What is Overmolding?

Overmolding is used for a variety of products in a wide range of industries. Essentially, it’s the process of molding a single part from two different substances—plastic over metal, rubber over plastic, etc.—so that one substance is layered of another. Think, for example, of the handle of a shaving razor, with plastic grips molded to the metal handle, or a toothbrush, where rubber grips are molded to the plastic handle.

For two-component overmolding such as plastic overmolding metal parts, the metal component undergoes a cleaning process and then a bonding adhesive is applied to it. Then, using equipment configured specifically for the part’s production, the prepared metal piece is inserted into the molding press and plastic is injected into the mold so it forms around the metal component, resulting in a complete part with an exceptionally strong bond between the metal and plastic components.

Why Overmolding?

Overmolding improves the functionality, look, and bond strength of a part. Even more, optimizing designs through the overmolding process eliminates the steps for assembling the metal and plastic components to form the part. Increasing the completed part’s manufacturability this way reduces both the time and costs to create it. And because of the close tolerances overmolding produces, overmolded parts are more consistent and more accurate, resulting in further savings by reducing the number of parts that are rejected and returned.

Configured for Overmolding Savings and Success

A great example of LMC’s success with this process is the plastic overmolding used on the sun visor arms in vehicles. A metal piece overmolded with plastic for safety, this assembly would be very dangerous to vehicle occupants without the overmolding. Using other processes to apply the plastic to the metal sun visor arms would require a variety of steps and additional processes to produce the part—at a great deal of expense. But LMC was able to configure existing machinery to do the job using only one overmolded step to produce the part. This means that our clients get the completed order more quickly and at a substantially reduced cost, with metal stamping and overmolding capabilities conveniently provided by a single vendor.

Is Overmolding Right for My Project?

Overmolding is an appropriate choice for varying applications. Depending on your exact project, it may not always be the best choice. Several factors have to be weighed when considering whether or not a part should be produced using the Overmolding process:

• Product design – any product requiring a soft touch, comfortable grip, stylish look, protection in the field, or easily identifiable features is a good candidate for production using overmolding.
• Materials selection – the key consideration is compatibility between the two materials your desired part requires. Plastic over metal is almost always compatible, while some combinations of plastic over plastic are not.
• Injection molding tooling – tooling for overmolding production can take months to prepare and cost hundreds of thousands of dollars to create, so you have to work with your designers and engineers to determine if it’s the right fit and create the part and savings you require.
• Production volume – with the high tooling costs, overmolding requires high-volume production to be cost effective

When deciding on overmolding production, always consult with your supplier’s engineers to confirm your project will benefit from both the features of overmolding production and the savings the overmolding process can provide.

LMC’s Overmolding Advantage

Overmolding is an exceptional way to use two different component materials to create parts with high manufacturability at a reduced cost, thanks to eliminated production steps and reduced part rejections.

LMC’s engineers are skilled and experienced at maximizing manufacturability for overmolded parts. With the advantage of metal stamping and overmolding capabilities under one roof here at LMC, we can readily identify solutions for even your most challenging projects and configure existing machinery to do the job with increased efficiency at a lower cost.

To learn more about how LMC can help you with your overmolding part project, contact us online or call us at 636.282.5214.