Saturday, January 24, 2015
Carding is the second stage of cotton spinning. It is defined as the reduction of entangled mass of fibres to filmy web by working them between two closely spaced relatively moving surfaces closed with sharp points i.e. wires.
The process of using a card (a thistle or teasel) for combing textile fibres. This consists of combing or brushing fibres until they are straightened and placed parallel. For this, the imperfect fibres and other impurities have to be removed. James Hargreaves and Louis Paul were two of the persons concerned with this invention and improvements to carding. Since then, innumerable attempts have been made to improve these machines, but in spite of this and also the latest improvements made, carding remains essentially the same as established nearly 200 years ago.
Since the functions of the card are to place the fibres parallel and remove other impurities so that perfect fibres can be drawn in sliver, the rollers of carding machine have to be so arranged, as would perform these functions perfectly.
Carding machine consists of 3 cylinders, covered with cards. (1) Taker-in is smallest, (2) Main cylinder is the largest and (3) The doffer. The outer contact cylinder lap feeds cotton to roller C, which rotates on a smooth iron table D. Here all the dirt is removed, and the fibres are straightened by combing. The cotton then passes along these cylinders as shown by arrows. The flats further flatten the fibres and also place them loose but parallel. When these are ultimately fed to doffer, its teeth draw these in light fleece and these are then further drawn into slivers, and deposited into coiler can G.
Originally wool carding was done entirely by hand where two flat boards with teeth and convenient handles were employed for teasing out, lock by lock, and fibre by fibre, so that a perfect fibre-blending resulted.
In mechanical cards, this process becomes continuous by use of rollers, the arrangement of which is as shown in the above figure. Wool is carries forward with the machine on a travelling lattice and is fed to first feed rollers. This in turn is striped off by third, the forward-carrying-card-cylinder, and then passes over all the cylinders until completely carded wool passes out into slivers. These slivers are then wound on light bobbins and these bobbins are then placed on Mules for final roving and spinning operations.
Sunday, February 2, 2014
Task of feed region | Taker-in region | Different parts of cylinder region | The flat region
Task of feed region:
i. To clamp the flock securely over its full length.
ii. To hold the material back against the action of taker in.
iii. To protect the flock to the taker-in such a manner that opening can be carried out gently.
i. To unwind lap or flock for continuous feed without uncontrolled stretching.
ii. To eliminate impurities.
iii. To transfer the fibres as evenly (both transversely and longitudinally) as possible.
iv. To perform the primary opening and cleaning.
Different parts of cylinder region:
a) Back plate:
i. To hold the fibres on the cylinder.
ii. To prevent the development of undesirable air current.
b) Top feather plate(edge size) :
i. To control the weight and thickness of the flat/feed sheet.
c) Cylinder stripping door: Used to strip wire point of cylinder.
d) Bottom sheet:
ii. To hold the fibres on the cylinder.
iii. To prevent the development of undesirable air current.
e) Cylinder under casing:
i. Removes dirt and fly.
ii. Maintain constant air flow.
The flat region:
i. Opening the flocks to individual fibres.
ii. Elimination of the remaining impurities.
iii. Elimination of the short fibres.
iv. Disentangling the neps.
v. Removes the dust.
vi. Perform high degree of longitudinal orientation of the fibres.
Tuesday, December 10, 2013
Definition of Carding
The reduction of entangled mass of fibres of filmy web by working them between two closely spaced relatively moving surfaces closed with sharp points is called carding. It is the preliminary in spun yarn technology just after the blow room process. Card is the heart of spinning mill and well carded is half spun.
Objects of carding
1. Opening and cleaning: To open and clean the fibres at single stage.
2. To make the fibre straight and parallel (Parallelization of fibres)
3. To remove the small trash particles which have not been taken out from the blow room line.
4. To remove the naps and motes.
5. Individualization of fibres ; i,e. separation of fibres from each others.
6. Elimination of the remaining impurities.
7. Attenuation; draft.
8. To produce thick rope form of fibres called slivers which is suitable for subsequent processing.
Tasks of carding
1. Opening of individual fibres.
2. Elimination impurities.
3. Elimination of dust.
4. Disentangling of naps.
5. Elimination of short fibres.
6. Fibre blending.
7. Fibre orientation.
8. Sliver formation.