Drawing, also called drafting, in yarn manufacture, process of attenuating the loose assemblage of fibers called sliver by passing it through a series of rollers, thus straightening the individual fibers and making them more parallel. Each pair of rollers spins faster than the previous one. Drawing reduces a soft mass of fiber to a firm uniform strand of usable size. In the production of man-made fibers, drawing is a stretching process applied to fibers in the plastic state, increasing orientation and reducing size.
Drawing's main purpose is to further align and parallel the semi-oriented fiber from carding. In accomplishing this, blending (or doubling) is also achieved. From 6 to 8 card slivers are combined to be fed to the initial drawing process, sometimes called breaker drawing. A series of pairs of rollers are used to reduce the multiple slivers being fed back down to the approximate weight of one sliver. These roller pairs consist of one rubber-covered top roller and one fluted steel bottom roller. Spring or air-generated pressure is used to hold the slivers firmly.
There are surface speed differences from the back pair of top and bottom rolls to the front set, with the back pair turning more slowly and gradually building in speed through to the front set. This mechanical speed difference, and the slipping action imparted to the gripped fibers, is called draft or drafting. This is where the drawing process gets its name. The machine draws out the slivers being fed and reduces their total weight back down to the approximate weight of one sliver. In doing this, the trailing ends of the gripped fibers, which may not be completely straight, are straightened out by the slipping and pulling action imparted to them. As the drafted fiber web exits from the front set of drafting rolls, it is condensed back into sliver form using a trumpet-like device and the resulting sliver is coiled into a can. Once again, this is for temporary storage and for transport to the next process. Depending on what spinning system will be employed, the end product, and other process considerations, the output sliver from breaker drawing may be drawn once more (called finisher drawing) or it may be used directly for the spinning process. This is the point that the breaker-drawn sliver may also be directed to the combing process.
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