Plastic injection molding is not a one-size-fits-all process. Different techniques can be used to achieve different types of end results.
Close up of a standard molded plastic part. Standard Injection Molding: This basic technique uses a single color and material to produce the plastic part. It is commonly used to manufacture everything from beverage containers, caps, electronics, medical devices components, Lighting parts to auto parts and toys, etc…
Overmolding: This is a two-step process used to produce items that require two different types of plastic — for example, a shaped handle with a soft outer material that makes it easier to grip.
First, the substrate plastic part is produced; then each part is individually moved to another mold where another thermoplastic part is molded over the substrate plastic part. The bond between the two materials can be mechanical or chemical.
Insert molding: Insert molding is an application in which a prefabricated part is used as the substrate. This substrate may be made of an alternative material to plastic (often it’s metal).
Knobs and dials that have a plastic exterior over a metal interior are examples of insert molding. The substrate is inserted into the mold, then plastic is injected onto it. Typically this process uses thermoplastic resin as the overmolding material.
A two-shot molding assembly setup, also called double-color injection molding. Two-shot (dual-shot) molding: This is also a two-step injection molding technique, but it is done in one molding press and it allows you to create a plastic part or product using multiple colors and plastic types simultaneously, without having to use a multi-stage assembly process. For instance, you might want to create a plastic power tool housing with a branded-color handle.
First, a substrate is injected by the primary press barrel. Then, mold steel is exchanged and a second injection unit molds the second shot. The bond between the materials can be chemical or mechanical.
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