WHAT IS AN OVERMOLD?
In overmolding, a single part is created using a combination of two or more different materials. The subsequent materials partially or fully cover the first material during the manufacturing process.
The base material (often called a "substrate") provides structural support. It could be almost anything: a machined metal part, a molded plastic part, or an existing product. It's the basis for what will eventually become a single continuous part, made from bonded materials of different types.
The overmold materials, on the other hand, usually provides a soft texture. They're often plastic-based pellets. These pellets are then mixed with colorants, foaming agents and other types of fillers. They're then melted down, and the resulting liquid is injected into the mold tooling.
Typical overmold combinations include:
- Plastic Over Plastic – This combination is often used when molding two plastics that differ in color or resin. A rigid plastic substrate is molded first, followed by another rigid plastic overmold on or around the substrate.
- Rubber Over Plastic – This process is often used to create a rigid plastic part with a soft grip area. The rigid plastic substrate is molded first, followed by a soft rubber or polymer overmold.
- Plastic Over Metal – To capture a metal component within a plastic part, the metal substrate is first machined, cast or formed. It's then inserted into an injection-molding tool, where the plastic is molded onto or around the metal.
- Rubber Over Metal – When creating a rigid metal part with a soft grip surface, the metal substrate is first machined, cast or formed. Rubber or polymer is then molded onto or around the metal.
Overmolding allows the use of two different materials without using additional adhesives or fasteners. The materials and overmold process ensure a strong bond between the components.
The most common reasons for using the overmold process are:
- To break up color (for aesthetics)
- To provide a soft grip surface around a rigid part (e.g., hand tools)
- To add flexible areas to a rigid part
- To capture one part inside of another part without the use of fasteners or adhesives
- To reduce production time. Overmolding eliminates the need to assemble two separately manufactured components.
Trust the Overmold Experts
At Prodigy Mold & Tool, we're experts in overmolding with a variety of materials. Our understanding of critical dimensions and details of each part ensures a successful project.
Contact us today to discuss your overmold project's unique requirements.