Functions of Carding

The card used in woollen spinning is traditionally the sort with cylinders (covered with clothings that are angled to varying degrees), which rotate at different speeds, effecting the three cardinal actions: carding, stripping and raising. Appropriately combined, these three actions allow opening of the tufts, continuous detachment of the fibres from the card clothing, which would otherwise soon become clogged up, and delivery of the material from the machine at the end of a processing cycle.

Carding fulfils a series of precise objectives, serving:

• to open the blend fibres fully and definitively
• to arrange (as far as their length allows) the fibres parallel with one another
• to remove impurities
• to blend the raw material further
• to reduce the blend to a web of fibres and to divide it up into rovings of the required count, suitable for feeding to the spinning machines.

Carding plays a crucial role in all spinning cycles, and its role is never more central than in the woollen spinning cycle, in which it incorporates different functions, all essential in order to obtain the level of quality required of the product.

Basically, passing the material over the card undoes tangles of fibres and therefore makes it possible to remove all kinds of impurity. This is achieved thanks to the action of the spikes covering the surfaces of cylinders that rotate around parallel axes.

The equipment also fulfils another function, which is both delicate and fundamental: it has to guarantee the accuracy and evenness of the web count and subsequently of the roving count. Indeed, the definitive spinning machines that operate within the woollen spinning cycle can impart only a very low draft, which means that there is practically no possibility, at this stage, of intervening to correct the yarn count.

The carding room equipment thus performs the same operations already carried out in the preparation stage, this time more thoroughly, supplying the divider with rovings of the right count.

Following are some of th defects in the Carding process

• Causes of high sliver variation
• Nep formation
• Holes or patches in card web
• High sliver variation in due to difference in draft between card
• Worn clothing and feed roller bearing also create variation in card sliver
• If auto leveler is not working properly than this will also create high sliver variation. If auto leveler is off then check the wrapping of carding after every 30 minutes.

Causes for Neps Formation

• Insufficient stripping
• Dirty under casing ( grid bar)
• Uneven flats setting
• Under casing chocked with fly ( waste)
• High roller speed

Causes for Holes or Patches in Card web

• Poor flat stripping
• Hooked or damaged wires on flats
• Damaged cylinder
• Cluster of cotton embedded on cylinder wires

In order to avoid sliver variation draft calculation should be correct. Testing of sliver must be on time at least 3 times during shift.

• High sliver variation problem may also be due to maintenance problem. So concentrate on maintenance. If our maintenance of machine will be there, then it will get more efficiency and better quality will be achieved. If expiry time of some part of the machine is there, then on time it must be replaced.
• Now a days in advance technology the cards, auto leveler are electronic which adjust the sliver weight automatically. For getting better result with automatic auto leveler, it is also necessary to check sliver weight manually as well.

Preventive action for nep formation

• Over hauling of machine must be on time. During over hauling, setting of every part of the machine has to be checked. Flat setting play very important role for reducing nep formation. So flat setting must not be uneven.
• Suction waste point should be properly working. This point must not be chocked. If there will be chock then neps formation will take place. Suction waste point also to be checked manually as well.
• This problem is also related to maintenance. Over hauling of every machine must be on time. Wire of flats and cylinder have specific time limit of production. After that specific time limit it must be changed. As these play very important role by quality point of view.