Process Flow Chart of Hemp Spinning

Hemp Preparation and Spinning:
In the case of hemp the processing of long staple yarns differs from the processing of tow. Hemp reaches the mill in form of 400 to 1000 g sheafs, which feed the hackling machine. The short fibers are collected in boxes and delivered to the packing department as hackling tows.

The preparation process of long staple fibers allows to transform the sliver produced by the hackling machine into a 2 - 4 g/m roving through a series of drawing passages and a high number of doublings, which ensure the high blending rate necessary for heterogeneous fibers like hemp. The flow chart is similar to that used for flax processing and the machines employed are practically the same. At the delivery from last drawing passage, the sliver can be subjected to one of two alternative processes:
  • Wet spinning, the typical process used for bast fibres, with bobbin drying and winding. As for flax, the roving can be degummed and bleached before spinning.
  • Dry spinning directly from sliver through the same spinning frames used for flax tow spinning.
Tow spinning, as also dry spinning of long staple yarns, follows the same criteria as wool spinning on machines characterized by wider pitches and by more rigid and firm opening points, which can stand the high stresses caused by extremely hard and stiff fibers.

We point out that the card sliver has not the cleanness degree which is necessary to produce a regular yarn, therefore it requires a hackling operation on machines very similar to wool combers.

Tows can be dry or wet spun. For dry spinning, two kinds of spinning frames are used:
  • With drafting cylinder systems which operate according to the typical criteria of the semi-worsted system, with settings suited to the high length of these fibres
  • With gill-bars, i.e. with needle bars placed in the drafting fields assigned to the guide of the fibres, which are similar to those used for long fiber dry spinning

 Flow Chart of Hemp Spinning

As already for flax, the prospects for a widening of hemp use are conditioned by the finishing operations. In fact the fibre can undergo some important changes, if the order and the crystalline lay-out of the fibrous cells are adequately varied ; moreover, if full advantage is taken of the inner channels (lumens) for fluid diffusion by preparing them for a more efficient migration of fluids capable of modifying the fiber’s physical properties, completely new handle and appearance effects, even adjustable by the finisher, can be obtained. 

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