What is Cotton Ginning?
Cotton Ginning is the process of separating the cotton fibers from the cotton seeds. Ginning plays a vital role in cotton quality preservation. Perfect ginning operation would be performed if the separation of fibers from seed was effected without the slightest injury to either seeds or to the fiber. A cotton gin is a machine that quickly and easily separates the cotton fibers from the seeds, a job previously done by hand. These seeds are either used again to grow more cotton or, if badly damaged, are disposed of. It uses a combination of a wire screen and small wire hooks to pull the cotton through the screen, while brushes continuously remove the loose cotton lint to prevent jams. The term “gin” is an abbreviation for engine, and means “machine”.
Fig: Cotton ginning
Ginning is a multi-stage process that consists of:
The drying, cleaning and dusting of the seed cotton,
The actual ginning process and
The cleaning of the lint cotton.
After the pre-ginning treatment, seed cotton is ready for seed extraction. The cotton gin separates seeds and removes the “trash” (dirt, stems and leaves) from the fiber. Saw Gin and Roller Gin are the two popular methods; both can be employed for short and medium staple varieties. In a saw gin, circular saws grab the fiber and pull it through a grating that is too narrow for the seeds to pass. A roller gin is used with longer staple cotton. Here a leather roller captures the cotton. A knife blade, set close to the roller, detaches the seeds by drawing them through teeth in circular saws and revolving brushes which clean them away. Even though the ginning percentage is higher, the neps are produced in Roller Gin. The Saw Gin, however, tends to damage the fibers owing to forceful blows of saw teeth during detachment of the fibers. Macarthy Gin is an-other type of gin which is slow in its working and hence production rates are comparatively much lower. However, the operation is more gentle and hence it can be beneficially used for long staple cotton.
The ginning process can significantly affect fiber length, uniformity, and the content of seedcoat fragments, trash, short fibers, and neps. The two ginning practices that have the most impact on quality are (i) the regulation of fiber moisture during ginning and cleaning, and (ii) the degree of gin cleaning used.
Objects of Cotton Ginning: The main purpose of ginning process is to separating the seed from the fibers in such a way that it protects the seed from crushing and cause minimum fiber fragmentation. Objectives of cotton ginning process are point out below.
To collect the seed and seedless cotton fiber separately.
To separate the cotton fiber from the root position of the seeds.
Preservation of cotton quality
Optimization of production
Preparation of cotton for further processing
Types of Cotton Ginning:
Previous to the introduction of Modern Machinery, ginning was performed by hand or by machines of a primitive character such as the “Foot Roller” and its improvement the “Churka”.
As the cotton industry developed, greater production than these were capable of was necessary, and machines driven by power were introduced. Numerous forms of gins have been tried, but at the present time only three are used to any large extent. They are:
1. Saw Gin: In this cotton ginning process, the cotton fibers are removed from the seeds by passing them through a series of circular saws. The saws have sharp teeth that grab the cotton fibers and pull them away from the seeds. Saw ginning is the most common method of ginning and is widely used around the world.
2. Knife Roller Gin / Roller Gin: In this method, the cotton fibers are removed from the seeds by passing them through a series of rollers. The rollers have specially designed grooves that grab the fibers and pull them away from the seeds. Roller ginning is less common than saw ginning but is sometimes used for certain types of cotton.
3. Macarthy Gin: Macarthy Gin is a type of saw gin that was developed by Eli Whitney in the late 1700s. The Macarthy Gin is a significant improvement over the earlier saw gins, which were prone to breaking and damaging the cotton fibers. It greatly increased the speed and efficiency of cotton ginning.
Three types of macarthy gins:
Single acting Macarthy Gin.
Double acting Macarthy Gin
Double roller Macarthy Gin / Double Roller Gin
Faults of Cotton Ginning Process:
Fiber are broken at the middle position so that it becomes shorter in length.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
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