The main difference between injection molding and overmolding lies in the number of materials and the process involved.

Injection Molding:

1. Single Material: Injection molding involves the injection of a single material into a mold cavity to form a solid, complete part.

2. Base Component: The mold is typically filled with a molten thermoplastic material, which solidifies to create the desired part shape.

3. Single Step: The entire part is formed in a single molding process, without the need for additional steps or materials.

4. Design Complexity: Injection molding allows for the creation of complex part designs with various features and geometries.

5. Material Properties: The material used in injection molding can be selected based on the desired characteristics, such as rigidity, strength, or transparency.

Overmolding:

1. Multiple Materials: Overmolding involves the injection of two or more different materials to create a single part with multiple layers or regions.

2. Substrate/Base Component: The process starts with a pre-formed base component or substrate, which serves as the foundation for the overmolding.

3. Multi-Step Process: Overmolding requires multiple steps, including the initial molding of the base component and the subsequent injection of the additional material(s) over it.

4. Bonding: The two materials used in overmolding bond together during the molding process, creating a cohesive final part.

5. Enhanced Functionality: Overmolding allows for the integration of different materials with distinct properties, providing enhanced functionality, improved aesthetics, or added features.

Overall, while injection molding involves a single material and a one-step process, overmolding involves multiple materials and a multi-step process to create a part with enhanced functionality, improved durability, and unique design possibilities.