw material procedure:
1. Feeding procedure: Generally settled according to gross weight (local cotton) or net weight (imported) or quasi-weight (Xinjiang cotton).
2. Workshop picking: Generally, factories calculate based on gross weight, and the production rate is based on the raw cotton situation: (1) Open-end spinning: with cotton grade: 4 to 6: 1.12 per ton spun. (2) Open-end spinning: When cotton grade 4-6 is added, spinning: 1.15-1.2 per ton, depending on the cotton mix. (3) Ring spinning carded card: When the cotton grade is 3, 1.08-1.1 can be spun per ton. (4) Ring spinning combed: When the cotton grade is 2, 1.34—1.38 is used to spin one ton.
(5) When the ring-spun combed long-staple cotton high-count yarn is grade 1-2, the spin rate is 1.38—1.46 per ton, depending on the long-staple ratio.
3. Calculation method:
Cotton collection in the workshop—gross weight weighing–cumulative total monthly inventory weight
Cotton yarn in the workshop–according to National standard yarn loading – cumulative monthly inventory and accumulated quantity in storage.
The weight of semi-finished products in the workshop at the end of the month – the number of semi-finished products in the inventory last month.
Example: A certain factory used 120 tons of raw cotton or usable waste in October. It produced 80 pieces of 10 tons, 40 pieces of 40 tons, and air-end spinning of 50 tons. A total of 100 tons of various types of cotton yarns were put into storage. The inventory of semi-finished products in progress in the workshop this month is 50 tons, and the inventory of semi-finished products last month was 60 tons. Then the completion rate of this workshop in October is calculated as:
120-(60-50)/100=1.1, then this workshop The monthly throughput rate of the workshop was 1.1.
When the usable waste waste or other waste produced is borrowed from other factories, the accrued raw materials will be reduced.
In order to reduce quality problems such as cloth surface rungs, the difference in micronaire value of cotton and cotton blended fibers in each batch must be controlled within 0.4. Raw cotton transactions in the international market also usually use the micronaire value as one of the price reference indicators. For raw cotton that exceeds or fails to meet the spinnability micronaire parameter, the price is reduced or discounted.
Single fiber strength is also one of the main indicators that determines the strength of the yarn. Cotton fiber has to constantly withstand external forces during the spinning process. A certain strength of the fiber is one of the necessary conditions for the cotton fiber to have spinning performance. 1. Under normal circumstances, if the cotton fiber is strong, the yarn will be strong. The cotton fiber strength is not only related to the fiber thickness, but also to the cotton variety and growth conditions. It is required to achieve the required single yarn strength when spinning different varieties. , special attention should be paid to the single fiber strength of cotton.
Raw cotton defects are substances harmful to spinning caused by poor development or poor rolling during cotton growth. Raw cotton defects are difficult to remove during the spinning process, or are wrapped in the yarn, or attached to the yarn. In the thread, the evenness will deteriorate, end breaks will increase, and the appearance will be very poor, which will directly harm the spinning production and the quality of the final product.
The sugar contained in cotton fiber refers to the general term for soluble sugars, including physiological sugars contained in the fiber itself and exogenous substances attached to the surface. When the sugar content in raw cotton is too high, fiber adhesion will obviously occur during carding, combing, drawing, roving, spinning and other processes, affecting normal production, especially the new domestic equipment that is gradually put into use. Raw cotton with too high sugar content is even more unsuitable. Therefore, no matter how favorable the price is for raw cotton with excessive sugar content, use it with caution, especially when it is used to make high-end knitted fabrics.
Doing a good job in trial spinning of raw cotton can avoid or eliminate the limitations and errors caused by sensory testing and instrument testing. Therefore, before the raw cotton is put into large-scale production, small batch trial spinning of new component raw cotton should be arranged, and then based on the trial spinning The spinning conditions and yarn quality are used to arrange the mixed use of new cotton.
When carrying out new processes and new technologies, small batch trial spinning should also be carried out to confirm the correct use of raw cotton. Doing a good job in trial spinning can reduce yarn quality fluctuations and correctly reflect the use value and economy of the fiber. Value, predicting yarn performance, can ensure that product quality will not fluctuate over time spans. Only then can product quality be recognized by the market.
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