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Insert Molding

Pilot runs, low volume production, bridge tooling

Insert molding is a great way to combine metal and plastics into one single part. It allows plastic to bond to inserts that go inside a mold cavity, helping you to create better parts.

About Insert Molding

  • Metal inserts will guarantee the function of threads and mitigate wear and tear over the part’s life.
  • Because it’s a “one-shot” process, insert molding can produce stronger parts than overmolding and other processes.
  • Insert molding is great for creating prototypes and production parts.

Advantages of Insert Molding

Eliminate assembly
  • You can make parts all at once instead of having to do assembly after the fact.
Reduce costs
  • Insert molding costs more than standard injection molding, but the costs are usually offset by the fact that you no longer need to do post-assembly.
Lower the size and weight of the part
  • A plastic part with a metal insert is generally lighter than an all-metal part.
Improve reliability
  • Metal inserts will guarantee the function of threads and mitigate wear and tear over the part’s life.
Improve part strength
  • Because it’s a “one-shot” process, it can produce stronger parts than overmolding and other processes.


Insert molding is a specialized type of injection molding that combines different materials into a single finished part. While 2 shot molding allows multiple types of plastics to be combined, insert molding allows the inclusion of metal components in a plastic part. For example, you could have a plastic cabinet-door knob with a metal fastening screw embedded during the molding process instead of having to assemble it later.

A wide range of metal components can be used in the insert molding process, including screws, limiters, threaded fasteners, magnets, filtering screens, tubes, clips, mounting brackets, and more. These components can be made from stainless steel, brass, copper, aluminum, nickel, or bronze. Your injection molding company will work with you to select the best combination of metal and plastic based on the part’s requirements.

Good design practices include carefully crafting molds to ensure proper retention of the metal in the plastic part. Some inserts may need to be heated prior to being molded to reduce the thermal difference between the plastic and the metal, which could cause quality issues.

Overview: What is Insert Molding?

What is Insert Molding?

Insert molding is a process in which plastic is injected into a mold that contains a pre-placed insert. The result of insert molding is a single molded plastic piece with an insert surrounded by the plastic. Inserts can be made of metals or different types of plastic. Insert molding is used in many industries. Applications of insert molding include insert-molded couplings, threaded fasteners, filters, and electrical components.

How is Insert Molding Used?

Insert molding has practical uses in a wide variety of industries, from industrial and consumer to aerospace and medical. This process can be used to create:

  • Instruments
  • Knobs
  • Housings
  • Devices
  • Electrical components
  • And more

The insert molding process is similar to traditional injection molding: solid pellets of raw material are melted and extruded into a mold. The plastic is solidified, the press opens, and the molded parts are ejected. For insert molding, the insert is placed inside the mold – either by machine or by hand – before the material is injected into the mold. This allows the material to flow into undercut features in the insert, anchoring it more securely than if it were assembled to a previously molded component.
There are a variety of inserts that can be molded into plastic components, including:

  • Bushings
  • Clips
  • Contacts
  • Magnets
  • Pins
  • Rivets
  • Screws
  • Spring contacts
  • Studs
  • Surface mount pads
  • Threaded fasteners
  • Tubes

Industries with Applications for Insert Molding:

Many industries can benefit from insert molding, such as:

  • Automotive and Trucking: Metal to plastic conversion parts reduce weight and improve fuel economy
  • Medical: Plastic parts with metal components are used in a wide range of medical and surgical devices
  • Consumer Products: Insert molding has applications in an array of industries from electronics to HVAC systems
  • Aerospace: Insert molding is used for parts for aircraft interiors, controls, communications, and guidance/navigation.

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