I. Uneven dyeing (color spots, medium thinning, rope marks)
This is one of the most common quality problems, manifesting as inconsistent color depth or streaks on the fabric surface.
1. Medium thinning/medium thickening: Inconsistent dye absorption between the center and edges of the fabric, often caused by improper curvature of the spreading device, uneven roller pressure absorption rate, or uneven airflow and temperature distribution.
2. Rope marks: The fabric knots into rope-like patterns during dyeing, resulting in irregular wrinkles after dyeing. This is usually caused by insufficient fabric pre-setting, excessively rapid heating, or an insufficient liquor ratio.
3. Poor dye dispersion or uneven dyeing: Incomplete dye dissolution or improper addition method causes localized differences in color concentration.
II. Clogging and blockage (hernia-like blockage, layer-by-layer blockage)
The fabric is obstructed during circulation; severe cases require machine shutdown for repair.
1. Excessive pump flow or imbalance: Too high a flow rate of dye liquor causes the fabric to slide and pile up at the top of the dyeing tank, especially thin fabrics.
2. Improper nozzle selection: The nozzle diameter does not match the fabric type, leading to poor conveying.
3. Poorly sealed partition: Dye liquor cross-flows within the dyeing tank, trapping the fabric in gaps and forming a "hernia-like blockage."
4. Inappropriate return valve opening: Excessive opening of valve III causes fabric to lag, become disordered, or even knotted.
III. Dyeing Shutdown Marks: After a sudden power outage or equipment malfunction, horizontal stripes of varying shades appear on the fabric surface.
1. During shutdown, the fabric is trapped between the rollers, continuously drawing in dye liquor or oxidizing, forming color difference bands. Uneven dyeing occurs after restarting.
2. Failure to adjust the circulation time after an emergency stop and restart results in localized over- or under-dyeing.
IV. Dye Liquor Leakage and Loss: This not only wastes raw materials but may also pollute the environment.
1. Aging or damaged seals lead to leaks in the cylinder or pipelines.
2. Loose or blocked pipeline connections cause abnormal pressure leaks.
3. Incomplete equipment cleaning results in residue crystallization and blockage, indirectly increasing the risk of leakage.
V. Control System Malfunctions
Affecting the precise execution of the dyeing process.
1. Timer or temperature control system malfunction leads to inaccurate heating rates and deviations in holding time.
2. Incorrect sensor feedback causes inaccurate temperature or liquid level control, resulting in dyeing that is too dark or too light.
VI. Mechanical Damage
Fabrics suffer scratches, tears, or uneven shrinkage.
1. Excessive tension between the nozzle and the guide roller causes "dry-blowing" damage to delicate fabrics.
2. Rapid heating or cooling rates cause uneven thermal shrinkage, especially noticeable in synthetic fibers.
3. Uneven tension distribution within the rollers leads to localized tensile deformation.
