Factors causing unstable colour in production

Colour can change between days or even several times in one production day. The following factors from the old-site article are worth checking when troubleshooting colour instability in injection moulding.

1. The machine temperature rises and falls. This is a major cause and should be checked first.

2. The production cycle is irregular, with frequent starts and stops, or excessive back pressure causes temperature drift.

3. Powder and resin were not mixed according to the specified procedure. Mixing time, addition method and sequence can all affect uniformity.

4. Drying is too hot or too long. Each resin and pigment has a suitable range. Exceeding it can alter the final colour. Uneven feeding can make temperature-sensitive colours, including fluorescent and pale shades, less stable. For some sensitive materials, avoiding drying or using a lower temperature and then adding powder after drying may help.

5. Hot air in the drying hopper causes powder to accumulate in one place. The colour gradually deepens and speckled products can show too many spots. A suitable dispersing oil can help the powder adhere to resin pellets.

6. The raw material is too moist, so the powder clumps instead of dispersing.

7. The powder formulation or measurement varies significantly between batches.

8. The amount of recycled material varies, which particularly affects pale products.

9. Resin grades or batches differ in base colour. Even batches from one supplier may vary. Products with tight colour tolerances may require incoming material colour checks.

10. The powder has poor quality or heat resistance, or the wrong powder has been selected for the resin.