What Is Overmolding? Process and Benefits

Overmolding and insert molding provide opportunities for unique product designs

Advances in injection molding have allowed manufacturers to design more complex parts produced with greater accuracy and precision. Two injection molding processes that allow for more complexity are overmolding and insert molding. If you aren’t familiar with these types of molding, think of some everyday products like screwdrivers, toothbrushes, and kitchen utensils with handles that have rubber molded over plastic to create a comfortable grip.

Overmolding and insert molding are used in almost every industry, including automotive, consumer products, electronics, agriculture, and medicine. Below we will answer the question ‘what is overmolding and insert molding?’ and offer the benefits of using these processes.

Overmolding and Insert Molding Explained

Simply stated, overmolding is the process of molding one material on top of another. In our examples above, the screwdriver, toothbrush, and utensils may have soft touch handles molded from two different materials. The overmolding may happen in the same mold, and components are molded on top of each other or can be done as transfer molding, where one component is molded and then transferred to another mold to complete the part. 

Overmolding is ideal for multi-color or multi-material plastic components. The ability to mold different colors provides unique branding opportunities. Additionally, when you work with a single resin, you are limited to the properties of that resin. Using multiple materials can offer additional properties such as shock absorption, impact resistance, and water-tight seals. 

Insert molding is a related process in which plastic is molded around a prefabricated substrate, most commonly a metal component, to create a finished part that combines the properties of both materials.

One thing to keep in mind is material compatibility. The materials should bond together. If the materials don’t bond completely, the design and mold become more complicated as undercuts and indents are needed to connect the overmold and substrate.

Problem Solved, Courtesy of LMC: Read how we helped a customer by designing an overmolded poultry feeding chain system when others said it wasn’t possible. 

What Are Overmolding Benefits? 

Overmolding (and insert molding) offer many benefits that improve the product and increase manufacturing efficiency. 

Product Benefits

• Components that are molded have increased reliability because of the additional protection offered. For example, parts that are vulnerable to vibration can be cushioned. 
• The component’s strength and stability can be increased.
• It can be used to improve safety for the user (e.g., ergonomic handle) or the part (e.g., using overmolding to act as an o-ring to provide water resistance).
• Eliminating the need for metal fasteners and connectors and eliminating the need for an entirely metal product by overmolding plastic decreases product size and weight.
• Overmolding offers greater design flexibility because it can handle complex geometries and multiple types of materials. 
• Parts have aesthetic flexibility by using textures and assorted colors and materials. 

Increased Manufacturing Efficiency

• Assembly requirements are reduced by combining parts in a single process, significantly reducing costs.
• The need for joining parts after molding is eliminated, allowing for reduced lead times and labor requirements. 
• Waste and cost from assembly defects are reduced or eliminated. 
• Automated insert placement provides excellent precision and accuracy.

Ready to Optimize Your Part Quality? Request a quote today and discover how LMC Industries get your parts program running like clockwork. 

Is Overmolding Right for My Project?

Overmolding is an appropriate choice for many applications, but depending on your exact project, it may not always be the best fit. Several factors should be weighed before committing to 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 overmolding.
• Materials selection — the key consideration is compatibility between the two materials your part requires. Plastic over metal is almost always compatible, while some combinations of plastic over plastic are not.
• Injection molding tooling — tooling for overmolding can take months to prepare and be costly to create. Work with your engineers to determine if it’s the right fit before committing.

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

Working With LMC Provides More Than Overmolding

Many plastic injection molders offer overmolding, but we believe receiving a high-quality product should be the price of entry for a contract manufacturer. We strive to form partnerships with our customers because their success means our success. 

As a committed partner, we strive to provide our customers with shorter lead times and competitive pricing. The record inflation and disrupted supply chain have strained everyone. We have positioned ourselves as problem solvers ready to ease those burdens. 

By offering extensive capabilities for plastic and metal parts, we strive to maximize the ROI of your program by ensuring the success of your programs from start to finish.

Contact us for a quote on your next overmolding project.