Yarn Manufacturing: Preparation for Spinning

Drawing, combing, and roving are the last three steps in yarn manufacturing. Familiarity with the steps in fiber preparation will help you make informed decisions when working with spinners towards your ideal product. Learn more at https://cottonworks.com/en/topics/sou....

Drawing’s main purpose is to further align, parallel, and blend the semi-oriented fiber after carding. Anywhere from six to eight card slivers are combined for the initial drawing process, sometimes called breaker drawing.

A series of rollers are used to reduce the multiple slivers back down to the approximate weight of one sliver. To do this, the rollers turn at different speeds as they pull the slivers through, which is called drafting. The back pair turns the slowest, and the rollers gradually build in speed through the front set. The trailing ends of the gripped fibers, which may not be completely straight, are straightened out by the slipping and pulling action of the rollers.

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. The resulting sliver is coiled into a can for transport to the next process. Depending on what spinning system will be employed and the desired final product, this output sliver may go through the drawing process again (called finisher drawing).

Combing removes short fibers from the yarn-making process. Depending on the cotton fiber being combed and the settings of the comber itself, what qualifies as “short” can vary. Generally, it means fibers that are half an inch or less in length.

Generally, combing is done to increase the yarn count range of the material being processed. A finer yarn can be made from combed cotton which tends to result in an end product with extra sheen, drape, and hand. Combed yarns and the resulting products tend to be softer and yield more durability. From an engineering standpoint, combing may be required for some yarn counts and product performance standards. For other products, combing may be a price point decision.

The combing process starts by preparing what is known as a lap, or drawn slivers that are wound in a ribbon-like fashion onto a spool. This wound lap becomes the input for the combing process.

For each combing cycle, a measured amount of the lap is fed out and held fast for the pass of the half-lap. The half-lap is a wire or needle-covered section mounted on a rotating shaft that passes its teeth or needles through the held beard — the measured lap that has been fed out and held fast.

The fibers that are not held fast are removed by the half-lap and are often recycled into a less critical yarn. The combed webs are condensed back into sliver and coiled into a can for transport to the yarn spinning process.

The roving process is a preparatory process used only for ring spinning. Finisher-drawn carded or combed slivers are fed into a simple roller drafting system where the linear weight is reduced to a size that is optimum for the yarn count to be spun.

Since the linear mass is now drafted to a very light weight, some twist insertion is also necessary to give the roving enough integrity to be pulled from the bobbin on the ring-spinning frame. The roving is wound in a precise manner onto a bobbin that is ready for the ring spinning process.

Learn about the first three steps in the process:    • Yarn Manufacturing: Opening, Cleaning, & C...  .

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