CARDING

 
INTRODUCTION
"Card is the heart of the spinning mill" and "Well carded is half spun" are two proverbs of the experts.
These proverbs inform the immense significance of carding in the spinning process.High production in carding to economise the process leads to reduction in yarn quality.Higher the production, the more sensitive becomes the carding operation and the greater danger of a negative influence on quality.The technological changes that has taken place in the process of carding is remarkable. Latest machines achieve the production rate of 60 - 100 kgs / hr, which used to be 5 - 10 kgs / hr, upto 1970.

THE PURPOSE OF CARDING:
to open the flocks into individual fibres
cleaning or elimination of impurities
reduction of neps
elimination of dust
elimination of short fibres
fibre blending
fibre orientation or alignment
sliver formation
 
TECHNOLOGICAL POINTS IN CARDING
There are two types of feeding to the cards
1. feeding material in the form of scutcher lap
2. flock feed system (flocks are transported pneumatically)

lap feeding
linear density of the lap is very good and it is easier to maintain(uniformity)
the whole installation is very flexible
deviations in card output will be nil, as laps can be rejected
autolevellers are not required, hence investment cost and maintenace cost is less
transportation of lap needs more manual efforts( more labour)
lap run out is an additional source of fault, as it should be replaced by a new lap
more good fibre loss during lap change
more load on the taker-in, as laps are heavily compressed

flock feeding
high performance in carding due to high degree of openness of feed web
labour requirement is less due to no lap transportaion and lap change in cards
flock feeding is the only solution for high prouduction cards
linear density of the web fed to the card is not as good as lap
installation is not felxible
autoleveller is a must, hence investment cost and maintenance cost is more

Rieter has devloped a "unidirectional feed system" where the two feed devices(feed roller and feed plate
are oppositely arranged when compared with the conventional system. i.e. the cylinder is located below and the plate is pressed against the cylinder by spring force. Owing to the direction of feed roller, the fibre batt runs downwards without diversion directly into the teeth of the taker-in(licker-in) which results in gentle fibre treatment. This helps to reduce faults in the yarn.

The purpose of the taker-in is to pluck finely opened flocks out of the feed batt, to lead them over the
dirt eliminating parts like mote knives, combing segment and waste plates, and then to deliver the fibres to the main cylinder. In high production cards the rotational speed ranges from 700-1400

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