What is the function of a core in sand casting?

In sand casting, the primary function of a core is to define internal cavities within the cast metal object. Cores are inserted into the mold before pouring the molten metal, and they create spaces that are not filled with metal, allowing for complex internal shapes and structures that cannot be achieved through the outer mold alone. This is crucial in many applications where internal features, such as passages for fluids or chambers for mechanical components, are necessary for the functionality of the final product.

While cores can be made from various materials, they typically are composed of a sand mixture that can be easily removed after the casting process. This allows for the creation of detailed internal geometries that enhance the design and use of the final product. The presence of cores not only facilitates more intricate designs but also enables better control over the weight and material distribution within the casting.

The other functions listed, such as adding strength, providing surface finish, and cooling the metal, are not the primary roles of cores in sand casting. Instead, these aspects involve different components and processes in the casting operation. Strength is generally derived from the quality of the mold and the material used, surface finishing is done post-casting, and cooling rates are influenced by factors like mold materials and thickness rather than cores themselves.