Overmolding Injection Molding Service
What is Overmolding
Overmolding is a process of taking a substrate part and then using injection molding to add additional layers over it, like thermoplastic or silicone rubber material. Traditionally, the substrate parts are plastic or metal with a higher melting point, once that part is cooled, the layer is injection molded over it. So the cycle time is a bit longer. Usually overmolding is used to create a grip or roller.
Overmolding Process
Overmolding is a multi-step manufacturing technique used to create complex, multi-material components.
- Initial Substrate Molding: The base or substrate part is first created using standard injection molding techniques.
- Substrate Preparation: The molded substrate is prepared, which may include cleaning and conditioning, to ensure proper adhesion for the overmolding process.
- Overmolding: The substrate is placed into a second mold where the overmold material is injected over or around it, forming a bond with the substrate.
- Cooling and Ejection: The assembled part is allowed to cool and solidify before being ejected from the mold, completing the overmolding process.
Overmolding Material
Substrate material for overmolding
Overmolding is commonly used to encapsulate one material (usually a softer or elastomeric material) over another rigid substrate. The most common substrate material for overmolding is thermoplastic, these material provides a stable base of overmolded components, the most common substrate material include:
- ABS
- PC
- Nylon
- PP
- ABS/PC
Bonding material for overmolding
The most common overmolded material is thermoplastic elastomer, known for its flexibility, resilience, and compatibility with various substrates. Some other common bonding materials include:
- TPE
- TPU
- TPV
- Silicone
Advantages of Overmolding
- Overmolding provides a protective layer, improving the overall durability and lisfespan of the product.
- Enables the incorporation of multiple materials with varying properties, enhanding design possibilities.
- Allows for the creation of ergonomic and comfortable surface for products like grips and handle.
- Eliminate the need for additional assembly steps, steamlining the manfuacturing process.
Application of Overmolding
Overmolding is widely used across various industries due to its ability to enhance product functionality and aesthetics by combining multiple materials. Common applications include:
- Cable connectors
- Soft-touch grips on devices
- Buttons
- Handles
- Protective housing
- Toothbrushes
Why Choose Us
Contract Manufacturing Solution
Mold & Tooling Service
Design for Manufacturability
Surface Finishing
Assembly Manufacturing
FAQs of Overmolding
What is the difference between overmolding and insert molding?
Answer:
Although both Overmolding and Insert Molding are injection molding technologies, there are significant differences in process and application:
- Overmolding: Molding a material (usually soft material, such as rubber, silicone, TPU) into the surface of a hard core material (such as ABS, PC) that is already formed. This process typically involves multiple injection mouldings, where different layers of material can be added to a part as needed.
- Overmolding is suitable for applications that require enhanced features such as non-slip, comfort, tightness.
Insert: The prefabricated part (e.g. metal, electronics, etc.) is embedded into the mold during injection Molding and then molded into plastic or other material to cover the insert. The main advantage of Insert molding is the efficient combination of components of different materials, reducing the steps for subsequent assembly.
Major points:
- Overmolding places more emphasis on adding functionality and aesthetics to the existing structure, while Insert Molding focuses on combining different materials, especially metal and plastic, for strong or complex applications.
Why choose Overmoulding over traditional secondary assembly?
Answer:
There are several technical and economic advantages to choosing Overmolding, which are mainly reflected in improving production efficiency, enhancing product features and reducing costs.
- Production efficiency: Traditional secondary assembly requires multiple steps, such as first producing the core part and then combining it with the soft material by bonding or other processes. This not only increases the process, but also there may be manual operation errors. In contrast, Overmolding is an all-in-one manufacturing process that combines different materials into one complete part, reducing assembly time and labor costs.
- Improved product performance: Overmolding can achieve multiple functions in a single part, such as increased slip resistance, softness, comfort, and tightness, which cannot be accomplished in one sitting with traditional secondary assembly.
- Cost savings: Overmolding helps reduce overall manufacturing costs by reducing assembly sessions, reducing scrap, and improving production efficiency. Especially in mass production, Overmolding is able to better control unit costs.
Major points:
- Overmolding not only simplifies the manufacturing process, it also ensures stronger material bonding and reduces the risk of later delamination or loosening, which traditional assembly processes can cause to loose or uneven joints.
How does Overmoulding ensure the combination strength of multiple materials?
Answer:
The bonding strength of the material is a crucial factor in Overmolding. In order to ensure a good combination of different materials, the following measures are usually taken:
- Surface treatment: The surface of the hard core material is treated (such as surface roughing, chemical pretreatment or spraying) before injection molding. These treatments significantly enhance the adhesion between the soft outer material and the hard core material.
- Choose compatible materials: Choosing chemically compatible materials is critical. The chemical structure of the hard material and the soft material must have a certain affinity in order to form a strong physical and chemical bond during the injection molding process.
- Temperature and pressure control: During injection molding, precise control of temperature and injection pressure ensures optimal melting and bonding between the two materials to avoid poor adhesion due to improper temperature.
- Mold design: Good mold design is a key factor in ensuring the combination between materials. Usually, material fluidity, temperature uniformity and molding pressure are considered in mold design to achieve the best combination effect.
What is the material selection criteria for Overmolding?
Answer:
Overmolding involves the combination of two or more materials, and several factors need to be considered when selecting the material, such as chemical compatibility, physical properties, machining characteristics, and cost control.
- Hard core materials: Commonly used hard materials are ABS, polycarbonate (PC), nylon (PA) and polypropylene (PP), which usually have high structural strength, impact resistance and rigidity.
- Soft outer materials: Commonly used soft materials are thermoplastic polyurethane (TPU), silicone, thermoplastic elastomer (TPE) and rubber (EPDM), which provide flexibility, non-slip, comfort and tightness.
Selection basis:
- Mechanical properties: Appropriate hardness and elasticity should be selected according to the application scenario of the product. For example, automotive parts may pay more attention to high temperature resistance and impact resistance, while medical devices need to pay more attention to the biocompatibility and antibacterial properties of materials.
- Chemical resistance: such as waterproof, oil resistance, etc., especially in the food industry or pharmaceutical industry, the outer material needs to have good chemical corrosion resistance.
- Environmental requirements: In high or low temperature environments, the physical properties of some materials will change, so it is necessary to choose materials that have the ability to adapt to extreme environments.
