In the process of manufacturing various sand molds and cores, based on their different bonding mechanisms when establishing strength, they can usually be divided into three categories:

(1) Mechanical bonding agent core - the bonding produced by clay core sand with clay as the bonding agent;

(2) Chemical bonding agent core - During the molding and core process, the core sand relies on the physical and chemical reactions of its bonding agent itself to achieve hardening, thereby establishing strength and firmly bonding the sand particles into a whole. Organic and inorganic binders, among which inorganic binders include sodium silicate and silica sol, while organic binders include thermosetting, self hardening, and gas hardening resin sand molds (cores);

(3) Physical consolidation refers to the use of physical principles to consolidate raw sand without binders together, such as magnetic casting, negative pressure molding, real sealing molding, film negative pressure molding, and lost foam molding.

（2） Clay wet type

1. Wet type and its characteristics

(1) It has high production flexibility and wide applicability, and can be produced by hand, machine, or assembly line. It can produce large and small parts, cast steel (medium and small parts), cast iron, non-ferrous alloys, etc.

(2) High production efficiency, short production cycle, easy assembly line production, mechanization and automation can be achieved. It is widely used in the automotive, diesel engine, and tractor industries (300-500kg cast iron thin crack parts).

(3) Low raw material costs and wide sources.

(4) Save energy, drying equipment, and workshop production area.

(5) Due to the lack of drying, the lifespan of the sand box is long.

(6) Disadvantages: Improper operation can easily lead to casting defects such as sand inclusion scars, rat tails, sand holes, sand swelling, sand sticking, etc.