Silicone Overmolding

As an advanced silicone rubber manufacturer, Yuanyi uses overmolding technology to provide global partners with advanced production capabilities, high quality, and stronger parts. From silicone buttons in electronics to toothbrushes in everyday products, silicone overmolding gives finished components rigidity, comfort, flexibility, and grip. It provides an efficient and more convenient solution for injection molded products with two or more materials.

What is Silicone Overmolding?

Silicone overmolding is often referred to as silicone overmolding or liquid silicone rubber (LSR) overmolding. It is a multi-step, cost-effective, and versatile injection molding process in which two or more components overlap during the molding process. The silicone overmolding process is a two-step process, so it is sometimes called overmolding. The process involves using a silicone rubber material to inject, bond, or encapsulate a base substrate or finished product to create a soft-touch, more durable, and stronger of product.

Commonly used base materials for silicone overmolding

The different performance and functional requirements of the parts determine the base material used for silicone overmolding. These substrates are usually made of thermoplastic materials.

PC/ABS
PC
PP
PPSU
PBT
PA+GF

Silicone Overmolding Process: Step-by-Step

The first step: basic substrate

Before liquid silicone rubber is injected, the molded part (which also becomes the base substrate) is completed and placed into the mold cavity.

Step 2: Overmolding

After the mold is closed, the silicone material is injected and molded directly onto the base substrate, creating bi- or multi-material parts that are not possible with a single substrate.

ilicone overmolding is often used to make everyday plastic toothbrushes with rubber handles to give the handles a better grip.

Advantages of silicone overmolding

Compared with single injection molding, double injection molding requires more complex design, processing, and material selection. But its advantages are significant.

Lower manufacturing costs and faster production: Compared to manufacturing methods that require moving parts to a completely different machine or mold, silicone overmolding eliminates assembly steps and reduces associated risks, meaning your project is produced more safely and uses fewer man-hours.
Unmatched Assembly Method: The silicone overmolding process fuses materials in a unique and superior way compared to traditional assembly methods.
Greater design freedom: You can use liquid silicone rubber materials with numerous properties to produce parts that are waterproof, airtight, and resistant to shock and vibration.
More cost-effective: By employing the liquid silicone rubber molding process, strongly bonded, cost-effective, high-precision individual parts can be produced.
Improve product functionality: Silicone overmolding can enhance the functionality and performance of components because it allows the use of two or more materials with different properties, such as different colors, textures, or hardnesses.
Enhanced durability: Silicone elastomers are often molded onto rigid substrates to increase the product's durability. Therefore, products manufactured using the silicone overmolding process are not prone to cracking, fading, or deformation.
Enhance aesthetics: Another useful application is aesthetics. The base substrate can have a recessed pattern filled with contrasting silicone overmold material to create logos, logos, text, or other designs.
Multifunction: Because it can be used to produce small and large components and combined with a variety of materials, manufacturers in many industries and applications often use silicone overmolding for different applications, including medical, automotive, and consumer products.

Limitations of silicone overmolding

Despite the wide range of benefits of silicone overmolding, there are some limitations to using this process.

Similar to traditional injection molding, silicone overmolding can have excessive upfront costs.
Although silicone overmolding eliminates the post-mold assembly process, dialing in a secondary injection machine is complex, and making, modifying, or adjusting metal molds is time-consuming and expensive, requiring manufacturers to mass-produce components to spread the cost.

Types of silicone overmolding

There are three types of silicone overmolding: secondary overmolding, insert overmolding, and multiple injection molding. Secondary silicone overmolding involves injecting different materials in a single molding cycle. Silicone insert overmolding involves injecting a thin silicone material onto the insert, while multi-injection molding involves injecting two or more materials over, under, around or through the substrate. Generally, silicone insert overmolding is more suitable for producing small batch orders, which helps reduce costs for customers.

Design and Manufacturing Considerations for Silicone Overmolding

There are some important considerations and tips to ensure successful production and optimal performance of silicone over-molding parts. Here are some of the key design and manufacturing considerations:

Wall Thickness

Used balanced wall thicknesses for your parts to ensure excellent adhesion between the base material and the LSR component. Therefore, in overmolding, it is recommended that parts have thicker walls of 1.5 to 3 mm (0.060 to 0.120 inches).

Dimensional accuracy

Because the overmolding material is a thermoset elastomer, potential changes in dimensions may occur as it cures. Therefore, it is recommended that you consult your mold engineer to help improve the geometry of the silicone rubber component, obtain optimal physical properties, and avoid drastic changes in thickness.

Material compatibility

Choosing the right material is critical for silicone overmolding parts. To obtain the required quality, please ensure the compatibility of the LSR material with the substrate and that the mold design and process support the bond between the LSR material and the substrate.

Applications of Silicone overmolding

Medical and healthcare products, automotive parts, and maternal and infant products often use silicone overmolding to produce products that are beautiful, more durable, more functional or reduce assembly requirements. The following are typical applications of the overmolding process:

Consumer products

Silicone overmolding is a versatile process that provides a popular, more convenient solution for many everyday plastic products requiring multiple colors and multi-layer designs. They include baby products, kitchen tools, electronics, bowling pins, children's play pieces, storage bins, and plastic containers.

Automobile industry

Silicone insert molding offers metal and plastic or rubber material combinations and is therefore commonly used in the automotive industry for electrical sensing, gears, fasteners, and other automotive parts. Silicone overmolding is also often used to produce automotive two-tone interior components such as handles, door and instrument panels, knobs, various controls, etc.

Medical industry

Because silicone rubber parts are biocompatible, chemically inert, and stable in harsh environments, the medical industry often uses insert molding to encapsulate medical cables and wires, and defibrillators in plastic to protect fragile internal components. Insert molding is also designed for use in medical devices implanted in the body and camera equipment for endoscopy and colonoscopies, this is due to the easy-to-clean and sanitize nature of LSR parts.

Electrical industry

In the electrical field, insert molding is suitable for wiring components, single wires, multiple wires, etc. with rubber exteriors. Windproof, rainproof, and safe components are crucial in electrical applications.

Beauty industry

Designers can use silicone overmolding or insert molding to create unique surface textures, multiple colors and more attractive custom packaging for products such as powder compacts, makeup brushes and perfume bottles.

Custom Silicone Overmolding Solutions from Yuanyi

Silicone overmolding is a flexible, efficient, and versatile manufacturing process that offers many advantages over traditional injection molding technology. Yuanyi's silicone overmolding services provide injection molded products in combinations of two or more materials for your project, with a variety of materials to choose from. The quality of incoming materials, mold manufacturing, and mature molding processes enable Yuanyi to provide parts with excellent performance, high precision, and consistency for medical and healthcare, automotive, and maternal and infant applications.

Perhaps you are looking for a reliable manufacturer to provide high-quality parts for your specific project. If you still have questions about the process, design, and materials of silicone overmolding, please contact our professional team immediately. They will quickly provide you with materials and solutions suitable for your project.