Insert Molding vs Overmolding – What’s the Difference?

In modern manufacturing, the selection of the processing technique is crucial for simpler and functional products. At our company, we work closely with OEMs and industrial clients to ensure every project gets the most efficient and cost-effective solution.

Insert molding and overmolding are often compared because both can make parts stronger and more durable—but they’re used for different reasons. To help manufacturers understand when to choose one over the other, we put together this practical insert molding guide. It breaks down real-world uses, the benefits of each method, and the key difference that sets insert molding and overmolding apart.

What Is Insert Molding?

Insert molding is essentially the molding of plastic around either a metal or previously made part. The insert can be anything, including aluminum and brass, stainless steel, or even another plastic piece. The whole point is to end up with one solid part where the insert is set right in.

From what we’ve seen, insert molding is especially useful when a part needs threaded inserts, reinforcement plates, electrical connectors, or tight-fitting metal features. It reduces the need for extra assembly steps and results in a strong and reliable part. The plastic is bonded directly with the insert, thereby providing a strong finished piece capable of performing well under even the toughest conditions.

What Is Overmolding?

Overmolding involves molding a second material over a first molded part to improve grip, comfort, insulation, or functionality. At our company, we use this technique for automotive components, consumer goods, electrical housings, and medical device handles. 

The overmolding process allows us to combine a rigid base material with a soft, rubber-like outer layer that improves user experience. Many manufacturers prefer overmolding when they need shock absorption, color coding, protective barriers, or ergonomic enhancements.

Since the overmolding process blends multiple materials into one seamless part, it also minimizes assembly needs and improves long-term durability. For manufacturers focused on feel, safety, and user-friendly designs, overmolding is one of the most versatile solutions available.