When discussing “copper for mold makers,” the reference is typically to the use of copper alloys in the creation of molds, particularly for the plastics injection molding and die-casting industries. The reason for this is the superior thermal conductivity of copper, which allows for faster cooling of the molten material, leading to shorter cycle times in the molding process.

Why Copper?

Thermal Conductivity: Copper has high thermal conductivity, which means it can rapidly draw heat away from the molded product. This rapid cooling helps reduce cycle times, making the molding process more efficient.

Machinability: Certain copper alloys are easier to machine than tool steels typically used for molds, allowing for faster mold production and modification.

Surface Finish: Copper can achieve a high polish, which is often desired for aesthetic reasons in molded products.

Wear Resistance: Specific copper alloys, especially beryllium-copper, have good wear resistance, which extends the life of the mold.

Reduced Cycle Times: As mentioned earlier, due to its high thermal conductivity, using copper can reduce cycle times, increasing production rates.

Key Specification

Alloy Type: While pure copper has excellent thermal conductivity, it’s too soft for most molding applications. Thus, alloys like beryllium-copper (BeCu) or tellurium-copper are often preferred for molds. These alloys combine the desirable properties of copper with additional hardness and strength.

Purity: The Presence of impurities in the copper can affect its Thermal Conductivity.

Hardness: Depending on the application, the hardness of the copper alloy can be an essential specification. For instance, beryllium-copper can be heat treated to achieve higher hardness levels suitable for specific molding applications.

Grain Size and Structure: The microstructure of the copper can influence its thermal conductivity. Generally, larger grain size can offer better thermal conductivity than smaller grain size due to fewer grain boundary interruptions for heat flow.