Sand casting
Introduction
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term "sand casting" can also refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. Over 60% of all metal castings are produced via sand casting process.
Sand Casting Process
The sand casting process involves the use of a furnace, metal, pattern, and sand mold. The metal is melted in the furnace and then ladled and poured into the cavity of the sand mold, which is formed by the pattern. The sand mold separates along a parting line and the solidified casting can be removed.
Pattern
The pattern is the replica of the external shape of the casting and is used to create the mold cavity. Patterns are usually made of wood, metal, plastic, or plaster. The pattern material is chosen based on the casting volume and process used. Patterns also have core prints that create registers within the molds to make room for core inserts.
Mold
The mold is made from a mixture of sand, clay, and water. The sand provides the structure of the mold, while the clay binds the sand grains together and imparts strength to the mold. The mold must have the physical and chemical characteristics that can withstand the high temperatures of molten metal and not disintegrate or react with the metal.
Core
A core is a device used in casting and molding processes to produce internal cavities and reentrant angles. The core is normally a disposable item that is destroyed to get it out of the piece. Cores are used for complex injection moldings in the fusible core injection molding process.
Pouring
The molten metal is maintained at a certain temperature in the furnace before it is poured into the mold. The pouring can be done manually or by a machine.
Cooling
After the metal has been poured into the mold, it is allowed to cool and solidify into the shape of the final casting. Cooling time can vary greatly depending on the thickness of the part, the type of metal, and the temperature of the molten metal.
Removal
After the metal has cooled and solidified, the sand mold is broken away to remove the casting. The sand from the mold is often reclaimed and reused in the casting process.
Advantages and Disadvantages
Sand casting has many advantages, including its low cost, flexibility, and the ability to cast complex geometries. However, the process also has its disadvantages, such as poor surface finish, dimensional inaccuracy, and the need for a large lead time.
Applications
Sand casting is used to produce a wide range of metal components with complex geometries. These parts can vary greatly in size and weight, ranging from a couple ounces to several tons. Some smaller sand cast parts include components as gears, pulleys, crankshafts, connecting rods, and propellers.
See Also
