Basic Steps in Casting Process

While each casting method creates unique challenges and process enhancements, all techniques retain the same basic steps. These steps are:

• Patternmaking

• Coremaking

• Molding

• Melting and pouring

• Finishing

• Patternmaking

  
  

To create a casting mold, a manufacturer must first design a physical model. The process of fabricating this model is called patternmaking. Using computer-assisted design (CAD) systems, the manufacturer designs dimensions and geometry of a mold, and then packs an aggregate material, such as sand, concrete or plastic, around the pattern. Once the pattern is removed, the mold cavity in the sand can be filled.

Coremaking

Many part designs require the inclusion of cores in the casting mold. Cores are solid materials placed inside the mold cavity to create interior surfaces of a casting. For example, a metal pipefitting will require a cylindrical core inside the mold cavity to create the hollow construction of the component's interior.

Molding

At this point, the manufacturer can create the casting mold. A material such as sand, plaster or wax is used in expendable mold casting, whereas metal and other durable materials are used in non-expendable mold casting techniques. The material fills the casting mold model and is allowed to harden, at which point the manufacturer removes it from the cavity and the casting of the component can now begin.

Melting and Pouring

Metal must be properly melted prior to being placed in the mold. Typically, this is done by using what is known as a crucible. Crucibles are containers made of porcelain or another melt-resistance substance in which a manufacturer can heat a metal beyond its melting point. Once properly melted, the molten metal is poured into the casting mold to cool and harden.

Finishing

Because metal can sometimes fill in cracks in a casting mold or sprues, the pouring channel for the mold, manufacturers must often finish the metal following casting. This can be accomplished through a variety of finishing techniques, including sanding, grinding and buffing. Once proper appearance and surface texture has been achieved, further post-treatment processes such as painting or electroplating may be necessary for some applications.