Om Raj Tech: Insert Molding and Overmolding Solutions for Innovative Manufacturing

Insert molding and overmolding are two advanced techniques in the injection molding family that help manufacturers create stronger, lighter, and more functional products. At Om Raj Tech, we specialize in these processes to deliver reliable, high-quality solutions for different industries. Both methods involve molding thermoplastic resin around an insert, but each process has unique steps and benefits. Let’s explore them in detail.

What is Insert Molding?

Insert molding is a process where a pre-formed part, often made of metal, is placed inside a mold, and then molten thermoplastic resin is injected around it. Once cooled, the result is a single, integrated unit that combines the strength of the insert with the flexibility of plastic. Common examples include electrical connectors, medical catheters, knife blades, and hand tools such as screwdrivers.

This method is valued because it reduces assembly costs, minimizes labor, and increases design flexibility. Instead of joining parts with glue or fasteners, insert molding creates one durable piece. Manufacturers prefer this approach when they want compact, lightweight, and dependable products.

The Insert Molding Process

The insert molding process begins with thermoplastic resin introduced into a hopper. It is heated to a temperature between 300° and 650° Fahrenheit until it becomes molten. Under pressure, the resin is injected into a strong steel mold where it flows around the insert. As it cools, the part solidifies into its final shape.

Two main types of resin are used: thermoplastic and thermoset. Thermoplastic can be reheated and reshaped multiple times, while thermoset becomes permanent once cured. Everyday examples of thermoplastic include milk jugs, whereas thermoset materials include items like car tires.

Molds used in this process are typically made of steel and include features such as water lines for cooling, ejection pins for releasing the part, and cavities designed for precision. A simple open-and-shut mold can work without complex components, though advanced designs may require additional parts for accuracy.

Role of Molding Inserts

Inserts are the base parts around which plastic is molded. These inserts can be as small as a dime or much larger, depending on the application. To withstand the high pressure and temperature during molding, inserts must meet strict durability requirements. Properly designed inserts ensure that the plastic bonds securely without altering the shape of the insert.

Undercuts or bosses on inserts often provide extra grip for the plastic, creating stronger retention. Another factor to consider is whether the mold can seal tightly around the insert to prevent excess plastic from escaping and creating unwanted flanges.

What is Overmolding?

Overmolding is similar to insert molding but takes the process one step further. It involves molding two different materials together to create a single finished product. For example, a toothbrush with a hard plastic core and a soft rubber grip is an overmolded item. In this process, one material is molded first, and then the second material is injected over or around it.

This method is often performed on a specialized machine that allows for two injections in one cycle. After the first material is molded, the machine rotates the mold, and then the second material is injected. This results in a part with a powerful bond between two different plastics.

Benefits of Overmolding

Overmolding allows manufacturers to combine materials with different properties—such as a hard base with a soft grip—without adhesives or secondary assembly. It improves the product’s functionality, comfort, and aesthetics. Examples of overmolded products include medical devices like cannulas and catheters, consumer goods like scissors, and industrial tools that require both strength and comfort.

By creating parts in a single process, overmolding reduces costs, shortens production time, and increases overall product quality.

Key Differences Between Insert Molding and Overmolding

While both processes involve molding around an existing part, the main difference is in the number of steps. Insert molding is usually a single-shot process, where resin encases a pre-formed insert. Overmolding, on the other hand, is a two-shot process, where two separate materials are molded together in sequence.

Insert molding is often chosen for applications where metal strength needs to be combined with lightweight plastic. Overmolding is ideal for creating products that need both rigidity and flexibility or a mix of textures.

The Role of Molds in Both Processes

Molds are central to both techniques. They guide the resin during injection and shape the final product. Key mold components include cavities, pins, and alignment tools. A well-designed mold ensures accuracy, structural integrity, and efficiency in production. At Om Raj Tech, we design and manufacture molds that deliver precision and reliability for even the most complex applications.

Real Case Study in Insert Molding

In the early 1980s, insert molding was used to solve a unique medical challenge. Traditional catheters were assembled with glue, which was inefficient and often unsafe. Engineers explored insert molding to create multi-lumen catheters in one piece without adhesives. The solution involved molding around stainless steel mandrels to form open passageways after removal. This innovative approach eliminated leakage risks and improved patient safety. Today, such solutions continue to be used in advanced medical devices.

Om Raj Tech’s Commitment to Innovation

At Om Raj Tech, we take pride in offering advanced insert molding and overmolding services. Our team has extensive experience in designing, prototyping, and manufacturing high-quality molded components that meet strict industry standards. Whether for medical, automotive, consumer, or industrial applications, we ensure that every part we produce is reliable, durable, and cost-effective.

We work with modern injection molding machines, top-grade materials, and expert engineers to provide solutions tailored to your exact needs. From concept design to full-scale production, Om Raj Tech delivers results that enhance performance and efficiency for your business.

Serving Multiple States with Excellence

Om Raj Tech proudly serves clients across the United States, including Michigan, Ohio, Indiana, Illinois, Wisconsin, Kentucky, Pennsylvania, New York State, and Iowa. Our reputation as a trusted partner in custom injection molding solutions continues to grow, thanks to our dedication to innovation, quality, and customer satisfaction.

Om Raj Tech specializes in advanced manufacturing solutions like thermoforming, fiberglass, and injection molding.