01.25.23 | 4 min read

What is Overmolding? How Does it Benefit Me?

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 subset of overmolding. Like transfer molding, insert molding creates a part by molding around a prefabricated substrate — often made of metal. The insert is loaded into the mold, and the plastic component is molded around it. In our examples above, insert molding could be used to mold the handle around the metal component of the screwdriver or utensil. This is an ideal solution for a plastic component that requires a threaded metal insert to accept a screw during assembly. Insert molding can be used for electrical components, pins, or any component that can withstand the temperatures and pressures of injection molding.

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. 

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.

Article | Plastics

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