Carding is the one of the most important process in cotton spun yarn manufacturing, because it determines the quality of yarn. This is the process, by which textile fibers are prepared to manufacture a yarn. In this process, fibers are opened at almost single, removal of dust, trash, neps and short fiber to produce a continuous strand of fiber called sliver. Carding machine is called mother or heart of spinning, because it prepares the fiber in such a way, which is ready to manufacture yarn because disentanglement, cleaning and intermixing of fiber are happened here.
Objectives of Carding Process:
- Opening and individualization of fibers.
- Elimination of remaining impurities that are not removed in blowroom.
- Reducing neps of fiber.
- Fibre mixing and blending.
- Elimination of short fibres.
- Elimination of dust
- Opening up to individual fibres
- Disentanglement of neps
- Fibre orientation or alignment
- To produce a thick sliver.
Carding machine mainly consists of feeding unit, taker-in, cylinder, doffer and a set of revolving flat-bar. The surface of taker-in, cylinder, doffer and flats are clothed with pin or wire. There are also many supporting arrangement presence in carding machine to assist the carding machine for better performance, e.g. mote knifes and carding segment etc. After opening and cleaning of fiber a condenser converts the carding web into sliver shape, which is suitable for the next subsequent process.
The word card clothing mean the placement or arrangement of wires a definite angle and density in a base material, which is suitable to cover the surface of taker-in, cylinder, doffer and flats. Among all the individual components of the card, the clothing has the greatest influence on sliver quality and productivity of the carding machine. There are mainly three types of card clothing, which are following:
- Flexible clothing
- Semi-rigid clothing
- Metallic clothing
Now a days metallic clothing is used in taker-in, cylinder and doffer but flexible clothing is used in flats. Card clothing is needed to regular grinding for its effectiveness. Grinding is a process of sharpening the wire point of card clothing.
Action in Carding Machine:
Mainly four types of action happen in carding machine, these are following:
1. Combing action: This action take place between feed roller and taker-in.
2. Carding action: This action take place between cylinder and flats.
4. Stripping action: This action take place
- Between taker-in and cylinder
- Doffer and stripper.
5. Doffing action: This action take place between cylinder and doffer.
Function of Flat:
The chain of flats revolves on the surface of cylinder and its functions are following:
- Opening the flocks of fiber into individual fibre.
- Orientate the individual fiber in longitudinal direction.
- Elimination of impurities, short fiber and dust.
- Untangling neps.
Function of Doffer:
- Collection of individual fiber from cylinder and condensed them into web.
- Straight fiber is converted into hook at the end of fiber.
- Supply the fiber web at condenser and delivery roller.
Product of Carding Machine:
The product of carding machine is called sliver. Sliver is a thick untwisted continuous rope of fibers, which is uniform in weight per unit length and suitable for subsequent process. The English count of card sliver is 0.1-0.14.
Characteristics of Card Sliver:
The characteristics of card sliver is as following:
- Fibers in card sliver are oriented in different direction.
- Hook and also projected fiber present in card sliver.
- The uniformity of sliver is not very good.
- In the web there are 50% fiber exhibit tailing hook, 15% leading hook, 15% both ends hook and a small portion without hook.
Cleaning efficiency of carding machine: 80-90%
Draft necessary at carding machine: 80-120
Production per carding machine: 30-70 Kg/hr
Recent development: The following process are associated recently in carding machine.
- Metal detector
- Auto leveling
- Continuous suction
- Electronic control system and display necessary quality report.
Carding Machine and Its Operation in Spinning Mill:
Following is the carding process summary to achieve the tasks of card:
Lap prepared from the blow room is placed on the lap roller. Material passes diagram through the lap feed card is shown in Figure 2 while chute feed card in Figure 3. Feed roller with the help of feed plate delivers it to the taker-in. The taker-in opens and cleans the cotton by dragging it on the mote knives and carding elements. Then this cleaned material in the form of tiny tufts and single fibres is transferred to the cylinder. Cylinder further cleans the cotton and converts it into individual fibre state with the help of stationary and movable flats. At this stage, neps are disentangled and short fibres are separated from cotton. A fan sucks all the waste as well as dirt and dust from the whole machine and collects them in a box.
The doffer takes the fibres from the cylinder in fleece form. From the doffer, the fleece runs through the doffing roller, crush rollers and tongue-groove rollers. These rollers scanned the cross-section / thickness of the carding sliver. The recorded results are compared with the set target value of sliver linear density. Deviations from the set value are corrected by altering the speed of the feed roller. From there, sliver in its final form is coiled into the cans with the help of coiler.
Where shown in figure 3,
- Conveying duct,
- Feed chute,
- Feed Roller,
- Card Feed,
- Knife Grid,
- Suction duct,
- Front Carding Segment,
- Cleaning Unit,
- Post carding segment,
- Cylinder Grid,
- Stripping Device,
- Calender Roller,
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