The core of aluminum castings is used to form internal cavities or local shapes of castings. Due to the surface of the core being surrounded by high-temperature liquid metal, it is subjected to buoyancy and baking effects of high-temperature liquid metal for a long time; When aluminum castings are cooled and solidified, the sand core often hinders the free shrinkage of the castings; Cleaning the sand core is also quite difficult. Therefore, the core sand used for core making has higher strength, breathability, high temperature resistance, yield resistance, and collapsibility than molding sand.

Handmade chip making is widely used due to the lack of chip making equipment and simple process equipment. According to the size and complexity of the sand core, there are integral core boxes, split core boxes, and detachable core boxes used for manual core making.