Draft is the process of drawing and drawing a fiber assembly (such as sliver, roving, etc.) regularly. Its essence is that the fibers are relative shifted along the axial direction of the assembly, so that they are distributed on longer segments. As a result, the linear density of the assembly is reduced, while the fibers are further stretched and parallel.

Broadly speaking, the essence of drafting is the redistribution of fiber in length direction in the direction of whisker, and the length of output product can be extended or shortened relative to the input product. If the process of transferring fibers from Cylinder to Doffer is considered as a drafting process, it is the process of distributing the fibers on shorter segments, similar to the drawing between the carding roll and the spinning cup in a spinning cup. One of the more ancient forms of draft commonly used by people is roller draft, which is a process of drawing and drawing the whisker strip to a fine length with the help of a system of rotating rollers with different surface speeds. In addition, the form of the input and output products before and after drafting can be the same or different, such as carding machine, winding machine and other winding forms are different; There are also the same, such as union, coarse and fine.

There are two main methods to achieve drafting, one is roller drafting, the other is airflow drafting.

The drawing of roller is realized by the action of front and rear rollers with different surface velocity and similar spacing to fiber length. It is widely used in traditional spinning process.

2. Secondary airflow drafting is realized with the help of airflow and is applied in non-traditional spinning processes.

In addition, with the help of centrifugal force, electrostatic force and other effects can also be achieved drafting.