Fabric Faults Created During Dyeing and Their Remedies

Fabric Faults Created During Dyeing

Atikur Rahman Sabuj
Marketing Executive at Ningbo Cixing Co.Ltd.
B.Sc in Textile Engineering
Primeasia University, Dhaka, Bangladesh
E-mail: atiksabuj27@gmail.com





Fabric faults created during Dyeing:
There are many reasons for occurring fabric faults during dyeing. Here dyeing faults and their remedies are point out below. 

1. Uneven Dyeing in Rope:
Uneven Dyeing
Uneven Dyeing
Causes:

1. Very rapid addition of dyes and chemicals.
2. Uneven pretreatments ( Scouring, bleaching, de-sizing)
3. Lack control of dyeing m/c like-
  • M/c speed.
  • Temperature
  • Dosing time
  • Circulation pump and reel speed
  • Plating device
  • M:L ratio
Remedies:
  • Check addition of dyes and chemicals at a steadily increasing rate.
  • Proper pretreatments.
  • Proper control of dyeing m/c.
  • Check the rope turnover time. Verify rope speed and chamber loading calculations.
2. Rope to Rope Uneven Shade:
The uniform colour and shade in all the ropes in a machine should not be the same.

Causes:
  • Not equal rope length in each chamber.
  • Not equal fabric flow speed in each nozzle.
Remedies:
  • Rope length in each chamber should be same or as near as possible.
  • Check and make sure that fabric flow speed in each nuzzles same.
3. Dye spots:
Dye spot
Causes:
  • This are most often causes by operators not correctly mixing and thoroughly dissolving the dyestuff, in the right amount of water
  • Dye bath hardness.
  • Not agitation of dyestuff.
Remedies:
  • Passing the dissolved dyestuff through a fine stainless steel mesh strainer, as it is added to the addition tank, will ensure that any large undissolved particles are removed.
  • Use adequate amount sequestrant to lower bath hardness.
  • Proper agitation.
4. Shade variation:

(i) Variation within batch: In case of continuous dyeing , shade variation within batch is commonly found which is unavoidable. This is termed as tailing or ending effect.

Causes:
  • Larger pad size than which is required.
  • Long batching is done in jigger.
  • Salt addition is not proper.
  • Dye liquor level difference in padder through in padding process.
Another type of dyeing fault within batch is listing effect which is actually the shade variation in with wise dye fabric. This occurs due to –
  • Improper padder presence in different zones of padder roller ( Left, middle and right zone)
  • Worn out squeeze roller in pad-bath.
(ii) Batch to batch shade variation: In exhaust dyeing batch to batch shade variation is occurred which is unavoidable.

The identical process conditions and identical products will produce an identical shade. If any one of the parameters are changed you may experience problems in batch to batch reproducibility.

Causes:
  • The fabric has the equal dye affinity and if pretreatment e.g. scouring and bleaching has taken place in different machined.
  • Liquor ratio changed
  • In each batch, time of the fabric ropes passing through the nozzle is changed.
  • Dyeing procedure is different for each batch.
  • Temperature and added bulk chemicals changed.
  • Low quality water especially PH, hardness and sodium carbonate content.
Remedies:
  • Check that the fabric has the same dye affinity and if pretreatment e.g. scouring and bleaching has taken place in different machined. If so, try to follow identical operation.
  • Maintain the same liquor ratio. Adjusting the batch volume according to the material weight.
  • Ensure that in each batch the fabric rope passes through the nozzle of the machine the same number of time during the actual dyeing process.
  • Use the same stand procedure for each batch. Make sure the operators add the right bulk chemicals at the same and temperature in the process.
  • Standards on your dyes and auxilarities. If different combination dyes and chemicals are used there may be difference in shade.
  • Check your water supply daily, especially the PH, hardness and sodium carbonate content.
5. Cockling:

Causes:
  • Small diameter nozzle.
  • Low liquor ratio.
  • Higher fabric speed
However in the case of heat sensitive or thermo plastic fabrics, care should be taken to arrive at a compromise speed, as running the material at very low speed during cooling will also cause cocking.

Remedies:
  • Larger diameter nozzle.
  • Increasing the liquor ratio and
  • Reducing the fabric speed.
6. Crack, rope and running marks:
Running marks are frequently related to the material construction and are caused by poor opening of the fabric rope.

Causes:
  • M/C loading higher.
  • Running at lower nozzle pressure.
  • In correct process procedures.
  • Low fabric speed .
  • High bath during temperature.
Remedies:
  • Reducing the m/c load and running at a slightly higher nozzle pressure, or using the next largest available nozzle size, may also help.
  • Either presetting or pre-relaxation of the fabric before dyeing can avoid this problem.
  • Running and crack marks can also be a result of incorrect process procedures. A higher fabric speed, combined with slower rates of rins and cooling will often correct the problem.
  • Care should be taken to check that bath draining temperatures are not very high especially viscose blends are involved.
7. Crows feet or Wrinkling:
Crows feet or Wrinkling can arise on almost all types of woven materials,

Causes:
  • Lower rope speed.
  • Lower liquor ratio.
Remedies:
  • Can be avoided by pre-setting or pre-relaxation of the fabric before dyeing.
  • Higher rope speed and
  • Increasing the liquor ratio.
8. Crush marks:

Causes:
  • Lower fabric speed.
  • Lower liquor ratio.
  • Higher rate of cooling.
Remedies:
  • Running with a higher fabric speed.
  • Increasing the liquor ratio and
  • A slower rate of cooling.
9. Elephant Skin or orange peel effect:
Often found on woven and warp knitted fabrics which have stopped running during the cooling stage. Manifest itself as irregular shapped creases over the fabric surface.

Causes:
  • Lower liquor ratio.
  • Overfeed of fabric.
  • Dropping the process bath at too high temperature and refilling it with cold water resulting shock shilling of the fabric.
Remedies:
  • Check the machine is not over loaded, and that there is sufficient liquor in the machine.
  • Pre-production tests in a suitably equipped laboratory will often save considerable production time and expense. Plus significantly improve the success rate of ‘’right first time’’.
10. Crease mark:
In knit dyeing crease mark is a common dyeing fault.

Causes:
  • More cycle time.
  • Faulty plaiting device.
  • Slack on tight selvedge causes crease at an angle to eh selvedge.
  • Incorrectly set bowed-expander.
  • Variation of heating and cooling rate.
  • Improper fabric movement.
Remedies:
  • Anti-creasing agents are used to avoid crease mark problem.
11. Patchy dyeing:
Patchy dyeing
Patchy dyeing
Causes:
  • Uneven heat in jigger m/c.
  • Improper impregnation in pad through.
  • Dye migration in intermediate dyeing .
Remedies:
  • Steam pipe should run along the full width of m/c.
  • Proper padding mangle should be used
12. Specky dyeing:
In continuous dyeing, Specky dyeing faults are observed.

Causes:
  • Excessive foam in pad trough.
  • Falling of water droplets on fabric surface before or after dyeing.
  • Insufficient after-treatment.
Remedies:
  • Using of antifoaming agents.
  • Water droplet should not fall on fabric.
  • Dyes and chemicals should not be deposited on guide roller.
  • Drops should be condensed in ager.
  • Sufficient aftertreatment.
13. Dark and light selvedges:

Causes:
  • Uneven batching in jigger m/c.
  • Prolong batching in jigger during vat dyeing.
Remedies:
  • Correct jigger batch.
  • Correct batch length in vat dyeing.
  • Adjust expander roller before padding. 
 

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