Carding Faults in Textile Production: Causes and Remedies

Carding is an important process in yarn spinning that transforms raw fibers into a uniform web. During carding operation, several types faults can occur, it can significantly affect the quality of the final yarn. Understanding these carding faults, their causes, and remedies is essential for smooth operations and high-quality output.

Common Carding Faults in Textile Production: Their Causes and Remedies

Common carding faults in textile production include nep count of the web unsatisfactory, patchy web, holes in webs, bulky sliver, lower nep removal efficiency (NRE%), sliver variation, cloudy web, snowball formation, sagging web, disappearing web, loss in yarn strength, higher breaks, malformed selvedges, higher U% of sliver, high card waste and fiber ruptures. These carding problems, causes and remedies in spinning mill are briefly discussed below.

1. Nep Count of the Web Unsatisfactory

Tiny fiber clusters or knots called neps appear in the web. The neps are formed in carding when the fibers go out of control and are allowed to roll during processing.

Causes and Remedies:

a) Condition of Wires
If the last grinding applied to the wires was done long time ago, the wires become dull and lose sharpness. A fresh grinding, therefore, is necessary. If the wire itself has been in use for a long time, it really becomes old. In this case however, it needs to be replaced.

b) Loading on the Wire Surfaces
When the cylinder wire surface becomes overloaded, the carding action suffers and as a result, neps are produced. It is possible that the wire surface where the loading is predominant is damaged or there is accumulation of some sticky dirt.

c) Settings
The back plate setting usually controls the distribution of fibers on the cylinder. If air currents around the cylinder in this region are not guided properly, they lead to turbulence and this allows uncontrolled movement of fibers, thus leading to formation of neps. The action of the flat is very important in removing neps. Both their speed and the setting with cylinder decide the nep removal potential. A closer setting between cylinder and doffer helps in effective transfer of fibers. A poor transfer in this region implies that the fibers are allowed to go around the cylinder repeatedly and this increases the nep level in the card web.

d) Immature Fibers
If the raw material contains a high proportion of immature fibers, it leads to high nep generation. This is because these fibers can curl, bend or roll quickly to form clusters. Especially with mechanical harvesting, it is highly likely that some immature cotton balls are picked-up along with the normal lot. In ginning, these fibers give rise to nep formation.

e) Production Rate
A higher production rate through higher doffer speed or lap weight always leads to higher nep generation (except in a modern high-production card).

2. Holes in the Web

A hole in the web means a very thin portion in the card web where fibers are missing or unevenly distributed.

Causes and Remedies:
When it is immediately followed by a lump of material, it means that at some point on the cylinder undercasing, the material has been temporarily held and then released. Checking the joints of two undercasings or any roughness on its working surface reveals the source.

If either cylinder or doffer has a damaged portion of blunt wires, the result will be occasional blanks in the web. Improper stripping of doffer by the comb owing to roughness developed on the comb blades also leads to formation of holes in the web. A light polishing by emery can be a remedy. A damaged blunt wire on the doffer is not in a position to receive fibers from the cylinder and also causes a blank or hole in the web.

3. Snowball Formation

When small balls come out with the web, the defect is termed snowball formation.

Causes and Remedies:
When the fibers accumulate at the cylinder undercasing they are picked up by cylinder wires in bunches and are usually allowed to pass as balls. The accumulation is basically due to rough surfaces at the undercasing and these must be smoothed out. The flat portion of the cylinder undercasing (middle portion) should sharply bend downwards so that fiber accumulation is prevented.

4. Cloudy Web

The card web shows uneven color or density, with light and dark patches instead of a uniform appearance.

Causes and Remedies:
A web consisting of unopened fibers in general or clusters of fibers emerging together is direct evidence of poor carding. The web appears cloudy mainly because of unopened material appearing in patches against the semi-transparent web. This is due to blunt or damaged wires of the flat and cylinder, thus hampering effective fiber-to-fiber separation. The cloudy web is also due to a wide setting between cylinder and flats, and improper back plate setting (setting too wide or too close), which leads to air turbulence.

5. Ragged Selvedges (With Lap Feed)

Ragged selvedges (with lap feed) means the edges of the card web become uneven, torn, or irregular instead of forming smooth, clean sides.

Causes and Remedies:
Uneven and weary selvedges are the result of improper setting of selvedge lap guides. These guides should be adjusted to give a quarterfold to the lap before it is gripped by the feed roller. If the lap width is smaller than the card width, wooden packing of suitable width should be provided at the lap stand to keep the lap correctly at the centre. Damaged wires at the edge of the licker-in, cylinder or doffer may also result in ragged selvedges.

6. Fluff Generation from the Cylinder Side

It happens when loose fibers escape from the sides of the carding machine, mainly between the cylinder and the side framing.

Causes and Remedies:
When considerable fluff is generated between the cylinder side and the side framing that support the flexible bends, it is owing to a wide gap between them. Especially in high production carding, when the cylinder speeds are higher, this wide gap allows an escape route for air currents, which also carry along with them, this fluff through the sides. Therefore, it is essential that these gaps be suitably sealed. Improper squaring of cylinder with respect to the framing also leads to this type of defect. A gauge between 0.635 mm (25/1000 in) and 0.864 mm (34/1000 in) is found to be satisfactory to avoid excessive air leakage.

7. Shifting in Web Stripping Point

In conventional cards using doffer comb, it occurs when the web detaches irregularly from the doffer, moving up and down around the doffer comb.

Causes and Remedies:
When the doffer wires become dull and blunt because of improperly scheduled grinding, the point at which the web leaves the doffer shifts up and down around the doffer comb. Though it cannot be truly termed as a defect, it certainly indicates the need to improve the doffer wire condition.

8. Web Sagging

In the conventional card, the web, as it leaves the doffer, slightly curves around the doffer comb and then moves further along a straight path towards the nip of the calender roller. However, when the major portion of the web sags low, it is due to different reasons.

Causes and Remedies:
When the cotton is very soft and humidity is very low, the web starts sagging due to the poor clinging power of fibers. The lower humidity also induces static generation, which further aggravates the situation and sometimes even allows dropping of the part of the web portion.

When the tension draft between calender roller and doffer is very low, the web may sag because of insufficient pull from the calender roller. Very high humidity, on the other hand, makes the fibers in the web absorb excessive moisture and thus the fibers are in a wet condition and become heavier. This may also lead to sagging of the web. Raising the mean oscillating position of the doffer comb was one of the remedies sought in the mills with conventional cards.

9. Poor Card Cleaning Efficiency

After the blow room, carding is perhaps the only major process for cleaning the remaining trash from the cotton. Therefore, cleaning efficiency at the card has an important bearing on the quality of the sliver produced.

Causes and Remedies:
In card, the major cleaning takes place in the licker-in region. Hence, for very effective removal of trash, the licker-in wire condition must be really good. The licker-in wire points for this purpose must be sharp enough to act very positively on the lap fringe presented to it. The speed of the licker-in, contrivances around it and the type of wire all play an important role in this action. The feed rollers must move smoothly and uniformly. The pressure must be adequate so as not to allow any snatching and at the same time should ensure uniform feeding of material to the licker-in.

Conclusion

Carding faults can severely impact the quality of cotton sliver and subsequent yarn formation. Regular maintenance, correct machine settings, and timely replacement of worn parts are key to minimizing these defects. Understanding the root causes of carding faults helps textile engineers keep production smooth and efficient.

References

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

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

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

[4] Lawrence, C. A. (2010). Advances in yarn spinning technology. Elsevier.

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