From the soft handle on personal care items to decorative car trim, overmolding is an injection molding process valued across industries, offering extended functionality and aesthetic appeal that isn’t easily achieved with injection molding alone. Overmolding, which seamlessly combines two plastic materials or components, provides a variety of advantages. Below, after a brief introduction to how it works, we discuss overmolding benefits and the industries and products that have come to rely on it.

Understanding Overmolding

High-performance and engineering-grade plastics are materials designed for applications that require higher strength, temperature resistance, chemical resistance, or other specialized properties. These materials are often chosen to create overmolded products for critical applications in the aerospace, alternative energy, medical, oil & gas, and electronics industries due to the materials’ superior mechanical and thermal properties compared to commodity plastics.

Overmolding is a two-step manufacturing process where a single part is created using two plastics or components. There are three types of overmolding: co-molding, overmolding dissimilar polymers, and overmolding non-polymer components.

Overmolding or joining the same base materials is called co-molding. Co-molding similar or the same materials creates a stronger bond than welding or gluing. This may be done to add structural components that could not be molded with a single mold, or when a complex external geometry cannot be achieved, co-molding can be an added operation resulting in the desired part.

When overmolding dissimilar polymers, a base component is molded, and then, either in the same mold or another mold, a second-stage polymer is overmolded around all or part of it. Dual injection molding machines have two barrels that feed and melt different materials into a single mold. This reduces mold complexity or the need for specialized equipment.

Sometimes non-polymer structural components, such as threads or wear surfaces, that cannot be achieved with polymers or molding complexity can be overmolded to increase functionality. This method is often preferred over heat staking inserts, a secondary process where plastic is melted as a heated metal component is forced into it. This stresses the plastic, and causes material degradation as higher heat is needed to insert the component. Having control over mold surface temperatures, melt, flow, and pressures creates a better bond with metallic or non-polymer components.

An important consideration when choosing materials is compatibility. The materials selected for both the substrate (base layer) and the overmold must be compatible in terms of chemical bonding and thermal processing. When dissimilar plastics are used, the melting temperature of the overmold material must be lower than that of the substrate to avoid deforming or damaging the base layer during the overmolding process. Additionally, achieving a good bond between the two materials is crucial. This can depend on the materials’ chemical compatibility, the surface texture of the substrate, and the molding conditions.

Overmolding Benefits

Overmolding, particularly with high-performance and engineering-grade plastics, offers customers a range of tangible benefits and value, which can be critical in enhancing product performance, user experience, and market competitiveness. Some areas in which customers derive value include the following:

  • Enhanced durability and longevity – Overmolding can significantly increase a component’s durability and longevity. By combining materials with complementary properties, such as a rigid substrate with a tough, wear-resistant overmold, products are better protected against impacts, abrasion, and environmental conditions. This durability translates into longer-lasting products, reducing replacement frequency and offering better value for the cost.
  • Improved product performance – High-performance materials used in overmolding can impart specific properties to a product, such as increased strength, thermal stability, and chemical resistance. For example, overmolding can create seals protecting sensitive electronics from water and dust, enhancing the product’s performance in challenging environments.
  • Enhanced safety and compliance – Overmolded parts can offer improved safety features, such as non-slip grips on tools or medical devices, which can prevent accidents and improve outcomes. Additionally, the ability to incorporate materials that meet stringent regulatory requirements (e.g., biocompatibility, flame retardancy) through overmolding can facilitate compliance with industry standards and regulations, unlocking broader market opportunities.
  • Increased user comfort and aesthetics – Overmolding can significantly enhance the ergonomics and aesthetics of a product. Soft-touch materials can make devices more comfortable to hold and use for extended periods, improving user satisfaction and loyalty. Additionally, overmolding allows for a wide range of colors, textures, and finishes, enabling distinctive product designs that can strengthen brand identity and appeal to target markets.
  • Cost savings and efficiency – While the initial setup for overmolding might be higher due to the complexity of mold design, the process can lead to overall long-term cost savings. Overmolding can reduce the need for secondary assembly processes, lower the risk of manufacturing defects, and decrease material waste. Additionally, the enhanced durability and longevity of overmolded parts can result in lower warranty and replacement costs.
  • Competitive advantage – By integrating multiple functions and materials into a single part, overmolding can help companies differentiate their products in crowded markets. The ability to offer products that are functionally superior, more aesthetically appealing, and more durable can be a significant competitive advantage.
  • Environmental impact – Overmolding can contribute to sustainability goals by extending the life of products and reducing waste. The efficiency of the overmolding process can minimize the environmental footprint associated with production. Some high-performance plastics used in overmolding are also recyclable or have better environmental profiles than traditional materials, such as some metals or less durable plastics, contributing to a product’s overall sustainability.

Industries Rely On Overmolding

Overmolding with high-performance and engineering-grade plastics plays a crucial role across industries, offering solutions that meet the rigorous demands for durability, reliability, performance, and safety in challenging environments. Here is how overmolding with high-performance and engineering-grade plastics is used in various industries:

  • Aerospace and defense – Overmolding creates lightweight, durable components that withstand extreme conditions, enhancing fuel efficiency and performance. It can also improve equipment’s ergonomics and functionality through better grips and handles, sealing, insulation, vibration damping, and noise reduction.
  • Alternative energy – In the alternative energy sector, overmolding is key for manufacturing durable, weather-resistant components for solar and wind energy systems, from overmolding solar panel frames with sealing gaskets to creating fuel cell bipolar plates that are conductive, corrosion-resistant, and lightweight.
  • Industrial applications – Overmolding enhances durability and ergonomics in heavy machinery, adds safety and efficiency in tooling and automation through non-slip grips and protective layers, and extends the lifespan of material handling equipment with improved shock absorption and resistance.
  • Medical applications – The medical field uses overmolding to produce ergonomic surgical tools, skin-friendly wearable devices, and robust medical enclosures that are resistant to contaminants, bodily fluids, and repeated sterilization, thereby enhancing patient care and device longevity.
  • Oil & gas applications – Overmolding is critical for oil and gas applications by providing durable seals and gaskets that resist extreme conditions, protecting downhole tools from harsh environments, and encapsulating connectors and electronics for reliable operation in demanding settings.
  • Semiconductor Industry – Overmolding benefits the semiconductor industry by encapsulating components for protection against stress and environmental factors and enhancing thermal management and electrical insulation. It is crucial for maintaining performance, reliability, and appeal in electronics ranging from consumer goods to automotive and industrial systems.

Experience Overmolding Benefits and Value with Ensinger

Making complex overmolded parts requires careful design matching to ensure the components fit and work as intended. We have the material expertise and overmolding know-how to manufacture parts with intricate shapes with high precision. Contact us to learn how you can experience the benefits of overmolding.