The purpose of carding is opening thoroughly the cotton received from blowroom and individualizing the fibers by carding action, and then converting the carded cotton web into a sliver form, coiling and delivering it in cans for next process. Carding is one of the most important operations in the spinning process as it directly determines the final features of the yarn, above all as far as the content of neps and husks are concerned. It helps us both way to open the tuft into a single fiber and to remove the impurities and neps. So it is said that “The card is the heart of spinning mill”. Card feeding is done by two ways. One is manually and other is through chute feed system. In manual case the lap which is produced in blow room and it is feed to the card. In chute feed the material is feed through air flow system to card machine. It is important to say that lower the feed variation better is the carding quality. Lower the feed variation then draft variation will also be less. Approximately 90% cleaning efficiency is achieved with the help of carding machine. During carding process, different kinds of problems occur. Among them neps is remarkable fault.
Main Problems / Defects in Carding Process:
- Patchy web
- Sagging web
- High card waste
- Low nep-removal efficiency
- Higher U% of sliver
- Bulky sliver
- Higher breaks
- Snow balls
- Hole in web
- Poor cleaning efficiency
- Ragged selvedges
- Fluff generation at cylinder sides
- Undercasing side fly at cylinder
- Feed roller lapping
- Fiber ruptures
Problems, Causes and Way of Remedies in Carding:
1. Patchy web:
May be due to loading on the cylinder, damaged or pressed wire points, waste accumulation below cylinder under casing or defective undercasing.
The following actions can be taken to solve the problem:
- Grind the flats and cylinder. In case of major damages replace the wires.
- Correct the settings between cylinder and flats, cylinder and back plate.
- Improve feed roller grip.
May be due to lap licking, less feed in chutes, part of carded web getting sucked by the waste extractor, damaged doffer wire and direct air currents hitting the web.
3. Sagging web:
May be due to insufficient tension draft, very high humidity, worn out key in the calendar roller gears, heavy material fed to card and inadequate calendar roller pressure. Increase tension draft between doffer and calendar roller. For excessive sagging reduce doffer speed, maintain RH between 50% and 60%.
4. High card waste:
High card wastes are due to damage under casings, higher flat speed, wider front plate setting, closer setting of flats, and higher pressure in suction unit and fibers getting ruptured.
5. Low nep-removal efficiency:
Blunt wire points, too wide setting between feed plate and licker-in, uneven settings, burrs in front plate/ back plate, and card wires of coarse type are the main reasons for low nep-removal efficiency.
To reduce neps, following actions may be taken:
- Ensure that the cylinder speed is high, appropriate to the type of card.
- Select proper wire points and ensure that they are sharp and in level.
- Ensure that the fl at and cylinder settings are as close as practicable.
- Keep all surfaces like back plate, front plate, cylinder undercasing, etc., which come in contact with fibers smooth. The smoothness can be achieved by periodic polishing with ‘00’ emery paper, and then applying a paste of French chalk and turpentine, allowing it to dry and the rubbing again with clean, non-oily hard waste.
- Make hank finer and increase the doffer speed to maintain production rate.
- Ensure proper gauge between cylinder and doffer.
- Prevent cylinder loading by ensuring uniform and light feeding.
6. Higher U% of sliver:
Worn out parts, eccentric movement in coiler calendar or table calendar rollers, uneven feed, waste accumulation in material patch, improper settings and loading of fibers on cylinder and flats are some of the reasons for higher U% of card sliver.
Reasons for higher U% of card sliver:
- Check the eccentricity, wobbling, worn-out gears, gears meshing too deep, oblonged bores of gears, loose keys, loose key ways, insufficient tightening of gears of table and coiler calendar rollers, and rectify the defects.
- Check the condition of trumpet and if it is damaged/oblonged/burred, replace it with a new one. Try bigger diameter of trumpet.
7. Bulky sliver:
Slivers become bulky by use of trumpet of a very large size and lower calendar pressure.
8. Higher breaks:
Very small trumpet, worn out trumpet, uneven sliver with bunches of fibers, worn out gears, damaged clothing, air currents disturbing the web, improper temperature and humidity, very high tension-draft, poor transfer of fibers between cylinder and doffer wires and short of feed from blow room in case of chute feed cards causes higher breakages of web and sliver.
Remedies of higher breaks:
To reduce tension draft between doffer and calendar roller in steps till the defect is controlled. Install barriers for air movement especially near the web. Install apron-doff system for collecting web and converting it into a sliver. Check and improve the mechanical condition of the machine, especially of table calendar roller.
9. Snow balls:
Small round balls are found in web. To avoid this, the horizontal portion of the cylinder casing should be sharply bent downwards.
10. Ragged selvedges:
This problem is due to nonalignment of feed to the cylinder. Center the lap in card width by putting wooden packing of equal thickness in the gap between the lap and lap stands at both the ends of lap.
Remedies of ragged selvedges:
This is necessary when the gap between the lap and the lap stand is more than 5 cm. Also set the selvedge guide to give a quarter fold to the lap on either side. Extend selvedge guides, in the form of aluminium strip, acting on the lap right from the lap stand up to feed roller.
11. Hole in web:
Damaged, especially pressed wire points on doffer are the main reason for holes in the web. This can happen due to any foreign matter like metal pieces, coir, leather or wet and entangled cotton lumps getting fed along with sliver. Locate the damaged wire portion on doffer and replace the damaged portion skillfully with new wire and then level it with the rest of the doffer wire points.
12. Poor cleaning efficiency:
The reasons for poor cleaning efficiency in a card are poor condition of wire points, improper fl at settings, poor transfer of fibers between cylinder and doffer wires, flats getting loaded because of improper cleaning by Philipson roller, improper gauge between lickerin to feed roller, improper cylinder to doffer gauge and improper humidity conditions.
13. Fluff generation at cylinder sides:
This problem is normally seen in old cards. Reduce the gap between the cylinder and cylinder framing to 34/1000 evenly on all sides. If the card design permits put flannel lining on the inside portion of the side curve framing.
14. Undercasing side fly at cylinder:
The reasons for side fly at cylinder undercasing are squaring of cylinder undercasing not done correctly, scratches on undercasing, gauge not slightly looser in the middle of the undercasing compared to the left and right side edges, improper setting of undercasing tongue and poor condition of cylinder and doffer wires.
15. Feed roller lapping:
The normal reasons for feed roller lapping are suction clearer/pneumafil box choked, very close setting between the feed roller and licker-in, worn out feed roller and feed roller wire, poor condition of rubber flap on the feed roller, rubber flap not touching the roller and improper loading of feed roller.
16. Fiber ruptures:
A very tight fl at gauge and too narrow settings of feed plate to licker-in are normal reasons for fiber rupture in carding.
- Training and development of technical staff in textile industry by B. Purushothama
- Handbook on Cotton Spinning Industry by B. Purushothama
- Reference book for spinning by Ezio Carissoni, Stefanno Dotti, Franco Fleiss, Luigi Petaccia, Lucia Pieri
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- Chute Feed System in Carding: Advantages and Disadvantages
- Neps in Carding: Major Defect in Yarn Manufacturing
- Doffer in Carding Machine: Types, Specification, Functions & Maintenance
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.