7.3.2.1 Rotor spinning

In rotor spinning, also known as open-end spinning, twist is introduced into the fibres without the roving rotating itself. Thanks to very large centrifugal forces, the fibres are pressed against the rotor wall and move from the collection surface of the rotor to the rotor groove. In the groove, a layer of fibres is formed, whereby an x-fold doubling is achieved and a regular yarn is obtained. The yarn is actually spun in the rotor groove and leaves the rotor through a spinning tube.

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Basic features of rotor (open-end) spinning. Copied from Carl A. Lawrence.^[1]

The production rate in rotor spinning is much higher than in ring spinning (Table in §7.3.2). This is because introduction of the twist is completely independent from winding the yarn on a bobbin. The rotation speed is also higher than for ring spinning, about 6,000 - 9,000 rotations per minute, versus 300 - 700 for ring spinning.

Rotor spinning is a dry spinning process and is mainly applied to short staple fibres. A more regular and less hairy but weaker yarn is produced than in ring spinning of staple fibres.^[2] With rotor spinning of staple fibres, yarns with fineness in the range of Nm 5 - 12 can be obtained.

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Semi-automatic rotor spinning. Photo Rieter.

[1] Carl A. Lawrence, ‘Fundamentals of spun yarn technology’, 2003 CRC press, www.eopcw.com/find/downloadFiles/237

[2] https://www.rieter.com/fiber-preparation/varioline/rieter-bast-fibers-processing-brochure.pdf