Limitations of single carding process are: 1 In a single carding process, when a thick sheet of flocks and tufts are fed, overloading of some areas of the cylinder surface and of the flats cannot be avoided with the result that wire points fails to control and card the fibres effectively.
When the skins and seeds are crushed by the purifying rollers or crush roller in High production cards, the liberated fibres remain entangled and unopened in the web as small fiber agglomerations resulted in uneven yarn appearance.
The levelling function of a single cylinder and doffer is not sufficient to completely eliminate the uneven distribution present in the carded web.
Tandem carding system is essentially a double processing of the web to eliminate the limitations in a single carding process. The tandem carding system has two high production cards linked together so that the second card is able to do a fine job of separating every fibre as well as removing the crushed impurities passed on by the first card namely breaker card.
Principle and passage of material through Tandem carding:
After first carding, the stripping roller remove the web from doffer.
From stripping roller the web is stripped by the redirecting roller which assist in controlling the feeding of the web into the nip of the web purifying roller(pressure roller or crush roll)
From nip of the pressure roller the web comes under control of two transfer roller, which carry the web over the top so that the quality of the web produced by the breaker card is exposed for inspection.
The web now passes through finisher card which receives a fine film of fibres instead of flocks.
The tangled tuft of fibres still present after breaker carding which causes variations, is further reduced by extra carding action of the finisher card.
Any impurities, which protected by the thick fibre layer when passed through first pair of web purifying roller, is crushed and eliminated in the India roll unit mounted at the end of the finisher card.
Advantages:
Improvements of yarn qualities:
Increase of 3% CSP
Improvements in U %
Reduction of 50% neps;
Reduction pf 20 % Thick thin place:
Reduction of 35%end breaks in ring spinning.
Upgrading: No single card can match the Tandem's ability to produce high quality yarn from low grade cotton.
In open-end spinning, the operating efficiency is improved by unmatched degree of trash removal & fibre individualization achieved in tandem card.
Economy in combing process:
ft reduction of 3 to 5 % waste at combing will still yield yarn
of equal quality.
Waste blends:
Tandem card can operate at high speed with ultra short staple blends of waste fibre etc, which may be impossible to process on single cards.
