Vacuum casting is a low-cost but reliable method for making a small number of high-quality prototypes based on a master model. This method is ideal for rapid prototyping used in engineering testing, proof-of-concept and display demos to name a few. At Star Rapid, we have a dedicated team of mold makers who are experts at creating vacuum casting molds which offer fine surface details while being robust enough to make up to 50 copies per mold with short lead times.

Vacuum Casting Process

Stage One: Making the Master Mold

* First, a solid master model or pattern is required. This can be made of any stable material, and can either be supplied by you or alternately created by Star using our 3D printing services or via CNC machining.

* Typically master patterns are made in plastic or metal, the only requirement being that they are able to withstand a temperature of 40° C for an extended period of curing.

* We then suspend this pattern inside of a casting box, which we half-fill with liquid silicone rubber. This is placed inside of a curing oven and heated at 40° C until the silicone is fully cured.

* The casting box is then filled with additional silicone liquid which is also heated and cured. The two halves are treated with a releasing agent for later separation.

* Once fully cured, the silicone rubber mold is opened up along the parting line and the original master removed.

Stage Two: Making the Parts

* During mold making, our craftsmen strategically place a series of fine holes surrounding the master pattern. These holes will be used to later draw air pressure out of the mold.

* Once the master has been removed, there is now a hollow cavity in the silicone mold which is an exact reverse image of the original.

* We can fill this cavity with any number of molding polymers to suit your design requirements. Once the cavity is filled, it’s placed into a vacuum chamber which draws air out of the cavity and pulls the liquid plastic into all of the recesses of the mold, ensuring an exact conformity to the original shape.

* Finally the mold goes into a curing oven one more time, creating a solid and stable replica of your original master pattern.