Quality Defect
An undesirable variation in colour depth between the edges of a fabric roll and its middle region indicates uneven chemical distribution or pressure across the width. Textile inspectors monitor side-to-center shading to ensure that garments cut from different sections of the fabric roll match perfectly in colour. This defect is verified by spectrophotometric measurements taken at the left, middle and right sections of the fabric.
System Mechanism
This variation often originates in the pad mangle, where uneven roller wear or bending of the rollers creates different pressures across the fabric width. When the center of the rollers has less contact pressure than the sides, it leaves more dye liquor in the middle of the fabric. During the subsequent drying stage, this excess liquid can lead to side-to-center shading as the moisture evaporates.
Unbalanced air flow or temperature profiles across the dryer width can also cause this defect by making the edges dry faster than the center.
Operational Control
Using crowned rollers that compensate for bending under load helps maintain uniform pressure across the entire fabric width. Operators adjust the pressure of the pad mangle to prevent the occurrence of side-to-center shading during continuous runs. Regular maintenance and grinding of the rubber rollers ensure a perfectly cylindrical shape.
Technicians use multi-point online moisture scanners to check the fabric dampness before it enters the drying oven.
Process Constraint
Correcting this defect is almost impossible without stripping and re-dyeing the entire fabric roll, which increases processing costs and risks fabric damage. This constraint makes early detection and continuous pressure monitoring essential in the mill.
