(QA)Analysis of Causes and Solutions for Common Fabric Problems --Causes and Solutions of Fabric Left-Right Color Difference

------What is fabric left-right shade variation?

Definition Fabric left-right color difference refers to inconsistent color shade and tone on the left, middle and right sides of the same fabric roll. There is obvious color deviation across the weft direction. It will cause distinct color difference between left and right garment pieces after cutting, which is a transverse color difference within one single roll.  

------ What are the main causes of fabric left-right shade variation?

Weaving & Grey Fabric Reasons

1. Uneven left-right tension on weaving looms leads to different warp & weft density and yarn tightness across fabric width, resulting in varied dye absorption.

2. Ununiform whiteness, hairiness and thickness on both sides of grey fabric cause inconsistent base color.

3. Uneven tension during warping and sizing leads to different fabric structure density on left and right sides.  

Pre-treatment Reasons

1. Uneven heat and chemical liquid penetration during desizing, scouring, bleaching and mercerization cause inconsistent whiteness on both sides.

2. Off-centre fabric feeding leads to unbalanced tension and uneven treatment effect.

3. Ununiform penetration of alkali and bleaching liquor causes over-treatment on one side and insufficient treatment on the other.  

Core Dyeing Reasons (Most Common)

1. Fabric runs off-centre and leans against dyeing machine wall, leading to uneven heating and dyeing.

2. Obvious temperature difference between left and right inside dyeing vat.

3. Unbalanced circulation flow results in different dye solution flow speed and concentration across fabric width.

4. Uneven spray from nozzles of overflow/airflow dyeing machines causes uneven dye uptake.

5. Excessively wide fabric cannot be fully stretched inside the vat, leading to uneven pressure and dyeing effect on both sides.

6. Uneven left-right tension during dyeing causes shade deviation.

Finishing & Setting Reasons

1. Uneven temperature on both sides of stenter oven.

2. Different chain speed, overfeed rate and stretching force on left and right sides of setting machine.

3. Unbalanced padding pressure causes different liquid absorption rate of fixing agent, softener and dyestuff on both sides.

4. Asymmetric hot air flow leads to different drying speed and visual wet & dry color difference.

5. Off-centre feeding causes excessive unilateral stretching and color tone shift.  

 Equipment & Operation Factors

1. Asymmetric hot air volume and wind speed of setting machine.

2. Uneven wear of padding rollers causes unbalanced pressure and uneven padding effect.

3. Workers fail to feed fabric in the middle position for a long time.

4. Poor dye dispersion causes local color aggregation and transverse uneven dyeing.  

Water Quality & Auxiliary Agents

1. Different absorption amount of auxiliaries on both sides leads to inconsistent color fixing and brightening effect.

2. Uneven distribution of impurities and pH value in water affects final color presentation.  

------How to solve the problem of fabric left-right shade variation? 

Control Grey Fabric and Pre-treatment

1. Adjust loom tension to ensure uniform density and thickness across fabric width.

2. Calibrate temperature and liquid flow of pre-treatment equipment for consistent full-width treatment.

3. Keep fabric feeding centered to avoid off-track running and unilateral stress.  

Optimize Dyeing Process

1. Adjust fabric guide devices to ensure stable and centered fabric operation without leaning against vat wall.

2. Maintain and repair heating system to eliminate internal left-right temperature difference.

3. Optimize dye liquor circulation and spraying system to achieve even dye contact on full fabric surface.

4. Reduce fabric loading capacity for wide-width fabrics to ensure full stretching.

5. Adopt dyes with excellent dispersibility and level dyeing property.  

Key Adjustment on Stenter Setting

1. Calibrate oven temperature to keep identical temperature on both sides.

2. Balance padding roller pressure to ensure uniform liquid pick-up rate.

3. Unify chain speed, overfeed ratio and stretching tension on both sides.

4. Adjust hot air outlet direction to realize synchronous drying.

5. Strictly implement centered fabric feeding.  

On-site Operation Management

1. Regularly calibrate symmetric parameters of dyeing and setting machines.

2. Randomly inspect color tone at left, middle and right positions per shift.

3. 3. Adjust fabric guide immediately once off-centre running occurs.  

Finished Inspection & Remedial Measures

1. Fold fabric along weft direction to compare left and right shade; reject unqualified goods with excessive deviation.

2. Slight left-right color difference can be corrected by low-temperature level dyeing and re-setting.

3. Seriously defective fabrics shall be used for small-sized cut pieces instead of symmetric garments.  

4. Quick Inspection Method Fold the fabric along the weft direction, align both sides, and compare under standard light source. Obvious difference in shade or tone is judged as unqualified left-right color difference.