Ginning

GINNING

IntroductionGinning is the process of separating the cotton fibres adhering to the seed for the conversion of the cotton into a continuous threadLints:Lints are the long cotton fibers that are recovered from seed during ginning.Object: To separate the cotton fibres from the seed.Perfect ginning operation would be Performed if the separation of fibres from seed was effected without the slightest injury to either seeds or to the fiber.

The cotton first goes through dryers to reduce moisture content and then through cleaning equipment to remove foreign matter. These operations facilitate processing and improve fiber quality.A typical gin will process about 12 bales per hour, while some of todays more modern gins may process as many as 60 bales an hour.

DIFFERENT TYPES OF GIN1. Knife roller gin2. Saw gin3. McCarthy gin Types of McCarthy GIN I. Single acting McCarthy gin.ii. Double acting McCarthy giniii. Double roller McCarthy gin.

Saw gin The Saw Gin stand uses the teeth of rotating saws to pull the cotton through a series of "ginning ribs", which pull the fibers from the seeds which are too large to pass through the ribs. The cleaned seed is then removed from the gin via an auger system.

It is suitable to process American cotton and wherever American cotton is grown, such as west Africa- India, Ceylon etc.These fibres are not too easily separated from the seeds, so heavier beating on seed is required to separate the fibres. This is achieved in this gin by giving heavier beating of the rapidly revolving saws on the seed cotton.

WORKING:The seed cotton is fed upon the lattice and carried forward to the spiked roller, which loosens the cotton and throw; it into the hopper.In hopper, the seed cotton comes into contact with rapidly revolving saw roller. App.70 saws are threaded on a shaft.As the saws revolve, the teeth carry the fibres forward, but it is impossible for the seeds to follow and also, due to the heavier beating of the rapidly revolving saws on the seed cotton, the fibres are separated from seed and taken round until the brush strips the fibre from the teeth.Empty seeds husks and other broken seeds are thrown into grid, through which they pass into suitable receptacle. An air current from the cage draw the fibres along the trunk passage, and on reaching the revolving cage are brought under the pressure roller and delivered as a sheet, from which it is taken to the baling press.

SETTINGS:The bars (I) are adjusted at K. The plate, adjustable at H, can be regulated to prevent the seeds falling away until thoroughly cleaned. An air current from cage should be optimum to 'suck only fibres. If air current is high - it will "suck seed also with fibres. If air current is low - fibre accumulation under brush roller causes to block the machine.

Modern gins can process up to 15 tonnes (33,000 lb) of cotton per hour.Drawback of saw-type cotton ginningTo fiber damage (increased short fiber content, reduced uniformity, and increased neps)Lower mill efficiency andLower yarn quality

ROLLER-TYPE GINNING (Using either a reciprocating knife or a rotary knife) It is used to process long staple Pima cotton around the world. gentler way of separating the cotton lint from the seed Most modern roller ginning facilities around the world are equipped with rotary-knife roller gins. The seed cotton is applied to the ginning roller, with the separation of fiber and seed taking place as the lint (adhering to the ginning roller) is pulled under the stationary knife (which is exerting high pressure against the ginning roller). The rotary knife directs seed cotton to the ginning point, sweeps cotton seed away from the ginning point, and releases the seed cotton that was not fully ginned to be drawn back to the tip of the stationary knife for further ginning.

The ginning roller is the most important and expensive component in the gin stand.Roller-covering material is made from 13 layers of plain-woven cotton fabric cemented together with a white rubber compound. The fabric lays on the bias so that neither the warp or fill yarn are parallel to the direction of cutting; this prevents the material from unraveling from the roller surface. The roller material mounts on to the roller core with the cut edges of the fabric layers serving as the ginning surface.

Rotary-knife roller gin stands separate fiber from seed by using the frictional forces between a moving roller and fixed stationary-knife surface. During normal ginning, The roller-to-fiber force is greater than the stationary knife-to fiber force; therefore, the fiber sticks to the roller surface and slips on the stationary knife surface.

Cotton is ginned as fibers adhered to the roller surface slip under the stationary knife which holds the seed.Each stroke of the rotary knife clears the stationary knife edge of accumulated seed cotton and ginned and partially-ginned seed. Partially ginned seed are either pulled back to the stationary knife and completely ginned or swept along with the seed and carryover and later reclaimed

McCarthy gins All type of McCarthy gins are suitable to process long stapled cotton such as sea island cotton, Egyptian cotton and long stapled Indian cottons. Long stapled cottons are of a type in which the fibres are easily separated from seeds, so light beating on seed is enough to separate the fibres, this is achieved in this gin by light beating action of the beater blade on seed, fibre damage & broken seeds are the results if processed through other gins of heavier beating points such as knife roller gin and saw gin.

SINGLE ACTING MACARTHY GINThe seed cotton is placed on the table. By means of the reciprocating motion of the table by the crank arrangement, the seed cotton comes into contact with the revolving leather covered roller.Some cotton fibres are carried in the direction of leather roller, but seed cottons are arrested by the doctor knife.A steel beater blade is connected by means of a connecting rod, with a crank on the driving shaft.

Due to the seeds being acted upon by the rapid reciprocating motion given to the beater blade by the crank, the seeds are separated from fibres.Ginned cotton fibres are carried onward in the direction of leather roller, stripping board strip the fibres from the leather roller and empty seeds are thrown into grid, through which they pass into suitable receptacle.

DOUBLE ROLLER MACARTHY GIN

There are two leather roller and a doctor knives is pressed against each leather roller.The beater knives act from above, and are given a reciprocating motion from a crank.Crank pin slide in a slot of arm carried by a vibrating shaft. Beater blades are fixed on arms projecting from vibrating shaft Also grid and fingers are fixed on vibrating shaft.Seedcottonisfed intohopper-spaces.

Thecrankmovementlowers this cotton into contact with leather roller inone side and raises it away from the roller on other side.When the cotton comes into contact with leather roller, some cotton fibres are carried in the direction ofleatherrollerbut seed cottons are arrested by the doctorknife due tothe seeds being acted upon by-the rapid reciprocating motion given to the beater blade by crank,the seeds are separated from fibres. Ginnedcotton fibres are carried forward in the direction of leather roller.Empty seeds are throwninto grid.As the grid lowers, the space in it permit the fixed finger to pass between them, and so shake the seed to cause them to fall out readily.

Knife roller gin It is suitable to process coarser and medium Types of Indian cotton. The Indian Cotton fibres are not too easily separated ' from seeds, so heavier beating on seed is required to. Separate the fibres. This is achieved in this gin by giving heavier beating of the rapidly revolving knives of the roller on the seed cotton.