Plastic Overmolding: What is Involved?

Gone are the days when fast and efficient technology was just a dream. We are living in the technologically advanced times where everything is possible. This rise in technology has provided efficient results to several industries to come up with products and new inventions. In this regard, plastic overmolding needs a special mention. This process has made a lot of things possible in the industrial environment and has added several possibilities.


What exactly is overmolding?

Overmolding is a process wherein two or more different materials are used in a combination to create a single part. Usually, the first material is referred to as substrate and that is partially or fully covered in the overmold material depending upon the requirement.

  • What is substrate?

Substrate could be defined as a molded plastic part, a machined metal part, or an existing product such as electrical connectors, screws or threaded inserts. This is the first piece that goes on to become single continuous part composed of chemically bonded and in most cases mechanically interlocked materials of different types.

  • The overmolding material

Typically the overmolding material or plastic is in the pellet form. Then for it to make suitable for plastic overmolding, the pellets are mixed with additives such as foaming agents, colorants, and other fillers. Then these are appropriately heated to melting point and injected as liquid into the mold tool. It is also good to know that there are certain limitations on the type of material suitable to be used for overmolding. However, you can use almost any plastic if it involves overmolding a metal part with plastic. The complication can be in situations where you want to overmold plastic part with other plastic or TPE or rubber because there can be compatibility issues. Typically the material manufacturer prepares a compatibility chart for plastic overmolding.

What is plastic overmolding used for?

The plastic overmolding is used for numerous reasons and it varies according to the applications. Some of the most common materials are handgrips for tools, toothbrushes, personal care products, industrial components, spare parts, and so on.

How is the process of plastic overmolding done?

Usually the injection molding part or substrate is placed into the injection molding tool and at this time the overmold material is then shot around or onto the substrate. The two materials join together as a single part when the overmold material solidifies or cures. It is a good idea to have the overmold and substrate material to interlock in some or the other mechanical capacity. This way the two material will be bonded chemically and also be held together physically.

Here are some of the reasons why you would want to go for plastic overmolding.

  • Aesthetics plays a crucial role in most areas and this could become one way in which a break up of colors can be added. This is true for domestic use as well as industrial use where standard color codes are put in place.
  • If there is a metal or any other such material, the overmold can be used to provide a soft grip surface around the material. This works out to be perfect for numerous tools that are used on a regular basis. A process that is widely used for the industrial setup as well.
  • It is also used to add more flexible areas to a rigid part. When it comes to industrial components there are several parts that need to have added flexible areas to it. At times, this is not possible to complete in the first stage and so plastic overmolding is used to get the best result.
  • It is also used to altogether eliminate the need for assembly line. So instead of a need to manufacture metal tool and a plastic handgrip separately and then manually joining to two together you can just get the metal overmolded with plastic handgrip and then eliminate the need for assembly altogether.
  • You can use it also to capture one part inside of the other without use of adhesives or fasteners.

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