What is Carding in Textile?
Carding is the action of reducing tufts of entangled fibers into a filmy web of individual fibers by working the tufts between closely spaced surfaces clothed with opposing sharp points. In carding process, fiber tufts are further opened and separated to almost single fiber stage by the card and thereafter reassembled the separated fibers in to a nice randomly placed overlapping array of fibers called sliver. Carding ensures that the fiber is thinned out and evenly distributed along a roll to facilitate spinning. It is known that neps are removed in combing. The combed yarns, in comparison to carded yarns, therefore, are more nep-free.
The card is the first machine in the spinning preparation that delivers a sliver. The main tasks of the card are:
- Removal of dirt particles and short fibers,
- Disentanglement of the fiber flocks into single fibers,
- Parallelizing of the fibers,
- Mixing thoroughly,
- Drafting,
- Sliver formation, and
- Sliver delivery and storage in a can.
Objectives of Carding Operation:
The objects of the carding machine can thus be summarized as:
- Fiber to fiber separation—individualization,
- Cleaning the foreign matter left over by the blow room,
- Removing neps and short, broken, immature fibers and
- Converting a lap or loose fibrous material from chute feed into a sliver.
Material Passage Diagram of Carding Machine:
The material passage diagram of a carding machine can be described as follows:
a) The lap produced in the blow room (in the case of chute feed, loose fluffy sheet directly entering the feeding system) is placed on the lap roller and a sheet of cotton is unrolled onto a horizontal table.
b) The material passes through a feed roller and feed plate, which grips the material firmly to prevent irregular plucking by the licker-in roller.
c) The licker-in, a fast-moving roller with saw-tooth wire points, opens the cotton fibres, removing impurities and trash with the help of mote knives and undercasing. The striking distance between the closest point of the feed plate and the points on licker-in saw tooth wires is very small (0.25 mm or 0.010 in).
d) The fibers are transferred from the licker-in to a larger and faster-moving cylinder, which further opens and distributes the fibers. The cylinder is considerably larger in diameter than the licker-in [50 in (127 cm) as compared to 9 in (approx. 23 cm)] and has almost twice the surface speed (660 m/min) than the licker-in (320 m/min). The wire points of cylinder and licker-in, at their closest distance, are merely 0.127 mm (0.005 in) apart.
e) The fibres enter the cylinder-flat zone, where flats with fine wire points perform a carding action, further individualizing the fibers.
f) The flats are cleaned by an oscillating flat wire comb and rotating brush, ready for the next carding cycle.
g) The fibers are transferred from the cylinder to the doffer, forming a thin layer that condenses into a thicker layer called a card web.
h) The card web is stripped by the doffer comb and condensed into a rope-like form called sliver, which is coiled into a can for further processing.
i) The card sliver cans, often equipped with casters, are transported smoothly to the next processing stage, typically the draw frame.
