Summary of injection mold surface treatment

Injection mold surface treatment methods such as grinding and polishing, sandblasting, hard chrome plating, and laser cladding can significantly improve welding quality and mold life. From mechanical treatment to composite processes, each technology is precisely working for smoother mold cavities, stronger wear resistance, and less metal resistance.

Mechanical treatment

· Grinding and polishing: Use sandpaper, grinding wheel and other tools to grind the cavity surface to remove surface roughness and flaws and make the surface smoother. This helps to reduce the resistance of the metal liquid flowing in the cavity, ensuring that the metal liquid can evenly fill the cavity, thereby improving the surface quality and dimensional accuracy of the welded joint. Further fine polishing can be done with polishing paste or polishing machine to make the cavity surface mirror-like, reduce the friction between the metal and the cavity surface, and reduce the occurrence of injection mold sticking.

· Sandblasting: Sand is sprayed at high speed to impact the surface of the mold cavity, so that the surface is slightly uneven and the surface roughness is increased. This can improve the adhesion between the molten metal and the surface of the mold cavity, facilitate exhaust, and reduce the generation of defects such as pores. At the same time, sandblasting can also eliminate the residual stress on the surface of the mold cavity and improve the fatigue life of the mold.

Chemical treatment

· Plating treatment

· Hard chrome plating: A layer of hard chrome is plated on the surface of the mold cavity. The chrome layer has the advantages of high hardness, good wear resistance, and strong corrosion resistance. It can improve the hardness and wear resistance of the mold cavity surface, reduce the wear of the mold during use, and extend the service life of the plastic injection mold. At the same time, the smooth surface of the chrome layer also helps the flow and demolding of the molten metal.

· Nickel plating: Nickel plating has good corrosion resistance and chemical stability, and can protect the surface of the mold cavity from erosion by the metal liquid. In addition, the nickel plating can also improve the wettability of the mold cavity surface, making it easier for the metal liquid to fill the mold cavity and improve the welding quality.

· Chemical conversion film treatment: A conversion film, such as phosphating film and oxide film, is formed on the surface of the mold cavity by chemical methods. These conversion films can improve the corrosion resistance and wear resistance of the mold cavity surface, and can also play a certain lubricating role to reduce the friction between the metal liquid and the mold cavity surface. The phosphating film can form a porous protective film on the surface of the mold cavity, absorb lubricants, reduce the friction coefficient, and improve the demolding performance.

Physical treatment

· Physical vapor deposition (PVD): In a vacuum environment, the metal or compound is evaporated and deposited on the surface of the mold cavity by physical methods to form a thin film. Common PVD coatings include TiN, TiC, TiAlN, etc. These coatings have the advantages of high hardness, high wear resistance, and low friction coefficient, which can significantly improve the performance of the mold cavity surface. TiN coating can improve the hardness and wear resistance of the cavity surface, and also has good anti-oxidation properties, which can protect the cavity surface at high temperatures.

· Laser surface treatment: Use the high energy density of laser to treat the cavity surface, such as laser quenching, laser cladding, etc. Laser quenching can improve the hardness and wear resistance of the cavity surface, while laser cladding can clad a layer of alloy with special properties on the cavity surface to improve the performance of the cavity surface. Laser cladding can clad a layer of high hardness and high wear resistance alloy on the cavity surface to improve the service life of the mold and welding quality.

Composite treatment

Combining two or more surface treatment methods to give full play to their respective advantages and further improve the performance of the cavity surface. The cavity surface is first plated and then laser surface treated, so that the cavity surface has both the corrosion resistance and lubricity of the coating layer and the high hardness and wear resistance after laser treatment, thereby significantly improving the welding quality and the service life of the mold.

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