What is the Difference Between Gravity Die Casting and Sand Casting?

1. Understanding gravity die casting

Gravity die casting is one of the oldest known manufacturing processes for metals and metal alloys. Gravity die casting designs pour molten metal from a crucible into a mold under the force of gravity alone, without the use of pressurized gas, vacuum, or centrifugal force. Small molds used for this form of casting are most commonly used for sand, limestone, and squid bone as well as charcoal and plaster, as these materials are generally easy to shape (unlike iron or steel) and do not decompose upon sudden exposure to high temperatures (unlike glass, wood or plastic), not easily deformed (unlike silicone) and widely used.

2. The difference between gravity die casting and sand casting

During sand casting, molten metal is poured directly from a ladle into a mold. A mold is created when a pattern made of wood (often called a matchboard) is placed inside the enclosure. Then fill the sand around the matchboard and inside the shell. Once the sand is added and the filling is dense, the fire plate is removed and the remaining cavity is filled with molten metal. After pouring, the metal solidifies, the mold opens, and the sand is shaken off the hot casting to create the product. At this point, the casting material can be removed and the casting is completed. So the same thing between sand casting and gravity die casting is that the metal is poured under gravity, not extra pressure.

The main difference between gravity die casting and sand casting is that the mold material for gravity die casting is metal, while the mold material for sand casting is wood. Sand casting is more suitable if the aluminum parts are larger. The surface finish and dimensional accuracy of gravity die casting are superior to sand casting processes. Gravity die casting costs slightly more.

3. Skills in choosing gravity die casting process

It is important to choose the right casting process for your design. Several factors should be considered before making a decision, such as process constraints, production efficiency, investment, dimensional accuracy, surface finish, lead time, etc. Sometimes, aluminum castings are designed for both gravity die casting and pressure die casting processes. Gravity die casting is recommended when order quantities are small as it has lower tooling costs. Keep in mind that not all metals can be cast by this process, only metals with a low melting point are suitable. But for thinner parts, if gravity die casting is the choice, consider pressure die casting as it is prone to defects.

Metal Casting
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