Why does injection molding have color difference?
In plastic product molding, injection molding is one of the most common forming methods. Various issues may arise during the injection molding process, and one such issue that has a minor impact on product performance but significantly affects appearance is color variation.
Plastic Resin: The resin itself can introduce color variation, especially when it has a certain inherent color. Even with the same type, color differences may occur between different batches. Experimental evidence indicates that the degree of color difference is approximately proportional to the inherent color of the resin—meaning the greater the inherent color difference, the larger the product's color difference.
Temperature Control: Variations in temperature during the injection molding process can lead to color changes. Ensuring the stability of temperatures in the injection molding machine is crucial for minimizing color variation. Control parameters such as melt temperature, mold temperature, and cooling time to ensure consistent product color.
Machine Pressure: The pressure settings on the injection molding machine can also influence product color. Adjusting injection pressure and holding pressure time ensures uniform plastic flow and filling.
Mold Design: The design of the mold affects the color distribution in the product. Ensure uniform mold channels, avoiding dead spots to minimize color differences.
Colorant Usage: The choice and use of colorants can impact product color. Ensure the use of the same batch of colorants and mix them in the correct proportions.
Process Control: Strictly control various process parameters during injection molding, such as injection speed, cooling time, mold temperature, to ensure product consistency.
Lighting and Environment: Lighting conditions and the environment can also affect color. When evaluating color differences, comparisons should be made under similar lighting conditions.
Quality Control System: Establish a robust quality control system, including the detection and recording of color parameters, to promptly identify and correct color variation issues.
By considering the factors mentioned above and optimizing material selection, process parameters, equipment, and quality management systems, color variation issues in injection molded products can be effectively controlled. Regular equipment maintenance and calibration are also recommended to ensure a stable production environment.
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