What Is Overmolding? Its Process and Example vs Insert Molding

2024-05-07 16:25:00

Overmolding is a versatile injection molding process that offers unique advantages in creating complex parts with multiple materials. To enhance your product's performance and aesthetics, overmolding and insert molding are structurally similar, but they are different. Learn about the overmolding process, materials used, and its advantages. Explore its applications across industries and understand the differences between overmolding and insert molding. Elevate your products with our expertise in overmolding technology.



What Is Overmolding?

Overmolding is an injection molding process that creates a machine part or component by joining two or more materials into one. These materials can be the same or different, offering endless combinations based on the desired end product. The process involves two main components: the substrate, which serves as the base material, and the overmolding, which is the secondary material that is "molded over" the substrate as the outer layer. The substrate can be any material, while the overmolding is the material that imparts specific properties or functionalities to the final product. Overmolding is applied in various industries where rapid prototyping of industrial machine parts is required, or where custom parts are made by overlaying plastic or rubber with other materials such as metals.

overmolding - two-shot injection molding and co injection molding


Two-Shot Injection Molding

Two-shot injection molding is a specialized process that uses two different materials or colors to produce a single part. It is achieved by injecting one material into a mold to form the initial part and then injecting a second material or color over the first to create the final part. This process is commonly used to create parts with soft-touch grips, integrated seals, or multiple colors.

Related product: Vertical Clamping Vertical Injection Machine  – YH Series


Co Injection Molding

Co-injection molding, also known as sandwich molding or multi-layer molding, is a process that involves injecting two or more materials simultaneously to form a single part. This process is often used to improve the strength, durability, or aesthetics of a part by combining different materials with complementary properties. Co-injection molding can also be used to reduce material costs by using a core material surrounded by a skin material.

Related product: Dual Injection Machine  – HDC Series



Materials Commonly Used in Overmolding

Commonly used injection molding materials for overmolding include thermoplastics like polyethylene (PE), polypropylene (PP), and thermoplastic elastomers (TPE). These materials offer a broad spectrum of properties, including flexibility, durability, and chemical resistance, making them well-suited for various overmolding applications.

Selecting the right materials for overmolding is crucial to achieving the desired properties and functionalities in the final product. Factors to consider when evaluating materials include:

  • Temperature resistance
  • Hardness and flexibility
  • Thickness for vibration dampening applications
  • Bonding capabilities
  • Friction levels



Advantages of Overmolding

Regardless of whether it is two-shot molding or co-injection molding, overmolding process offers several advantages, including:

  • Enhanced Functionality: Overmolding unlocks a new dimension of functionality by enabling the fusion of materials with contrasting properties. Imagine a medical device where a rigid plastic substrate offers structural integrity while an overmolding elastomeric layer provides a soft, non-slip grip. This exemplifies how overmolding elevates a product's capabilities.
  • Improved Durability and Strength: The fusion of materials through overmolding often results in a more robust and resilient product. This characteristic is particularly valuable in applications where the product is subjected to frequent wear and tear or demanding environmental conditions.
  • Cost-Effectiveness: While the initial setup costs for overmolding can be higher, it often streamlines the manufacturing process by eliminating the need for secondary steps like painting, gluing, or assembling separate components. This translates to long-term cost savings.
  • Aesthetic Appeal and Design Flexibility: Overmolding empowers manufacturers to craft products that are not only functional but also visually enticing. Incorporating various colors, textures, and finishes unlocks a world of design possibilities, enhancing brand identity and consumer appeal.
  • Design Freedom: Overmolding transcends the limitations of single materials, creating complex geometries that might be difficult or impossible to achieve with traditional methods. This design freedom fosters innovation and the development of groundbreaking products.
  • Simplified Assembly: Overmolding can integrate multiple components into a single unit, streamlining the assembly process. This not only reduces manufacturing time and costs but also enhances the overall product integrity.
  • Improved Ergonomics: Overmolding allows for the incorporation of ergonomic features into a product's design. For instance, handles and grips can be overmolded with soft, comfortable materials, reducing fatigue and improving user experience.
  • Vibration Damping and Noise Reduction: Overmolding with specific materials can effectively dampen vibrations and reduce noise levels. This particularly benefits products like power tools, appliances, and electronic devices.
  • Weather Resistance and Chemical Resistance: Certain material combinations achieved through overmolding can significantly enhance a product's resistance to harsh weather conditions and chemical agents. This characteristic is crucial for products intended for outdoor use or those exposed to chemicals.



Example of Overmolding Application

Overmolding finds applications across various industries and serves a wide array of purposes. Whether it's providing a better grip, dampening vibrations, enhancing comfort, creating water-resistant seals, or absorbing sound, overmolding offers a versatile solution for manufacturers looking to improve their products.

  • Consumer Goods: such as tools, appliances, and electronics
  • Automotive Industry: such as handles, grips, and trim pieces
  • Medical Industry: such as handles and grips for medical devices
  • Electrical Industry: such as connectors and cables
  • Beauty Industry: such as toothbrushes and cosmetic containers



What is Insert Molding?

Insert molding involves forming a secondary part over a pre-existing substrate. A prefabricated part, often made elsewhere or by another company, is inserted into a mold, and a secondary layer is molded around it. This technique is frequently used to add a plastic layer onto a metal substrate, such as adding a plastic handle to a metal screwdriver.

Further reading: What Is Insert Molding? Process, Advantages and Applications



When to Use Overmolding vs. Insert Molding?

Overmolding and insert molding have their strengths and are suitable for different applications.

Overmolding is ideal for:

  • Thermoplastics and/or rubber-finished pieces
  • Designs with multiple layers, materials, and/or colors
  • Parts where both the substrate and secondary layer are manufactured
  • Parts that do not need to be disassembled
  • Creating parts with different colors, materials, or properties
  • Achieving complex designs that require the integration of multiple materials in a single part
  • Improving production efficiency by reducing the need for secondary operations like painting or assembly of multiple parts

Insert Molding is preferable when:

  • Using a prefabricated substrate
  • The substrate is made of metal, wires, or computerized parts
  • A one-piece finished part is desired



Elevate Your Products with Overmolding Expertise

Overmolding is a versatile and innovative process that offers a wide range of benefits, at Huarong Group, we understand the importance of overmolding in the manufacturing industry. As an experienced injection molding machine manufacturer, we offer a complete range of injection molding machine models to meet our customers' needs. If you are interested in an injection molding machine, please contact Huarong.



Feel free to contact us.


Previous news : Innovations at ChinaPlas: A Recap of Huarong's Injection Molding Solutions

Next news : Plastic injection molding material selection and their Molding Technology

Contributor - Wei