Introduction to empty bale and machine bale spandex yarn

Sexual network dots of yarn. The fabric feels soft and smooth; mechanical covered yarn (abbreviated as machine package, English abbreviation as SCY) is a continuous rotation and winding of the outer fiber filament on the core spandex that is drawn at a uniform speed. It is twisted and has twist (English abbreviation TPM), the smooth and crisp fabric style is its main feature.

Empty machine-wrapped yarns have their own advantages and disadvantages when weaved in downstream weaving factories. Empty bales generally need to be sized when being warped on an air-jet loom, otherwise the fabric is prone to fluffing and broken wires, etc. However, it can be used directly after beating up. Considering the cost alone, the production capacity of empty bales is much higher than that of machine bales, making the price lower than that of machine bales, which facilitates the reduction of costs for downstream weaving mills. Although the core yarn is not exposed in machine bags, it is generally not prone to quality problems during spinning and weaving except for uneven twist. However, the output is low, and the price is therefore more than RMB5000/T higher than empty bags of the same specification. The price of fine denier covered yarn It is even higher than RMB10,000/T for empty packages of the same specifications, thus greatly increasing the cost of using machine packages.

In the spinning process, the pre-draft ratio of spandex (Spandex? Stretch) is an important process parameter. It affects the elasticity of the covered yarn (Covered? Yarn) and fabric, and also affects the elasticity of the covered yarn. The strength, elongation, evenness and creep properties of the covering yarn. The pre-draft multiple of spandex is too small, which cannot give full play to the advantages of elastic fabric. When the draft is too high, it is difficult to spin, and it is easy to cause wire breakage, and the product quality will decrease; in addition, the percentage of spandex fiber also affects The elasticity of the covered yarn is high, and the elasticity is good. When the spandex yarn specifications are certain, increasing the draft ratio will reduce the percentage of spandex yarn, that is, the pre-draft multiple of spandex is inversely proportional to the percentage of spandex in the finished yarn.

The strength and elongation of the covered yarn increases with the increase of the spandex pre-drafting multiple. After the spandex is stretched to a certain value, the retractability of the spandex yarn causes the outer fiber to be in a curled state, and the spandex core yarn Straightened; increase the pre-drafting ratio appropriately, reduce the percentage of spandex, and curl the outer fiber to a large extent. However, when the draft is too large and the deformation amplitude of the spandex yarn approaches the critical value of deformation, the strength and elongation of the covered yarn will decrease, but it will help the evenness of the covered yarn.

The phenomenon of deformation changing with time under the action of constant drafting force is called creep. The covered yarn has good creep resistance when the spandex yarn is pre-drafted 3.5 times.

The twist of the machine package affects the quality, elongation and evenness of the yarn. Increasing the twist can increase the cohesion between the covering fiber and the spandex yarn, thereby increasing the strength of the covering yarn. The elongation of the machine package is mainly determined by ammoniaDetermined by the performance of the spandex core yarn, if the twist is too large and the outer fiber is wrapped too tightly, the elastic effect of the spandex yarn cannot be fully exerted, causing the elongation to decrease. As twist increases, evenness improves. The twist is too small and the outer fibers are loose. During the spinning process, the fibers will move slightly along the axis of the yarn due to friction and other reasons, so the evenness deteriorates.

The presence of spandex yarn in the machine bag will weaken the cohesion between the outer fiber filaments. The twist is too low and the outer fiber will be loose, which will affect the covering effect and lead to core exposure. Therefore, the twist should be adjusted during mechanical wrapping. On the high side. But if the twist is too high, the fabric will feel hard and have poor drape. Generally, the twist needs to be adjusted as the denier of the yarn changes. For example, for N40D+20D machine packages, the twist is 600 twists, while for N70D+40D or T150D+40D machine packages, the twist can be controlled at around 480. Some small In order to consider delivery time and reduce production costs, spinning mills will reduce twist or increase equipment speed to increase output, which is not conducive to the quality of wrapped yarn.