Uneven Dyeing in Soft-flow Dyeing Machine - Reasons & Tips:

Uneven Dyeing in a rope.

Uneven dyeing in a rope can be caused by rapid addition of dyes and chemicals in to the machine. The use of Multi Product Injection( MPI) system will overcome this fault. The MPI unit will control the time, rate and amount of addition taking place and avoids manual operator mistakes.

The use Glauber's salt (Na2SO4), which contains lesser impurities and is of consistent quality will give better control of the dyeing and batch to batch processing.

Common Salt (NaCl), has more impurities and of varying quality, not only produce uneven dyeing and other problems but also corrode the stainless steel itself in the long run.

Check that the rope turn over time is correct. Verify your rope speed and chamber loading calculations.

Uneven shade - rope to rope.

To achieve uniform color/shade rope to rope across te machine, it is important to have as near as possible the same rope length in each chamber.

Batch to Batch Shade reproduction.

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

To ensure a consistent batch to batch reproduction of a shade or color you should;

Check that the fabric has the same dye affinity and if pretreatments e.g., scouring and bleaching, has taken place on another range, that the standard of preparation is identical.
Maintain the same liquor ratio. Adjusting the bath volume according to the material weight. The easiest method is by the use of a programmable water meter.
Ensure that in each batch the fabric rope passes through the nozzle of the machine the same number of times during the actual dyeing process. A change in the rope speed - depending on the batch size - may be necessary to do this.
Use the same standard procedure for each batch. This may vary with the depth of shade, light/medium/dark, and dyes and chemicals used, but for reproduction of the same color should be identical.
Make sure that the operators ass the right bulk chemicals at the same time and temperature in the process.
Standardize on your dyes and auxiliaries. If you use a different combination you may have to vary your program to achieve the same shade.
Check you water supply daily, especially the pH, hardness and Sodium carbonate content.

Pretreatment test in a suitably equipped lab will often save considerable production time and expense. Plus significantly improve the success rate of " RIGHT FIRST TIME".