The purpose of a genuine compact spinning process is to arrange the fibres in a completely parallel and close position before twist is imparted. This is the most important criterion for perfect compact yarn. The eliminated spinning triangle is a by-product of this concept. This close and parallel arrangement of fibres immediately before twist is imparted is responsible for the characteristic advantages of compact yarn. Compact technology is the new spinning advancement revolutionary version of ring spinning process, which achieves a remarkable improvement in yarn quality & yarn structure through better utilization of fibre properties.Compact spinning creates new possibilities for ring spinning and improve the quality of the yarns manufactured .compact spinning is a real innovation in spinning staple fibres. Compact spinning allows us to manufacture yarns of decreased hairiness and increased strength, and therefore compact yarns are generally used for manufacturing high quality woven and knitted products.In classical ring spinning, a twisting angle is formed while yarn is spun.
A fibre stream of a given width is led to the delivery rollers. This width depends on many factors, such as linear density, roving twist, and drawing ratio of the drawing apparatus. After leaving the delivery rollers, the fibres are condensing in the twisting triangle, and next screwed into the twisted fibre stream. During twisting, the fibres, which lay around the symmetry axis of the stream, are arr-anged in the middle part of the stream, and the border fibresform the outer layer which insert a pressure on the remaining fibres. The fibres, which lay in the twisting angle, are affect by different tensions. The highest tensions are inserted on the fibres positioned at the triangle boundaries, the smallest those which are in the middle.
Therefore, over further processes, while yarns or the products manufactured from yarns are affected by tensions, the fibres, which are placed in the yarn cross-section, do not break at the same time. First break the fibres which are affected by the highest tensions in the twisting angle. This explains why the yarn tenacity is smaller than the tenacity of singular fibres. The twisting angle cannot gather all fibres. Many of the border fibres remains free, forming the spinning fly, or are twisted into the yarn in a fully not controlled process, increasing the yarn hairiness. In a spinning frame with acompact drawing apparatus, the twisting angle is eliminated or minimised.
The fibre stream is condensing after it left the main drawing zone as the result of the negative pressure existing in the condensing elements.Air in the condensing elements causes fibre rotation around its own axis and condensing of the fibres’ stream. The twisting angle decreases, so that all fibres, which are placed in the fibre stream, can be gathered and twisted into the yarn. The formed yarn has a circular cross-section, is stronger and smoother. This can be achieved by condensation of the fibre band in the drafting zone.
The condensation can be achieved by the following means-
- Roving twist
- Mechanical condenser
- Aerodynamic condenser
1) Roving twist: The twist in the roving has twofold objective. Firstly, it prevents the roving from being disturbed before it enters the drafting unit of the ring frame. Secondly, the twist contains spreading of fibre sheet during drafting. The roving twist therefore acts as a condenser, quite effectively in the pre-draft zone and partly in the main draft zone. The condensation influence of the roving twist is very positive but not sufficient to really make sure that all fibres are caught by the forming yarn.
2) Mechanical condenser: The condensation of the fibre flow can be improved by a mechanical funnel shaped condenser, located between the aprons and the delivery rollers. The use of condensers provides a very effective condensation effect, but it disturbs the actual drafting process by exerting unavoidable friction forces on the fibre flow. Due to these adverse effects the condensation possibilities of such mechanical condensers are very limited and can not be justified in many cases.
3) Aerodynamic condenser: An aerodynamic condensation after the drafting zone is a new and ideal solution to the condensation problem, because condensation happens after the drafting procedure, but before the yarn formation, by gentle aerodynamic forces. Its effect is shown in Figure 1. The fibre flow (fibre band) reaching the spinning triangle is so narrow that the value of ∆ becomes zero, i.e. all fibres are caught by the spinning triangle. The size of the spinning triangle becomes very small which allows excellent yarn formation.