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Yarn inspection and quality analysis

November 17, 2021

Definition of yarn

In the textile industry, "yarn" refers to the general terms "yarn" and "thread". Many short fibers or filaments are arranged in a nearly parallel state and wound along the axis to form a slender object with a certain strength and linear density, namely "yarn"; "thread" is a strand of two or more single yarns .


The influence of spinning on yarn quality

Only when the yarn is formed from short and relatively uniform fibers, it has a stable quality. In order to obtain this kind of fiber, the fibers from different production areas and batches must be mixed together, and then the fiber is removed and mixed using a cotton opener, a cotton blender, and a cotton cleaner. In this process, most of the dust and impurities are removed by gravity and centrifugal force.

Compared with the yarn produced by the intermittent system, the yarn produced by the automatic unit is more uniform and strong. In addition, the continuous production speed of the automatic unit is higher, which can save manpower and ensure that the factory maintains a clean environment. No matter what processing system is used, the final quality of the yarn mainly depends on the selection of raw materials and the procedures of opening, removing impurities, and blending.


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Why analyze yarn quality?

There are two main processes in weaving, which are divided into spinning and weaving.
Yarn is the secondary raw material for organic fabrics and knitted fabrics. Suede thread, sewing thread and embroidery thread are all finished yarns. Compared with fibers, yarn structure has a more direct impact on the internal and external quality of textiles. Therefore, when analyzing the quality of textiles, it is necessary to conduct a comprehensive and systematic analysis of the structural factors of the yarns used in textiles, such as type, shrinkage, fineness, twist direction, etc.


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Indexes for evaluating yarn quality-yarn fineness, yarn count and yarn density

Fineness refers to the thickness of the yarn. Since it is difficult to measure the diameter and size of the yarn cutting surface in actual production, we use the yarn count, that is, the yarn density to express the thickness of the yarn. Yarn density refers to the mass or weight of the raw material per unit length.

Yarn density has a great influence on the appearance, feel, weight and mechanical properties of the fabric, so it is necessary to choose a reasonable yarn density according to different uses. For example, the winter coat fabric should be heavy, hard-wearing, insulating, and made of medium or high-quality yarn. Summer clothes need to be made of lightweight, breathable yarn.


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Twist direction

Yarn twisting means that in order to make the yarn have some physical and mechanical properties, such as strength, elasticity, elongation, gloss, hand feeling, etc., it changes the structure of the yarn by generating the relative displacement of the yarn cross section. Tilt the original parallel fibers to the central axis of the yarn.

Twisting is a necessary condition for short fibers to form yarns. In addition, twisting will change the yarn density, yarn strength and gloss, thereby affecting the structure and performance of the fabric.


Single yarn strength

Yarn strength, also known as yarn fastness, is an indicator reflecting yarn quality. The yarn must have a certain strength to ensure the normal operation of the knitting process. Yarn strength can be measured with a single yarn strength meter. Yarn strength indicators can be divided into absolute strength and relative strength. Absolute strength refers to the strength required when the yarn is directly stretched and broken by an external force, also known as the breaking strength, expressed by cn/tex.


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Yarn appearance quality

Determine its appearance quality by winding the yarn on the blackboard: Observe the yarn samples wound on the blackboard according to the specified requirements by visual observation to obtain the results. This method is mainly used to observe yarn slubs, thin spots, defects, system unevenness and NEP.


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Significance of yarn quality testing

Yarn is used as a raw material for weaving, different weaving densities, different fabric surface expressions, and different printing and dyeing requirements also have different requirements for yarn structure. Generally speaking, there is no absolute good yarn or bad yarn. The appropriate yarn is woven into the appropriate cloth, so as to achieve the best use effect, not to create excess quality, but also to meet the basic needs of customers for goods.