Plastic Overmolding

Ever wonder how products like toothbrushes to car bumpers are made? It’s from a process called plastic overmolding, which is an integral part of modern-day manufacturing. But what is this process, exactly? How can it be used to make a variety of products? And, how can this process help you create the product you’re envisioning?

What is Overmolding?

Overmolding is a molding process that combines multiple materials to form a single component or a complete product. Typically, this entails one material being partially or fully covered by subsequent materials during the molding process.

To perform this process, plastic injection molders need specialized equipment. Specifically, they need unique injection molding machines that are equipped with two or more barrels. This is needed to allow the injection molder to insert two (or more) materials at a time during the molding cycle.

Now you may be wondering why plastic overmolding is performed. The answer is simple — it's done to protect the first material or to reinforce the component or product as a whole. We will discuss this in-depth later on.

What Materials are Used in Plastic Overmolding?

One of the materials that can be used in this process is, of course, plastic. Common resins include (but are not limited to):

  • PEI (Polyetherimide)
  • ABS (Acrylonitrile Butadiene Styrene)
  • PEEK (Polyetheretherketone)
  • PMMA (Polymethyl methacrylate)
  • HDPE (High-density polyethylene)

The point of plastic overmolding is to bring together various materials, so aside from plastics, there are dozens of other options to choose from. This includes things like rubber and metal. For example, you can use a combination of rubber and softer polymer or thermoplastic — the possibilities are endless.

But, material selection for this process can be tricky, so we at Richfields follow a strict compatibility chart when helping you pick out your overmolding materials. This ensures that the resins and additional materials you select are both chemically and thermally compatible and the best fit for your application.

What is the best plastic for overmolding?

Choosing the best plastic for overmolding really depends on what you're trying to achieve. It's a bit like picking the right ingredients for a recipe. In overmolding, you usually have a rigid plastic part (like a handle) and you want to cover it with a softer, more flexible plastic.

Now, if you want a softer feel, TPE (Thermoplastic Elastomer) is a good choice. It's a bit like rubber and gives a nice grip.

But if you want something tough and durable, you might go for a material like ABS (Acrylonitrile Butadiene Styrene). It's strong and can handle a lot of wear and tear.

It's a bit like choosing between a soft pillow and a hard pillow for your bed. The best one depends on how you want it to feel and what you'll be using it for.

So, in a nutshell, TPE for softness and grip, and ABS for durability. But remember, there are many other options out there too, depending on your specific needs.

an ergonomic glue gun made by plastic overmolding

What is an example of overmolding?

Think about a toothbrush. The handle of a toothbrush is usually made of hard plastic, right? That's the part you hold in your hand. Now, to make it more comfortable to grip, they sometimes add a softer, rubbery material on the outside of the handle.

Imagine if your toothbrush handle was all hard plastic; it might feel a bit uncomfortable to hold. So, they use overmolding to put that soft, rubbery layer on top of the hard plastic. This way, when you hold your toothbrush, it's more comfortable and less slippery because of that extra layer of soft material.

So, overmolding is like giving your toothbrush a comfy, non-slip grip by adding a different type of plastic on top of the main plastic part. It's all about making things more user-friendly!

a set of plastic overmolds

What are the Applications of Plastic Overmolding?

As this process can accommodate a wide selection of materials in a variety of combinations and formats, it can be used for nearly every application you can think of. From rubber grips to waterproof seals, plastic overmolding is a cost-effective and quick process that can create many kinds of products with reliable quality.

Richfields can help you make your plastic products using this method. We have experience fabricating products using this method for a variety of applications, such as (but not limited to):

  • Commodity items/Consumer goods
  • Automotive parts
  • Medical tools and devices
  • Appliances and appliance components
  • Electronic devices and enclosures
  • Product packaging and enclosures
  • And more!

Why Use Plastic Overmolding?

This process is typically used to fulfill a very important purpose: to improve the stability and ergonomics of a product. But, it can also be used to add flexibility to rigid parts, fuse components of a product, and add aesthetic appeal to a final product.

One of the most common examples of plastic overmolding being used in everyday products is household items. Things like your hairbrushes, kitchen tools, screwdrivers, and more use this process to combine different colored components, or to create rubber grips to improve the functionality of the product.

You might want to consider using plastic overmolding for your plastic project if you want to use a cost-effective way of mass-producing your products with functionality, stability, aesthetics, and ergonomics in mind.

What are the Benefits of Plastic Overmolding?

Another great reason to use this technique in plastic injection molding is that it offers many benefits for your project, such as:

  • Proper alignment, as the different components/materials are molded together. This helps improve stability, as well as resistance to vibration and sock.
  • Waterproof seal and electrical insulation for your product/component.
  • Improved part strength and structure.
  • Improved grip and ergonomics.
  • Enhanced design flexibility, and the capacity for multi-material components.
  • Reduced secondary processing, assembly, and labor costs — as everything is molded together in one shot.

Thanks to the strong bond that is created between the materials during plastic overmolding, you gain many of these benefits while also potentially reducing production time and costs.

 hand drill and other workshop tools ergonomically made by plastic overmolding

Get the Best Plastic Overmolding Services from Richfields

Overmolding is an essential tool to achieve functional, great-looking, and high-quality plastic products. At Richfields, you’ll receive not only the best plastic overmolding services but also an experienced team that will help you every step of the way.

From initial designs to packaging, our expert team will provide the ideal solution for your exact project requirements. And, thanks to our vast selection of equipment and materials, we have everything you need to create even the most complex and customized plastic projects. Contact us today to learn more!