Operating principle


Fig. 4 – The friction spinning principle

This process is included in the open-end group because the fiber strand (drawframe sliver) must be opened completely into individual fibers and then reassembled to a new strand (yarn). The formation of a new strand is carried out by using suction to bring the individual fibers into engagement with the rotating open end of the yarn, e.g. by perforated drums with an internal vacuum. Binding-in fibers and imparting strength are effected by continuous rotation of the yarn end in the converging region of two drums. The rotation of the yarn end arises from the rotary movement of the two drums and is generated by frictional contact at the drum surface. The yarn formed in the convergent region by collecting fibers and binding them in can be continuously withdrawn and wound onto a cross-wound package.
The fineness of the resulting yarn is determined by the mass of fiber feed per unit of time and the withdrawal speed of the yarn; the number of turns is determined by the relationship between yarn end revolutions and withdrawal speed. The rate at which twist is imparted to the yarn is markedly lower than that which would be expected from the rolling of the yarn end between the two drums. This fact, often attributed to slip, is the result of the very complex details of the yarn formation process. The economic and technological limits of friction spinning and rotor spinning systems are in approximately the same count range. They are direct competitors in the marketplace.