Carding section
This section includes the following topics: 1. Carding action between cylinder and flat 2. Heel and Toe arrangement. 3. Cylinder arch and concentric bends. 4. Flexible bend.5. Front plate.6. Back plate 7. Cylinder under casing
1. carding action between cylinder and flat.
Purpose of the cylinder and flats are
i) To card the fibres which means to open the cotton, even to the separation of one fibre from all the others(fibre to fibre separation)
ii) To separate short fibres, dust and dirt and collect outside the cylinder under casing through spacing of the under grid.
The wire points of flat oppose the direction of the cylinder wire point, i.e. point vs point wire system is placed between cylinder and Flat. Flat slowly moves at the rate of 2.5 inches/min and rotates in the same direction of cylinder, because of these reasons, carding action takes place between cylinder end flats which means fibre to fibre separation is achieved.
The flats gets full charge of cotton as the flats come in to position over the cylinder.
INTERCHANGE OF FIBRES:
The fibres protruding from the charges in the flats are hooked by the cylinder wires in their passage and may be carried forward out of that flat region. Similarly, fibres hooked by the cylinder wires, if they protrude can again be gripped by the flat wires and removed from the cylinder, and this interchange can take place over the top portion of the card where the flats are situated.
2.Heel and Toe arrangement
The wire surface of the flat is not parallel to that of the cylinder.
Wire point setting between cylinder and flat is wider where the cotton enter and closed where the cotton leave.
This arrangement is called as heel and toe arrangement. Object of heel and toe arrangement is to achieve gradual carding action at each flats.
Necessity: When the cotton is carried forward from one flat to another, the air current, centrifugal force, elasticity of fibre causes the fibre to raise from the surface of cylinder. These raised fibres would be rather severely dealt with if they were dragged into the narrow setting between cylinder and flats. This suddenness action is avoided by heel & toe arrangement.
3. Cylinder arch and concentric bends.
On each side of the main cylinder, a strong cast iron cylinder arch is fixed. Cylinder arches support the flats.
On cylinder arch, front concentric bend, back concentric bend and flexible bend are assembled with cylinder grinding and Front plate encloses the space between flat and doffer. Back plate is filed on back concentric bend. This encloses the space between flat and licker in.
4. Flexible bend
On each side of the cylinder, a strong cast iron cylinder arch is fixed. On cylinder arch, front concentric bend, back concentric bend and flexible bend are mounted.
Flexible bend supports the flats. Flexible bend is used to adjust and correct the setting between flat and cylinder .Flexible bend is provided one on each side of the card.
This bend is not flexible but their curvature can be altered, to correct the cylinder to flat setting.
The repeated grinding of the cylinder wire points need accurate adjustment to set the flat as close as 0.010.
To get wider setting between cylinder and flats, the lacking screw should be released first and then by operating the circular nut the regulating screw is raised. The flexible bend will also
be raised, carrying the flate away from the cylinder. This will result in a wider setting between the flats and cylinder. When the correct setting is obtained, locking screw is fully tightened so that the position of flexible bend will be fixed till next adjustment.
5. Front plate or percentage plate
BEQ; what will happen if front plate setting is adjusted How will you control the % of flat waste
On each side of the cylinder, a strong cast iron cylinder arch is fixed. On cylinder arch, front concentric bend, back concentric bend, flexible bend are mounted.
Front concetric bend supports 3 pieces of front plate i) Top percentage plate setting:
Upper edge-10 thou to 60 Thou( 10 Thou means 0.010 inch Lower edge-32 Thou. The object of this setting is to control flat strips waste
The flats are stripped when they have left the cylinder area by an oscillating comb, and the strips hang at the front of the card like a curtain, being connected together along their lengths by some fibres which bridge from one strip to another.
Top % plate setting is very important because it control the thickness and weight of the flat strip.
If this setting is too close- the flow of air over the top edge and between flat is so fast and flats are effectively stripped and flat waste in the flat is transferred to the cylinder again which causes poor web buy results in lighter flat strips.
If the setting wider- flow of air round the top edge is reduced but, cotton is now moved from cylinder Wires to flats, bridging them with them with good cotton, i.e. good material is lost as flat strip waste.
The best setting is that strip should barely hold together by bridging fibres as they are stripped at the front of the* card. Middle plate provides access to the cylinder wire for sripping and grinding.
6. Back plate
Back plate is fixed on back concentric bend. This plate encloses the space between flats and licker in. The object of the back plate is to hold the fibres on cylinder wire and to prevent undesirable air current.
Setting: Upper edge- 0.010" Lower edge-0.012" Wider setting causes cloady web due to uneven distribution of fibre across the cylinder because of the uncontrolled air current.
7. Cylinder under casing.
The objects of cylinder under casing are: i) To hold the good fibres on the cylinder ii) To permit the short fibres, dust, dirt particles to fall down and collect outside the cylinder grid through spacing of under casing.
Settings:
Back 0.012 " Middle - 0.032" Front:0.064" This setting influences air current and production of fly. Wider setting causes loss of fibres. The setting is wider at front because, here the cotton first makes contact with under casing.
