Insert Molding: Process, Advantages and Applications

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Insert Molding: Process, Advantages and Applications

Are you looking for a cost effective and standout industrial process to create a wide range of plastic parts? You might want to consider injection molding, and to be specific, insert molding.

Insert molding presents various benefits that reflect on the products. We take a moment to review this manufacturing method in more detail. Join us as we expound on the process basics, advantages, and applications.

What is Insert Molding?

As we have intimated, insert molding is a popular manufacturing technique that closely resembles the conventional injection molding process. As the name suggests, insert molding involves the inclusion of an insert in the mold cavity. After the production process, the plastic segment and the insert merge seamlessly.

There can be multiple inserts in the mold cavity. Equally, the complexity of the inserts is not limited. You will find motors and other complex inserts. The inserts can be metal, wood, or any other material. Most manufacturers add inserts to the mold cavity to enhance the functionality of the final product. As you will see in the coming sections of this article, insert molding has brought numerous benefits to the manufacturing sector.

How Does Insert Molding Works?

We can divide the insert molding process into five major steps: Loading the inserts, adding the molten plastic, uncovering the molded parts, removing the sprue, and post-processing. Here is a brief explanation of each of these steps of how insert molding process works.

Loading the Mold Inserts

The first step in insert molding is to load inserts, either manually or automatically. In the case of automation, a special machine inserts the inserts into the cavity. The advantage of this method is that the process is fast and accurate. It is a preferred method for large production volume. The manual insertion approach is done by skilled personnel. While it is good for cost savings, the manual method may only suit low volume production of parts.

Molten Plastic Addition

Next, molten plastic is injected into the mold cavity under intense pressure. A high level of pressure is necessary for the plastic resin to cover the inserts and fill the cavities. The type of plastic and the design of the nozzle are only some of the factors that determine the amount of injection pressure.

Opening the Mold

After giving the molten material enough time to cool and solidify, you can open the mold. Again, this can be a manual or automated step. By this time, the insert and the rest of the molded components should be perfectly merged.

Cutting off the Sprue

Often, the sprue will remain attached to the molded parts. You don’t need the sprue now, so you need to cut it. Any form of cutting can apply here.

Post Processing

This step of insert molding depends on the kind of product you are looking to achieve. Surface finishing followed by a final quality check are common where post-processing is part of the production process.

Common Insert Molding Materials

Your choice of insert molding materials can determine the quality and functionality of the resulting product. Apart from using plastic materials that are suitable with the process, the inserts too need to be compatible.

That said, a wide range of materials are applicable for insert molding. Thermoplastic resins are the most popular option for the plastic molding process. Their molding capability is good. Also, these resins have a variety of properties. Examples of these thermoplastic resins are nylon, polypropylene, ABS, and polycarbonate.

When it comes to the materials for inserts, the material options are also broad. Metal inserts that you may come across include brass, aluminum alloys, and stainless steel. However, the materials for the molding can also be non-metal insert. Some insert molding products are made up of wires, plastic, clothing, or even glass.

Advantages of Insert Molding

The insert molding designs present several advantages as compared to alternatives.


Insert molding delivers products that have a blend of good properties from different materials. A combination of plastic resin and a good sturdy insert results in an excellently structured final part. This combination can make the product more durable.

The metal insert provides rigidity while the plastic part offers damping capabilities. The result is a durable product that experiences reduced friction with surrounding components, but also withstands external knocks.

Weight Reduction

Plastics are typically lighter than metal components used to manufacture items such as connectors. Using insert molding components for such parts helps reduce the weight of a product. The best part is the strength of insert molded parts is excellent.


Insert molding results in products whose assembly requirements are reduced. The products tend to be smaller because of a higher strength-to-weight ratio.


The production process is economical because it results in reduced assembly and labor costs. A variety of inserts can be put in the mold cavity. The need for secondary processes is avoided, thus reducing production costs.


Insert molding can enhance efficiency in the manufacturing process in various ways. Consider the reduced assembly time when several components are integrated to make a single part. Also adding to manufacturing efficiency is the improved quality of the part. A better quality part translates to better performance.

Variety of Materials

The variety of materials in insert molding is huge advantage. It impacts heavily on material compatibility because the manufacturer has a lot to select from. This wide variety is also results in more functional products that ultimately lead to improved performance.

Variety of Designs

With the wide array of materials possible and different setups that one can achieve, the variety of designs is endless. Insert molding offers unmatched design flexibility.

Applications Of Insert Molding Parts

Many industries use insert molding products because of the higher product functionality, cost-efficiency, durability, and all the other advantages. Below are notable industries that extensively use insert molded parts:


The aerospace industry is also a popular user of insert molded parts. By using insert plastic injection products, the industry is able to reduce the weight of aircraft. Components that use this technology include controls, communication, seating, and door handles.


Before the emergence of this technology, many automotive parts were metallic and hence, extremely heavy and bulky. With insert molding solutions, many automotive parts are now smaller and lighter. Electronic devices, dashboard switches, and door handles are typically products of insert injection molding process.

Consumer Electronics

Insert injection molding products are popular in consumer electricals and electronics, mostly because of the insulating properties of plastic. In the absence of insert molding, many items would not be available or safe to use. Wall sockets and screwdrivers are good examples of this application. On electronics, this technology is evident in remote controls, smartphones, and laptops.

Medical Devices

Advancements in medical device technology has relied on the capabilities of insert molding. The industry is able to develop lighter and more hygienic components. Insert molding allows for the use both metals and plastics in test tubes, surgical devices, oxygen masks, etc.

Design Considerations For Insert Injection Molding Process

While insert molding has many advantages and applications, it can be messy. Some issues can arise and render the process unsuccessful. When you are designing an insert molded part, you want to wary of potential problems. We are talking about plastic resin incompatibility, insert breakage, sink marks, poor adhesion, and budget problems. There are ways to make the design a success, as discussed below:

Examine the Cost/Budget

The first thing you want to look at is your budget. It will cost you to buy the inserts, pay the molding expert, and so on. Figure out whether the total cost of the project is something you are ready for.

Identify Properties of Selected Insert

There are so many insert material options, but you need one that perfectly fits your project. Narrow those options and identify the properties of the insert.

Insert Location

The insert location determines many things: The force on the insert, the amount of plastic resin needed to cover it, and so on. Choose this location carefully for the overall functionality of the product.

Narrow Gap between Metal Inserts

Having a gap between metal inserts is understandable, but the distance should not be too much. First, you need the item to be as strong as possible. When the metal inserts are closer, the adhesion is stronger.

Choose the Appropriate Material

Equally important in the insert molding project is the choice of plastic resin. Make sure the type you choose is compatible with the insert. Some inserts are delicate, so you want to be careful about the insert material too.

Use the Right Mold

The design of the mold used in this process does more than just hold the molten plastic. It also keeps the insert intact. Make sure that the mold you have selected is capable of performing these roles effectively.


The possibilities in the manufacturing world continue to expand. Despite the transformations, we can all agree that insert molding continues to occupy a unique place. By simply fusing materials, it enhances the performance, durability, and visual appeal of a product.

If you are in the manufacturing business, incorporating insert molding can help minimize production costs. The quality of the products from this method is unquestionably good.

To inquire more about the possibilities in insert molding and the offerings at Aria Manufacturing, get in touch today.


Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.