Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Vacuum casting, also known as urethane casting or polyurethane casting, is a manufacturing process used to produce high-quality plastic or rubber parts in small quantities (typically 5–50 pieces). It is particularly popular for rapid prototyping and low-volume production, offering a cost-effective alternative to injection molding without the need for expensive hard tooling.

How the Vacuum Casting Process Works

The process involves creating a flexible silicone mold from a master pattern and using a vacuum to draw liquid resin into the mold, eliminating air bubbles for smooth, detailed parts.

1.Create a master pattern: A high-quality prototype (master) is produced, usually via 3D printing or CNC machining. This master must be flawless, as it replicates every detail.

2.Make the silicone mold: The master is suspended in a frame, and liquid silicone is poured around it under vacuum to avoid bubbles. The silicone cures (often heated), then the mold is cut open to remove the master.

3.Cast the parts: Polyurethane resin (often two-part) is mixed, degassed, and poured into the silicone mold inside a vacuum chamber. The vacuum ensures the resin fills all details without air entrapment. The mold is then cured in an oven.

4.Finish the parts: Cast parts are removed, trimmed, and post-processed (e.g., painted or assembled).

A single silicone mold typically produces 10–25 parts before degrading.

Advantages

1.Low tooling costs (silicone molds are inexpensive compared to metal injection molds).

2.High detail reproduction, including undercuts and complex geometries.

3.Excellent surface finish and material properties similar to production plastics (e.g., ABS-like, rubber-like).

4.Fast turnaround (often days to weeks).

5.Wide range of polyurethane resins for rigidity, flexibility, transparency, or heat resistance.

Limitations

1.Limited mold life (not suitable for high-volume production).

2.Slight shrinkage (typically 0.15–0.25%).

3.Manual aspects can affect consistency compared to fully automated processes.

Applications

Vacuum casting is widely used in automotive (lenses, dashboards), consumer products (housings, toys), medical devices, and electronics for prototypes, market testing, or bridge production before scaling to injection molding.