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What is overmolding and what it means for products and profits

What is overmolding?

Overmolding is a unique injection molding process that seamlessly combines multiple materials into a single part or product. It typically consists of a rigid plastic-based component covered with a thin, flexible, rubber-like outer layer of thermoplastic elastomer (TPE) or other material, using a single shot (insert molding) or two shots (multiple shots) injection molding) technology.
Simply put, overmolding is an injection molding process in which two or more materials are used to combine wires and connectors to form a single part.
Overmolded or overmolded cables are complete assemblies that combine wires and connectors into one seamless part. Place the cable assembly inside the mold. Next, molten plastic material is injected into the mold cavity. Once the plastic material cools and solidifies, it conforms to the shape of the mold and encapsulates the connection point between the connector and the wires.
Overmolding is becoming increasingly popular with manufacturers, and when you consider the significant advantages it offers, you may find that overmolding is an excellent choice for your next project.

Why overmolding?

Manufacturers who want to add a soft-touch appearance to their products to enhance grip or “feel” and provide a sleek look that is attractive to consumers are prime candidates for overmolding. Overmolding can also reduce shock and vibration, dampen sound, provide electrical insulation, and improve chemical/UV resistance – thereby extending product life. While improving product viability and customer satisfaction, overmolding also reduces production costs.

Benefits of using the overmolding process

All the advantages of overmolding boil down to two things: longer life and reliability. Overmolding shields internal components and enhances the quality of protection.

1. Better product performance

The primary reason for using overmolding to design and manufacture a product or part is to improve product performance.
TPE is an ideal material to create a soft, non-slip grip for any number of products where tactile sensitivity is not only comfortable but critical,  medical products such as surgical instruments. 
In addition, the TPE surface can act as an environmental barrier, protecting the product and extending its shelf life by reducing shock, vibration and noise—a key advantage of overmolding.

2.Reduce production costs

Overmolding is rare because it adds value in a number of ways, while also reducing production costs.
how? Overmolding reduces the number of manufacturing steps involved. In the automotive market, for example, it can eliminate the need for injection molding and assembly of components such as gaskets or bumpers, as well as secondary finishing operations (priming, painting or coating).


The design engineering of an overmolding mold is a task in itself. Design must be considered with any overmolding project, as mistakes can have a significant impact on production costs, cycle time, time to market, and the overall quality and performance of the product—especially when designing multi-cavity molds and handling high rolls. Thanks to the growing sophistication and accessibility of prototyping technology, engineering teams can now 3D print tools and test their functionality and manufacturability before cutting them into production steel. The ability to prototype significantly reduces cost, time and material waste.
The right manufacturer will have the ability to offer fully custom overmolded components, as well as high volume, fast turnaround production.

How does the overmolding process work?

Below are three types of overmolding.

insert molding

Insert molding is the best form of overmolding when molding soft elastomers or rigid plastics. It is the best type because it is more economical and less difficult than the other. In insert molding, the hard segment is first separated into the tool, and then the soft material is ejected.
It also involves the use of elastomers as adhesives. This can be in the form of mechanical locks, chemicals, etc. In order for chemical adhesion to occur, you must heat the elastomer to the right temperature. This is required to heat the hard segment surface.

secondary molding

Unlike insert molding, overmolding requires you to use two injection molding machines. You will first inject the hard segment into the elastic mold and then into the injection molding machine.
The heated substrate used is always in a semi-solid or gel state. The design of the mold can be modeled to project the lateral portion of the hard segment onto the substrate. For those who value a stable mechanical bond, the overmolding process is the right choice.


Of the three types of overmolding, co-injection molding is the most expensive and difficult to control. Its process is also different because it requires injection of the substrate and elastomer into the same mold. This also requires that the materials be compatible.
In terms of quality overmolding, co-injection is the best. This is because all materials are in the same molten state.

Overmolding Applications

car vibration reduction

he overmolding process is ideal for making products that are isolated from vibrations. A rubber-like connection between one component and the other eliminates vibrations. This makes the process necessary for the manufacture of motors and pumps

Overmolding process for making comfortable tools

Overmolded material provides comfort thanks to better grip. This makes the process ideal for making products that offer better ergonomics. The molding process can take many shapes and can fit just about anything. That’s why it’s ideal, and overmolding is suitable for making bicycle handlebars or kitchen utensils

Overmolding process of waterproof products

Depending on the type of plastic used, overmolding is an excellent process for making waterproof products. This makes it suitable for the electronic world. This makes plastic overmolding an ideal waterproof alternative to traditional seals such as O-rings. Not only are they waterproof, but they can also be made flexible.

Making sound-absorbing products

Overmolding is an ideal process for making products that need to absorb sound waves. Making an enclosure that absorbs the sound of the motor is the right process, making the device quieter.

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