The raw materials used in sand casting are generally casting sand and molding sand binder. Silica sand is commonly used as casting sand.
The reason for casting shrinkage is that the alloy used in the casting mold will absorb a large amount of oxygen, nitrogen and other gases in the air when dissolved, and will contract and release these gases when the alloy solidifies, resulting in casting shrinkage.
The casting mold is usually made as the pattern of the product replica. The mold is used to create the mold cavity, and then filled with molten metal or plastic.