How do casting and molding shape materials in a liquid state?

In materials science, casting and molding are processes used to shape a fluid or plastic substance into a desired finished product by utilizing a cavity or matrix known as a mold.

The process generally involves the following steps:

• Preparation: A mold is created using materials such as sand, hardened steel, plaster, or flexible substances like rubber, depending on the application and the material being cast.12
• Filling: The material, typically in a molten or liquid state (such as metal, plastic, or clay slip), is poured or forced into the mold cavity. While gravity is frequently used to fill the mold, some industrial processes employ pressure injection or centrifugal force.1234
• Solidification: The material is allowed to harden or set within the mold. For plastics, this may involve heating to induce polymerization or gelation, while metals solidify as they cool.23
• Removal: Once solidified, the finished object is removed from the mold. In some techniques, such as the lost-wax process or sand casting, the mold may be destroyed to extract the final piece.2

Engineers must carefully manage factors like shrinkage and gas-forming impurities to prevent porosity, which can create internal cracks or pores in the final product.5