What is OverMolding Injection

Overmolding is a unique custom injection molding process that results in a seamless combination of multiple materials into a single part or product.

The Overmolding process applies to a wide variety of industrial and manufacturing industries. The process involves a technique known as injection molding but it is also possible by urethane casting to make high-end prototypes. This injection molding helps to mold two or more layers of material together.

The process can be helpful in plastic overmolding, as well as rubber overmolding.

Overmolding is helpful in industries where they need to rapidly manufacture prototypes of various industrial machine parts. The process also comes in handy where custom parts are made by overlaying plastic or rubber with other materials such as metals.

The result of the overmolding process is a machine part or component that’s created by joining two or more materials into one. The materials used can either be the same materials or different materials. The combinations of materials are virtually endless.

In order to get a better idea of how the process works, we need to understand the two components of the process. Every overmolding project breaks down into two parts. The first part of the process is the substrate and the second part is the overmold.

The substrate is your base material. It can be any type of a wide variety of materials. Your overmold is the secondary material. It’s the material that you want to “mold over” the substrate.

Overmolding is a versatile process that has numerous benefits:

• Increased Material Flexibility - Overmolding allows designers to leverage the benefits of multiple types of materials to create complex parts with different properties, add visual complexity, or add haptics.

• No Adhesives Required - Overmolding allows different materials to be fused in the mold, thus eliminating the need for glues or other permanent bonding methods. This increases the part’s overall durability and reduces assembly costs.  

• Embedded Seals - Overmolding offers the option of molding soft seals into parts. An example would be an electronics enclosure that needs to be IP rated. Usually, the part will have a groove into which an o-ring can be installed later. However, it is far more cost-efficient and robust to permanently mold the seal as an integral component.