Overmolding and Insert Injection Molding

Manufacturers can achieve custom prototypes in one of two ways: insert injection molding and overmolding injection molding. These two injection molding processes are similar in ways, but there are a few important differences to note. Schmit Prototypes is proud to offer both services and can help you decide which would be best for your product.

The Insert Injection Molding Process

Insert molding is when a plastic material is injected around a pre-placed insert piece (typically metal). The injected plastic material then molds around the insert piece and they create one strongly bonded, single-molded plastic piece.

The insert injection molding process is a good option for a wide range of applications including medical devices, knobs, military equipment and more. This process has specific benefits that include:

  • No need for secondary assembly operators such as snap fits, glue, screws or fasteners. This reduces the size and weight of parts since the parts are joined with light-weight resin instead.
  • Reduced assembly and labor costs, since pieces are molded as one assembly.
  • Integration of design features such as the inclusion of essential metal parts, not possible by plastic alone.

The Overmolding Injection Molding Process

Overmolding is a standard injection molding that creates one product using two or more different materials together. The first material is known as the substrate, which is then covered by the other materials, or the overmold materials. The substrate can be any object, but it’s usually a rigid, plastic or metal-base component. There are then options for liquid silicone overmolding, polyurethane overmolding, and plastic silicone overmolding. Which material you choose for the overmolding process will determine whether your product has a soft rubbery-feeling outer part, or a harder plastic outside.

Common products made from using the overmolding injection process include toothbrushes, razors, and tools. This process has specific benefits including:

  • Improved grip for tools
  • Waterproof seals
  • Company-branding since more than one color can be used in the injection process
  • Dampening vibrations or absorbing sound