Permanent Mold Casting Process

Permanent mold casting is a metal casting process that employs reusable molds ("permanent molds"), usually made from metal. The most common process uses gravity to fill the mold; however, gas pressure or a vacuum are also used. A variation on the typical gravity casting process, called slush casting, produces hollow castings. Common casting metals are aluminum, magnesium, and copper alloys. Other materials include tin, zinc, and lead alloys, and iron and steel are also cast in graphite molds.

Mold Creation

The process begins with creating a permanent mold around a pattern, typically crafted through machining. These molds are most often made from iron or steel, ensuring durability and reusability.

Mold Preheating

Preheating the mold is a crucial step to ensure the molten material flows smoothly without premature cooling. This step minimizes thermal shock, which can occur due to the temperature difference between the mold and the molten metal.

Optional Core Placement

To achieve complex features such as cavities and undercuts, cores can be placed within the mold before pouring the material.

Material Pour

The liquefied metal, such as aluminum, is poured into the mold cavity via sprues. While gravity is commonly used, methods like low-pressure casting and vacuum casting are also available for specific applications.

Cooling

The cooling time varies based on the size and shape of the casting, ensuring complete solidification before proceeding to the next step.

Part Removal/Ejection

Once cooled, the mold halves are separated to remove the solidified part. To prevent sticking, the cavity surfaces might be coated, and ejector pins can be used to aid removal. Post-removal, any excess material is trimmed, and the casting may undergo further processes like heat treatment to enhance its properties.