Liquid Silicone Rubber Overmolding

SIMTEC's Overmolding Process

As a provider of custom LSR solutions for over two decades, the combination of our high-performance molds, advanced molding technology, and 20+ years of expertise in LSR molding have established SIMTEC as a leader. We offer a variety of manufacturing options for producing LSR components to offer our customers the best solution possible: LSR LSR two-shot, LSR multi-shot and LSR overmolding.


What Is LSR Overmolding?

The LSR overmolding process allows manufacturers to produce specialized components consisting of two different substrates. Unlike LSR 2-shot molding in which both materials are molded during the same molding process, in the LSR overmolding process, LSR is molded around a finished molded part, or a metal or other substrate.

SIMTEC’s LSR Overmolding Process

SIMTEC’s LSR overmolding process is a two-step process:

  • Step one: The finished plastic or metal substrate is robotically placed into the cavity of the specialized LSR mold.
  • Step two: The mold closes initiating the injection of the LSR material into the cavity, the LSR fills the designated area of the substrate to form a complete LSR integrated component.

Working with an experienced manufacturer that has the experience and knowledge of the tooling and LSR overmolding process, and an understanding of the nuances and differences between LSRs and thermoplastics is mandatory. It can make the difference between success and failure.

SIMTEC has the expertise, experience and knowledge required, we have produced billions of custom silicone rubber overmolded parts for customers all over the world. We specialize in delivering exceptional quality across large volume orders, customizing our molding process and QA procedures to meet your specific requirements. Every aspect of the LSR overmolding/insert plastic molding process can be customized to produce liquid silicone parts to your specifications.

Contact SIMTEC today to learn more about our customized solutions.

When Is LSR Overmolding Best?

Liquid silicone overmolding produces components with valuable properties, making it ideal for many different industries. Common applications for LSR overmolding include:

Life Sciences

LSR has a long list of desirable characteristics, such as being highly biocompatible, hypoallergenic, odorless and tasteless. These properties are crucial to the medical and life sciences industry, especially when manufacturing items such as respiratory devices, surgical devices, wearables, IV, and syringes and others that must be sterilized. The medical industry also relies on LSR overmolding for LSR grips for stainless steel instruments and hand-held devices.


Liquid silicone rubber overmolding offers automotive manufacturers temperature-resistant seals for engine components, headlights and electric connectors. These silicone rubber seals also keep water away from electrical systems throughout the vehicle. LSR overmolding is used for incorporating seals to connectors and other plastic components requiring LSR seals.

Consumer Goods

Since LSR can withstand constant exposure to cleaning products, water and other environmental elements, and has electrical insulation properties, it is a suitable material for a wide range of consumer products, including shower heads, electronic devices and dispensing valves. LSR overmolded components are utilized in consumer electronics, food and beverage dispensers and preparation products, beauty and cosmetic products, and many others.

Industrial and Special Applications

LSR components can operate and endure high temperatures and pressures, allowing industrial manufacturers to use LSR overmolding for seals and gaskets in demanding systems such as water heaters and furnaces. LSR overmolding is ideal for parts with tight tolerances since it can yield precise results.

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Overmolding vs. 2-Shot Molding

Both overmolding and 2-shot processes combine two substrates during the molding process to form one multi-substrate component.

In LSR overmolding an LSR substrate is molded over a placed metal mass or a plastic part to produce the multi-substrate component, offering a wide array of substrate combinations.

In a 2-shot molding process both materials are molded in the same process and machine with cavity-to-cavity alignment for superior bonding, and secure precise placement.


Benefits of LSR Overmolding

One of the benefits of liquid silicone overmolded parts and components is that the manufacturing process allows for the use of a non-plastic substrate, such as steel. It is important to note that overmolding is the only way to incorporate materials, aside from other thermoplastics and LSRs, into the injection molding process.

LSR/plastic injection molding is a cost-effective and versatile process used by manufacturers in a large number of industries and applications. From LSR overmolded handles to complex electronic assemblies, there are multiple reasons why rubber overmolding is a good choice for your project:

  • Benefits & characteristics from both materials: Overmolded components exhibit the characteristics and benefits of both materials – such as rigid and flexible, sealing, and insulating.
  • Use of Non-plastic substrates: Overmolding is the only way to incorporate substrates, aside from other thermoplastic and elastomer substrates, in the LSR injection molding process.
  • Cost and time savings: Molding silicone rubber directly onto a metal or plastic substrate eliminates the need for secondary post-molding assembly processes, and saves the associated costs and time for completed assembly.
  • Design flexibility: By incorporating silicone rubber in the plastic or metal part design, it produces parts that are waterproof, airtight and more resistant to shock and vibrations.
  • Quality: The accuracy and control in a stable LSR molding process yields precision, high-quality, securely bonded parts and mitigates the risk of seal displacement.

Custom LSR Overmolding Solutions from SIMTEC

Collaborate with an expert who understands LSR overmolding and the different nuances of working with LSR and thermoplastics as well as the appropriate tooling and processes for each. SIMTEC has produced billions of custom silicone rubber overmolded parts for some of today’s leading Fortune 100 and Fortune 500 companies.

We specialize in delivering exceptional quality control across large volume orders, and we can customize our QA procedures to meet your specific requirements.

In addition to quality control, every aspect of the LSR overmolding/insert plastic molding process can be customized to produce liquid silicone parts to your specifications. We can assist with economical mold design and development, prototyping, and more. Contact SIMTEC today to learn more about our full list of services.

Contact SIMTEC To Discuss Your Project Today

With design flexibility, advanced technology and exceptional quality, there’s no better partner to manufacture your high volume Liquid Silicone components than SIMTEC. Contact us today to discuss your requirements.

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