What is Overmolding: A Guide to  the Process and its Applications

If you’ve been researching manufacturing solutions for your plastic component needs, you may have come across the process of overmolding and found yourself wondering, what is overmolding?

At the most basic level, overmolding is an injection molding process that adds a new plastic feature onto an existing part. Used in a variety of applications across a range of industries including medical devices, consumer goods, electrical components, and automotive parts, the process provides versatility and streamlines overall production by removing the need for complex assemblies.

What is Overmolding: A Look at the Process

When done correctly, overmolding is an ideal process for creating bonds between two materials without the need for adhesives or secondary assembly processes. While the specific details of the process may vary according to the characteristics of the materials being used, equipment, and part design, overmolding can generally be broken down into four typical steps:

Step 1: Part and Mold Design – First, the part needs to be designed for manufacturability, with elements such as geometries, material selection, and functional requirements usually being addressed early on. After that, a mold is created that will be compatible with the substrate (the initial part) and provide a cavity for the material that will be injected over the substrate.

Step 2: Preparing the Substrate – The substrate may need some additional preparation prior to the overmolding process.  Preparation varies based on what the substrate is and the material being molded over it, but may include surface treatment or pre-heating.  This helps to enhance the strength of adhesion between the substrate and the overmolding material.

Step 3: Injection Molding – Next, the substrate needs to be inserted into the mold and secured to prevent any movement during the process. Once done, the overmold material is heated to its melting point and injected into the mold cavity so that it flows around the substrate. 

Step 4: Post-processing – After the component has cooled and is released from the mold, any necessary post-processing steps can be completed. This might include trimming excess material, removing flash or imperfections, and quality control inspection.

Material Selection

With any precision parts manufactured through injection molding, the right material selection is critical. This is especially the case in overmolding, where the materials must not only meet the needs and requirements of the application but be compatible with one another as well.

Strength, durability, and adhesion are characteristics that need to be taken into account, along with the inclusion of additives in the substrate, which can impact adhesion quality.

What is Overmolding: Common Applications

Overmolding is an essential manufacturing process for a wide range of industries due to its versatility and efficiency. Some of the more common industries and applications include:

    • Automotive – components for headrests, doors, seats, structural reinforcements, underhood electronics, and suspension and braking system components.
    • Consumer goods – grips and handles for kitchen utensils and toothbrushes, pot covers, electronics components, and aesthetic details.
    • Electronics – cable covers, strain reliefs, cable connectors and housings
    • Medical devices – surgical instruments, handheld devices, diagnostic equipment, implants, and AEDs.
    • Aerospace – seating, gaskets and seals, user interface switches, and electronic components.

    Advantages and Limitations

    Like any manufacturing process for critical components, overmolding comes with some limitations and advantages.

    One limitation of overmolding has already been mentioned: the need for material compatibility and adhesion. This may be straightforward or complex based on the materials being used, and sometimes the bond may need to be “forced” by either physical or chemical means to ensure that the part does not fail when in use.

    The higher initial cost of overmolding can also be prohibitive. With the complexity of the part and mold design, the material selection, and any post-processing steps that might be required, overmolding can be a relatively expensive process.

    However, the long-term advantages of overmolding often outweigh these limitations. For instance, overmolding often produces parts with enhanced functionality and performance due to the nature of the bonded components. Depending on the application, overmolded parts can lend a level of durability and protection that is unrivaled by any other manufacturing method.

    Overmolding may also save on overall production costs and speed up production timelines by removing the need for assembly processes and labor later on.

    Partner with an Overmolding Expert at Noble Plastics

    At Noble Plastics we offer tailored overmolding manufacturing services to meet the needs of your specific application. From part and mold design to post-processing and quality control, we are a one-stop shop for all your overmolding needs.

    With nearly 25 years of experience and a commitment to utilizing the latest technological advancements in manufacturing and automation, Noble is at the forefront of producing high-quality and high-performance plastic parts with maximum efficiency.

    Reach out to our team today to get started on your next overmolding project.


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