Category Archives: Yarn Dyeing

Costing Factors Of Yarn Dyeing Mills

Costing is an important factor. This task is done by the accounts department. They have to calculate the costing of specific products. Generally, the methods of costing are nearly same for all textile departments. But costing depends on the factory types or business types. Sometimes it could be composite mills or sometimes single unit. Anyhow, I have given a short list of costing factor which is applicable for a single yarn dyeing mill.

In a yarn dyeing mill, the raw materials are grey yarn and the finished products are dyed yarn. The business could be run by two ways.

  1. To sale dyed yarn to the buyer. In this case, raw yarn is bought by the mill authority and they dye the grey yarn and sale the finished dyed yarn.
  2. To dye the grey yarn which is supplied by the buyer. In this case, the mill authority fixed a specific dyeing rate for specific yarn. Most of the case, this method is run.

Factors of Costing of a Product: The following factors are considered for costing of any dyed product.

  1. Total dyes and chemical cost
  2. Total utility cost
  3. Salary
  4. Lunch
  5. Entertainment cost
  6. Government cash incentive
  7. Yarn cost
  8. Cost of dyeing
  9. Labor cost (direct & indirect)
  10. Factory cost
  11. Sales and caring cost
  12. Others cost

Above costing factors are the most common. The costing methods could be varying depending on the men’s method. But the basic will be same for all.

So, if you want to calculate the costing, consider the above factors.

Dyed Yarn Drying Process | Drying Mechanism of Stray-field FASTRAN Textile Dryer

Dryer is essential to remove remaining water from the package. About 60-80% water removes by dryer. After passing Hydro section package move into drying section. Following is most used yarn dryer use in yarn dyeing industry.

  1. Stray-field FASTRAN Machine
  2. GALVANIN (Hot Air Dryer)

Drying Mechanism of Stray-field FASTRAN Textile Dryer: There are lots of dyed yarn dryer for drying the dyed yarn which passed hydro-extractor. I have written about the drying mechanism of Stray-field FASTRAN Textile Dryer.

Direct method of heating are those where the heat is generated within the material itself with ratio frequency and microwave method being typical examples. This method of heating is also referred to as dielectric heating.

Most non-metallic substances undergo a uniform rise in temperature when subjected to a high frequency electric magnetic field. Each time the direction of the applied RF field reverse, so the polarization of the individual molecules within the substance changes. The constant molecular movement causes friction which in turn leads to a rise in temperature. As may be expected the higher the frequency of the electromagnetic field the faster the molecules process, thus creating more friction and consequently more heat is produced.

The frequency of the RF fields generated by devices for dielectric heating is centered on 13.50 MHZ and 27.12 MHZ.

Here, I like give a simple idea about the Stray-field FASTRAN Textile Dryer.

Brand Name                : Stray-field

Country Origin             : UK

Supply Voltage            : 380-420

Supply Frequency        : 50 HZ

Supply Phases             : 3

Supply KVA                 : 230

Supply Power Factor    : 0.9

Maximum Weight         : 3800 Kg

RF Power Output         : 100 kW

Operating Frequency    : 27 MHZ

Points Need to Consider During Drying: Following points are need to consider during yarn drying. They are:

  1. Machine Speed: Machine speed varies according to the shade of the yarn. Conveyor runs in high speed for dark shade and comparatively at low speed for light shade.
  2. Feeding System: Plastic package feed in vertical form, but spring package feed in horizontal form because fire can be form by feeding in vertical form.
  3. Yarn Type: Same type yarn should run at same settings. Otherwise it can damage the yarn quality. Cotton, Polyester, Acrylic, P/C or CVC yarn should feed separately.
  4. Moisture: Machine settings should be according to the amount of moisture remain in the package.

Evaluation of Efficiency of Stray-field Dryer: It needs to know the efficiency of a dyed yarn dryer. For this reason, I have presented a sample calculation of dyed yarn dryer efficiency.

Weight of double yarn package before dyeing               =  1.2 Kg

Weight of double yarn package with water before Dryer = 2.034 Kg

Weight of water in double yarn package before Dryer = (2.034 – 1.2) Kg =  0.834 Kg

Weight of package after Dryer          =          1.2 Kg

Water remain in package after Dryer   =          (1.2 – 1.2) Kg =  0 Kg

Water remove by Dryer                     =          (0.834 – 0) Kg = 0.834kg


=   {(Weight of water before Dryer – Water remain after Dryer) / Weight of water before Dryer}   X 100%

=   {(0.834 – 0) / 0.834} X 100%

=    1 X 100%

=    100 %

Efficiency of Dryer = 100 %

So, yarn dryer is essential for dry the dyed yarn. After drying, dyed yarns transferred for re-winding or random section.

Process Flow Chart Of Polyester Dyeing | Disperse Dyes Dyeing Process

Polyester is the most used synthetic fiber of the world. Polyester fiber is dyed with disperse dyes. If we want, we can dye the fiber during yarn preparation. Also we can dye the yarn after yarn preparation and in fabric form. The fastness properties of polyester dyed yarn are excellent. Day by day the use of synthetic fiber increases rapidly.

Process Flow Chart Of Polyester | Disperse Dye Dyeing ProcessDyeing sequence of polyester is given below:

Carrier and vessel washed by hydrose and caustic at 1000 C for 20 min

Load the package in the carrier and feed in the vessel

Add washing agent and run at 800 C for 20 min

Dyeing period

Add leveling agent and acid, run at 600 C for 10 min

PH check

Color mixing at 700 C for 40 min

Color dosing at 600 C for 20 min

Polyester dyeing at 1350 C at 20 gradient for 50 min

Sample check


Temperature cool down at 780 C and drain

Hot wash for 10 min

Rinse for 15 min for light shade and 25 min for dark shade

Add hydrose, soda ash, run at 800 C for 20 min


Rinse for 10 min

Neutralization by acetic acid at 500 C 20 min


So, that’s all about the polyester dyeing as well as synthetic yarn dyeing. You can try it in your practical life and give me a feedback about the result of dyeing process of polyester.