Terminology

Casting metal is one of the oldest manufacturing methods known to humans. It involves creating a hollow shape or cavity, called a mold or casting, and filling it with a molten metal that solidifies into the desired part. The casting process can vary depending on the type of metal and the method of creating the mold. After the metal part is removed from the mold, it may undergo further processing such as machining, heat treatment, or surface finishing to achieve the required specifications and quality.

Designing for casting requires choosing the appropriate metal and casting method for the part. The choice depends on several factors such as the performance and material properties of the part, the dimensional accuracy and surface finish, and the production cost and time. Different metals have different melting points, fluidity, shrinkage, and mechanical properties that affect the casting process and outcome. Different casting methods have different advantages and disadvantages in terms of complexity, flexibility, repeatability, and efficiency.

Follow Along with Professor Cummings on Casting/Mold Fundamentals

Metal Cast Part Properties and Behaviors

Using casting methods to generate metal parts affects the material properties and the places some restrictions on the realistically achievable dimensional tolerances. Why would you select casting compared to other ways of manufacturing a part such as machining or direct forming from blanks?

Some of the advantages of metal casting are:

• It can use metal alloys that are hard to work with using other methods, such as machining or welding. This gives more flexibility and variety in the choice of materials.
• It can produce complex shapes in large quantities cheaper than machining. This reduces the cost and time of production, especially for mass-produced parts.
• It can generate parts with internal cavity features more economically than other methods. This allows for the design of hollow or lightweight parts that can save material and improve performance.

However, metal casting also has some challenges or drawbacks, such as:

• Material properties in parts are often not anisotropic, meaning that they can be stronger in some directions than others. This can affect the performance and reliability of the parts, especially under stress or load.
• Casting can introduce defects such as poor surface finish, porosity, cracks or inclusions. These defects can reduce the quality and durability of the parts and may require additional processing or inspection to correct them.
• Achieving very tight dimensional tolerances is difficult with casting due to material shrinkage. This means that the parts may not fit well with other components or have gaps or misalignments. This can affect the functionality and aesthetics of the parts, and may require further machining or adjustment to fix them.

Watch Professor Cummings Explain What Happens to Metal When Cast