Vacuum casting is a manufacturing process used to produce high-quality plastic prototypes and small batch parts.
The process involves pouring liquid resin into a silicone mold under vacuum conditions to eliminate air bubbles. This helps in producing parts with high accuracy and smooth surface finish. Vacuum casting is commonly used for product development and functional testing.
Working Principle of Vacuum Casting
The working principle of Vacuum Casting is based on producing parts by pouring liquid resin into a silicone mold under vacuum conditions. First, a master model of the part is created, often using Stereolithography or another 3D printing method. This master model is used to make a silicone mold.
After the mold is prepared, it is placed inside a vacuum chamber. Liquid polyurethane resin is then poured into the mold while vacuum pressure removes air bubbles and ensures complete filling of the mold cavity.
The mold is then heated to cure and solidify the resin. Once the material hardens, the mold is opened and the finished part is removed. This process allows accurate reproduction of the master model with smooth surface finish and good dimensional accuracy.
Materials Used in Vacuum Casting
In Vacuum Casting, different materials are used to create molds and produce the final parts. These materials help achieve good surface finish, strength, and accuracy.
1. Silicone Rubber
Silicone rubber is used to make the mold. It is flexible, durable, and capable of capturing fine details from the master model.
2. Polyurethane Resin
Polyurethane resin is the most common casting material. It is poured into the silicone mold and then cured to form the final plastic part.
3. Epoxy Resin
Epoxy resin is sometimes used when higher strength and better heat resistance are required.
4. Coloring Pigments
Color pigments can be added to the resin to produce parts in different colors according to design requirements.
Often, the master pattern used to create the mold is produced using Stereolithography, which provides high accuracy and smooth surface finish.
Specifications of Vacuum Casting (VC)
The specifications of Vacuum Casting define the accuracy, material properties, and production capability of the process.
Specification
Typical Value
Mold Material
Silicone Rubber
Casting Material
Polyurethane / Epoxy Resin
Mold Life
15–25 parts per mold
Dimensional Accuracy
±0.1 to ±0.2 mm
Surface Finish
Smooth, similar to injection molded parts
Minimum Wall Thickness
0.5 – 1 mm
Maximum Part Size
Up to ~500 mm (depends on machine)
Curing Temperature
60–80 °C
Curing Time
30–90 minutes
Production Volume
Low-volume production (10–50 parts)