Free-end spinning is one of the new modern spinning methods. As early as a century ago, people had the idea of â€‹â€‹free-end spinning. The beginning of the 20th century began with the discussion of several spinning methods. Spinning, spinning, and other spinning methods are limited by package and speed, and cannot meet the needs of spinning production. This has led people to further explore and study new spinning methods and equipment. From the 50s to the early 70s, various new spinning methods emerged one after another. In 1965 Czechoslovakia exhibited the prototype of the first rotary cup spinning machine, and after further research and improvement, in 1966, a more complete rotary cup spinning machine was made. Since then, free-end spinning has begun to develop into a practical stage of industrial production.
Free-end spinning not only has the advantages of high speed and large package, but also can simplify the process, reduce the labor intensity of workers and improve the working environment, but the quality of yarn can only adapt to the requirements of limited products. Therefore, although free-end spinning has developed rapidly, it is still not widely used compared with ring spinning. Some countries in the Soviet Union and Eastern Europe use slightly more.
Principle The spinning process of free-end spinning usually involves opening, agglomeration, twisting and winding. First, the fed fiber slivers are opened into single fibers with a high-speed rotating opening roller, and some of them can also be separated into single fibers by a high-speed rotating roller combined with airflow. At this point, the bar is no longer continuous. The separated monofilament is generally conveyed by a gas stream and then condensed on the tail end of the twisted yarn. Condensation on one side, twisting into yarn. In this free-end spinning process, the number of fibers on the yarn ends gradually increases and has a uniform effect on the convergence. When twisting, the yarn tail rotates with the twister. If the twist point is not coincident with the fiber agglomeration point and the yarn tail is completely free, the yarn tail is not twisted and is easily broken, making it difficult to continuously perform the spinning. Therefore, the general free-end spinning yarn tail should have an appropriate twist to meet the needs of continuous spinning.
In free-end spinning, twisting and winding are performed separately. The speed of twisting is generally more than 30,000 rpm, and the winding speed is relatively low. The two are not constrained and high speed and high output can be achieved. And directly into a large package bobbin. Spinning of free-end spinning is generally the same as ring spinning. In order to enhance the dust removal of the rotor spinning, a special pre-spinning equipment is required.
The conditions for free end spinning to ensure good quality and reduce spinning breakage are: 1 fully loosen the fiber strip into a single fiber state; 2 the single fiber needs uniform conveying and agglomeration, and the fiber should be straightened and oriented as far as possible. Obtained agglomerated yarn tails with good geometry; 3 The strands that have been agglomerated into a good structure during the twisting process should not be damaged, and the yarn tails must have a certain strength when they are twisted to withstand the necessary spinning tension. It is well formed and easy to unwind.
The classification free-end spinning is divided according to the method of forming the free end. There are: 1 pure mechanical methods, such as roller clamp spinning; 2 airflow conveying and mechanical agglomeration methods, such as rotor spinning, dust cage spinning and pin spinning Yarn, etc.; 3 Air flow and turbulent agglomerating methods, such as vortex spinning (vortex twisting); 4 liquid flow and mechanical agglomeration methods, such as liquid spinning; 5 airflow or electrostatic transport and electrostatic agglomeration methods, such as Electrospinning. The following table lists some of the more mature free-end spinning methods:
The principle and process of yarn formation in free-end spinning differ from ring spinning, so the structure and physical and mechanical properties of the yarn are also different. The yarn-forming structure of free-end spinning is characterized by: (1) The structure is loose, the degree of straightness of the fibers in the sliver, and the degree of transfer of the inner and outer layers are poor; the distribution of the inner and outer layers in the cross section of the 2 yarns is different. The physical properties show that the strength of the yarn is low, the twist is high, the elongation is large, the strip is even, wear resistance, dyeing and sizing are good.
At present, free-end spinning is mainly suitable for spinning medium-sized (medium-low branch) yarns, and there are limitations on the types of suitable spinning raw materials for some methods. Studying the scope of expanding raw materials and spinning and improving the technical and economic effects are important topics in the development of free-end spinning.
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