- 1 Introduction
- 2 Different Types Of Ginning
- 3 Causes For Broken Seeds In Ginning
- 4 Causes For Fibre Damage In The Ginning
- 5 Conclusion
The first process of the pre-spinning process includes the ginning process. In the ginning process, the seeds are separated from the cotton and the extracted cotton are took to other process and finally, the yarn is being made after passing the initial input that is the cotton.
The separation of seeds from the cotton could be done easily but both the seeds and the cotton would be damaged. A perfect ginning process is said to be one in which the seeds are separated from the cotton without the slightest injury to both the seeds and the cotton.
Different Types Of Ginning
Initially, the process of ginning was performed by hands or by the machines of a primitive character. As the cotton industry developed there were the greater demand of this and modern machines were introduced.
Out of the different forms of gin, only a few are used to a large extent. They are knife roller gin, saw gin and McCarthy gin. The McCarthy gin is further divided into three types as single acting McCarthy gin, Double acting McCarthy gin and the last one is Double roller McCarthy gin.
Knife Roller Gin
This roller is used to process Indian cotton as Indian cotton are coarser and medium. The Indian cotton is not separated by the seeds easily. Through heavy and continuous beating only the cotton would be separated from the seeds.
Heavier beating is achieved here by giving heavier beating of the rapidly revolving knives of the roller on the seed cotton. The construction of this roller consists of two leather rollers on either side of a knife roller.
On either side of the knife roller doctor’s knife is placed. The auxiliary roller is placed on top of the knife roller which breaks the large cluster of the cotton seed and also provides a constant supply of the cotton to the knife roller.
Knife roller is arranged in such a way that anything comes between it and contact it then it is given a to and fro motion and striking action is being performed.The seed cotton is carried out to the knife roller until it comes to contact with the leather roller.
The leather roller has a very rough surface because of the spirally formed saw cuts. The cotton fibres that come to the leather roller adhere or stick to it and are carried round past the knife. In this only the cotton passes and it is impossible to the seeds to follow.
Thus the seeds will remain at the point of contact of the doctor knife and the knife roller. Due to the combined action of to and fro movement, repeated quickly and because of striking and pressure the seeds are separated from the fibres and the seeds fall down and are collected in the grid bar. The separated cotton are further stripped by the means of stripping roller.
Adjustments And Precautions
- Care should be taken as the seeds could not go through the dish rail and the knife roller. A small carelessness could cause a heavy damage here by crushing a lot of seeds.
- According to the tenacity through which the fibres adhere to the surface and with the help of screw the degree of pressure of doctor’s knife over the leather roller could be varied and adjusted.
- The settings should be somewhat far because if the settings are closer the seeds would be broken. The settings should be at an optimum distance because a large distance big and large seeds would not be acted upon doctor’s knives and the machine could be damaged by blocking itself.
- The fibres are being protected as the sharp edges of the doctor’s knife do not cut the fibres.
This process is used for American cotton and the places where American cotton are grown such as west Africa, India, Ceylon and many other places. the American cotton is the types of cotton in which the seeds are not easily separated from the seeds.
Hence to separate the cotton from the seeds it requires a heavier beating. In this process, heavier beating is given by the rapidly revolving saws on the cotton seeds. The seed cotton is fed to the feed lattice which brings the seed cotton to the spiked roller.
The spiked roller loosens the cotton and passes it to the hopper region. In the hopper region, the seed cotton come in contact with the saw roller which is continuously revolving.
As the saws are revolving continuously the teeth of the saw gin carries the fibres forward but here it is impossible to the seeds to follow and only the cotton fibres pass which is being separated by the heavier beating of rapidly revolving saws on the seed cotton.
The waste that includes the empty seed husks and other broken seeds are being collected in the grid bar. The fibres are drawn through the trunk passage by using air current from the cage and on further reaching the revolving cage are brought under the pressure roller where it is delivered as a sheet from where it is taken to the baling press.
Adjustments And Precautions
- The bar near the saw roller could be adjusted according to the feed received.
- The plate near the drum could be adjusted to prevents the seeds falling away until cleaned thoroughly.
- An air current from the cage should be optimum that should suck only the fibres because if the air current is high then it will suck the seeds also along with the fibres and if it is low then even the cotton fibres won’t be sucked and the fibre under the brush roller causes to block the machine.
Single Acting McCarthy Gin
All the McCarthy type of ginning is used to process long stapled fibres such as sea island cotton, Egyptian cotton, and even the long stapled Indian cotton. The long stapled cotton are the one in which the seeds could be easily separated from the cotton fibres.
As it could be easily separated so here only light beating is required. The light beating is achieved by the action of the beater blade on the seed. Here if heavier beating is done then the seeds are broken and the fibres are damaged. Initially, the cotton seeds are placed on the table.
The table has a crank arrangement and-and by reciprocating motion, the seed cotton comes in contact with the revolving leather covered roller. Few of the cotton fibres are carried in the direction of leather roller but here the seeds are arrested by the doctor’s knife.
The seeds due to the reciprocating motion is given by the crank to the beater blade the seeds are separated from the fibres. The opened fibres are stripped through the stripping roller and the empty seeds and all other waste are collected in the grid bar.
Adjustments And Precautions
- The vertical movement of the beater blade should be 3/8 inch above the doctor knife.
- Here the sharp edges of the doctor’s knife do not cut the fibres.
- The distance between the blade and the leather roller could be adjusted.
- By adjusting the screw and the spring the degree of pressure of the doctor’s knife over the leather roller could be varied according to the tenacity with which the fibres adhere to the seeds.
- The distance between the leather roller and the doctor knife and the pressure of the doctor knife should be adjusted in such a way that no seeds would be allowed to pass in the direction of the leather roller.
Double Acting McCarthy Gin
It is similar to single acting McCarthy gin. Here also by the reciprocating motion of the crank arrangement of the feed roller the seeds are separated from the fibre.
But in this process, two beater blades are used at the two cranks where as in the single acting McCarthy gin only one beater blade is being used . in this method the crank rise and fall alternatively.
This process has many advantages than the single acting McCarthy gin. Some of the advantages of this gin are the production is more, the two beater blades are well balanced which reduces the vibration.
Double Roller McCarthy Gin
In this process type of gin, the cotton seeds are passed into the hopper spaces. Here also crank movement is provided which lowers the cotton into the contact with the leather roller on one side and raises it away from the roller on the other side.
Here also the cotton fibres are carried in the direction of the leather rollers where the seeds are arrested by the doctor’s knife. Due to the seeds being acted upon by the rapid reciprocating motion given by the crank to the beater blade, the seeds are separated from the cotton fibres. The empty and damaged seeds are collected in the grid bar.
Causes For Broken Seeds In Ginning
Some of the causes for the breakage of the seeds in the ginning process are due to the improper setting between the knife roller and the dish rail, improper setting between the knife roller and the leather roller, improper setting of the adjustable plate, bars in the saw gin, improper setting between the beater blade and the doctor knife in McCarthy gin.
Hence the arrangements should be made carefully or there will be a great loss in production and will lead to damage of seeds and fibres and even the machine could be damaged.
Causes For Fibre Damage In The Ginning
The fibre may be damaged because of the following reasons such as the excess of pressure of doctor knife over the leather roller, knives of the knife roller are very sharp, a sharp edge of the saw disc, improper setting between the doctor knife and the leather roller.
In the ginning process, the risk of nep formation may also occur. Neps formation may occur due to the high speed of the knife roller and saw roller, blent edges of knife disc and saw disc.
Hence to get maximum production and to avoid defects in the ginning process all the arrangements should be made properly, the rollers should have a correct speed depending upon the feed and the type of cotton, the knife roller and the saw disc should not be too sharp.
It is the initial process so care and attention should be taken during this process.
If there is any defect in this method then the yarn and the fabric made out of these fibres would be of cheap quality.
The cotton fibres separated are used in further pre-spinning process.