There are several specific categories and processes that might be used within the broad realm of plastic injection molding, and one that’s often used across many industries is known as over-molding. Referring to the layering of multiple polymer application techniques to create a single component, over-molding is quite valuable for many applications.

At EnviroTech Custom Injection Molders, over-molding is just one of several injection molding processes we’re happy to provide to varying clients depending on their needs. Let’s look at some of the simple terms involved in this process and how it works, plus how over-molding compares to other similar processes and some of the applications over-molding is typically best for.

Over-Molding Basics and Terms

Over-molding, as we mentioned above, refers to the layering of at least two polymer application techniques onto the same part or component. The first layer is known as the substrate, which is usually a base plastic material that can be heated and then molded into shape using a specific injection molding process.

The second layer of over-molding involves injecting additional polymer onto the part in order to create a more complex shape or form. This secondary material can either cover the entire part, or just certain sections of it – and this is known as the over-mold.

A Simple Example of Over-Molding

For those just learning about this process, a simple example that may help you visualize it is to consider a typical toothbrush. This product usually features a handle made of a hard plastic material, which serves as the substrate, and then a softer rubber material (the over-mold) that covers the handle.

To create this kind of product or many others that utilize this concept, over-molding is used to combine the two different plastic materials into one component.

Interlocking Plus Bonding

During the over-molding process, the substrate and the over-molded material will often be physically connected in more than one way. Not only will the two materials bond together, but they may also be interlocked due to their shape and form. This kind of physical connection makes over-molding a particularly useful process for many types of products.

Comparing Over-Molding to Co-Molding

It’s important to note that there is another technique similar to over-molding: Co-molding, which involves mixing materials within a mold. The major difference here, however, is that co-molding uses the same molding technique for different materials; over-molding, on the other hand, uses different techniques within the same mold.

For this reason, co-molding is more often used for components that require more complex structures; over-molding is typically best used for parts and products that need to be made with different materials but don’t necessarily need as much complexity.

Comparing Over-Molding to Insert Molding

Yet another process that’s similar here is insert molding, which refers to inserting or incasing a fully completed plastic part inside another material. In this way, the insert part will stay in place due to the surrounding material – but with over-molding, the different materials are more connected and intertwined.

Insert molding is common for products that will see repeated use, such as medical device components or sports gear. Over-molding, on the other hand, is most often used for products that require more intricate shapes and designs, such as consumer electronics or automotive parts.

Over-Molding to Create Flexible Product Areas

Another common use of over-molding is found on distinct parts of a given mold rather than the entire mold itself. For instance, certain products that are rigid in most areas but require certain flexible sections for ease of use can be created by over-molding. The flexible sections are usually made from softer materials, and the rigid sections are made from harder materials – all combined within one single molding process.

Over-molding is an extremely useful plastic injection molding process that has applications in many different industries. By layering different materials together, it’s possible to create components with both interlocking and bonding qualities – making it a valuable technique for many products.

Whether you’re looking for increased complexity or requiring flexible sections on a product, over-molding can be used to provide the desired outcome. When deciding if this type of process is right for your application, it’s important to consider the types of materials you’re working with as well as your product’s desired complexity. By analyzing these factors and understanding the benefits of over-molding, it’s possible to make an informed decision on whether this process is right for your project.

And at EnviroTech Custom Injection Molders, we specialize in helping our customers make wise decisions about their product’s design and molding. By utilizing our wealth of experience and expertise, we can work with you to create the perfect solution for your unique needs. Contact us today to learn more about how EnviroTech can help you find success with over-molding or any other plastic injection molding process.