1. The process begins with an existing model or prototype, often made from silicone. This model is placed in a box and liquid silicone is poured around it to create a mould.
2. After the silicone mould is set, it's cut open and the original model is removed, leaving a hollow shape of the desired part.
3. The silicone mould is then placed in a vacuum chamber. A casting material, often a two-part polyurethane resin, is mixed and degassed in the vacuum chamber to remove any air bubbles.
4. The degassed material is then poured into the silicone mould, which is still in the vacuum chamber. The vacuum ensures that the material fills every part of the mould, capturing all the details of the original model and preventing any air bubbles from being trapped in the final part.
5. Once the resin is cured, the silicone mould is cut away to reveal the cast part.

Vacuum casting is popular for its ability to produce parts with fine details, excellent surface quality, and accurate dimensions. It's often used for creating prototypes, models for user testing, and small production runs.