15 December 2011
Cotton Carding Process | Working Process of Cotton Carding
Carding
Carding is one of the most important operations in the spinning process
as it directly determines the final features of the yarn, above all as
far as the content of neps and husks are concerned. There are many
objectives of the carding process and these can be summarised as:
- Opening the tufts into individual fibres;
- Eliminating all the impurities contained in the fibre that were not eliminated in the previous cleaning operations;
- Selecting the fibres on the basis of length, removing the shortest ones;
- Removal of neps;
- Parallelising and stretching of the fibre;
- Transformation of the lap into a sliver, therefore into a regular mass of untwisted fibre.
Fig.A Section view of the card with hopper
Wiring and Clothing
There are different types of cylinder wiring, in particular:
- rigid wiring, for rotating parts;
- elastic clothing, for mobile flats;
- clothing for fixed flats.
The
most common on the machine are the wiring type. They are made up of a
steel wire with sharp cutting teeth, the sawtooth like edge of the
wiring is hardened in order to better resist wear caused by the abrasive
action of the fibres. The base of the wiring is thicker than the
toothed parts, both to guarantee support to keep the teeth in a vertical
position, as well as to prevent lateral contact between the teeth and
to permit the necessary momentary penetration of fibre into the wiring.
The sizes of the teeth vary notably and depend on how compact the material is, on the quantity and on the fineness of the fibre. The parameters which permit one type of wiring to be distinguished from another are:
The sizes of the teeth vary notably and depend on how compact the material is, on the quantity and on the fineness of the fibre. The parameters which permit one type of wiring to be distinguished from another are:
Concentration,
meaning the number of teeth in a square inch of the wiring (for the
various devices of the card the concentration is different and is
strictly linked to the type of fibre used; for fine fibre, for example,
wiring with a high concentration is used);
- The height of the teeth, which can vary according to the wired element;
- The angle between the teeth and the base in a longitudinal sense.
It is a known fact that a wired element moves in:
- a positive way when it moves in the same direction as the inclination of the teeth;
- a negative way when it moves in the opposite direction to the inclination of the teeth
The
fibrous material is found between the two wired elements which, by
moving, act on the fibre in an alternate manner: first they trap it then
they remove it. Depending on the
layout of the teeth, the direction travelled and the speed of the
devices, two conditions are possible, called:
- Carding position which is obtained when the teeth of the wired elements are inclined in an opposite direction and their movement occurs with a certain speed and in a direction that permits a reciprocal grasp of the fibre and then the disentangling of the neps and elimination of trash and dust.
- Position of cleaning or brushing , which is obtained, on the other hand, when the devices have converging teeth and their movement occurs with such a speed and in such a direction to permit the passing of fibre from one organ to another.
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