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This heading covers synthetic staple fibres (including waste of synthetic staple fibres or filaments) after they have been carded, combed or otherwise processed for spinning.
In carding, staple and waste fibres are passed through machines which render the fibres more or less parallel, and deliver them in the form of a wide web or lap which is then generally condensed into a sliver (a strand of fibres loosely combined without twist).
In combing, the carded sliver is passed through further machines which render the fibres almost perfectly parallel and, in the case of waste, remove the shorter fibres (noils). The combed sliver is usually wound in coils or balls, known as "tops".
Tops are also made directly from filament tow by what are known as "tow-to-top" processes.
The tow is passed through a device which breaks or cuts the filaments without disturbing their continuity or their parallel arrangement. The operation may be carried out, for example, by passing the tow through rollers operating at different speeds thus causing a tension which breaks the filaments; or toothed rollers may break the filaments by direct pressure; or the tow may be cut diagonally with knife mechanisms. During passage through the machine the tow is drawn out into slivers. These processes avoid the necessity for cutting up the tow into staple fibres and eliminate carding or, usually, both carding and combing.
Slivers, whether produced by carding, combing or by the "tow-to-top" processes, are drawn out into rovings - thinner strands of parallel fibres with a slight twist - which can be spun in one operation into yarn.
The heading does not cover wadding (heading 30.05 or 56.01).
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