Singeing of Fabric: Objectives, Flowchart, Methods and Machines

What is Singeing?
When a yarn is spun from staple fibers it is natural that the ends of the fiber (may or may not) will be projected outside the body of the yarn. In a multi- filament yarn there may be broken out or cut out ends which can be projected outside the yarn even though the number of ends may be very less. Even after weaving/knitting these fiber ends will be shown on the surface of the fabric, which may not give a good appearance to the fabric/yarn. In case of a brushed or napped fabric it may not be a problem. In case of a normal fabric it may hamper the reflection of the shade and will affect the brightness of the fabric. Hence it is necessary to remove these fibers, which is done by singeing.

Singeing is a part of the pretreatment processes carried out in textile processing, and is usually the first step carried out after weaving. It is a process of passing an open-width fabric over a gas flame or hot plate at such a distance and speed that it burns only the protruding fibers but does not damage the main fabric. The main objective of the singeing process is to produce a clean fabric surface and reduce fabric pilling tendency by removing the protruding fibers from the fabric surface. In singeing process the surface of yarn or fabric in order to improve the luster and smoothness of the material. The ‘fuzz’, as the protruding fibers also tends to scatter incident light on the yarn or fabric surface and contributes to a dull appearance of the textile material. Removal of ‘fuzz’ results in a smoother and more uniform surface that reflects more light and therefore gives a brighter appearance.

Objectives of Singeing:

  1. Burning of projecting fibers from yarn/fabric surface.
  2. Fabric/yarn surface become smooth, even and clean.
  3. To develop maximum luster in the textile materials.
  4. Help to create smart design by printing.
  5. Save from uneven dyeing and printing.
  6. To make the textile materials suitable for subsequent next process.

Flow Chart of Singeing Process:

Batch

Pre –Brushing

J-Scray

Gas-singeing

Post-Brushing

Padding

Squeezer

Batching

Different Methods of Singeing:
The natural fabrics are usually singed in grey form as there can be burned ashes and some sort of yellowing on the fabric which are cleared in the subsequent processes. On the other hand, synthetic fibers and their blends are to be singed after dyeing, otherwise molten amorphous beads take up more dyes making dark spots. Polyester melts at higher temperature and requires a powerful flame.

There are various methods of singeing:

  1. Hot plate singeing
  2. Hot rotary cylinder or roller singeing
  3. Gas flame singeing

Different singing positions may be used for different fabrics in order to attain different intensity of singeing. Main singeing positions are: singeing onto free guided rollers; singeing onto water-cooled rollers and tangential singeing. The main parameters of gas flame singeing include gas flame intensity, fabric speed over the flame, singeing position (or angle between the fabric and the flame), distance between the fabric and the flame, and width of the flame.

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The commonly used methods to assess the singeing efficiency include observation of fabric surface with magnifying glass or stereo microscope, and fabric pilling test. A harsher fabric hand-feel may also be an indication of over-singeing. Commonly encountered problems in singeing operations include incomplete singeing, uneven singeing along the fabric length, uneven singeing along the fabric width, horizontal / width-way singeing stripes, vertical / length-way singeing stripes, over-singeing or thermal damage to fabric, and formation of molten fiber beads in synthetic or blended fabrics.

Different Types of Singeing Machine:
There are three different types of singeing machine:

1. Hot plate singeing machine:

Advantages:

  • Hot plate singeing machine is suitable for back filling finishing process as the fiber ends in the interstices are not removed.

Disadvantages:

  • Fiber ends in the interstices of warp and weft are not singed.
  • Produces an undesirable fabric luster due to the frictional contact with the hot plate.
  • Causes uneven singeing due to difficulty in maintaining uniform plate temperature.

2. Roller singeing machine:

Advantages:

  • Roller singeing machine is suitable for back filling finishing process as the fiber ends in the interstices are not removed.
  • The uneven singeing takes place to a lesser extent in roller singeing.

Disadvantages:

  • Fiber ends in the interstices of warp and weft are not singed.
  • Produces an undesirable fabric luster due to the frictional contact with the hot plate.
  • Causes uneven singeing due to difficulty in maintaining uniform plate temperature.

3. Gas singeing machine:

Gas singeing

Advantages:

  • Both sides of the cloth are singed simultaneously.
  • Uniform singeing of the cloth is obtained.
  • There is no question of unwanted cloth sheen as there is no contact with any metal surface as in the case of the other singeing machines such as the roller and hot plate singeing machine.
  • Fibers in the interstices between the warp and weft threads are also burn effectively. This is not entirely possible in the case of other singeing machines.
  • Different varieties of fabric can be singed.

Disadvantages:

  • The major disadvantage of gas-singeing is obviously that there is a great risk of fire, if proper care is not taken on this count. However, any risk of fire can be avoided completely if,
  • The flame is adjusted to be at its optimum size.
  • Careful monitoring of the singeing process is carried out.
  • The necessary fire-fighting equipment is available close at hand.
  • The operators at the machine are properly trained to run the singeing machine and to use the fire-fighting equipment in an emergency.

Standard parameter of singeing machine:

Quality Intensity of flame in mbar Burner Position (1-3) Speed in m/min
1 100%Cotton direct route 16 3 90
2 Viscose/Modal 16 3 90
3 100% Tencil 16 3 80
4 100% DesizingMerc 14 2 90
5 Voil/Cambric/All grey Merc 14 2 90
6 All Lycra 14 2 90
7 100% Linen,Cotton/Linen DesizeMerc route 12 2 90
8 All Y/D 12 2 90
9 Polyester/Viscose 12 2 90
10 Modal/Viscose Mosscrepe/Pc 9 1 90
Burner Position Position of burner with rollers
1 Angular (90° with roller)
2 Under roller(Parallel with roller)
3 Directly touches the fabric (Tangential with roller)

Machine used: OSTHOFF SINGEING (42327 Wuppertal Germany)

Gas Used: “LPG gas + oxygen” in the ratio (1:4)

Temperature of fabric in singeing chamber: 80°C -90°C

Threading length of fabric: 54m

Singeing burner and its position
Fig: Singeing burner and its position

Procedure:

  1. Cloth is withdrawn from the batch and passed through the guide rollers to the pre-brush roller.
  2. And passed through the guiders to the J-scray.
  3. Again with the help of guiders and guide rollers it is passed to the singeing machine.
  4. The guide rollers then take the fabric to the post-brushing roller, from where it is taken to the padding unit if other route is to be taken.
  5. At the end fabric is taken to the winding unit through the squeezer by the help of mangle rollers.

Service and Maintenance of Singeing Machine:

  1. Ensure the feed fabric before brushing is always bone dry.
  2. Clean pre-brush bottom SS ducts every day to maintain constant efficiency of brushing.
  3. In the Cyclone Dust Collector, change the plastic collector bag once it is filled up to 80% of its capacity.
  4. Clean burner slit with cleaning gauge before beginning the singeing process everyday with machine in cleaning mode.
  5. Ensure the ramp bodies mounted on burner should be aligned properly (straight). There should not be any gap between two adjacent ramp bodies.
  6. Ensure while aligning ramp bodies, the edges should be properly matched.
  7. When the machine is in cleaning mode, make sure the air pressure should be 20 mbar.
  8. Do not clean the ramp bodies with compressed air.
  9. Always feed dry compressed air to the machine for proper functioning of pneumatic system for burner.
  10. Maintain cooling water pressure
  11. Maintain gas pressure at 1 bar (before regulator cum shut off valve).
  12. Always feed dry LPG or CNG to the machine to avoid fluctuation.
  13. Always feed ambient temperature (30-35 degree) water to the water cooled guide rollers to avoid sticking of fluff to the roller.
  14. Pre washer should be thoroughly cleaned every day.
  15. Ensure proper cleaning of indirect heating coil in desizing tank to avoid uneven dyeing.
  16. The bottom rollers in desizing tank should be thoroughly cleaned every day to increase life of spherical carbon bearing.
  17. Always use oil cups suggested by Osthoff on squeezer rollers to increase life of bearings.

You may also like:

  1. Typical Preparatory Process of Dyeing
  2. Scouring Process of Cotton in Textile Industry
  3. Different Methods of Degumming of Silk
  4. Singeing and Desizing Process in Textile Industry
  5. Bleaching Process in Textile: Its Purposes and Chemical Requirements
  6. Concept Development of Mercerization with Different Parameter and Comparison
  7. Production Parameter of Yarn Dyeing Section

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