Insert Injection Molding Complete Guide - FOW Mould

Insert Injection Molding Complete Guide

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As industries continue to evolve, striving for enhanced product performance and design innovation, insert injection molding stands as a foundational technique, bridging the gap between diverse materials and cutting-edge manufacturing.

Insert injection molding is a quintessential method that seamlessly integrates different materials, most commonly metal and plastic, into one cohesive component. This ensures a tight bond between the insert and the plastic, allowing the product to leverage the strength of metal and the flexibility of plastic.

In this article, we’ll delve deep into the concepts of insert molding, its working principles, fields of application, and other comprehensive information. Continue reading as we demystify this intricate molding technique for you.

What Is Insert Injection Molding?

Insert molding is an injection molding process that involves integrating inserts, especially metallic ones, into the injection-molded part. Before the injection of molten plastic, these primarily metal-made inserts are incorporated into the mold. As the plastic cools and solidifies, the insert becomes an inseparable component of the final product.

The technique of insert molding not only fortifies the structural integrity of the molded piece but also augments the mechanical attributes of the plastics or thermoplastics employed. This results in components that marry the virtues of being lightweight and sturdy. As a consequence, an increasing number of industries are acknowledging the merits of insert molding, positioning it as a pivotal procedure in the modern manufacturing domain.

Insert Injection Molding
Insert Injection Molding

How does Insert Injection Molding Work?

Insert injection molding is a specialized technique within traditional injection molding processes. It embeds metal or other material parts into molten plastic, creating an integrated component. Here are the steps to successfully execute insert injection molding:

  • Placement of Inserts in the Mold

Before the molding procedure commences, inserts, typically crafted from metal or other materials, are manufactured in advance to ensure they meet precise specifications. These are then positioned into the injection mold either manually or via robotics. To guarantee precise placement, the mold often has specially designed slots or cavities tailored for these inserts.

  • Injecting Molten Plastic into the Mold

Once it’s ascertained that the inserts are securely in place, molten thermoplastic resin is injected into the mold. Under high pressure, the molten plastic is forced to fill all parts of the mold, with vents ensuring air is evacuated, ensuring the plastic encompasses the inserts completely.

  • Allowing the Plastic to Solidify Within the Mold

Post-injection, the mold is maintained at a set temperature, allowing for the plastic to solidify uniformly. Additionally, throughout this cooling phase, the plastic and the insert fuse together, forming a unified bond.

  • Ejection of the Component and Post-Processing

After the plastic solidifies, the newly formed part can be ejected from the mold using a demolding system. Any excess plastic or flash can then be trimmed or further refined to achieve the desired shape, ensuring a flawless surface finish.

Considerations During Insert Injection Molding

When actually operating the complex process of this technology, it is crucial to understand the various factors that play a key role in the results of injection molding.

One of the foremost factors to consider in the insert molding process is the design of the insert mould itself. The mold design, especially the cavities or pockets where the inserts are placed, needs to protect the inserts from the influences of temperature and pressure to prevent any potential damage. It is imperative that the mold facilitates the easy placement of inserts and ensures their accurate fixation during the injection process.

Next, the choice of molding materials comes into play. The selection of the material is influenced by factors such as the nature of the end product, production costs, and the availability of raw materials. It is essential to consider the compatibility between the insert material (typically metal) and the plastic material to prevent issues like warping, sinking, or poor adhesion.

The positioning of the insert within the mold is another pivotal factor. Throughout the insert molding process, fixtures or robotic systems are required to maintain the insert in its appropriate position, as any deviations can jeopardize the entire procedure.

To heighten the chances of success, controlling the process parameters stands as a crucial task. Given the sensitive nature of thermally-reactive materials, the temperature of the molten plastic and the mold itself must be meticulously managed. If the plastic’s temperature is too high, it could damage the inserts, while too low a temperature can result in incomplete filling. Concurrently, the right injection pressure and speed ensure that the mold is filled completely.

Insert Mould
Insert Mould

Advantages of Insert Injection Molding

Insert molding, a typical injection molding process, opens up new design possibilities in the field of material integration, but the process also offers many advantages to improve the quality and efficiency of manufactured products.

Reduced Assembly Time

Insert molding eliminates the need for post-molding assembly and individual component installations. This reduction in steps not only saves on labor but also accelerates the production timeline, making it one of the most cost-effective manufacturing processes favored by manufacturers.

Enhanced Product Strength and Durability

By embedding materials such as metals within plastics, products draw from the collective advantages of both components. This fusion enhances the product’s structural integrity and prolongs its lifespan. Additionally, the appropriate injection pressure and speed ensure the mold is fully and evenly filled.

Improved Design Flexibility

Insert molding facilitates a higher degree of design creativity by allowing the integration of varied materials into a singular unit. This provides designers with added flexibility in product conception. Furthermore, this technique enables a smoother transition from plastic components to metal parts, ensuring efficiency and seamlessness in the final product.


Variety of Insert Molding Material Options

The choice of insert material depends heavily on the intended application and expected performance of the final product, and is the preferred method of creating complex, multi-material assemblies that meet specific industry standards and consumer needs.FOWMould has a variety of options for insert molding materials used in the injection molding process.

  • PP
  • PE 
  • PC
  • PS
  • POM
  • PVC
  • PLA 
  • ABS
  • PMMA
  • Nylon
  • PA66

Application For Insert Injection Molding

Plastic insert molding allows for a seamless combination of materials to produce quality, durable and innovative products. Its versatility and benefits make it a popular choice for a wide range of industries.

Electronics Industry

One of the most common application areas for plastic insert molding technology is the electronics industry. Parts such as terminals, connectors and pins, for example, are often embedded in plastic housings. This provides insulation, structural support and protection from environmental factors while maintaining electrical conductivity.

Automotive Components

The combination of metals and plastics used in insert molding technology is utilized to manufacture many automotive components such as sensors, switches and electronic controls. This reduces weight while ensuring durability – a key factor in automotive design.

Medical Devices

In the medical industry sector, insert molding technology is used to produce a variety of medical devices, including surgical instruments with ergonomic plastic handles and components for wearable medical devices. The insert molding process is widely used in this industry for its ability to sterilize integrated products and ensure patient safety.


Consumer Products

In everyday life, insert molding is used to integrate metal components into plastic designs for the production of items such as toothbrushes, kitchen utensils, and power tools. The objective is to enhance the product’s functionality, durability, and overall user experience.

Comparison of Insert Injection Molding and Overmolding


As specialized technologies in the field of injection molding, both insert molding and overmolding are capable of integrating different materials to produce multifunctional parts. The biggest difference between these two processes is the slightly different steps required in the injection molding process.

Insert molding is a single injection molding method that reduces processing time while controlling the amount of material used, making production more cost-effective, but costs may increase with the addition of non-plastic components at a later stage.

In contrast, overmolding is a dual injection molding technique that involves adding a rubber-like, more plasticky layer to an already molded plastic part. Although the upfront cost is higher, production using this technique improves product durability, extends product life, and enhances functionality.


Insert molding, as a specialized process that combines plastic and non-plastic materials, makes full use of the advantages of both materials to save costs and extend the service life of the product at the same time, and thus is widely used in a variety of industries, providing a highly efficient and versatile solution for integrated manufacturing.

If you want to customize insert mold parts, FOWMould will provide professional one-stop injection molding service for you!

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