Vacuum Casting

A. Process

Vacuum casting, also known as urethane casting, involves a silicone mold made using a master model to produce a small quantity of plastic or rubber prototype parts. Vacuum casting is excellent for prototypes that resemble the quality of injection molded parts, but without the level of financial investment required for tooling development. Prototypes made using vacuum casting are precise replicas of the master model. Depending on the complexity of the prototype, each mold can produce up to 15 replicas and any textures, patterns, or features on the master model can also be reproduced.

vacuum casting process

Vacuum casting begins with the creation of a master pattern. The model for the master pattern is made using stereolithography 3D printing technology or CNC machining. This master model is then suspended into a box, or mold casting frame to produce the silicone mold. The prepared silicone rubber mixture is then poured into the mold casting frame. Once cured and dry, the mold is removed from the casting frame and cut along the parting line, which splits it into two parts. Then, the master model is removed, and the mold is ready to begin producing replicas. The mold is then moved to the vacuum casting machine and the resin of your choice is poured into the mold under vacuum. Once casted, the mold goes into a heating chamber for curing. The cured casting is then removed from the mold and it is ready to produce another replica. The molds can be single cavity or multi-cavity and depends on the combination of mold and part size.

B. Materials

1. AT-1/AT-3
This casting material is ABS-like and is best suited for large thick-sized prototypes.
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2. AT-2
This casting material is also ABS-like and has the highest heat deflection among the three thermoset (AT series) polymers.
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3. AT-1/AT-3 (Temperature Resistant)
This casting material is ABS-like and is best suited for small to mid-sized prototypes.
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4. CU-1
This casting material is like acrylic and is used to build small or large prototypes.
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5. PP-1
This casting material is a tough, impact resistant polyuria formulated for vacuum casting and short mold cycle times.
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6. SR-1
This casting material is a clear silicone rubber designed for its hardness, clarity and tear resistance.
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7. UR-1
This casting material is a urethane rubber which is ideal for parts such as hoses, bumpers or strain relief components.
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8. US-2
This casting material is a high impact urethane which is used for producing prototypes with very high izod impact strength with the added benefit of excellent fire retardant characteristics.
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C. Tolerances

Final prototype parts manufactured using vacuum casting technology are ±0.3% from master model dimensions.

D. Applications

Prototypes made using vacuum casting technology are ideal for commercial product testing, functional assemblies, public surveys, field testing models, and visual or aesthetic evaluations. Few examples include electronic housings, keyboards, handheld devices, outside monitor panels, inhalers, surgical bins, flat screen TV casings, power tools and machines, cameras, and under bonnet enclosures and side panels in automotive vehicles.

E. Finishes
Some of the urethanes available may be dyed or have pigment added to them before casting. They can also be spray painted, textured or vacuum metalized to match the desired aesthetic quality.

Created by RedOrum