How Vacuum Casting Works ?

Nov 14 , 2025 | Blog

Vacuum casting uses a silicone mold and a vacuum chamber to create detailed plastic or rubber parts with smooth surfaces and minimal defects

Here’s a step-by-step breakdown of the process:

1. Create a 3D Model
As with most modern manufacturing processes, the first step is to design a 3D model of the part.

Use CAD software such as AutoCAD, SolidWorks, or CATIA.
To get optimal results, follow injection molding design rules, including draft angles, uniform wall thickness, and allowances for undercuts.

2. Build the Master Pattern
Produce a master pattern from the 3D model using SLA 3D printing or CNC machining.

While CNC was traditionally used, it still offers higher dimensional accuracy, especially for pre-series parts.
3D printing speeds up prototyping and reduces cost during early design validation.

3. Create the Silicone Mold
Place the master pattern in a casting box along with any cores, inserts, and gating systems.

Pour liquid silicone over the pattern to capture its geometry and surface details.
Cure the mold in an oven at 40°C for 8 to 16 hours, depending on its size.
Once cured, cut the mold open along the parting line to reveal the negative cavity.
Apply a mold-release agent to prevent sticking and avoid surface flaws.

4. Mix and Pour the Resin
Prepare a two-component polyurethane resin and add any required pigments.

Preheat the mixture to ~40°C for better flow.
Install the mold in the vacuum chamber and connect the pouring gates.
Mix and deaerate the resin under vacuum for 50–60 seconds to remove air bubbles.
Apply vacuum to the mold so gravity fills the cavity evenly without trapped air.

5. Demold the Parts
Cure the filled mold in an oven for 1 to 4 hours, depending on the material.

After curing, remove the hardened part from the mold, then trim gates and perform any needed finishing.
A single silicone mold typically produces 10 to 20 parts, depending on the geometry and resin used.
Illustration of the vacuum casting process

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How Vacuum Casting Works ?

Vacuum casting uses a silicone mold and a vacuum chamber to create detailed plastic or rubber parts with smooth surfaces and minimal defects

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