Friction spinning is a kind of free end spinning. Like all free end spinning, it has a feeding opening mechanism similar to rotor spinning, which decomposes the feeding fiber into a single fiber state. The coagulation and twisting of fiber is realized by a screen with a suction device. The screen can be either a large diameter dust cage or a flat continuous mesh belt. There are many types of friction spinning in the world. The most representative friction spinning frames are DREF - Ⅱ and DREF - Ⅲ from Austria. The screens of these two types are a pair of dust cages (or a dust cage and a friction roller) rotating in the same direction. So it is also called cage spinning.
1、 Spinning principle of friction spinning
Take the dust cage friction spinning as an example. The spinning principle of friction spinning is shown in Fig. 9-4-1. Due to the suction inside the dust cage 2, the fibers fall into the wedge-shaped grains between the two dust cages and agglomerate into whiskers. The agglomerated whiskers cling to the surface of the dust cage. The two dust cages rotate in the same direction. One produces an upward friction R1 on the agglomerated whiskers and the other produces a downward friction R2 on the agglomerated whiskers, When the guiding yarn is drawn out from the guiding roller 3, the condensed strand is the end of the yarn; The yarn ends are twisted and rotated by the dust cage, so the yarn ends can be twisted back. Since the yarn ends are fed with fibers at the same time, the yarn ends can be continuously output.
Because the condensing whiskers on the surface of the cage are free, this friction twisting method belongs to free end twisting yarn. In the twisting process, the linear speed of the cage surface is approximately equal to the rotation surface speed of the yarn itself, so the low speed of the cage can make the yarn obtain higher twist, which can greatly improve the stripping speed to obtain high yield. The direction of yarn twist back is opposite to the direction of dust cage rotation. The amount of yarn twist back depends on the speed of dust cage, the contact state between the surface of dust cage and yarn and the suction of dust cage.
2、 Technological process and yarn forming characteristics of D2 friction spinning frame
The dust cage type friction spinning machine is named after the abbreviation DREF of Dr Ernst fehrer of Austria, which has gradually developed from type I to type II and type III, and referred to as type D2 and type D3
The technical characteristics are shown in table 9-4-1.
（1） The technological process of D2 friction spinning frame is shown in Fig. 9-4-2. Four to six fibers are led out from the sliver barrel and fed into the three roller drafting device 1. After the evenness and fiber straightness are improved by the combined drafting, the fibers are combed and decomposed into single fibers by the carding roller 2, and the fibers are separated from the saw teeth by the centrifugal force of the carding roller and the air flow of the blowing tube 3, Along the baffle plate 4, it falls into the wedge-shaped grains between the two dust cages 5. The opening of the inner container 6 of the dust cage faces the wedge-shaped grains between the two dust cages, and one end is connected with the fan through a pipe. Under the suction of the air suction device, the fibers are absorbed in the wedge-shaped grains of the two dust cages and agglomerated into whiskers. The yarn is led into the dust cage and overlapped with the agglomerated whiskers, The two dust cages rotate in the same direction to twist the condensed whiskers into yarn, and the output yarn is frictionally wound into a package by the winding roller 8.
（2） Yarn characteristics of D2 friction spinning
1. The structure of D2 friction yarn. In friction yarn, the arrangement of fibers is disordered. The number of fibers arranged by conical helix and cylindrical helix is less than that of rotor yarn, accounting for only 12%. More than 40% of the fibers are kinked and twined, and the rest are hook and folded fibers.
Due to the traction of the guiding roller, the yarn tail moves towards the output direction, and the fibers are continuously added to the yarn tail, resulting in a gradual increase in the number of fibers on the yarn tail from a to B. (see Fig. 9-4-3). When the yarn is rotated due to the friction of the dust cage, the rotation speed of the strips between ab varies with the diameter of each section. The diameter near point a is thin, but the rotation speed is high, and the diameter near point B is thick, but the rotation speed is low, Each section is twisted back due to the speed difference. Since the spinning twisting of yarn tail is carried out at the same time with adding fiber and moving towards the output direction, although the part close to point a has obtained twisting back, it can still obtain twisting back with the outer fiber after moving along the output direction and adding fiber, so the twisting back of yarn core is more than that of outer layer, and it changes layer by layer. As a result of this layered twisting, the layered structure of friction yarn is formed, and the inner yarn core is firm due to more twist, while the outer yarn is loose due to less twist.
News