# Rieter

### Draft and attenuation

#### Index

In most spinning mills today, the first intermediate product is a card sliver. It contains about 20 000-40 000 fibers in cross-section.

This number must be reduced in several operating stages to about 100 in the  yarn cross-section. The reduction can be effected in two ways:

• through the draft, i.e. the distribution of an approximately constant total number of fibers over a greater length of the product [13]; or
• through elimination of fibers (loss) into waste (p).

Elimination is not an intentional reduction of the number of fibers but arises as an unavoidable side effect of the necessity for cleaning; it occurs in the blowroom, in carding, and in combing. (Fiber loss is intentional in combing, as the aim is to remove short fibers.)

However, since drafting takes place simultaneously here, the term “attenuation” is used. This is defined by:

$Attenuation = Draft \times \frac {100}{ \left(100 -p \right)}$

p is the waste percentage.

The reduction of the number of fibers in the cross-section logically leads to a reduction in diameter of the strand. In terms of fineness, the following relationship is obtained:

$\frac {d_A}{d_Z} = \frac { \sqrt{tex_A}}{ \sqrt{tex_Z}}$

where
dA = diameter of delivered product;
dZ = diameter of infeed product.