Urethane casting is a process of soft tooling with a mold to simulate production injected molded parts.
Compared to hard tooling, the creation of parts for urethane casting parts is quick and cost efficient. Urethane casting is well suited for smaller volume runs, serving as a resource for development, testing a product design, and conducting market research for consumer response. A main benefit of the process is the variety of properties, qualities, and color variations created with urethane. Within the same mold, it is possible to use different types of urethane – hard or soft, clear or tinted – providing variety in use. The range of urethane properties allows for flexibility in testing throughout the development process and can help simulate materials such as glass or lenses.
To begin, we create a master pattern part from a CAD model using a variety of processes including CNC machining, CNC turning, 3D printing or hand sculpting. The master is used to create a mold, typically made of silicone. The creation of the mold for soft parts, like foams, uses a harder material such as tooling board.
For a silicone mold, the master goes into a mold box, a part line is created for alignment, and the mold is filled with catalyzed liquid silicone. This process repeats for the second side of a simple A and B side mold. After the mold cures, it is split, the master is removed, and the result is a void the size and shape of the desired part. The mold has a gate or pathway cut into it in order to allow urethane to fill the space and air to escape. To fill the mold, the urethane is chosen, prepped, and degassed then injected into the mold. Once set, the part is removed from the silicone, trimmed, finished, and ready for assembly.