Sunday, December 5, 2021

Objectives of singeing, types of singeing machines, structure and working principle of singeing machines


Objectives of the singeing process:

Singeing is one process of cotton fabric processing. It is the first process of the fabric process. The main objective of the singeing process is to remove the protruding or projecting fibres appearing on the fabric surface by burning them through the flame. The grey fabric is passed through the flame, rollers, or heat plate. as the fabric comes in contact with the flame, the protruding fibres get burnt. Since the fabric passes through the flame at a very high speed, the fabric does not catch fire. The protruding fibres appearing on the fabric surface get burnt.

Importance of singeing: 

1- The improved fabric appearance results after singeing process. 

2- The fabric surface gets cleaned after singeing process. 

3- The singed fabric looks brighter after dyeing because singeing reduces fogginess in the fabric. 

4 - The uniform light reflection from the fabric surface results due to reduced fogginess in the singeing process. 

5- Since we know that protruding fibres generate the pills or balls on the fabric surface during use and these pills formation looks very odd on the fabric surface so that it gets necessary to remove the protruding fibres from the fabric surface. Now, we can say that singeing process improves pilling properties

6- The singed fabric does not soil easily. 

7- If the unsigned fabric is printed directly, the fogginess on the fabric surface gets appeared. a properly singed fabric is essential for effective printing. 

Fabric appearance before and after singeing: 

Please see the below picture:

The reasons behind the protruding fibres appearing on the fabric surface: 

1- When the spinning of staple yarn takes place, the twist helps to hold the fibres together within the yarn. Since the yarn is made of many fibres and each fibre has a different fibre length. The yarn contains many fibres of different lengths in its cross-section. If the number of the short fibres is more, the protruding fibres on the yarn surface get increased, the yarn made of short-staple and medium staple length fibre shows more protruding fibres than the yarn made of long and extra-long staple fibres. 

2-The twist present in the yarn holds all the fibres together in the yarn but the tails of the fibres get projected outside of the fabric surface. 

3- When the yarn is used for fabric manufacturing, it passes through the weaving process. The yarn passes through the drop wire, eye of heald wire, and the dent of reed. The abrasion between the yarn surface and the metallic part is created. The friction between the yarn surface and metallic surface generates the protruding fibres on the yarn surface and these protruding fibres generated during weaving help to increase the protruding fibres on the fabric surface. 

Types of singeing: 

1. Hot plate singeing 

2. Roller singeing 

3. Gas singeing 

Hot Plate Singeing: 

Dried Fabric is made to pass over the heated bright red plates at speeds up to 200 yards per minute, according to quality which burns out the protruding fibres and provided a clear fabric surface. since only one side of the fabric gets singed at a time so that the same fabric is processed two times for singeing of both sides.

Roller Singeing: 

In this type of singeing machine, the cloth passes over a hollow cylinder which revolves slowly in the opposite direction of the goods. The hollow cast iron or copper cylinder is fired internally. The fabric gets singed and runs through a water bath for quenching and plaited. since only one side of the fabric gets singed at a time so that the same fabric is processed two times for singeing of both sides.

Gas singeing: 

The most common singer is a row of gas burners arranged so that the material passes rapidly through the open flame and it burns out the protruding fibres from the fabric surface. While singeing is a simple process, care must be taken to not damage the fabric. 

Structure of automatic singeing machine: 

The main parts of gas singeing machine are given below: 

1. Inlet feeding unit:

To feed the fabric into the machine It has guide bars ensuring smooth passage of fabric and one compensate (fabric tensioner) to set the necessary fabric tension. 

2. Selvedge guide: 

To align fabric centrally and It helps in passing the fabric without folds into the machine. 

3. Brushing unit: 

Cleans the running fabric and raises the loose fibres, It has two rotating brushing rollers, which rotate in a direction opposite to that of fabric passage. The fabric gets cleaned and the loose fibres also get straightened up to face the flame for singeing.  

4. Dust collector: 

Dust Collector is a cyclone separator in which the dirt (fluff) coming from the brushing unit gets collected into a dust bag. 

5. Burner unit : 

It burns protruding fibres coming out from both sides of the fabric. This unit has two burners with a direct gas supply. LPG (liquefied Petroleum Gas) is used in burners to burn the protruding fibres. Both the burners can be turned into three different positions to get singeing positions. 

Position A – Singeing directly onto the freely guided fabric. 

Position B – Singeing on roller 

Position  C – Tangential singing 

6. Spark extinguisher roll:

To extinguish glowing or burning fabric selvedges The selvedge guiding ribbons are pressed against burning selvedges, to extinguish the spark. 

7. Pulling device: 

For transport of fabric through a machine (to pull the fabric) It reduces the fabric tension throughout the machine. It has a compensator/dancer which adjusts the fabric tension and trips if the tension in the fabric goes beyond the tolerance limit. 

8- Beating unit: 

Cleans the running fabric by removing burnt-off fibres It consists of two rotating beating rollers which rotate in opposite direction to the direction of passage of fabric. The small burnt-off fibres fall into the suction tubes and go into Air Washer (Wet Filter). 

 9. Air washer/water filter:  

The Air washer consists of 2 spray pipes for spraying cold water on the burnt-off fibres coming from the Beating unit. The burnt-off fibres thus become wet and settle down due to gravity (which can be drained) while the cleaned exhaust is led to the waste collection point. 

10- Digital control panel: 

the machine is equipped with a digital control panel. all the required process parameters and data are entered into this digital panel. 

Working principle of gas singeing machine: 

- First of all, the fabric gets passed over a brush roller. This brush roller helps to raise the stuck protruding fibres on the fabric surface. 
Now the fabric enters the protruding fibres burning zone.

- Two rows of flames are used in this burning zone.

- One flame row is used for the bottom surface of the fabric and another flame row is used for the top surface of the fabric.

- The L.P.G. is used for the flame.

- When the fabric gets passed between these rows of flames, the protruding fibres present on the fabric surface are burnt. 

- In the standard process, the fabric is passed rapidly between two rows of gas flames at high speed (50-300 m/min).

- Finally, the fabric goes into a quench bath to extinguish the sparks and cool the fabric.

Merits: The gas singeing machine poses below merits over other singeing machines: 

1- the uniform singeing gets resulted in the gas singeing machine. 

2- both surfaces of the fabric gets singed at a time. 3- the productivity of the gas singeing machine is very high. 

4- the speed and the temperature is easily controllable.  

Please watch the below video to learn the full topic in Hindi:

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