The open end yarn poses good abrasion resistance. This is the special character of open-end yarn getting produced in rotor spinning. The open end yarn consists of wrapped fibres around the yarn surface. The open end yarn also contains a thin outer layer of fibers with hardly any twist or even with twist in the reverse direction. The new fibres get joined on to the already well-twisted fibre strand during each rotation of the rotor. These latecomers receive only a fraction of the desired twist level. If this low twist is lower than the false-twist, the fibres get twisted in the reverse direction.
The function of the feeding system is to pass the sliver from the sliver can to the fibres opening assembly. First of all the sliver passes over the guide then the feed roller. The feed roller carries forward the material to the feed table. The rotating feed roller helps to grip the sliver and carries it forward over the feed table into the opening roller. The feed table is equipped with spring-loaded pressure which ensures strong gripping of the fed sliver toward the feed roller. This assembly gets equipped with automatic stop motion. When sliver a yarn end down, sliver feeding gets stopped immediately by disengaging of feed clutch. The feed roller also stops to rotate. The signal pulse causing this is generated by a yarn-sensing device called a thread monitor.
Since a very little amount of twist gets employed to carded or drawn sliver to hold the fibres together so that it needs to open the fibres completely. The opening action gets performed with the help of a combing roller in the rotor spinning machine. This roller gets covered with saw tooth wire clothing. When the sliver gets passed through a rotating combing roller, the individual opening of fibres takes place. The fibre to fibre opening of material is necessary before it enters the drafting assembly.
In the drafting zone, the fibres get further opened. The parallel arrangement of fibres also gets performed. When the fibres get opened completely, these fibres are sucked with the help of a transport tube. An air current flows in this tube which carries the opened fibres to the rotating rotor. These fibres get accumulated on the inside wall of the rotor. The air current is produced by the main duct in the section and then through a vacuum in the rotor housing. A central fan is used to create a vacuum. This fan draws air by suction through small ducts from each rotor housing. To facilitate the generation of this negative pressure, the rotor box must be hermetically sealed as far as possible. The suction current in the fibre channel helps to pick off the fibres from the surface of the opening roller and send them into the rotor. In the course of this movement, both the air and the fibres are accelerated due to the converging shape of the feed tube. This represents a second draft following the nip trough/opening roller and results in further separation of the fibres. The fibres are straightened in this air current. A third draft creates upon the arrival of the fibres on the wall of the rotor. Since the peripheral speed of the rotor is many times greater than the speed of the fibres, the parallelization of fibres takes place in this zone. The arrangement of fibres improves. When the fibres slide down the wall of the rotor into the rotor groove due to the high centrifugal force generated within the rotor. The fibres are straightened finally here.
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Nice explanation on rotor spinning. You can takerotor spinning book.ReplyDelete