Silicone Overmolding and Insert Molding: From Prototyping to Production

Silicone Overmolding and insert molding tend to get confused for one another. Understandably, since both processes are types of injection molding that are used to create structurally similar parts. But if you take a deeper look, you’ll find that insert molding and overmolding are actually quite distinct, and each offers unique advantages.

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Overmolding is a multi-step injection molding process

What Is Overmolding

Overmolding is a multi-step injection molding process where two or more components are molded over top of one another. Overmolding is sometimes referred to as two-shot molding because it is a two-step process.

First, a base component (otherwise known as a substrate) is molded and allowed to cure. Overmolded substrates are often made of plastic. Then, a second layer is molded directly on top of the first to create a single solid piece. Overmolding is commonly used to manufacture plastic parts that feature a rubber handle. The two-shot process of overmolding a toothbrush, for example, consists of forming a base layer for the plastic handle and a top layer of rubber (to make the toothbrush less slippery to hold).

The Benefits of Silicone Overmolding

Overmolding offers many benefits. You can manufacture products with multiple materials and/or colors relatively simply. Overmolding also uses fewer man-hours (and thus, costs less) compared to other manufacturing methods where a part would need to be transferred to a completely different mold or machine. This technology reduces the need for product assembly because parts are manufactured right on top of one another—resulting in a stronger, more durable overall design.

Applications of Silicone Overmolding

Manufacturers use overmolding and insert molding to produce products for a wide range of industries. Here are some examples of products that are commonly made through one or a combination of these processes: