How to solve problem of dark color and poor gloss of injection mold?

How to solve the problem of dark color and poor gloss of injection mold?

The problem of dark color and poor gloss in injection molded parts can be attributed to several factors related to material selection, processing conditions, and mold design. Here are some solutions to address these issues:

  1. Material Selection:
    a. Choose High-Quality Resins: Select high-quality plastic resins with good color stability and processing characteristics. Cheaper or recycled materials may lead to darker colors and reduced gloss. b. Color Masterbatch: Consider using color masterbatch instead of direct pigment addition. Color masterbatch ensures better dispersion and color consistency. c. Opt for Lighter Colors: If possible, opt for lighter color options for the plastic resin, as dark colors are more likely to show poor gloss.
  2. Processing Conditions:
    a. Temperature Control: Maintain precise control over the barrel and mold temperatures during the injection molding process. Proper temperature control can prevent degradation of the material and improve gloss. b. Injection Speed: Adjust the injection speed appropriately to ensure proper material flow and prevent visual defects like streaks or splay marks. c. Injection Pressure: Optimize the injection pressure to achieve consistent filling and minimize the chances of dark spots or poor gloss. d. Cooling Time: Allow sufficient cooling time for the molded part to solidify completely. Proper cooling helps in achieving a smoother surface finish.
  3. Mold Design:
    a. Venting: Ensure proper venting in the mold to allow air and gases to escape during injection. Inadequate venting can cause air traps and lead to darker spots and gloss issues. b. Surface Finish: Pay attention to the mold surface finish. Highly polished molds can result in parts with better gloss. c. Gate Design: Optimize the gate design to achieve good flow of the molten material without causing excessive shear stress or material degradation.
  4. Mold Maintenance:
    a. Regular Cleaning: Regularly clean and maintain the mold to prevent contamination or build-up of residue, which could affect the part appearance. b. Mold Release Agents: Use appropriate mold release agents to ensure easy part ejection and minimize the risk of surface defects.
  5. Colorant Dosage and Mixing:
    a. Proper Mixing: Ensure accurate measurement and mixing of colorants or masterbatch with the base resin to achieve consistent color distribution. b. Dosage Control: Carefully control the amount of colorant or masterbatch added to achieve the desired color and avoid excessive darkening.

By addressing these aspects during material selection, processing, and mold design, manufacturers can significantly improve the color and gloss of injection-molded parts, resulting in visually appealing and high-quality finished products. Regular monitoring and adjustments may be necessary to fine-tune the process and achieve optimal results.

Injection mold is a tool for producing plastic products; It is also a tool to endow plastic products with complete structure and precise size. In the process of processing and manufacturing, injection molds often encounter the phenomenon of dark color and poor gloss. What is the reason for the dark color and poor gloss and how to solve it?


In the normal production, processing and manufacturing process of injection mold, the luster of mold surface is mainly determined by the type of plastic, colorant and mold surface finish. The causes and solutions of dark color and poor gloss are as follows.

  1. The injection mold has poor finish, the cavity surface has rust, etc., and the mold has poor exhaust.
  2. Too many recycled materials are used, the quality of plastics or colorants is poor, water vapor or other impurities are mixed, and the quality of lubricants used is poor.
  3. The pouring system of the injection mold has defects, so the cold well, runner, polishing sprue, splitter and gate should be increased.
  4. The material temperature and mold temperature are too low. If necessary, local heating at the gate can be used.
  5. The plastic shall be fully plasticized, but the degradation of the material shall be prevented, the heating shall be stable, and the cooling shall be sufficient, especially for the thick wall.
  6. The clamping force shall be sufficient during the production and manufacturing of injection mold.
  7. The processing pressure of injection mold is too low, the speed is too slow, the injection time is insufficient, and the back pressure is insufficient, resulting in poor compactness and dark surface.
  8. To prevent cold materials from entering the parts, use self-locking springs or reduce the nozzle temperature when necessary.
    The above 8 points can be well done to avoid the dark color and poor gloss of the injection mold. Even if this phenomenon occurs in the production process, remedial measures can be well done to minimize the impact on the production progress of the enterprise and increase the production efficiency of the enterprise.

Injection molding is a widely used manufacturing process for producing plastic products. However, the process can sometimes result in dark color and poor gloss, which can be a problem for the final product’s appearance. In this article, we will discuss some possible solutions for this issue.

  1. Material Selection: One of the most important factors in achieving good surface quality is choosing the right material for injection molding. Some materials have a higher propensity for dark color and poor gloss, so it’s important to select materials that can achieve the desired appearance.
  2. Injection Molding Process Parameters: The injection molding process parameters can also affect the appearance of the final product. Adjusting the injection pressure, temperature, and speed can help to achieve the desired surface finish.
  3. Mold Design: The mold design can also play a crucial role in achieving good surface quality. The design should be optimized for the specific material being used and should have the correct venting to allow air to escape from the mold cavity.
  4. Mold Maintenance: Regular maintenance of the mold can help to prevent problems with dark color and poor gloss. The mold should be cleaned regularly, and any signs of wear or damage should be addressed promptly.
  5. Post-Processing: Post-processing techniques such as polishing and painting can help to improve the appearance of the final product. These techniques can be used to remove any surface imperfections and achieve the desired surface finish.

In conclusion, achieving a good surface finish in injection molding requires attention to detail in the material selection, injection molding process parameters, mold design, and mold maintenance. Post-processing techniques can also be used to improve the final appearance of the product. By following these steps, manufacturers can produce high-quality products with the desired surface finish.