7.2 Spinning of short fibres from the scutching and hackling line

Scutching tow is used for making coarser yarns with a dry spinning process. Dry spinning is based on the same principles as making roving yarn (§7.1.4), but using a finer flyer, spindle and cop. Before spinning, the scutching tow is combed, made into sliver and drawn and doubled, like is done for long fibres. Based on scutching tow, yarns with a fineness of Nm 3 to 7 can be spun.

The successive steps are:

• Prepare mixing plan for bales of scutched short fibres.

• Roller card: The fibres are split by the sharp needles of the carding machine and made into a carding sliver. The shives that were still attached to the fibres and the fibres that are too short ‘fall out of the main stream of fibres’ and are collected in the dust container under the large carding drum.

• Drawing: The fibres are laid in parallel.

• Comber: Extra treatment for more regular yarn. The fibres are further parallelised to form combed sliver. Production is about 8 kg/hour where there is a loss of 20% comber noils or combers.

• Drawing frame: The combed sliver is drawn and doubled, thus obtaining carded sliver which is collected in a rotating drum. During the successive 3 to 4 passages, a smaller number of doublings is applied each time and the combing zone becomes finer at each passage, as well as delivered roving.

• Roving frame: the slivers are further refined into wicks with a slight twist

• Dry spinning: Based on the principle of roving preparation, but with a finer flyer, spindle and cop.

• Semi-wet spinning: Performed on similar spinning machines as for dry spinning. The difference is that the wick is moistened after drawing by feeding it over a copper, continuously wetted roller. This water makes the formed yarn smoother but it retains the character of a dry-spun yarn.

Hackling tow fibres are longer and cleaner and finer than scutching tow, and can therefore be processed into finer yarns that are slightly more regular and stronger. To achieve this, it is necessary to partially dissolve the pectin from the hemp fibres so that the elemental fibres can slide better relative to each other, and thus finer yarn numbers can be spun. Hackling tow is usually semi-wet spun and yarns with a fineness of Nm 6 to 15 can be obtained.

Typical applications of yarns based on short fibres of the scutching line are ropes and coarser/heavier textile fabrics. The finer fibres of hackling tow are used in clothing, knitting yarn or upholstery.