What Is Overmolding?

Overmolding is an injection molding technique used to layer one silicone component (often a rubber-like silicone called TPE) on top of another (substrate). The substrate is frequently a plastic component that has been injection-molded, but it can also be composed of a variety of different materials. In many different sectors, overmolding is employed for a variety of reasons.

What Is Overmolding?

Advantages Of Silicone Over molding

The process of overmolding silicone onto plastic or metal substrates is cost-effective, adaptable, and used in a variety of industries. Overmolding is a fantastic choice for your silicone molding projects because to its many benefits, including the following:

  • Wide Range Of Applications

The silicone over molding procedure makes it easier to combine different materials. This enables the manufacturing of several silicone goods that are difficult to make with conventional silicone rubber.

  • Time and money efficient

It will be less expensive and time-consuming to overmold silicone onto substrates as opposed to hand manufacturing a complicated item. The initial tooling expenses may be somewhat more than the total of 2 molded and assembled pieces due to the more complicated nature of the procedure.

  • Streamlining the procedure

There are additional ways to make goods that are produced via overmolding. The distinction is that overmolding facilitates production in two processes or less. As a result, as opposed to alternative manufacturing methods, the process flow has been streamlined.

  • High Design Flexibility for Silicone Overmolding

With the use of this particular silicone molding technique, LSR goods with sealing, anti-compression, waterproofing, and other distinctive qualities may be produced.

  • Product Performance Improvement

Better product performance is one of the main justifications for developing and producing a product or parts utilizing the overmolding technology. TPE, for instance, is the perfect material to use for creating a soft, non-slip grip for a range of items. This is due to the fact that comfort in the usage of such items is determined by tactile sensitivity. Examples include pharmaceuticals and surgical tools.

Materials Commonly Used in Overmolding

Overmolding can be used with a wide range of materials, including:

  • TPE (Thermoplastic Elastomers)

  • TPU (Thermoplastic Polyurethane)

  • TPR (Thermoplastic Rubber)

  • Silicone Rubber

Properties Of Overmolding

For applications needing certain functionality, material qualities are significant (like vibration absorption or grip). There are a few essential qualities for overmolding TPE materials:

  • Tensile Related PropertiesHow well a substance stretches is determined by its tensile characteristics. This is a crucial attribute if your project calls for the overmolded features to stretch and return appropriately.
  • Compression PropertiesBecause TPE plastics are so flexible, it may be crucial for your project to know how much compression the part can withstand without suffering long-term damage.
  • Friction Coefficient The amount of force required to move one surface across another is known as friction. Various TPE varieties have different coefficients of friction. Another element is the mold's surface roughness.
  • Flexural ModulusFlexural modulus is the amount of bending resistance a material has. The second component of TPE's "feel," this trait should be taken into account while designing grip features.
  • Material ThicknessFrom a design standpoint, the thickness of the material will change how well the material's qualities function. The TPE's capacity to absorb vibration will be reduced by its thin wall section.

Overmolding Applications

Although at first look overmolding appears to improve the appearance of some items, its usage is crucial for highly technical and highly regulated products. It may be used for a wide range of things, such as:

  • Surgical Devices & Instruments
  • AED Units
  • Electrical Applications
  • Navigation and Communication Devices
  • Automobile
  • Personal care – Toothbrushes, Razors, Pens, Sports-Grips, Cosmetics, Handles

Surgical Devices & Instruments

Surgical Devices & Instruments

Over molding is used in a broad range of health-related businesses, most notably in the creation of surgical tools and instruments.

Many things, including surgical suites and overmolded items like portable monitors, must be sterile. All of this is made feasible through overmolding, which also satisfies FDA medical criteria.

Automotive Industries


The automobile industries require plastic components, which are often produced using the injection overmolding technique. This entails the creation of a sizeable component of the external and interior automotive designs, including dashboards, headlights, and many more. The manufacture of vehicles has been transformed by the use of overmolding.

What is overmolding and insert molding?

In order to create the substrate and the overmold, two injections of material are injected. Although the metal insert must be bought or made separately, insert molding only requires one injection of molten plastic.

What is the difference between injection molding and overmolding?

In essence, overmolding is a form of insert molding. Overmolding, as opposed to insert molding, involves molding plastic over another molded item. The initial component is created in an injection mold, and the over-molded material is then added before it is put into a second mold.

What are the four types of moulding?

1) Compression molding. Compression molding is a technique used to create rubber and plastic components.
2) Melt the mold. Melt molding refers to compression molding when it is used with thermoplastic materials.
3) Transfer molding.
4) Injection molding.

What temperature should I overmold?

The injection temperature for the TPE overmolding PP material is typically between 170-190 degrees Celsius, while the temperature for the overmolding ABS material is between 220 and 220 degrees Celsius. The temperature for the overmolding PC material is only marginally higher than the injection molding temperature.

Can silicone be overmolded?

To create the final product, silicone is molded over, beneath, or through a substrate material using the injection molding technique known as silicone overmolding. This manufacturing method accommodates differences in durometer and stiffness by enabling product designers to blend the best of two materials.


Over the past ten years, improvements in materials and injection molding techniques have led to overmolding's evolution. For a variety of businesses, including the medical and electrical sectors, this may assist to provide new technological and creative potential. Beyond a smooth touch, overmolding offers a variety of design options for goods with enhanced features, better looks, better brand recognition, and more value. Additionally enables OEMs to gain financially from the use of two or more materials by combining various qualities into molded components.

We’d love to speak with you about overmolding, whether you ultimately choose to work with us or not. Give us a call


About Frank

With a background as an injection molding engineer at Kaysun, Frank brings unique depth and insight to his role as Business Development Engineer. His ability to synthesize information and pair need with opportunity is a benefit to prospects and customers alike.

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