Injection molding machines in a large factory

Primary Differences Between Overmolding & Insert Molding

Plastic injection molding has made the mass production of plastic products faster and more economical for all types of industries, ranging from automotive to consumer goods. As a versatile manufacturing process, there are many types of plastic injection molding methods, two of which include overmolding and insert molding. 

Both overmolding and insert molding are used to mass produce a wide range of plastic parts, and they can also help manufacturers achieve lower costs per part. However, there are some differences between the two, and certain methods may be better for different industry applications. 

In this article, we’ll discuss how each method works, their benefits, and how to choose between the two. 

What Is Overmolding?

Overmolding is a multi-step method. After a base component has been molded, a second layer (or component) is molded on top to create the final product.

There are many reasons why overmolding is used in manufacturing. For example, a manufacturer may need to create a hard plastic implement that also has a soft grip or handle; this type of design means that the product will require two materials—one that is very rigid and another that is softer and more flexible. With overmolding, it’s possible to create products like this.


  • Flexibility: In overmolding, manufacturers can use more than one type of material to produce a wider range of products, including components that are hard
  • Lower Production Costs: Overmolding allows manufacturers to join multiple substrates together in just one single process.
  • Enhanced Product Performance: Many overmolded products have shock dampening properties, as well as better chemical and UV resistance.

What Is Insert Molding?

Like overmolding, insert molding is a plastic injection molding process used for unique applications. Specifically, insert molding is used to create products that consist of both a plastic component and a metal part. This may be a fastener or a pin that will extrude from the plastic body, or an inner metal stiffener rod that is interior to the plastic component.

Once the inserted metal component is precisely positioned inside the final mold, the mold will close, and plastic resin is injected over the insert. The end result is a single part composed of both metal and plastic. With insert molding, manufacturers can eliminate extra parts like fasteners by including them within the final plastic product.


  • Great for Heavy-Duty Applications: Plastic products can be stiffened with metal, which increases their durability for use in heavy-duty applications. 
  • Fewer Defects: Because there is no assembly process after insert molding, the likelihood of assembly errors is totally eliminated.
  • Cost-Effective: In general, plastic resins are more affordable than all-metal products. 
  • Design Versatility: A wide range of plastic and metal materials can be used during the insert molding process.

Should You Choose Overmolding or Insert Molding?

There are distinct advantages to choosing insert molding for prototyping or production. If the final product has metal, wires, or computerized parts, or if multiple assembly steps will be necessary, then insert molding is the more economical choice. Additionally, if manufacturers want to save money by utilizing plastic materials, but don’t quite trust the strength of plastic over metal, they can instead create metal-embedded plastic products via insert molding.

Overmolding is preferred for multi-layered components, like hard thermoplastics overlaid with soft elastomers. Overmolding is the most economical choice for manufacturers that produce both the substrate and the additional layering materials in-house. 

Choose Silver Basis Engineering for Your Overmolding or Insert Molding Project

Do you still have questions about overmolding and insert molding? Talk to our team at Silver Basis Engineering. We’ve been providing a wide range of plastic injection molding services to manufacturers around the world for over two decades. If you’re not sure whether overmolding or insert molding is the most economical option for you, we’re happy to help. Contact us today to request a consultation or to get started with a quote.