The Difference between Gravity Casting and Sand Casting

Gravity Casting:

Gravity casting is a metal casting process that utilizes the force of gravity to fill a mold with molten metal. In this process, the molten metal is poured into the mold, and gravity aids in the flow and distribution of the metal throughout the mold cavity. Gravity casting is typically used for non-ferrous metals, such as aluminum and copper alloys.

Sand Casting:

Sand casting, also known as sand mold casting, is a casting process that involves creating a mold from a mixture of sand and a binding agent. The mold cavity is formed by compacting the sand mixture around a pattern, and then the pattern is removed to leave a cavity. Molten metal is then poured into the mold cavity, and after solidification, the sand mold is broken to reveal the casting.

Differences:

1. Process: In gravity casting, the molten metal is poured into the mold under the influence of gravity, while in sand casting, the molten metal is poured into a sand mold.

2. Mold Material: Gravity casting usually utilizes permanent molds made of materials like steel or iron, which can be reused multiple times. On the other hand, sand casting employs molds made of sand, which are typically disposable and can only be used once.

3. Surface Finish: Gravity casting generally yields better surface finish and dimensional accuracy compared to sand casting, as the use of permanent molds provides better mold cavity definition. Sand casting often results in a rougher surface finish and may require additional finishing operations.

4. Complexity: Gravity casting is suitable for producing complex shapes and thin-walled castings with high integrity. Sand casting is more versatile and can accommodate a wider range of geometries and sizes, including large and intricate castings.

5. Production Rate: Gravity casting is generally faster than sand casting, as the use of permanent molds allows for rapid mold preparation and repeated casting cycles. Sand casting requires pattern-making and mold preparation for each casting, which can be time-consuming.

6. Cost: Gravity casting usually involves higher upfront costs due to the fabrication of permanent molds. Sand casting typically has lower initial costs, as sand molds are more affordable, but may incur higher material and labor costs for each casting.

These differences distinguish the processes of gravity casting and sand casting, making each suitable for specific applications depending on factors such as part complexity, required surface finish, production volume, and cost considerations.