What is Insert Molding? Process, Considerations & Applications

One of the most cost-effective processes in mass production in the modern times is insert molding. Aside from providing multi-material parts, insert molding enhances the durability of parts and offers more stable and stronger insert points for more complex parts.

In this post, all things about insert molding shall be laid down. A step-by-step process, as well as advantages are also included for your reference.

From basic information, to considerations before, during, and after using the method in various applications, you can have a better view of what insert molding is.

Defining Insert Molding: What is It and Why is It Preferred?

What is Insert Molding- Process, Considerations & Applications

As the term implies, insert molding is a production process where additional parts are injected or inserted in an already injection molded part. Before, the most common material used in insert molding was metal.

But at present, given the demand of mass production and the tight competition to more cost and energy efficiency, many have switched to plastic materials.

According to Lomont, injection molding now commonly refers to the process of molding plastic parts around other materials. While metals are still a common insert, plastics against plastics are now more prevalent in insert molding for many reasons.

Some of the common plastics used in insert molding are polycarbonate, polyethylene, thermoplastics, and other engineered plastics.

How Does Insert Molding Work?

When it comes to insert molding, timing is everything. It all starts with the preparation of the work space and the loading of the materials. The mold is pre-fabricated and then loaded in the machine.

Heat and pressure are thereafter applied. When the desired heat is achieved, the materials are inserted into the mold for forming.

Before the molten injection cools off, the inserts or additives are injected in the mold cavity. When it has already cooled down, the inserted part becomes an intact component of the insert molded part.

Upfront Advantages of Insert Molding

Upfront Advantages of Insert Molding

Due to the production of durable, shock absorbent, and lightweight products through insert molding, it has become a revolutionary method in mass production.

Thus, insert molding remains to be a cost-efficient and production efficient process with products with higher functionality and value.

Given all of these, insert molding is a go-to method in various fields. The most popular applications of insert molding are found in consumer production, aeronautics and aerospace industry, automotive, digital and electronics production, agriculture, and the medical field.

Step-by-step Guide on How Insert Molding Works

Step-by-step Guide on How Insert Molding Works

For you to have a more comprehensive view of how insert molding works, here are the steps that the process goes through.

Some companies incorporate other sub-methods in the whole insert molding process for greater precision and other more complex parts.

Step 1: Insert the Load Into the Mold

As basic as it may seem, the first step is the most important one. Positioning the inserts in the mold is the key to production success.

Keeping the parts to be inserted also needs a lot of skill and precision. Holding the inserts in place require other sub-methods such as the following:

a) Automated Insertion:

As the term implies, automated insertion is convenient but more expensive. This is because it makes use of robots and other high-end machines to ensure precision in loading the inserts into the molds.

The high turnaround of automated insertion is a good choice for bulk and uniform products. The higher capital outlay needed is its only downside.

b) Manual Insertion:

If you are only into low-bulk production, manual insertion is a more cost-effective technique. In this sub-method, the insertions are inserted manually by hand.

As such, it requires a full-time operator to oversee the production and to make the necessary detailed inspection.

On the downside, low precision and the tendency for repetition cloud the efficiency of this type of insertion. Exposure of the operator to high heat may also affect production and precision.

Step 2- The Molten Plastic is Injected Into the Mold

Step 2: The Molten Plastic is Injected Into the Mold

The use of the injection device takes place in this step. Here, the injection unit is injected into the pre-molten plastic, directly into the mold.

High heat and pressure are also incorporated in this phase so that all the canals of the mold are properly filled. Through high pressure and heat, excess air exits in the vents so that all the inserted parts completely adhere to the mold.

Step 3: The Mold is Opened to Get the Molded Part

The main objective of this step is solidification of the molded part. In this phase, the temperature is set very low to keep a uniform solidification. This also avoids backflow in the barrel, and shrinking in the molds.

When the right cool down temperature has been met, the mold is opened and the molded part is removed.

Step 4: The Molded Part is Separated From the Sprue

Sprues are the frames which will ensure that all the part components to be molded are present and intact. Sprues are common especially that most molded parts already come attached to them when they were first molded.

Thus, in this step, the sprue is separated from the molded part for post-processing. Much precaution is needed in this step so that the molded part will not break and not be damaged.

Step 5 Post Processing

Step 5: Post Processing

Post-processing includes further treatment to make the product more functional and polished. As such, this step involves various sub-steps depending on the need for the product. The following are the sub-steps included in post-processing:

a) Deburring:

Removing the excess parts or the unnecessary attachments to the molded product is called deburring. Using simple tools only, these excess parts are trimmed so that the right, precise product is achieved.

b) Heat Treatment:

To alleviate internal stress and foster greater durability for the product, the molded part is pressed in an increased temperature. It should be at a temperature which is higher than the temperature when it was molded.

Internal stress highly reduces product quality, hence, such heat treatment is needed to avoid deformation.

c) Humidity Control:

Part of the solidification process is humidity control. In this process, the molded parts are dipped in hot water with a temperature of 80-100C. The objective of adjusting humidity is to make moist absorption faster. In doing so, oxidation is prevented.

d) Finish:

This particularly points to surface finish. You must note that there are various types of surface finishing. Some of the most common, however, is surface printing and electroplating.

What you need to consider in this aspect is what the finish aims. Is it for material durability or purely aesthetics?

Points to Consider During the Insert Molding Process

Points to Consider During the Insert Molding Process

There are a lot of considerations during the insert molding process. For you to expand your knowledge on how to go about this process, you need to familiarize yourself with the following basic considerations:


The mold’s design is very important. The appropriateness of the mold design provides greater protection to the mold inserts particularly from the pressure and heat which could eventually damage them.

Properly Positioning the Inserts

Note that all drastic repositioning and the location of the inserts shall hinder an effective insert molding process. As a matter of fact, it will reduce product value as it would not be precise.

As such, you must position the inserts using all tools necessary to keep the molds intact during the whole process of insert molding.

Undercut Features

Undercut Features

For insert molding to be more effective and cost friendly, you should consider undercut features. The function of undercuts is to give additional strength to the molded parts. Such reinforcement as to strength is specifically true for the interior components. 

Consult With Reputable Firms

And if you are a newbie or would want better reinforcements for your insert molds, there are always reputable firms to consult with. These firms shall directly tell you which tools and technologies are most appropriate for your insert molds.

Factors to Consider Before Starting Insert Molding

Points to Consider During the Insert Molding Process

Although cost-efficient, insert molding is not that simple. Because it has its own complexities, there are different considerations to follow before insert molding. To get the best out of the process, the following factors need to be considered beforehand.

Insert Types

There are various types of inserts depending on the part to be produced. Thus, we must narrow it down to what should be found in a good insert type. The main factors to consider in choosing a type of insert is its endurance to heat and pressure.

Insert Location

When it comes to insert location, you must put in mind the function of the part to be produced and the volume of plastic that the mold can take.

These two sub-considerations are essential as they would determine, as you go on and master the process, the factors that would damage or strengthen the mold.

Making the Metal Part Inserts More Intact

The gaps between the metal part inserts allow moisture, hence, oxidation. You would not want this as it hampers even solidification. Thus, to ensure the production of stronger and more durable composite products, narrow the gap between the metal part inserts.

Choosing the Right Resin

Choosing the Right Resin

The right choice of resin is also a determining factor in the insert molding process. This is particularly important in the electronics field to lessen decay amongst glass, coils, and electronics parts.

Appropriateness of Mold Choice

Aside from making sure that the shape and size are precise, choosing the right mold is imperative. More than that, the right mold also provides more stability and holds the insert in place.

The Cost

Another important consideration is understanding the costs of production in insert molding. Aside from the materials cost, labor, maintenance, and operators’ costs must also be understood.

You also have to note that the piece-by-piece price of materials and components could also change through time. You must also be updated with such changes.

Production Volume

A proper cost-benefit analysis of production makes proper management of the production volume. Be it manual or automated insert molding, you must understand production volume trends coupled with an accurate analysis of the costs and benefits of the whole injection molding process.

Switching to Insert Molding: Advantages of Insert Molding in Production

Switching to Insert Molding- Advantages of Insert Molding in Production

Perhaps, the more interesting aspect of insert molding is the benefits that a producer can reap from it. As is the case, the following are the best and most common advantages of insert molding for producers and in various fields.



Insert molding is a one-shot, one-cycle process. As is the case, post-processing or post-assembly is eliminated in the process. Separate installation of parts is no longer done due to insert-molding.

The absence of assembly and the costs that go with it is one of the main reasons why insert molding remains to be a cost-efficient method.

Lightweight and Size-Efficient Products

Note that insert molding does not require a lot of materials and super elaborate tools. Thus, extensions and other material wastes are no longer included in the costs. Further, the lack of need for fasteners and other connectors makes the end-product lightweight and reduced in size.

Flexible Designs

Flexible Designs

Although a one-shot, one-cycle method, insert molding allows more versatility in mold designs even during the process.

Greater strength reinforcements and to keep in place the molds can be freely made during the insert molding. Most importantly, it makes the plastic to metal transition more flexible and hassle less.

Generates More Reliable Designs

Plastic mold is a very flexible material. Thus, design reliability is achieved especially with thermoplastic molds. Such material has higher shock absorption capacity, higher durability, and helps in preventing misalignment and infirmities in the mold design.

Applications of Insert Molding in Key Industries

Aside from knowing the advantages of insert molding, the applications of this process are also equally worth knowing. Here are the most common industry applications of insert molding.



This one is considered as an industry of the future. It banks on precision and lightweight materials. At the same time, it mostly uses high-end metals and materials for specific functions and assemblies.

With insert molding, these have all become possible. Thus, you would find insert molded products in the aerospace industry specifically in the production of communications and controls devices, interface switches, aircraft seats, and more.



This is another field which relies so much on insert molding. The primary reason is that it has replaced metal parts production using plastic molding. This makes a more cost-efficient production but with more durable and easier to replace automotive parts.

Medical Devices

Medical Devices

Like the automotive industry, insert molding allows the better and cost-effective production and manufacture of simple to complex tools and medical devices. Insert molds are also used in implants, sutures, prosthetics, surgical instruments, enclosures, knobs, blades, and electronic devices in hospitals.

Consumer Electronics

Consumer Electronics

The most extensive application of insert molding occurs at the level of consumer electronics. From solders, to fasteners, cords, coils, and home appliances, knobs, and electric wires, insert molding is a relevant process in this field.


A lot of military equipment used in tactical and defense exercises also benefit from insert molding. From battery packs, mono and binoculars, munitions, ballistic enclosures, and communication equipment, insert molding is a key factor in defense reinforcement.

Where to Avail Custom Insert Molded Parts?

If you want to avail of custom insert molded parts, you can always consult with reputable manufacturers. For instance, you can consult with Kemal Manufacturing for your custom insert molded parts.

You can check Kemal’s main website to know more about custom insert molded products and other production services for your needs.

Differences Between Insert Molding vs. Overmolding

Differences Between Insert Molding vs. Overmolding

It is a common misnomer that insert molding and overmolding have no stark differences. According to Rapid Direct, they are two distinct production processes but both are considered beneficial in a more cost-effective production.

As to process, insert molding involves the combination of non-plastic and plastic parts. On the other hand, overmolding makes use of plastic, molded into another plastic.

Both injection molding processes combine various materials, however, overmolding includes more steps compared to overmolding.

As to cycle and cost-efficiency, insert molding is a one-cycle method while overmolding is a multi-cycle process. While insert molding is easier and more convenient as a process, overmolding creates more durable, and ergonomic products with increased product value.


Generally, insert molding follows a rigid process. First, the materials are loaded in the machines. As the heat rises, the molten plastic is inserted into the mold.

After which, the molded plastic is cooled down before it is removed from the mold. The removed molded plastic is now separated from the spruce and prepared for post-processing.

There are a lot of reasons why insert molding continues to be a go-to production method for many manufacturers.

Aside from the cost-efficiency it brings, it is also beneficial in various fields and industries because of the durability of products and the usability of these products.

If you want to avail of the benefits of insert molding, you can check out reputable companies whose banner service is insert molding and more.



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