Insert Molding vs. Overmolding


Injection molding can be used to create multi-layered items with multiple materials. The process starts similar to any injection molding process. A steel, aluminum or other material is used to create a mold. The mold is made to not only match the specific component being created, but also to allow for expansion or shrinkage of the specific material being used.

After the first layer is created, a second layer is molded over the first. This layer can be a different color, material or both. Just like single-step injection molding, two-step overmolding is  a fast and efficient process to create in-demand components at high rates of production.

Common Applications

Manufacturers use overmolding to mold two materials together into a single, efficient component. Here are a few common examples of this production method:

  • Automotive steering wheels
  • Hand tools
  • Power tools
  • Phones
  • RFID

Every step needs to be carefully engineered to create a fully finished product at the right dimensions. Overmolding procedures need to take into account the shrinkage of both layers of material to ensure a proper fit.

Benefits of Overmolding

This industrial process is more cost-effective than two separate injection molding stages. By molding the second layer of material directly over the first, the process removes a post-molding fabrication step.

It also creates a more durable product with a longer service life. Post-molding fabrication and installation can create weak points in the component, causing it to break or become compromised with heavy use.

Products with two layers of plastic or other material can be used in a wider range of applications. Mold a seal directly onto a component or create a soft, textured grip on a handle without compromising its rigid structure. Two diverse materials can come together to create a single component with improved qualities and greater areas of use.

Insert Molding

Another two-step process that can save time and improve product efficiency is insert molding. An insert molding production line uses the standard injection molding process, but inserts a fully finished component into the mold.

Similar to overmolding, this process can be used to create a dual-material component for complex tasks. It can also be used to create complex shapes and dimensions that would be difficult in a single injection molding step.

Typical Uses of Insert Molding

Insert molding is used to create precision components, often with two separate materials. Here are some common components that are efficiently produced using this process:

  • Air ducts for automobiles
  • Medical syringes
  • Industrial equipment components
  • Fine mesh filters
  • Hose connectors for vacuums

Filters insert a fine mesh to add a second material to the insert molded product. Hose connectors and air ducts insert a distinctly different shape into the product for a complex component that would otherwise be difficult to create.

Advantages of the Insert Molding Process

Injection molding, overmolding and insert molding all offer distinct advantages for industrial manufacturing. Consider insert molding if you need to create a small, specialized component using injection molding technology. This process allows you to insert a complex part into a small injection mold, creating components like medical syringes at precise design specifications.

This process also allows for faster assembly times for complex parts. Connecting two components during the injection molding process reduces the need for post-injection assembly, similar to overmolding.

Create the components you need at less cost and production time using insert molding. Encapsulating an insert in plastic removes the need to create multiple components and seal them together. The alternative to insert molding in this instance is to create two separate pieces, install the insert and then connect them together. Insert molding removes this post-production task and allows you to save money on your mass-produced injection molded components.

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