Neps in Carding: Major Defect in Yarn Manufacturing

Last Updated on 24/10/2025

Neps in Carding: Major Defect in Yarn Manufacturing

Bhavdip Paldiya
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
Email: bhavdipk9009@gmail.com

Neps in Carding:

Textile terms and definitions define a `Nep’ as a small knot of entangled fibers that usually comprises dead or immature fibers.

Neps are tangled masses of fibers. They appear as specks in white cloth and as uneven dyed spots in colored fabrics. They tend to lower the yarn strength and increase the end breaks in spinning. The tangling or rolling over of the fibers during the process leads to formation of neps9 and the phenomena is basically due to loss of control over the fiber movement.

Neps in cotton continue to be a major problem in the cotton yarn manufacturing process. The two main factors affecting nep formation are fiber characteristics and mechanical processing. The mechanical processes affecting neps formation include ginning, opening and blending, carding, combing, drawing and spinning.

A cotton with a low maturity level is highly susceptible to nep formation. This is because the immature or dead fibers tend to easily roll or curl around when subjected to beating or rubbing action. Thus, the maturity level of the raw material greatly influences the appearance of neps in the card web—the more the immaturity of the material, the more neps in the card web. The fibers which form the neps are essentially shorter in nature. In certain situations, however, higher neppiness may also mean heavy fiber breakage. This is because neps may also be formed when processing longer-staple fibres which are under strain during processing. However, with man made fibers, where there is no element of maturity, neps are still seen in the card web.

It has been observed that the nep level in carding increases when its production rates are increased. However, even at the same doffer speed, when the feed is increased (coarser hank of lap), the neps in the card web are found to increase. On the other hand, when the sliver hank is made lighter, the nep level falls down. A well set card with good mechanical condition should remove more than 50% of the neps presented to it. When the conditions are adverse, a card may also create neps. The most important influence on this is the condition of the card wires; if the wires are not sharp, they lead to high nep levels in the card web.

Neps are associated with poor yarn and ultimately with poor fabric appearance and have an effect on yarn uniformity and dyeing quality.

Neps in the raw material can be classified as mechanical neps or biological neps. Mechanical neps are those made up of only fibrous material containing at least five or more fibers.

Neps containing foreign material such as seed coat fragments, leaf or stem materials were designated as biological neps.

A third category of neps found on the surface of the dyed fabrics was named pancake type neps. This type of nep appears as light or white spots in the finished fabric.

Ginning conditions that influence nep formation are the ginning process itself, the amount of lint cleaning, heat history and the amount of energy input into the individual fiber. In one study, it was found that ginning using three tower driers and two lint cleaners significantly increased the amount of card web neps compared with one lint cleaner and without using heat for drying.

Carding both generates and removes neps. Carding is the most significant process where significant decrease in the level of neps can take place.

It was also observed that with finer cottons, increasing the card licker-in speed increased the card web neps.

A closer flat-cylinder setting, on the other hand, reduced the web neps. It was also found a good correlation exists between the card web neps and the yarn neps.

Hence trials are to be concluded based on critical nep size reduction. The number of neps above critical nep size shall be eliminated in carding by optimizing setting, grinding frequency, wire condition/replacement, suction, process parameters, etc.

It is to be noted that neps below critical nep size will not influence yarn quality/fabric appearance significantly. This analysis and controlling / minimizing of critical nep size is highly significant for yarn dyeing quality requirements.

It is also advisable that any trials/R&D study should be concluded based on knitted fabric appearance/critical nep size in carding to impress / delight yarn buyers by manufacturing premium yarn quality.

Effect of Carding Parameters on Neps

1. A proper synchronization between licker-in and cylinder speed not only reduces nep formation but also permits higher production rates. With an increase only in licker-in speed, there are:

• Few fibers per licker-in tooth
• Better opening and cleaning of the material processed
• Uniform distribution of fibers on cylinder

2. The speed of the flats is important only when flexible tops are used. A higher flat speed is reported to have better nep removal. However, with strip-less or metallic flat tops, the flat speed hardly seems to matter. The closer setting of the flats to the cylinder avoids any rolling of fibers and this is likely to reduce neps.

3. The closer setting between doffer and cylinder is conducive to better transfer of fibers on the doffer. This leads to less reworking of fibers around the cylinder and reduces nep formation.

4. When the doffer speed is increased at a constant production rate, the neps content in the web is reduced. This is because, in this case, the doffer strips the cylinder more effectively making more fresh wire points available for the incoming fibers from the cylinder. Even when card production is increased by increasing the overall speed of the machine, the neps do not seem to increase significantly. However, when much higher production rates than the normal are tried by simply increasing the doffer speed, the neppiness of the sliver as well as that of the yarn increases. This is also accompanied by a fall in the yarn strength and more end breaks at ring spinning.

5. The neps are highly correlated to cylinder loading where the fibers start accumulating on the cylinder wire surface. For a given production rate, the rate of cylinder loading increases rapidly when the feed is increased. With excessive humidity and damaged wires, the cylinder loading becomes a serious problem. Especially when the cylinder wires get contaminated with oil licking from shattered seeds or with waxy material present on the fibre surface, or even “honeydew”, its surface becomes sticky. All these factors lead to more cylinder-loading and leads to more nep formation. The loading on the doffer is comparatively very small and does not seem to affect the nep formation much.

6. With flexible wire, the stripping frequency had a profound influence on the formation of neps. However, with metallic card, the stripping frequency does not much influence the nep generation.

7. Use of split tops or reversing the direction of flat has been reported to give an advantage in controlling nep level.

8. The frequency of grinding the cylinder–doffer wires is perhaps the most important criterion governing nep level. Dull and rough wire points give the rolling action to the fibers. This is purely because of inadequate control over the fibers by wire points. The need for grinding of wires on these two organs, and especially the cylinder, can be judged correctly if regular quality control checks on the neps in the card web are observed. The nep level in the card web is such a good measure of the condition of the wire points that, if the nep readings before and after grinding do not show significant difference, it clearly indicates improper grinding.

Conclusion:

Neps are a significant yarn defect originating from carding, influencing yarn uniformity and fabric quality. Controlling carding parameters and maintenance are crucial to reduce neps and produce superior yarn.

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Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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