Friday, April 10, 2009

Friction Spinning

The need to rotate the package at the twist insertion rate coupled with rapid increase in spinning tension with spinning speed sets a limit to the spindle speeds achievable in ring spinning. Open end spinning methods where open-end of the yarn alone needs to be rotated for imparting twist was therefore, developed to achieve high delivery rates. Rotor spinning which is one of first methods developed on this principle has well established itself as an alternate to ring spinning in course count range for certain end uses. Friction spinning represents an alternate open-end spinning method to rotor spinning which holds promise of still higher delivery rates.

Frictions spinning technologies works on the principle of open-end or wrap (Fasciated)/core spinning. The general principle of working of friction spinning in its simplest form can be described as below.

As in the above diagram, separating them from slivers generates a stream of fibres, which is transported through a duct. The fibres are then directed towards the nip of two rotating drums called friction drums .The fibres are collected close to the nip of these drums. The friction drums have perforations on it and suction from inside holds the fibres on the surface. There is a long slot inside the friction drums located close to the nip point along the length of friction drums and the rest of the area inside the perforated drum has a shield. So, the yarn at the nip of the friction drum is subjected to a radial force generated as a result of airflow over yarn.

This is shown in figure 2 , This radial force serves as a normal load and frictional force is generated between the yarn and the surface of friction drum. It can be observed from the same figure that at the closest proximity of the friction drums they rotate in opposite direction and the frictional force thus developed, produces a torque on the yarn tail. Continuous rotation of the drum produces twist in the yarn leading to gradual integration of fibres in the yarn tail. The yarn is withdrawn in the direction of the axis of the friction drums and is wound on a bobbin.

Fig.2 : Forces acting on the yarn tail and the vector diagram.

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