Overmolding vs Insert Molding

Last Updated on October 13, 2023 by assistant

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As two variants of injection molding, overmolding and insert molding are different in many aspects. Overmolding combines multiple plastic materials into a complete part or product, while insert molding is where a metal insert and injection-molded plastic form a component. This article aims to take you a step closer to understanding the principles, advantages and disadvantages of overmolding and insert molding, as well as a wide range of applications.

What Is Overmolding?

The principle of Overmolding:

This technique is also known as multi-material molding. The first component, also called the base plate, is molded in an injection mold, while the second component is additively molded on top of the base plate. There are many common overmolded columns around us, such as the plastic parts of different colors on the toothbrush. The substrate is generally made of hard plastic, and the top layer is softer plastic.

Overmolding and Insert Molding

Materials Commonly Used in Overmolding:

There is an array of plastics suitable for overmolding.

HDPE(high density polyethylene )


ABS(acrylonitrile butadiene styrene)




PA(nylon polyamide)


PEEK resin                                                               

PEI resin

Advantages of Overmolded Products:

Overmolding Parts2Plastic Overmolding4

If you choose overmolding for your project, there are a few advantages of it.

  1. Increase the aesthetics of the product. The combination of multiple plastics gives more design possibilities. We can use plastics of different colors and properties to combine into a more designed product to attract more customers.
  2. Enhance grip strength. Overmolding generally uses a harder plastic as the substrate, and the top layer of plastic is a softer material such as TPE. Therefore, this design can effectively enhance the grip of the product.
  3. Reduce production cost. Overmolding allows dissimilar materials to fuse in a mold and form a seamless product, which eliminates the need for assembly and reduces the number of man-hours involved. Thus, the required production costs are greatly reduced.
  4. The product is more durable. The seamless combination of different materials adds to the firmness of the entire product.

Disadvantages of Overmolding:

Before choosing overmolding as a processing method, you also need to fully consider its shortcomings to reduce unnecessary losses of the project.

  1. Degumming and layering. Different materials may in some cases present the risk of debonding and delamination. For example, the processing temperature is not enough.
  2. Multi-step. Because it involves two processing, so in the early design stage,

What Is Insert Molding?
Insert Molding
The principle of insert molding:

Insert molding refers to placing a metal-like insert into a mold in advance, and the molten thermoplastic material cools and solidifies around the insert to form a complete assembly.

Advantages of Insert Molding:
1. Reduce the assembly cost. Like overmolding, insert molding can use different kinds of metal inserts and thermoplastic materials to form a complete assembly, and does not require changing molds to form a component, reducing the cost of assembly.
2. Light weight. A layer of plastic on the outside of the molded component can effectively protect the metal inside.
3. Improve the strength of the product.

Insert Molding

Disadvantages of Insert Molding:
1. Need a variety of process support. Metal inserts may require other machining methods, such as die casting.
2. The design is difficult. This requires engineers to have a good understanding of both metalworking and insert molding.

Applications for Overmolding and Insert Molding:
Wide range of applications for overmolding insert molding:

1. Household items. The most common applications of overmolding in household items include toothbrushes, kitchen cookware, chargers and more. These applications can effectively increase the grip of furniture products, while also reducing wear and tear.

2. Automotive. In the field of automobile transportation, the application of both is also very extensive. For example, car doors, car bumpers, car decorations, dashboards, motors, handles, etc.3. Electronic products.

4. Medical devices.

5. Fitness equipment.

6. Agricultural equipment.

If you understand the difference between overmolding and insert molding before the project starts, you will know which processing method is more suitable for your project needs. The above is just a brief introduction to the two, I hope to help you. If you need our help, we will be happy to assist you too.