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What Is Insert Molding? Process, Considerations & Applications

Most of the products made now are a combination of both plastic and metal parts. However, to achieve a perfect cohesive product, insert molding is the preferred process. 

The reason behind using an insert molding process to encapsulate a metal component into a plastic component is its cost-effectiveness. Usually, the insert is a basic object, like a rod or a thread, but sometimes it can be quite complex, such as a motor or a battery.

The process is simple and consists of two major steps; firstly, you need to load the component in the mold. Secondly, fill the mold with molten plastic. Now, before getting into knowing more about the process of insert molding, let’s start with understanding what insert molding is all about. 

In this article, you will have answers to various questions, such as what insert molding is. What is the process to do it? What are the considerations to make during or before the process? And about its application. 

Understanding insert molding

The traditional manufacturing process involves melting the plastic at high temperatures and then molding it into desirable shapes using different techniques. Going by the same basic principle of plastic injection molding technique, insert molding also works similarly to it.

Usually, the geometric parameters of the product are measured, and plastic raisin is injected into the mold. Then, the solidification happens, and the finished product is removed from the mold. 

However, in insert molding, there is one difference. Before the mold closes in insert molding, the metal is inserted into the molten raisin. This means that the plastic will cover the product nicely, and there will be no uneven broken portions or cracks.

The primary objective of insert molding is to eliminate the need for additional screws or nails to join the products. Hence, you can have finished products with a smooth texture and firm grip that you can obtain all at once, such as a blade or a knife. 

Insert Molding, process

The process of inserting molding

There are four steps to perform this procedure:

Step 1 -Mold design with the inserts put in properly

For starters, you have to identify the type of insert material you are using and its thermal properties. Next, see if the mold cavity has enough space to fit the insert and the plastic can flow easily. If not, you may have to design a new mold design. Make sure that the insert material is compatible with the plastic raisin of your choice.

Always consider the size of the parts you are trying to mold in. When the size, depth, etc., are taken care of in advance, the molding process will take less time to finish. It is best to have inserts that have no sharp corners. Besides, the mold should have drafting angles so that the removal of the plastic portion is easy.

Step 2 – Mold preparation

Mold preparation is the first step in the insert molding process. There is meticulous planning and construction of the mold, which serves as the foundation for creating the final product. 

Make sure you have a clear understanding of the product specifications, such as its dimensions, material requirements, placement of inserts, etc. Moreover, a blueprint of the mold is generated that includes the shape, size, etc., of the product.

While engineering a mold, pay attention to cavity and core inserts. The overall goal should be to fill every void or space within the mold that shapes the final product. The cavity inserts form the external shape of the product, and cores create an internal part.

Step 3 – Insert placement

Performing this step is essential for the precise positioning of inserts within the mold before the injection phase begins. You can do it in two ways: 

  • Automation insertion – In this method, robots or automated processes are used to insert components into a mold. This brings accuracy and consistency while insertion is happening. Also, the automation process can handle high pressure and temperature. The process is quite fast, and you can have more production with this method. However, the drawback of this method is the high initial capital requirement.
  • Manual insertion: In this method, you will have to insert components into the mold with your own hands. However, remember that this method is ideal for low-production projects only. The major advantage is that you can keep a full-time operator and get a complete inspection of each part manually. 

This does not mean that there is no drawback to utilizing this method. You can miss out on accuracy, and repetition of commands also takes place in this method. The manual operator needs to wear gloves for manual insertion, and that can influence the talent. 

Step 4 – Inject the plastic into the mold

Once the insert is ready, it is now time to inject plastic into the mold. For this, you can use an injection unit to fill the mold with plastic. The high pressure in this phase forces the molten plastic to reach all corners of the mold. Besides, the air is evacuated through the vents in the mold, and you can be assured that the plastic is fully set in the inserts.

After this, it is essential to maintain the temperature for the uniform solidification. Moreover, to ensure that there is no backflow happening into the barrel, just apply pressure. The mold will eventually open up after cooling down, and then you can remove the finished product from the inserts. 

Types of insert molding

There are seven types of insert molding, namely:

Metal insert molding, plastic insert molding, glass insert molding, silicone insert molding, cavity insert injection molding, compression molding, & film insert molding. 

Considerations during insert molding

The major factor to consider is the design of the mold because it protects the inserts from high temperature and pressure. That is why it is important to design it perfectly. Other essential factors during the molding process include:

Insert placement

It is a must to keep the insert in a proper place to ensure proper execution of the process. Any disturbance in its location or placement can disturb the entire process. 

Compatibility of materials

Make sure the material you choose will always bond well during the molding process. This guarantees that the inserts and the surrounding material have strong compatibility.

Testing and quality assurance

It is necessary to keep an eye on the insert and the molded material. Please take a moment to observe how they work together to finish the process.

Reputable partner

Take some time before deciding on the final working partner because they have a significant impact on the final product. Make sure the company you are working with has all the information and experience needed for your project at hand.

Considerations before inserting molding

Please consider the below-mentioned factors to avoid any disaster during the process:

Design and insert selection

Pick a design that gives you compatibility between insert material and molding material. Moreover, they need to bond for a durable final product. 

Location of inserts

Always consider the function of the insert while trying to decide on its location because proper location determines the usage of forces on it. It also guides you on how much plastic you would need. 

Insert placement accuracy

It is important to position the inserts accurately for proper functionality and aesthetics. You can choose an automation method if capital investment is not a big deal. Otherwise, you can go for a manual method for insert placement. 

Cost consideration

Before starting with the project, it is important to create a budget map and evaluate the cost of different materials required in the insert molding process. To avoid any monetary pressure, make sure to manage the cost differences effectively. 

Advantages of insert molding

Insert molding is the best choice, considering the amount of time it saves you. Here are eight advantages:

Structural integrity

There is a permanent bond between the metal and plastic parts of the product in insert molding, which is quite questionable in other molding methods. The creative use of threads, undercuts, etc., is for a much better shelf life. 

Durability

With insert molding at your disposal, you can have enhanced product designs and manufacturing. It is surprising to see the precise way inserts are placed into a mold design. You can hardly achieve it with other molding processes. To put it briefly, it is much better to integrate plastic parts with metal parts to make it strong and durable. This way, there is less chance of error and malfunction.

Weight

Plastic is pretty lightweight compared to metal parts. This is the main reason why it is beneficial to combine plastic with metal for more strength. Most industries are using plastic as a molding material for this very reason only.  

Size

The best part is that you can cover much smaller or slimmer products with plastic using the insert molding method. You will not have to sacrifice any durability characteristic or any important feature, even if the product is small. 

Simply stated, size does not matter in this case. For instance, when the interiors of a vehicle are covered with plastic, there are many smaller or thin areas, such as a door. Now, it not only increases the interior leg space, it causes no harm to performance. 

Economical

You can save money in two ways with insert molding. It allows you to use cheaper material, and it is a one-step process. Traditionally, other methods involve many steps, and that means more use of energy & machinery, which leads to more expense and usage of power, unlike insert molding, where you can wrap the metal part in a plastic part in one go, and that too with your own choice of material. 

Efficiency

The entire process is so efficient that you will not have to perform it twice. This way, you can save a lot of time and any extra labor money. You just have to accurately align the design and other important components in the molding step for a beautiful finished product.

Variety of designs

When using insert molding, you have the liberty to make as many designs and shapes as you may wish to have. This isn’t easy to achieve when you are working only with metal products. However, when you combine plastic and metal, the possibilities are unlimited. There is much room for the product to expand, and engineering possibilities are more numerous in this case. 

Variety of materials

You have the opportunity to use different types of plastic resins in the insert molding technique. There are options to have eco-friendly thermoplastics. You can recycle them when you wish to discard them. They are lightweight and durable. These are ideal for heavy-duty industrial products. 

Applications of insert molding

Insert molding has various applications, such as: 

Insert Molding, applications

Automotive industry

Insert molding is used in the automotive industry to keep the electrical units covered with plastic. The standard components that need to be covered are connectors, sensors, wiring, etc. This way, you can protect them against environmental damage and keep them running for a long time.

The same technique is also used to cover handles, knobs, dashboards, and panels. Primarily, this is done to make them aesthetically appealing and improve their strength. You can also employ it on parts like housings, manifolds, and gaskets.  

Electronic and appliances

There are some delicate electronic components, such as PCBs, sensors, and microcontrollers, that require insert molding. It is for the protection against moisture, shock, and vibrations. 

Medical devices

Nothing is better than having protection for medical devices. The insert molding works wonders for devices like catheters, pacemakers, and surgical tools, ensuring precision, biocompatibility, and durability. Moreover, medical sensors, probes, and connectors are encapsulated to improve their functionality. 

Consumer goods

Use the insert molding technique for products such as screwdrivers, power tools, and gardening tools to improve grip. The tool’s metal portion can be expertly inserted into the plastic grip. 

They will become stronger and more resilient as a result. It may also be necessary for commonplace items such as kitchen utensils, toothbrushes, and razors in order to enhance both appearance and functionality.

Industrial and manufacturing applications

There are some parts of machines, like gears, bearings, seals, etc., that need inserted molding to increase their strength. The best part is that everyone can design a solution as per their own requirements and product specifications. 

Aerospace and defense

The aerospace and defense sectors also aid from insert molding. They use it to ensure lightweight yet robust parts for things like housings, connectors, and structural elements are safe & sound. Insert molding is also needed to cover common defense industry items like battery packs, munitions, weapons, binoculars, etc.  

Final words!

The bottom line is that insert molding is a cheaper method of producing high-quality products. The process only requires a step setup and gives you a precise final product. This technology is being adopted by many industries, with the primary goal being a profitable long-term investment. When done correctly, they can have a longer shelf-life for the products and save time by not having to assemble them twice. The use of high pressure and temperature does not bother the product at all. 

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