Urethane Casting and Vacuum Casting

What is Urethane casting?

Urethane casting is a manufacturing process similar to injection molding where urethane resin is cast in a cavity between two silicone mold halves. The process replicates a master model by pouring a silicone mold around it. In a highly skilled procedure, the mold is sliced into two halves, the master model is removed, and then a gating and ventilation system is added. Subsequently, the model maker casts a urethane-based resin into the resulting cavity and cures it under a vacuum to prevent air bubble intrusion. Vacuum casting is better known as urethane casting or polyurethane casting in the US.

Vacuum Casting Process

Step 1: Master Building

Masters represent 3D solids derived from your CAD designs. Typically crafted via CNC machining or 3D printing, they are meticulously fabricated under controlled conditions, often at 40°C. Once the masters are meticulously finished and thoroughly inspected, the next phase involves progressing to silicone mold creation.

Step 2: Mold Making

The creation of casting molds commences with liquid silicone. The casting box is partially filled with this liquid silicone, and then subjected to controlled heating until the silicone is fully cured. Following this, the mold undergoes a 16-hour curing process within an oven. Additional batches of heated silicone are poured to complete the mold, ensuring comprehensive coverage. Once fully dried, the mold is carefully cut open to extract the master component.

Step 3: Part Production

Production of parts begins by pouring casting resins into the emptied mold cavity. This process results in the creation of highly precise replicas of the original master. The flexibility extends to the possibility of overmolding with multiple materials. Typically, silicone molds maintain their effectiveness for approximately 20 reproductions of the initial pattern.

This structured approach ensures the replication of intricate designs with fidelity and efficiency, leveraging the precision of CAD designs and the versatility of silicone molding techniques.

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