Overmolding with silicone offers powerful protection and enhanced functionality for a variety of substrates, from plastic to metal. Through this process, liquid silicone material is applied onto the chosen substrate before being cured to create an unbreakable bond that stands up against wear and tear.

What is Silicone Overmolding?

Silicone overmolding is a manufacturing process where a layer of liquid silicone rubber is molded over an existing substrate or part to provide additional protection or improve its functionality. The process of silicone overmolding involves the following steps:

Preparing the substrate: The substrate or part to be over-molded is first cleaned and prepared for the application of silicone. The surface must be free from dust, oil, or any other contaminants that could interfere with the adhesion of the silicone.

A mold release agent: A mold release agent is then applied to the substrate to prevent the silicone from sticking to the surface.

Preparing the silicone: The silicone material is prepared by mixing two components, typically a base and a curing agent, in a specific ratio. The mixture is then degassed to remove any air bubbles that may have formed.

Overmolding: The silicone material is then injected onto the prepared substrate using a specialized injection molding machine. The liquid silicone fills the mold and cures to form a solid rubber part that is bonded to the substrate.

Post-curing and finishing: Once the over-molded part is cured, it is removed from the mold and undergoes post-curing to ensure that it has fully cured. The part can then be trimmed or finished to meet the desired specifications.

Materials Used in Silicone Overmolding

The materials used in silicone overmolding are:

Substrates: The substrate is the base material that is over-molded with silicone. It can be made of various materials such as metals, plastics, and even other rubbers.

Silicone Rubber: The silicone material used in overmolding is typically a liquid silicone rubber (LSR) that is composed of two parts, a base, and a curing agent. LSR is a high-performance elastomer that has excellent properties such as flexibility, heat resistance, and chemical resistance.

Mold release agents: Mold release agents are used to prevent silicone from sticking to the substrate or mold. They can be made of various materials such as silicones, waxes, and polytetrafluoroethylene (PTFE).

Dyes and pigments: Dyes and pigments are used to color the silicone material. They can be added in small amounts to achieve different colors and shades.

Fillers: Fillers are added to the silicone material to improve its properties such as stiffness, hardness, and electrical conductivity. Examples of fillers include glass fibers, carbon fibers, and metallic particles.

Applications of Silicone Overmolding

Healthcare products: silicone composite is commonly used in the production of healthcare products, such as surgical instruments, catheters, prosthetic equipment, etc. The superforming process provides a smooth and seamless surface that is easy to clean and disinfect, making it ideal for these types of applications.

Auto parts: Many auto parts, such as washers, seals, and connectors, require high durability and resistance to heat and chemicals. Silicone remolds can provide these properties, as well as improve the overall beauty of a part or component.

Consumer electronics and devices: Silicone remolds are commonly used in the production of consumer electronics and devices such as mobile phone cases and remote controls. The overmolding process can provide a soft and comfortable grip, as well as protect the equipment from shock and damage.

Industrial equipment and machinery: Industrial equipment and machinery often require parts that can withstand harsh environments, such as exposure to chemicals, heat and vibration. Silicone compound molds can provide these properties, as well as improve the overall function and life of the equipment or machinery.

Aerospace and Defense: Silicone supermolds are used in the production of aerospace and defense products such as electrical connectors, sensors and sealing components. Superforming processes can provide lightweight and durable solutions that meet the high performance and safety standards required by these industries.

Advantages of Silicone Overmolding

Silicone overmolding is an important manufacturing process that offers several benefits and advantages over other types of molding techniques. Some of the key benefits and advantages of silicone overmolding are:

Improved Product Durability: By adding a layer of silicone over the substrate, the overall durability and lifespan of the product can be greatly improved. The silicone layer provides additional protection against harsh environmental conditions, abrasion, and impact damage.

Enhanced Product Functionality: Silicone overmolding can add features to a product, such as a grip or insulation, that were not present in the original substrate.

Improved Aesthetics: Silicone overmolding can provide a clean and smooth surface finish, making the product look more professional and aesthetically pleasing.

Better Performance: The silicone layer can improve the product’s performance by providing better adhesion, insulation, and resistance to chemicals and extreme temperatures.

Cost-Effective: Silicone overmolding is a cost-effective manufacturing process, as it eliminates the need for multiple parts and assembly processes.

Customizable: Silicone overmolding allows for customization of the product by using different colors, textures, and materials.

How to Achieve Successful Silicone Overmolding?

Achieving successful silicone overmolding requires careful attention to several key factors throughout the process. Here are some key considerations to ensure successful silicone overmolding:

 Proper substrate preparation: The substrate should be thoroughly cleaned and prepared for the application of silicone. Any contaminants or impurities on the substrate surface can compromise the bond between the substrate and silicone.

Mold design and manufacturing: The mold used in overmolding should be designed and manufactured to ensure that the silicone flows and adheres properly to the substrate. The mold should have the correct dimensions, surface texture, and vents to allow air to escape.

Proper selection of silicone material: The silicone material used in overmolding should be selected based on the specific application and desired properties. The silicone should have the right durometer (hardness), color, and additives such as fillers to enhance its properties.

Curing: The curing process of the silicone material should be carefully monitored and controlled to ensure that it cures fully and evenly. The temperature, humidity, and time required for curing should be optimized for the specific silicone material.

Post-curing and finishing: The over-molded part should be post-cured to ensure that it has fully cured and achieved its desired properties. The part can then be trimmed or finished to meet the required specifications.

Quality control: Quality control measures should be in place throughout the overmolding process to ensure that the final product meets the desired specifications. This includes inspecting the substrate and mold, monitoring the silicone material and curing process, and inspecting the finished part for defects.

All in all, successful silicone overmolding requires careful attention to every step of the process, from substrate preparation to finishing. By following these key considerations, manufacturers can produce high-quality over-molded parts that meet the required specifications and perform as intended.

F.A.Q about Silicone Overmolding