Ginning process
Once the stored raw material is ready for ginning process.
In the Conventional method, Cotton fed into the gin via pipe inches is 16 inches in diameter, which swung over the cotton.
In the modern method, Cotton feeds into gin via a module of the feeder which is known as a cotton dispensing system. In the module feeder, a conveyor belt at the bottom and spiked rollers are present for the extraction of the largest pieces of foreign material from the cotton.
With the help of another conveyor, belt materials pass from the storage space to the process house. Following is the machine's sequence in the process house.
Feeding unit
Top Trolley feeder/ Feeder trolley
- In some cases feed cotton to the individual machine by top trolley feeder. In this system, a large trolley is arranged on top of all machines. Trolley first fills itself and then provides materials to each machine with the help of the SACS50N cotton sensor. This sensor senses whether either machine is running empty or not. They sense and provide data to the top trolley for the action of feeding.
- This system is widely used because the feeding of materials is always equal for each machine.
Individual feeder
- In some cases feeding cotton to each machine by individual suction line for each machine or by a conveyor belt which reaches each machine's feeding area.
- This system is not suitable for every ginning process because in this system material feeding is sometimes unequal and huge problem of blockage of materials.
Ginning Machine and its types
- In ginning machine our main process takes place. Knife roller, saw gin machine, Macarthy Gin machine, and Double roller gin the types of these machines.
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| Modern gin machine |
There are main three principle-based ginning machines is available.
- Knife roller gin / Roller Gin
The knife roller or Roller Gin machine is mainly suitable for short to medium staple fibre.
In the Knife roller gin, the seed cotton is placed in bulk on the feeder hopper.
With the help of compressing roller materials feed between the rollers. When the cotton seed comes into contact with the knife roller, the separation of seeds from cotton lint takes place.
The knife portion is arranged in such a manner that anything coming into contact with it is given reciprocating motion as well as being sub-iced to shrinking action to its revolution.
This roller has a 10-inch diameter with an rpm of 150,300,150 respectively from left to right. But the middle roller's motion is anticlockwise while others are clockwise.
This roller is arranged in such a way that cotton lint travel from the middle roller to the third roller and with the help of a stripping board it separates from the knife roller and finally falls down into a receiver box.
The friction between fibre and roller affects this action. The distance between rollers is arranged in such a way that seeds are not moving up to the third roller and are separated from the cotton. Though dust and other impurities are removed with the help of grids, arranged beneath the middle roller.
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| Knife roller gin |
- Saw Gin
The Saw Gin machine is mainly suitable for short to medium staple fibre.
In Saw gin cotton material is fed into the feeder hopper, The cotton is delivered by a feed lattice and a pair of spike cylinders into a hopper, which leads it to the projecting saws through the metal ribs.
With the help of a feed roller and lattice belt, it feeds into the main saw roller through a perforated drum and knife bars.
The clearance between the saw and ribs is sufficient which allows only cotton fibres to drag so, cotton seeds are separated from cotton between the revolving saw and drum.
On the circumference of the saw roller dust and other impurities are removed with the help of grids and a dust roller.
Here dust roller (generally 18-inch diameter) plays a vital role in cleaning cotton fibres to create perfect lint. With the use of condenser lint flue outside of this machine due to suction.
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| Saw gin |
- Macarthy Gin
Macarthy Gin machine is mainly used for long-staple fibre. This is widely used in Egyptian cotton for ginning exiting the staple fibre.
In Macarthy Gin there are three types.
- Single-acting Macarthy Gin
- Double-acting Macarthy Gin
- Double roller Macarthy Gin / Double Roller Gin
In Knife Macarthy Gin the cotton is placed in bulk on the feeder hopper. With the help of feed bar materials feed between the roller and knife bars. When the cotton seed comes into contact with the knife, the separation of seeds from cotton lint takes place.
The fixed knife portion is arranged in such a manner that cottonseed comes into contact with it, the fixed knife separates the seed from cotton. At this motion, if any seed is not able to separate so during the leather-covered roller's rotation movable knife takes place.
The movable knife is fixed on the crank leg which is mounted on the bottom crank and controlled by an arm. When required bottom crank moves and the knife moves in a reciprocating manner (up and down). When this knife comes in contact with a leather-covered roller, cottonseed is separated from cotton lint. At that time feeder bar was also controlled by the top crank.
During the motion of the movable knife, this feeder bar stops feeding materials. Once the knife goes downward, With the help of the top cranks feeder bar again start the reciprocating motion and continue the feeding process. This leather-covered roller is arranged in such a way that cotton lint travel from the main roller to the doffer roller and with the help of the doffer roller cotton lint is finally falling down into a receiver box.
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| Macarthy gin |
- Comparison of saw, McCarthy and knife roller gin
Saw Gin | Macarthy Gin | Knife roller Gin | |
Staple fibre length | Short to medium | Long | Short to medium |
Lint cleaning | Using Air -jet (suction) and controlled batt saw type | with the help of a doffer roller | With the help of lint reclaimer and mill-type cleaner |
Seed separation | Bigger sharp stand ( easily damaged) and grid bar | Fixed and movable knife on the roller surface | Narrow sharp stand (less damage) and roller |
Lint quality | medium fibre quality | Better fibre quality | medium but better than saw gin's lint quality |
Neps generation | higher | average | lesser |
Questions -
- Explain the ginning process.
- How does knife roller/roller gin works?
- How saw gin work?
- How does McCarthy gin work?
- Give a comparison between a saw, knife roller, and McCarthy gin.
References
Cotton: From field to fabric- ginning. (n.d.). Cotton.org. from https://www.cotton.org/pubs/cottoncounts/fieldtofabric/gin.cfm
Shaikat, N. M. (2019, August 17). Ginning: Cotton ginning, process, types, and objectives. ORDNUR. https://ordnur.com/spinning/ginning-process-of-cotton/
Sharratt, B., & Auvermann, B. (2014). Dust Pollution from Agriculture. In Encyclopedia of Agriculture and Food Systems (pp. 487–504). Elsevier.
Textile School. (2011, May 3). Cotton fibre ginning. Textile School. https://www.textileschool.com/366/cotton-fiber-ginning/
The Editors of Encyclopedia Britannica. (2022). cotton gin. In Encyclopedia Britannica.
The story of Cotton- how Cotton is Ginned and marketed. (n.d.). Cotton.org. from https://www.cotton.org/pubs/cottoncounts/story/gin-and-market.cfm
Further reading -
Part-2 Ginning process and its types
Part-3 Technical aspects of the ginning process
Writer - DSPAT Team
