Overmolding, also known as two-shot molding or multi-material molding, is an injection molding process used to combine two or more materials to create a single integrated part. In overmolding, a base substrate (typically made of a rigid material) is molded first, and then a second material (often a softer or more flexible material) is molded over it to form additional features, inserts, or surface coatings.

Here's how the overmolding process typically works:

1. Mold design: The first step in overmolding is designing the mold to accommodate multiple materials or components. The mold consists of multiple cavities, each corresponding to a specific area or feature of the final part. The cavities are designed to allow for precise placement and integration of the different materials or components.

2. First shot: In the first shot of the injection molding process, the base substrate is injected into the mold cavity to form the primary structure of the part. This substrate may be made of a rigid thermoplastic resin such as ABS, PC, or PP, depending on the requirements of the part.

3. Mold rotation or movement (optional): In some cases, the mold may be rotated or moved to position the second cavity for the second shot. This allows for precise alignment of the different materials or components and ensures that they are integrated seamlessly.

4. Second shot: In the second shot of the injection molding process, the second material is injected into the mold cavity to form additional features, inserts, or surface coatings on top of the base substrate. This second material may be a softer thermoplastic elastomer (TPE), thermoplastic polyurethane (TPU), silicone, or another compatible material.

5. Cooling and ejection: Once both shots have been injected, the mold is cooled to solidify the materials, and the integrated part is ejected from the mold cavity. The part may then undergo additional finishing processes, such as trimming, deburring, or assembly, as needed.

Overmolding offers several advantages over traditional molding processes, including:

- Enhanced part functionality: Overmolding allows for the integration of multiple materials with complementary properties into a single part, enhancing its functionality, performance, and aesthetics. For example, a rigid substrate can be overmolded with a soft grip or seal to improve ergonomics or sealing properties.

- Cost-effective assembly: By combining multiple components or features into a single part, overmolding can eliminate the need for secondary assembly operations, reducing labor costs and assembly time.

- Design flexibility: Overmolding enables designers to create parts with complex geometries, multiple colors, textures, and surface finishes, giving them greater flexibility in part design and aesthetics.

Overall, overmolding is a versatile and efficient process that is used to produce high-quality, multi-material parts for a wide range of applications, including automotive, consumer goods, electronics, medical devices, and more.