moulding-additive-manufacture > Vacuum Casting - Plastic

The Vacuum Casting Process is often used to produce a number of small batch, highly accurate parts.

The process involves a number of steps. A master pattern is made and placed in a casting frame. Silicone Rubber is then mixed under vacuum and poured into the casting frame, surrounding the master pattern. The frame is then placed in a Vacuum Chamber until all air bubbles have escaped the Silicone. It is then cured in an oven. The Silicone is split revealing an accurate mould of the master tool. When needed the two halves of the Silicone Tool are clamped together and placed under vacuum, typically Polyurethane Resin is mixed and "sucked" into the cavity. The resin is left to cure either at room temperature or in an oven. Once cured the Silicone Mould is split and the solid resin replica component is released. 

 Vacuum casting tooling lasts up to around 50 parts.

Wall thicknesses as low as 0.5mm are achievable, and surface finishes can be comparable with injection moulded components.