1. Definition and principle
Die casting is a metal casting process, also known as pressure die casting. Its characteristic is to use the mold cavity to apply high pressure to the molten metal, so that the metal crystallizes under pressure and fills the mold cavity to form a casting. In this process, the molten metal is injected into the die casting mold cavity at high speed and solidifies under pressure. The commonly used injection pressure is 30-70MPa, the filling speed is about 0.5-50m/s, and the filling time is 0.01-0.2s. In some cases, the pressure can be as high as 4-500MPa, and the filling speed can reach 0.5-120m/s.
2. Advantages
High precision: die castings have high dimensional accuracy, small surface roughness values, dimensional tolerance grades can reach CT3-CT6, and surface roughness is generally Ra0.8-3.2μm.
High output: easy to realize mechanized and automated production, high production efficiency.
Excellent surface quality: castings have high surface finish and do not require subsequent large-scale processing.
Inlay-cast parts: Inlay-cast parts can be embedded in die castings, saving materials and machining time, and replacing the assembly process of parts.
3. Disadvantages
High cost: The structure of the die casting mold is complex, the manufacturing cycle is long, the cost is high, and it is not suitable for small-batch casting production.
Expensive equipment: The die casting machine is expensive and requires a large investment. It is also limited by the clamping force and die size of the die casting machine, and is not suitable for the production of large die castings.
Limited alloy types: It is mainly suitable for non-ferrous alloys such as zinc, magnesium, and copper.
Possible defects: The liquid metal filling speed is high during die casting, and it is difficult to completely remove the gas in the cavity. The casting is prone to defects such as pores and cracks, and usually cannot be heat treated.
2. What is sand casting
1. Definition and principle
Sand casting, also known as sand casting, is a casting method that uses sand to make a mold. It requires placing a finished part model or a wooden model (pattern) in the sand, and then filling the sand around the pattern. After the pattern is taken out of the box, the sand forms a mold. The mold should be made into two or more parts so that the model can be removed before pouring the metal. During the sand casting process, holes for pouring metal into the mold and vents must be left to form a gating system.
2. Advantages
 Low cost: Sand casting has low cost and is suitable for the production of small, medium and large castings.
 Wide range of applications: It can be made of various materials, including iron, copper, aluminum, zinc, etc.
 High flexibility: Sand mold production is relatively simple and suitable for castings with complex shapes.
3. Disadvantages
 Relatively poor surface quality: The surface quality of the sand mold is not as good as that of the die casting mold, so the surface quality of the casting is also relatively low.
 Low production efficiency: Compared with die casting, sand casting has lower production efficiency and requires a new mold for each casting.
 Heavy cleaning work: After the casting is taken out, the sand mold is destroyed and the cleaning work is heavy.

III. Summary
Die casting and sand casting each have their own advantages and disadvantages. Which process to choose depends on the specific application scenario and needs. For castings with high precision, high output and high requirements on surface quality, die casting is a better choice; while for castings with cost sensitivity, complex shapes and low requirements on surface quality, sand casting is more suitable.