5 Reasons To Choose Insert Molding for Plastic Parts

5 Reasons To Choose Insert Molding for Plastic Parts

Polymers have come a long way in the past 20 years—they’re so versatile that they can replace metal components in many applications. This has a host of benefits for you, but one of the biggest advantages is that plastic parts can lead to cost savings of over 25 percent. One of the main processes to produce plastic parts is insert molding, a process not known to many people!

Read on to discover five reasons to choose insert molding for plastic parts and explore a basic overview of what insert molding is.

What Is Insert Molding?

The term “insert molding” requires an understanding of each word. If you know anything about injection molding, you know that it’s a process in which molten plastic is injected into a mold with a particular shape. When the molten plastic cools and becomes released from the mold, it holds a particular shape.

Plastic functions in the same way in insert molding. It is injected as a hot liquid into a mold with a particular shape, then cooled until the liquid becomes a solid. However, this process introduces a new concept into the mix: the insert.

The insert is exactly what it sounds like—it’s a non-plastic part that is inserted into a mold so that the plastic and non-plastic will become bound together. Think about a pair of scissors. Most of the time, you’ll have two metal pieces connected by a plastic handle. The metal pieces are the inserts, while the plastic is created by molding.

Insert molding is an incredibly precise process. The plastic and the inserts need to be exactly aligned so that everything comes together properly. It takes a highly advanced facility, like the one at Polymer Molding, to ensure everything goes off without a hitch.

Insert Molding vs. Overmolding

If you’ve ever heard of insert molding, you may have also come across the term “overmolding.” Even though these processes may sound similar, it’s important to understand the distinctions that separate them.

Whereas insert molding uses a non-plastic part and molded plastic, overmolding uses plastic at all levels. In other words, one component of a product is produced using injection molding, and an additional layer of plastic (or potentially multiple layers) is molded over that first one. After two or more layers, you’re left with a finished product that’s the result of overmolding.

Either option will result in a high-quality product, but they produce much different results. While you cannot produce scissors through overmolding, you can make something like a vibration-dampening device for automobiles or tools.


With all that said, knowing how a process works isn’t the same as knowing why you should use it. Let’s take a closer look and examine the many benefits of insert molding for your component creation needs.

One major advantage that you’ll experience when choosing insert molding is durability. When you work with parts that have precise tolerances, you also work working with components that are far more reliable than you could hope to experience with other processes.

Let’s return to our scissor example from earlier. If you don’t work to ensure the plastic housing that holds the metal shears is formed exactly to the shears, you’re liable to experience shifting when the scissors cut. This leads to less reliable scissors and may even present dangers for your customers. When tolerances are tight, you don’t need to worry about things going wrong.

In addition, by removing the assembly step of the production process, you’re leaving less space for human errors to occur. Any time you rely on people to put your products together, you may experience unexpected results, even if you work with a fantastic producer.


The world is in a constant march toward smaller and thinner products. Do you remember what iPhones looked like back in the late 2000s? Things used to be much chunkier, but now, size is a drawback. When you produce your components with insert molding, you can shrink your overall products without sacrificing the durability of the components.

Consider all the plastic components of a car interior. When you shrink down the depth of car doors and dashboards, you expand the interior of the car, allowing the driver and passengers to enjoy more room.


Some people are inclined to make everything out of metal. While that may sound good on paper, you need to consider the overall weight of your components. Switching a few parts here and there from metal to plastic will greatly reduce the weight of your product. Just as the world moves toward smaller products, it is also moving toward lighter products.

When you design something that’s lighter, you improve usability, functionality, and performance. In addition, you cut down on your shipping costs!

Economic Option

Speaking of cutting costs, have you seen how much metal costs to purchase and work with? Plastic is the more economical choice by far, and you won’t need to sacrifice performance for savings! While you may assume that metals are far stronger than plastics, there are many plastics that have incredible strength.


If you’ve heard the phrase, “time is money,” you probably already have an idea of why insert molding is a great choice for you. Waiting for people or machines to take two separate parts of a product and combine them means that your customers need to wait that much longer before they can buy your product. Insert molding saves time, therefore saving you money.

When you need custom-molded plastic parts, Polymer Molding is the place to be. We can help you determine whether standard injection molding, overmolding, or insert molding will be the best option to get the results you’re after.

Now that you know these five reasons to choose insert molding for plastic parts, consider Polymer Molding for your next product. Reach out to our team to discuss the design process of your custom-molded plastic parts. We can help you figure out the best material for your product and provide you with a quote! Contact us today to learn more.

5 Reasons To Choose Insert Molding for Plastic Parts

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1655 West 20th Street
Erie, PA 16502

Phone: 814.455.8085
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