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Yarn Engineering

Yarn engineering is the process of constructing yarns utilizing procedures designed to change the desired properties of the yarn itself. Conventionally, the textile industry has leaned towards a more experienced based and technological approach to making yarn; however, an engineering approach can provide an alternate viewpoint and wisdom that can possibly be overlooked by other methods. The specifics of this approach are geared toward optimization of cost and utility of the fabric being made.

Yarns are possibly the most versatile fibers used in fabric making. The ways in which they are put together as well as their individual properties determines the properties that they possess as a final product. The process of manufacturing yarn is a complex one and each step in this process can change the porosity, thinness, and flexibility of the final fabric. The steps are comprised of carding, combing, drawing out, twisting, and spinning.

Yarn Classifications

Yarns are either synthetic of naturally made from fibers. There are differences between the two and one type may be chosen over another depending on the manufacturer and what they are looking for in their product. The two most common classifications in yarn making are staple spun and continuous filament yarn. Staple spun yarn consists of fibers that have restricted lengths and can be divided into the two subcategories of short and long staple. Any fiber with lengths of more than 2 inches crosses over into the long staple category. Continuous filament yarn is the second type of yarn and is make from long strands that do not break into smaller strands.

Synthetic

Synthetic fibers are much easier to handle and the process for making them requires much less energy and time. Most synthetic fibers are continuous filaments and made in chemical factories.

• Polyesters-Durable fibers resistant to stretching and shrinking and often using in clothing.
• Rayons-Thin fibers made from cellulose used to make comfortable feeling clothes.
• Nylons-Complex synthetic fiber that has myriads of uses. Properties differ depending on manufacturing methods.

Natural

Microscopic fibers of silk, wool, and cotton respectively

Natural fibers normally fall into the staple spun category and require much more experience and time to manufacture. Vast technological advancements have continued to make manufacturing natural fibers simpler and has contributed to them still being viable resources.

• Cotton-The most commonly used staple spun yarn. Used in clothing, coffee filters, book binding, etc.
• Wool-Another common textile that must go through a purification process involving the removal of animal fat and plant based matter before being made into yarn at a spinning mill.
• Silk-The only natural continuous filament fiber. It has gained its reputation as being soft and comfortable. It is produced by special worms and cultivated on farms.

There are other fibers that can fall into the natural and synthetic categories. These are the most common fibers used today and are provided as exemplary fibers.

Manufacturing Process

As stated above, each step in the process of making fiber into yarn is unique and can contribute different properties to the yarn. These steps are carding, combing, drawing out, twisting, and spinning.

Before the fibers can be carded they must be cleaned and separated. Natural fibers are normally the ones that need to be cleaned while synthetics only need to be separated. Each preparation process may be slightly different for individual fibers. Once this is finished the step by step process ensues.

1. Carding-During the carding process fibers are separated via a carding machine and pulled into a web form where all the fibers line up in parallel. The result is a thin string-like rope wrapped around a cylinder.
2. Combing-After the carding process is complete and depending on the type of fiber used, combing may be appropriate. Not all fibers use the combing process and it is normally reserved for softer, smoother yarn. This process removes shorter fibers and further shapes them into parallel form within the strand using a comb-like device.
3. Drawing out-Sometimes these first three process can be combined to provide the most efficient strands or slivers as they are sometimes referred to. During the drawing out process slivers are lengthened by rollers rotating at different speeds. This allows for the strand to become smoother and more consistent. This step is repeated multiple times if the fibers are carded and is performed once before the combing process and twice afterwards. This is an example of how the first three steps of this process can be combined.
4. Twisting-Slivers are put into another machine where they are stretched and twisted further to strengthen the strands. Slivers are referred to as roving after they pass through this stage of the process.
5. Spinning-There are several methods that can be used for the spinning process. The methods that dominate the manufacturing process today are the open-end and ring spinning process. In the open-end process the twisting step is omitted and instead, the sliver of fibers is put through the spinning part of the machine. In this step the sliver is beaten until the fibers are separated into thin streams which are dropped into V-shaped grooves along the sides of a rotor. the rotor then rotates producing twist in the slivers which come out of the other end of the machine as yarn. The other process that is the most common is the ring spinning process. This process includes the twisting stage and feeds the roving from the spool into rollers which further lengthen them. From here the roving is fed into an eyelet and through a traveler. This part of the machine looks much like a fishing reel. The traveler is rotated at high speeds while spindle also rotates the bobbin. These two rotational processes when performed together twist the yarn and wind it at the same time.

Visualization of Modern Spinning Machine

Qualities

Yarns come in many forms, shapes, and each have different qualities as well. Some factors during manufacturing can change the properties of the yarn itself as well. For instance twist. Twist in yarn redirects the effects of pressure and tension radially and allows the yarn to carry extra force without breaking. This can be useful if one wanted to make a durable yarn. other important qualities to consider include thinness, flexibility, and porosity to name a few. Porosity refers to the amount of wet the yarn will soak up, and is affected and can affect a number of other properties such as the feel of the yarn and how long it lasts.. Thinness and flexibility respectively refer to how fine the yarn may be and how much it stretches when axially loaded.

References

Yarn Engineering

Yarn Engineering System

Fundamentals of Yarn Technology

Classification of Fibers

Textile Textbook

Manufacturing Process