Overmolding and Insert Molding

Overmolding and Insert Molding

At MJM Industries, we produce molded components that deliver durability, consistency, and reliability. Our in-house engineering team will work closely with you to design and build insert molded and overmolded parts for cable assemblies, connectors, and other critical applications. With U.S.-based production and responsive support, we help you move from concept to production with clarity and confidence.

Insert Molding vs Overmolding

Both insert molding and overmolding create durable multi-material parts, but each process serves a different purpose.

Insert Molding

Insert molding uses a single shot of molten plastic that flows around a pre-placed insert made from materials such as steel, copper, or brass. Common inserts include pins, blades, threaded inserts, sleeves, bushings, and contact elements within a connector or housing. As the material cools, the insert and plastic form a strong, unified part that maintains consistent quality and eliminates many secondary assembly steps.

Overmolding

Overmolding is a two-stage process. A rigid substrate is molded first, then a second material is applied over or around it to add protection, flexibility or visual features. This process supports parts that require strain relief, shock absorption, ingress protection, improved grip or added color and branding.

Comparison Table

	Insert Molding	Overmolding
Process	Single shot of plastic that flows around insert	Two-shot process with a substrate and outer layer
Speed	Faster	Longer due to two-shot process
Cost	More cost-effective for prototypes and small runs	Higher cost due to two tools and two-step cycle
When to Use	Encapsulating inserts, creating rigid structures, and eliminating secondary assembly	Adding soft outer layers, strain relief, shock absorption, color, or grip features