Carding Process in Textile: Definition, Objectives, and Functions

What is Carding Process in Textile?

The carding process is a crucial step in textile manufacturing, especially in cotton yarn spinning. The final stage of the blowroom process is carding. It is a mechanical operation that disentangles, cleans, and aligns fibers to produce a uniform web or sliver suitable for further processing. In this stage, the cleaned and blended tufts of fibers are opened up and turned into individual fibers. Carding is considered as the heart of the spinning process. This is the first stage in the blowroom where fiber orientation is very important. Carding is a mechanical action of reducing tufts of entangled fibers into a continuous web of individual fibers suitable for subsequent processing. Fibers begin to straighten and align in one direction.

Once aligned, the fibers are gathered together into a soft, untwisted rope called a carded sliver. The fibers hold together through inter-fiber friction, not twist. The sliver is then coiled into large cans, ready for the next stages of spinning.

A carding machine has two main parts: a large inner cylinder and an outer belt known as the flats, both covered with fine wire points. These wires gently comb the fibers, separating and arranging them into a mostly parallel form. At the same time, they remove remaining trash, impurities, and small entangled fiber lumps called neps.

During doffing, a secondary cylinder called the doffer—also covered with saw-tooth wire—takes the thin fiber web from the main cylinder and converts it into the rope-like sliver. This sliver stays intact because of the friction between the parallel fibers.

Besides cleaning and aligning, the carding process also helps in blending different types or qualities of fibers, ensuring a more uniform product for the next spinning steps.

The card is the first machine in the spinning preparation that delivers a sliver. The main tasks of the card are

• ƒRemoval of dirt particles and short fibers,
• ƒDisentanglement of the fiber flocks into single fibers,
• ƒParallelizing of the fibers,
• ƒMixing thoroughly,
• ƒDrafting,
• ƒSliver formation, and
• ƒSliver delivery and storage in a can.

Objects and Function of Carding Operation

Though a function of the blow room—a process prior to carding—is to open the matted mass of fibers received from the bales, the process never achieves complete fiber-to-fiber separation. This remains true even with modern blow room lines. The main focus of this earlier operation is to open the baled cotton into the smallest possible tufts and to carry out effective cleaning. Therefore, it is the card that must complete the action of fiber-to-fiber separation.

Apart from fiber individualization, another important task that carding must perform is to complete the cleaning action left unfinished by the blow room. Many improvements have been introduced in modern carding machines to achieve this objective. While the combined cleaning efficiency of conventional blow room and card systems used to be around 80–88%, the modern sequence now achieves a much higher efficiency—between 95% and 98%. This improvement is possible due to a completely new approach to cleaning, where the opening process itself is intensified and made more effective.

Despite the fact that modern blow rooms use new types of beaters equipped with finer spikes or saw teeth and focus mainly on producing very small tufts, the material that exits the blow room still does not reach complete fiber-to-fiber separation. Similarly, even though a greater proportion of trash is extracted in the blow room, the unlocking of very small tufts in carding is primarily responsible for releasing finer trash, which almost completes the cleaning process.

With highly effective seed traps used in modern blow rooms, broken seed particles are rarely allowed to reach the card. In general, the material delivered by the card contains only a negligible proportion of trash. The sliver from a modern card is thus much cleaner. Such a clean sliver (less than 0.2% trash) can easily meet the demands of new spinning technologies such as Rotor, Dref, or Air-Jet spinning. In fact, the latest modern card is so well-equipped that it has surpassed nearly all the advantages of the Tandem card, which was an intermediate stage between conventional and modern cards. The features of this technology are discussed later in this book.

Apart from cleaning and individualization, the card performs one more important function: the removal of neps. Neps in carding are tiny knot-like structures of highly entangled fibers that are very difficult to remove. They are usually formed due to the rolling action of fibers, which occurs when fibers rub against each other, pass over machine surfaces, or move through transporting pipes.

The removal of neps occurs in the card, primarily in the region between the cylinder and the flats. However, it should be noted that worn-out wires on both the cylinder and the flats can also cause the formation of neps. Thus, the excessive nep formation in the card is due to the deterioration of card wires. This is because, when the wires lose their sharpness, they allow the fiber material to roll over their surfaces rather than precisely carrying it around. With more vegetable-originated impurities and a higher immature fiber percentage, this tendency of fiber rolling has been observed to increase. In fact, the presence of neps in the card sliver web is one of the indicators of the quality of carding. The various features incorporated in modern carding aim at producing almost a nep-free yarn. If, however, some of the neps are left over, in spite of the best carding conditions, they would continue their journey up to the yarn stage and appear more prominently on its surface. Further, this would mar the appearance of the yarn, especially when it is dyed later. This is because these neps appear as tiny specks owing to more dye absorption.

It is known that neps are removed in combing. The combed yarns, in comparison to carded yarns, therefore, are more nep-free. However, it may also be noted that the nep removal in combing is only incidental. This is because the basic object of combing is to fractionate the short fibers. While carrying out this fractionation, the neps are also segregated.

In the card, the transformation of the lap or loose fibrous material (in the case of chute feed) into a sliver thus involves not only a great reduction in the size and thickness of material but also fiber-to-fiber separation.

The thinning-out operation, therefore, requires a very high draft to be employed in the card. Usually, this draft is around 100, and its value is kept slightly flexible so that a required hank of sliver can be produced after condensing the web delivered by the card. The typical arrangement of fibers in the card is discussed later in this book. The web condensed into a sliver is subsequently coiled into a card can for its further processing.

The objects of carding can thus be summarized as:

1. Fiber-to-fiber separation—individualization,
2. Cleaning the foreign matter left over by the blow room,
3. Removing neps and short, broken, immature fibers,
4. Fiber blending,
5. Drafting and orienting of fibers and
6. Converting a lap or loose fibrous material from chute feed into a sliver.

Conclusion

Carding is a fundamental mechanical process in textile manufacturing that prepares fibers by individualizing, cleaning, aligning, and forming them into uniform slivers. It ensures the production of high-quality yarn by meeting key objectives such as fiber separation, impurity removal, blending, and maintaining fiber integrity for further processing.

References

[1] Khare, A. R. (2021). Carding and draw frame in spinning. CRC Press.

[2] Sinclair, R. (2014). Textiles and fashion: Materials, Design and Technology. Woodhead Pub Limited.

[3] Kumar, R. S. (2014). Process management in spinning. In CRC Press eBooks. https://doi.org/10.1201/b17452

[4] Gries, T., Veit, D., & Wulfhorst, B. (2015). Textile Technology: An Introduction. Hanser Pub Incorporated.

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