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What’s Insert Molding and What Is It Used For?

A whole spectrum of items we use in our day-to-day lives are constructed using more than one material. Take the kitchen knife, for example, it has a fine metal blade with a plastic handle. While it may seem one of the simplest tool around the house, it calls for careful and creative thinking when it comes to what techniques should go into adhering the different materials together and making the end product handy as well as functional.

One such amazing technique is insert molding that finds surprising applications in various industries and makes things aesthetic, easy to handle, as well as easy-to-execute in terms of the process. Scroll down for some in-depth information on insert molding, its benefits, applications, the process, as well as how does it differ from overmolding.

insert molding

What is Insert Molding?

Insert Molding is the process of injecting plastic into a mold cavity and insert piece before plastic injection molding in order to yield a single piece with the insert engulfed by the plastic. It’s a process used to bolster the shape and functionality of plastic injection molded components. In other words, it refers to integrating other components, mainly metal parts into the injection-molded product directly.

For example, if you need to bond some metal inserts to plastic, insert molding calls for putting the metal carefully inserts inside the mold before heading towards the injection of plastic. Subsequently, the inserts are going to be covered by the plastic during the process, firmly bonding the insert to the material after properly cooling and curing the same.

Insert Molding clubs plastics and metal, as well as several other combinations of components and materials into one unit. The idea is to employ engineering plastics for enhancing the tensile strength and wear resistance of products, while keeping them lightweight at the same time. In a nutshell, the process involves molding or building plastic parts around other components and inserts that can be non-plastic in nature. The inserted item itself can be a simple object, such as a rod or a thread, while being a complex motor or battery at other times.

What is Overmolding?

Overmolding is termed as a form of insert molding by some. As the name clearly suggests, overmolding is the process of molding plastic over some other already-molded component. The primary component is created inside an injection mold, further being placed into another mold to integrate the over-molded material.

The technique of overmolding combines more than one plastics to achieve different results in terms of aesthetics as well as practicality. For instance, more than one durometer plastics are used to mold a much softer plastic over a tough one to allow for an easier grip on a part. Adding multi colored plastics to an overmolded component can make it stand out from other similar products out there. Items like toothbrushes, power drills, screwdrivers and other tool handles are often worked up using the technique of overmolding.

Overmoldeding finds numerous applications in different industries. The process is not solely used to build consumer products, but also many high-value items, such as engine components. When it is used in the medical industry, it can make delicate items more clean, stable, and moisture-resistant, while it eliminates the need to perform additional assembly steps using glues and adhesives when employed in the automobile sector. It’s also used to make appliance knobs, controls, electrical parts, and encapsulated electronic devices.

Insert Molding vs Overmolding

Going through the two processes, it can be stated that insert molding and overmolding are two very different techniques that yield their own types of products. Some might wonder what’s the chief difference between insert molding and overmolding. In simple words, insert molding is all about molding plastic over a component that’s not plastic in itself, while overmolding involves covering another plastic component with a rubber-like plastic layer Overmolding is often applied to create elements like ergonomic grips, aesthetic features, or bump stops.

The overmolding process actually happens when a particular material is coated over another material. The primary layer is carefully molded first, followed by molding the additional plastic layer or multiple layers around the initial component to finally end up in a single well-crafted product.
On the other hand, insert molding happens when insert materials are carefully injected into a specific mold cavity before heading to plastic injection. The end product here is a piece having the insert finely encapsulated or engulfed by the plastic. The process is all about a cost-effective and fast assembly process, while yielding compact products.

The Process of Insert Molding

Typically, the process of plastic manufacturing calls for softening or melting plastic at very high temperatures, followed by molding it into different shapes with various techniques to yield a final product. Insert molding works quite similar to the same, wherein molten resins are carefully injected into a mold specifically designed to cater to the the geometric requirements of a component. The resin is then allowed to harden, further removing the same from the insert mold. What makes insert molding different is that the metal part is inserted into the resin in the molten form prior to closing the mold. As a result, the plastic covers the component or part completely without any cracks while ensuring a consistent wall thickness throughout the product. The products can range from complex machine parts to basic items such as a blade or a tube.

The Benefits of Insert Molding

Insert molding comes with numerous benefits that are evident across a range of industries. Some of them are listed below.


Insert molding increases the individual strength of each component, resulting in plastic parts with integrated components that are corrosion-resistant, durable, strong and reliable. The process makes enhanced product designs with great precision in terms of the manufacturing. In fact, any other molding process can’t yield the level of precision with inserts are placed into a mold design with insert molding. The fact that the process doesn’t involve any assembly minimizes manufacturing errors.

Compact and Lightweight

Plastic components are much lightweight than their metal counterparts, which enhances their functionality and performance, ranging from increasing fuel efficiency to making surgical instruments more handy. The process helps in manufacturing much compact and smaller parts, that too without compromising on their performance or durability.


Insert molding allows the use of affordable materials, such as going for resins that are cost-effective than metals. Plus, the molding production is quite cost-effective in itself, while the insert molding process is a one-step deal. This in turn, streamlines labor charges and assembly expenditures, further serving as a low-cost technique to produce reliable finished items.


The manufacturing process involving insert molding doesn’t call for a second assembly step as the insertion of components is performed within the molding stage. The step of placing an insert into the mold achieves some form of automation, thereby sparing the time and effort of the technicians and being very efficient.

Variety In Design and Material

Insert molding employs a variety of plastic resins for the process, mainly eco-friendly thermoplastics such as nylon, polyethylene, and polystyrene. Apart from being recyclable, they are all durable, lightweight, and apt for heavy-duty industries as well as consumer products. Other common materials include elastomers, epoxy, and flexible natural rubber. Speaking of design, insert molding allows a range of shapes and designs for the components, thereby suiting numerous industries.

Common Applications for Insert Molding

Insert molding is widely used in a bunch od industries ranging from medical devices and instruments, automobiles, consumer products, and electrical parts or components.

Consumer electronics

Circuit boards or electronic components are put in the injection mold, further embedding them within the material to waterproof and protect them. This prevents shock and vibration damage to delicate electronics. Insert molding is also used to create functional strain reliefs on cables. Its applications extend from small electronics to large HVAC systems.

Automotive and Trucking

The process is used for replacing several metal components to plastic for minimizing their weight and improving fuel economy.


A whole range of delicate surgical instruments and medical-grade devices employ insert molding for making plastic parts with metal components.


Insert molding is used for manufacturing aircraft interiors, communications, controls, as well as navigation components.


The process is used-in mold decorating and-mold labeling which has many advantages over conventional labeling methods. It provides tough, wear-resistant and chemical-resistant labeling on high wear surfaces. This labeling technique is used to label refrigerated containers tubs exposed to moisture during transportation and storage.


Whether its insert molding or overmolding, the two different techniques serve their purposes in the most unique ways and come with vivid applications across different sectors and industries. Speaking of insert molding, the technique is witnessing increased usage across the globe due to the amazing benefits it brings along, ranging from the great efficiency it provides to the whole team and the process, the cost-effective process, the amazing possibilites of integrating variety into the designs, as well as yielding compact products that are lightweight in nature. It’s surely amazing how a layer of plastic can make even the most complicated products weather-resistant, stronger, durable, handy, more functional as well as budget-friendly.

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