Overview of Injection Mold Surface Finish

1. Common Injection Mold Surface Treatment Methods

There are various surface treatment techniques used to improve the finish and properties of injection molds:

Polishing - Using manual or mechanical polishing to create a smooth, mirror-like surface finish. This improves surface quality and ensures easier mold release.

Chrome plating - Electroplating a 20-100 μm thick chrome layer onto the mold surface. The hard chrome coating improves wear and corrosion resistance.

Hard chrome plating - Applying a thicker 400-600 μm chrome coating and subsequent nitriding process. This achieves an extremely hard 800-1200 HV surface.

Titanium nitride (TiN) coating - Using PVD or CVD deposition to apply a thin 2-5 μm TiN coating, which has high hardness, toughness and corrosion resistance.

Titanium carbonitride (TiCN) coating – A PVD applied superhard coating with high wear resistance and lubricity.

Diamond-like carbon (DLC) coating – An ultra-hard and smooth carbon-based PVD coating with excellent tribological properties.

Anodizing - Electrochemically generating an oxide layer up to 50 μm thick. It improves corrosion and abrasion resistance.

Laser polishing - Using a laser beam to selectively melt the mold surface and create a smooth finish without affecting part geometry.

Electropolishing - An electrochemical process that removes surface high points through anodic dissolution to achieve a smooth specular finish.

2. Considerations of injection mold surface finish

When selecting the surface treatment method for injection molds, several factors need to be considered:

Product requirements: Firstly, the requirements of the injection-molded products should be taken into account. Different products may require different surface effects, such as high glossiness, texture, or anti-slip properties. Understanding the product design and market demands will help determine the suitable surface treatment method.

Material characteristics: The characteristics of the materials used in the injection molds are also important factors to consider. Certain materials may be better suited for specific surface treatment methods, while others may not be compatible with certain treatments. For example, some high-temperature plastics may require heat-resistant surface treatment.

Mold material: The material of the injection molds should also be considered. Certain materials may be more suitable for specific surface treatment methods, such as polishing or chrome plating. The hardness, corrosion resistance, and thermal conductivity of the mold material can influence the choice of surface treatment.

Production volume and cost: Production volume and cost are also crucial factors to consider. Some surface treatment methods may require longer processing time or higher costs. For large-scale production, it may be necessary to select efficient and cost-effective surface treatment methods.

Mold lifespan and maintenance: Different surface treatment methods have an impact on the lifespan and maintenance requirements of the molds. Some treatments may require regular maintenance or reprocessing, while others may have a longer lifespan. Considering the expected lifespan of the molds and the associated maintenance costs is an important factor in selecting the surface treatment.

3. The Advantages of Injection Mold Surface Finish

Proper mold surface finishing provides significant benefits:

Improved part quality - Mirror surface finish, free of flow lines, jets, and other defects.

Increased mold life - Hard protective coatings prevent premature failure modes.

Higher productivity - Smooth surfaces facilitate demolding, reducing cycle times.

Lower costs - Lower rejection rates and longer mold life lead to cost savings.

Process flexibility - The ability to mold highly filled or abrasive compounds.

Consistent production - Maintaining initial surface finish ensures consistent quality over long production runs.

Reduced maintenance – Surface treatments minimize damage accumulation and the need for refinishing work.

4. Conclusion

Injection mold surface finish is a critical aspect of the injection molding process. It affects both the quality and aesthetics of the final molded parts. By considering factors such as mold design, processing parameters, and surface enhancement techniques, manufacturers can achieve the desired surface finish for their products, meeting customer expectations and enhancing market competitiveness.