Sub Assembly

 In manufacturing, a sub-assembly refers to a collection of components or parts that are assembled together to create a smaller unit or module, which is then integrated into the final product. Sub-assemblies are intermediate steps in the manufacturing process that help streamline production, improve efficiency, and simplify quality control.


What is the difference between insert molding and overmolding?


Insert Molding

Insert molding is a manufacturing process where metal components are placed into a mold, and then molten metal is injected around the metal insert to create a finished part. This process results in a single integrated part with the inserts securely embedded within it.




Insert molding offers several advantages in manufacturing: 

  • Strengthened Structure: Inserts can enhance the strength and durability of the part, especially with inserts that are made of metal.
  • Reduced Assembly: By incorporating inserts during the molding process, the need for additional assembly steps is eliminated, reducing production time and labor costs.
  • Complex Geometries: Insert molding allows for the creation of parts with intricate shapes and features that would be difficult to achieve through traditional assembly methods.
  • Design Flexibility: Designers can integrate functional components seamlessly into the part.
  • Enhanced Aesthetics: Inserts can be used to provide a polished and professional appearance to the final product.

Common applications of insert molding include electronic connectors, medical devices, telecommunication satellites, automotive parts, and consumer products.

Injected Metal Assembly (IMA)

Injected metal assembly (IMA), a form of insert molding, is a manufacturing process that uses a molten zinc alloy to join and strengthen two or more components together to create a single, assembled part.
The IMA process starts with the creation of a custom tool that has the cavities for the two or more components. The components are then placed in the tool and the molten zinc is injected. The zinc alloy flows into the cavities and hardens to create a permanent bond between the components.
Like other types of insert molding, the IMA process has several advantages over traditional assembly methods. It is a fast and efficient process that can produce parts quickly and cost-effectively. The parts are also strong and durable, and they have a smooth, finished surface. In addition, the IMA process can be used to join similar or dissimilar materials, which gives designers more flexibility in their designs.


IMA (Insert Metal Assembly) step-by-step process:

IMA (Injection Molding) step-by-step process flow

IMA is used in a variety of industries, including automotive, aerospace, medical, and electronics. Some of the common applications of IMA include:
  • Joining metal fasteners to metal components
  • Joining metal housings to electronic components
  • Joining metal brackets to metal parts
  • Joining metal components to create a single, complex part



Overmolding is a manufacturing process in which a single part is created by combining multiple materials. This process involves molding one material (often a softer or more flexible material) over another material (usually a rigid substrate) to create a finished product.


Sub Assembly Insert Molding Overhead View of Production cell

Overmolding offers several advantages in manufacturing: 

  • Enhanced Functionality: By combining materials with different properties, overmolding can add features, like soft grips, to products.
  • Improved Aesthetics: Overmolding allows for the use of multiple colors and textures, enhancing the visual appeal of the product.
  • Ergonomics: Soft surfaces can be added to make products more user-friendly.
  • Reduced Assembly: Overmolding eliminates the need for separate assembly steps to combine different parts.
  • Cost Savings: Overmolding ultimately saves costs by streamlining production and reducing the number of parts needed.

Overmolding step-by-step process:

Sub Assembly overmolding step-by-step process flow

Common applications of overmolding include tool handles, electronic device grips, medical devices, and automotive interior components.


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Last updated 08.29.2023