Overmolding is one of the many injection molding services offered by Proto-Cast, LLC. Overmolding is the process whereby two or more materials are combined to create a single part. The first material (referred to as the substrate) is partially or fully covered by subsequent materials (aka “overmold” materials) during the manufacturing process. Overmolding is a very similar process to insert molding, where plastic pellets are melted and extruded into a mold which shapes the final part.
Substrate: the Overmold’s Origin Story
The substrate can be anything: a molded plastic part, a machined metal part, or an existing product such as screws or electrical connectors. This first piece will be chemically bonded with other materials to form one continuous part.
Overmolding Material: Bringing It All Together
Plastic overmold materials begin in pellet form. The pellets are then mixed with various additives, depending on the needs of the final product. These include colorants, foaming agents, and other fillers. The pellets are then heated into a liquid and injected into the mold tooling.
Depending on your substrate material, there may be limits on what you can use for your overmolding material. If your substrate is metal, you can use basically any plastic. If the substrate itself is plastic – or a rubber or thermoplastic elastomer (TPE) – there may be compatibility issues. Our experts can advise you on what plastic is best for your overmolding project.
Examples of typical overmolding applications include:
- Plastic over plastic – First, a rigid plastic substrate is molded, then another rigid plastic is molded onto or around the substrate. The plastics may differ in color and/or resin to produce a specific look.
- Plastic over metal – Begin with a metal substrate that has been machined, cast or formed. The substrate is then placed into an injection molding tool and plastic is molded onto or around the metal. Common examples of this are scissors, razors, and screwdrivers.
Overmolding: What is it Good For?
Overmolding allows you to offer products in a greater variety of styles, colors, and textures. Ultimately, this is about making the customer happy. You can create soft or molded grips (in toothbrushes, for example) to make hand-held items more comfortable, or offer color combinations that are pleasing to the eye. Other benefits include:
- Adding flexible areas to a rigid part.
- Capturing one part inside another without the use of fasteners or adhesives.
- Eliminating the need for assembly. (For example, why manufacture a metal tool and its plastic handle separately, joining them later via assembly, when you can overmold the handle directly onto the tool?)
Choose Proto-Cast, LLC to Fulfill All Your Overmolding Needs
If you have an overmolding project on the horizon, choose a company backed by over 50 years of experience. Proto-Cast, LLC has the equipment and expertise to complete your project on time, on budget, and in keeping with the highest quality standards. For more information on our overmolding process, call us at 610-326-1723.