Three Methods of Cotton Blending in Spinning

It is necessary to control the physical properties of the blended cotton and ensure the stability of various indicators of the successive batches of raw cotton.

First of all, formulate the sub-indicators (length, fineness, maturity, strength, short fiber content, etc.) and the allowable difference ranges for each indicator of cotton blending for each yarn variety to be spun. The specific indicators and difference ranges of raw cotton can be set either strictly or leniently during formulation.

Secondly, the raw cotton reserve volume needs to be taken into consideration. A strict standard can be adopted when the inventory is large, and a lenient one when the inventory is small to avoid difficulties in implementation. For cotton blending of the enterprise’s key product varieties, careful consideration should be given to minimize the difference range. That is to say, it is required not only to control the average value of various indicators of the blended cotton within the specified range, but also to ensure that the indicators of the two batches of cotton before and after replacement are close to each other. Meanwhile, the simple arithmetic mean should not be used for calculating the average value of various indicators; instead, the weighted average based on weight percentage should be adopted.

For cotton blending of general products, the indicators and their difference ranges can be relaxed, with only the requirement that the average values of the main indicators of the blended cotton fall within the specified difference ranges. Generally speaking, the smaller the difference between successive batches of raw cotton, the better, while the difference between different marks in the blended cotton can be slightly larger. Sometimes, even if the differences in certain properties of raw cotton are relatively large, it will not be harmful to the yarn quality; on the contrary, it may improve the quality.

For example: properly blending longer fibers into the cotton blend dominated by shorter fibers, or adding finer fibers to the blend dominated by coarser fibers, is beneficial to improving the yarn evenness and enhancing the yarn strength. The key is to ensure the consistency of the subsequent batches of raw cotton.

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Take the yarn strength as an example for illustration: the main indicators affecting yarn strength among the physical properties of raw cotton include length, fineness, maturity, and short fiber content. Longer fibers mean a larger contact area between fibers and more bonding points, resulting in stronger cohesion and naturally higher yarn strength. Finer fibers lead to a greater number of fibers in the yarn cross-section, which also increases the yarn strength. Fibers with good maturity have high strength, thus contributing to higher yarn strength. As for short fibers, they remain in a floating state during the drafting process, which can cause unevenness in the yarn structure and form weak points when the yarn is under tension. In addition, a high short fiber content will reduce the cohesion between fibers and increase the probability of fiber slippage under tension, which is unfavorable to yarn strength.

Another example: the neps, impurities, and hairiness of yarn are directly determined by the properties of raw cotton under the same process conditions. A high short fiber content in raw cotton will lead to excessive yarn hairiness (excluding the factor of mechanical friction) and a high yarn evenness CV value. High impurity content, many defects, and poor maturity of raw cotton will result in more neps and impurities in the yarn. Based on the above analysis, after the cotton blending design scheme is determined, suggestions can be put forward for some related processes in production, so as to effectively control a specific process in a targeted manner, grasp the initiative in production in advance, eliminate potential quality hazards caused by raw cotton before yarn formation, and implement early control and elimination to play a predictive role.

The “classification and queuing” method referred to by general cotton mills is an early approach to cotton blending design. Although it is quite primitive, it is highly practical and is still adopted by many cotton mills at present.

Classification refers to dividing raw cotton suitable for spinning a certain yarn count into one category (and several categories in total) according to the properties of raw cotton and the different requirements of various yarn varieties.

Queuing means arranging the raw cotton in the same category into a queue according to different factors (such as origin and similar properties) for successive use. Cotton blending should take into account both the present and the future, both key product varieties and general ones. Based on actual needs and feasibility, cross replacement should be carried out according to priority to make reasonable and appropriate arrangements, so that the raw cotton composition used for each variety does not undergo significant changes, so as to maintain the stability of production and yarn quality.

In addition, it must be mentioned that a certain degree of control should be exercised when using the waste cotton generated in various processes (such as cotton lap scraps, sliver scraps, roving waste, roller waste, and fly waste) and reclaimed cotton (such as mixed waste seeds, scutcher waste, and comber noil). They should be used rationally; otherwise, although a small amount of cotton is saved, the yarn quality will be damaged, resulting in more losses than gains.

In a word, relying on a single method for cotton blending can no longer adapt to the current situation of increasingly fierce competition in production and the market. In today’s information age, the adoption of computers for cotton blending is an inevitable trend in the development of cotton blending technology, which can also elevate the yarn quality to a new level.