The design of the roving twist coefficient is one of the important process parameters that changes the intrinsic structure of the roving. The reasonable selection of the roving twist coefficient is directly related to the stability of the cohesion between the roving fibers. It not only plays a key role in reducing unexpected elongation, but also improves the draft of the spinning yarn. During the process, the stability of the drafting force and the prevention of edge fiber diffusion play a key role, thereby improving the evenness level of the yarn, reducing the hairiness of the yarn, improving the flatness of the cloth surface and reducing the occurrence of long details.
How to set the roving twist coefficient
1 Different twist coefficients are set according to the fiber length, linear density and short lint content of the cooked strips. Under the same roving weight, the fiber length is long, the cooked sliver short staple rate is low, the fiber-to-fiber contact area is large during the twisting process, and the twist coefficient can be controlled to be smaller.
2 The fiber linear density is different and the twist coefficient settings are also different. For raw materials from the same manufacturer, under the same roving weight, the greater the fiber linear density, the smaller the number of single fibers contained in the roving cross section, so the roving twist coefficient should be controlled on the larger side. For example: if 1 dtex×38 mm and 1.67 dtex×38 mm polyester are used to make 5.0 g/10 m roving, the twist coefficient of 1.67 dtex polyester should be larger than that of 1 dtex polyester.
3 The influence of temperature and humidity on the setting of roving twist coefficient. This has a greater impact on fibers with good hygroscopic properties, such as viscose fiber, cotton, etc. After the fiber absorbs moisture, the friction factor on the fiber surface changes, thus affecting the cohesion between fibers. The twist coefficient should be larger in the dry autumn and winter seasons, and smaller in the summer with high temperature and humidity.
4. The roving twist coefficient should be set based on the equipment status, component status and the draft size after spinning. Good equipment condition is the basis for spinning. The setting of the roving twist coefficient must ensure that the fine yarn does not break up and the roving end does not appear. The spinning spindle rotates inflexibly, the twist coefficient is small, and accidental drafting causes many details. , The roundness of the rubber roller is poor, the hardness is too large, and the twist is too large. During the drafting process, the holding force is smaller than the drafting force, resulting in hard ends.
5 Prevent accidental elongation during roving spinning. As we all know, improving the internal structure of semi-finished products is the key to improving the quality level of yarn. The internal structure of semi-finished products includes the degree of fiber separation, straightening parallelism, number of knots, amount of short lint, and the degree of cohesion between fibers. The strong cohesion of the roving is high, and the accidental elongation is small and the ends are less broken during the spinning process of the roving machine. Of course, it is also necessary to reduce the elongation of the roving and adjust the winding tension. In recent years, our company has attached great importance to the selection of the roving twist coefficient in terms of technology. At the same time, the equipment has been well coordinated with the adjustment of the roving winding tension. The unevenness of the roving has increased, the long details caused by accidental elongation of the roving have been significantly reduced, and the cloth surface has been smoothed. The degree is greatly improved.
6 Prevent accidental elongation before feeding the back roller into the spinning frame. When unwinding the roving on the spinning machine, there must be enough strength to overcome the rotational resistance of the roving during unwinding, and prevent accidental elongation. Otherwise, the unexpected elongation of the roving will eventually lead to the slenderness of the cloth.
7 Appropriate roving twist coefficient is helpful to improve the tightness of the yarn and improve the level of evenness. The key to improving the evenness level is to control the regular movement of the fibers in the drafting area. Therefore, in addition to the appropriate additional friction and strength under the condition of sufficient holding force, the tightness of the yarn itself is also a very important aspect. The appropriate roving twist coefficient gives the yarn appropriate tightness, which is more important for the simple roller drafting area in the rear area. At the same time, the slivers fed into the front area have enough residual twist to prevent the edge fibers from spreading, and the fibers have regular speed changes. The coarse details of the finished yarn are significantly reduced.
8 Appropriate roving twist coefficient is beneficial to improving yarn hairiness. In addition to the hairiness of the finished yarn being related to the temperature and humidity of the workshop, the cooperation of the ring traveler, and the twist coefficient of the fine yarn, the reasonable selection of the twist coefficient of the roving also plays a role in improving the hairiness of the finished yarn to a certain extent. Under other identical conditions, the twist coefficient of the roving is appropriately larger, the rear area of the spun yarn is appropriately smaller, the yarn density in the front feeding area is good, the side fiber diffusion is less, and the untwisted triangle area at the front roller significantly reduces the yarn hairiness. . Strengthen the production and management of rubber rollers so that the rubber rollers have good holding effect, the back area of spun yarns is reduced, the twist coefficient of rovings is appropriately increased, and the evenness level of the finished yarns is significantly improved, while its hairiness is also significantly improved.
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