What Is Vacuum Casting?
Vacuum casting is a casting method in which the inside of the cavity (recess of the mold) is depressurized in advance using a vacuum tank before molten metal is cast.
When molten metal is poured into a mold under atmospheric pressure, air can become trapped, forming “cast cavities” inside the product. Vacuum casting prevents the formation of such cavities by creating a vacuum in the mold, resulting in high-quality castings. The advantages of vacuum casting include the following:
- Suppression of casting cavity generation
- Improved flowability of molten metal due to reduced gas interference within the mold
Vacuum casting can be divided into several subcategories. It involves creating a constant negative pressure to draw molten metal into the mold cavity. There are unidirectional vacuum suction and multidirectional vacuum suction methods. Other approaches include vacuuming the mold cavity and then pressure-filling it. After filling, maintaining pressure during crystallization and solidification results in a denser microstructure and improved mechanical properties.
Although vacuum casting primarily refers to metal casting, it is occasionally used to describe the vacuum molding of plastics.
Uses of Vacuum Casting
Vacuum casting is widely used due to its high precision and ability to reproduce complex shapes. Below are the main applications of vacuum casting:
1. Metal Products
Vacuum casting is used when high mechanical quality, excellent surface finish, or large parts with high dimensional accuracy are required. Major products cast using vacuum casting include:
- Parts for automobiles and heavy trucks (die casting)
- Railroad vehicles
- Industrial machinery parts
- Construction machinery
- Logistics equipment
- Precision parts for computers, cell phones, digital cameras, etc.
- Parts intended for heat treatment or welding in subsequent processes (to prevent internal defects caused by cast cavities)
- Household electrical appliances
- Medical equipment
2. Plastic Products
Vacuum casting is sometimes used to describe the vacuum forming of plastics. The vacuum reduces defects caused by air bubbles, enabling the production of precision products. Examples include:
- Medical devices (artificial limbs, orthotics, hearing aids, etc.), and surgical organ models
- Resin automotive parts (dashboard panels, knobs, gauges, emblems, etc.)
- Robotic and industrial machinery parts
- Artwork, figures, and scale models