Metal Casting Guide

Metal casting is the process of forming a product or part from molten metal, using any type of mold to control its final shape. On the other hand, metal castings are products or parts produced by the metal casting process. In this article and elsewhere on our website, we use the term "casting" interchangeably as a substitute for the metal casting process or as a substitute for the object. During the manufacturing process, molten metal is poured into a mold that maintains the metal in a specific shape as it solidifies.

Expendable and Permanent Molds for Metal Casting

Many different metal casting processes are used in the manufacture of parts. The two main branches of the process may be distinguished by the basic design of the mold used. You can choose between ready-to-use and permanent molds. As the name suggests, expendable molds are only used for one form of metal casting, while permanent molds are used for other castings. All have benefits and drawbacks when considering the production process.
Expendable Mold
Metal castings only
● Made of sand, plaster, or other similar material
● Binders hold the material in the form
● The mold must be destroyed to remove casting
● Intricate geometries are possible

Permanent Mold
● Suitable for multiple metal castings
● Made of metal or ceramic
● Permits removal of the casting
● Limited part shapes  

Metal Casting Patterns

Consumption molds require certain patterns. The internal cavity of the mold is where molten metal is solidified, which is formed by the indentation of this pattern. Pattern design is crucial to the successful manufacturing of expendable mold metal casting. The pattern is essentially a geometric copy of the metal casting that you want to create. It is slightly larger in size to compensate for the shrinkage of the metal during the solidification of the casting and any amount of material that will be machined from the casting in the future. Although machining increases the manufacturing process of parts, machining can significantly improve surface finish and part size.

Metal Casting Cores

For metal castings with internal geometry cores. The goal is to create a replica of the component 's internal features. Unlike the template, the core size is designed to withstand shrinkage during metal casting. By comparison to the formulas, the core stays in the mold when casting metal. As a consequence, the core is normally made of a mold-like material. When the metal casting is hardened, the core is broken and removed like a mold. Based on the position and configuration of the casting center, assistance can be needed during the service to prevent it from moving or changing.

General Steps of Metal Casting

1. Master Pattern and Corebox Creation
The first step in metal casting is to create objects whose shape is similar to the desired product, called patterns. The pattern is the tool used to produce the mold and must be slightly larger than the final product to account for shrinkage during solidification.
2. Mold and Core Creation
In order to successfully produce castings, the manufacturer must first create a mold cavity to contain and form molten metal. In many cases, they must also produce a core that fits inside the mold, thereby forming a hollow cavity inside the final part.
3. Alloy Melting
Generally, the metals used for metal casting are alloys or mixtures of elements, which together provide the best mechanical properties.
4. Molten metal is poured into the mold
The melting process is different: the simplest form of melting is to put the alloy in a container with a higher melting point and then heat it with a burner or open flame.
5. Metal Solidifies
After pouring, the manufacturer must create the best conditions for the metal to solidify in the mold. Similarly, the manufacturer must consider the shrinkage of the molten metal as it cools, as well as the release of gas accumulated inside the mold during the casting process.
6. Casting Removal
When the metal has sufficiently cooled and solidified, the manufacturer must remove the casting from the mold. In the one-time mold method, the operator only needs to remove the mold from the casting.
7. Casting Finish
Most castings must undergo finishing processing, such as unloading, heat treatment, and quality control inspections.

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