Neps in Carding: Major Defect of Yarn Manufacturing

Neps in Carding
Bhavdip Paldiya
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
Cell: +91 9662020909

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

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

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 fibres.

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 fibre. 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.

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.
Figure shows the neps in the card sliver over neps in the raw material.
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 optimising 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/minimising 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.
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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