Rieter

The fiber friction field

Index

The top rollers must be pressed against the bottom rollers with considerable pressure to ensure that the fibers are transported. This pressure is not only effective in the vertical direction but also spreads through the fiber stock in the horizontal direction. The compression of the fibers, and thus the inter-fiber friction, is transmitted into the drafting zone. The intensity declines, however, with increasing distance from the nip line and finally reduces to zero. The friction field is an extremely important medium of fiber guidance  [18]. It keeps the disturbing effect of drafting within tolerable bounds.

Each drafting zone has two friction fields – a rear field spreading outwards from the infeed roller pair, and a front field spreading backwards from the delivery roller pair. If the rollers are set too close to each other, so that the fields overlap, then drafting disturbance will arise.

If, on the other hand, the spacing is too great, and the intermediate zone between the two friction fields too long, then poor guidance of the floating fibers results in high unevenness. The ideal condition is achieved when the rear field extends far into the drafting zone in order to guide the fibers over a long distance and the front field is short but strongly defined, so that as far as possible only the nipped fibers are drawn out of the fiber strand.

Fig. 48 – The friction field created in the fiber strand by applied pressure