What is insert molding, and how does it work? This question is pretty standard, especially among newbies. Interestingly, people are well aware of injection molding. However, this molding method has various types, including insert molding. As you know, manufacturers prefer advanced processes.
The reason is that modern processes enhance product quality and precision and consume less time. Similarly, insert molding is also an advanced process that ticks all the boxes and manufacturers’ requirements. In this article, I will explain everything about inserting molding, how it works, and its applications. So, let’s get started!
Overview of Insert Molding
It is a type of injection molding that uses pre-premade parts (insert). This part is placed inside the mold cavity. The material (molten plastics) fills the mold. After solidification, the material dries on the surface of the insert or premade part. As a result, we get a product with metal and plastic covering around it.
This insert molding process is similar to the regular injection molding process. However, there is a single difference: It involves the usage of an insert. An insert is a premade material placed inside the mold. Remember, in injection molding, we don’t put anything inside the mold. Instead, only molten material fills the molds and adopts the mold’s shape.
Insert molding involves placing the insert inside the mold cavity. So, we don’t get a whole new product in this type of molding. Instead, we add a plastic covering or structure to the premade part of the insert. Let me give an example of a screwdriver. As you know, screwdrivers have plastic handles. The part made of steel or brass (thread) remains inside the plastic handle.
Such handles are made through the insert molding method. The screwdriver undergoes the insert molding process. The premade screwdriver is placed inside a cavity of the mold. The plastic material is then injected into the cavity of the mold. The mold is then closed, and the material undergoes solidification at a specific pressure.
After a set duration, the material solidifies in the mold cavity and makes the handle have a thread inside it. Remember, this handle helps you grip the screwdriver. The plastic joins the metal insert without any joints or gluing. Moreover, the bond between the insert and the plastics is powerful and can last for years.
How Does Insert Molding Work?
The process of insert molding is relatively straightforward. The whole molding is complete in a few steps. I will explain the steps in inserting the molding method in the section below.
1- Formation of Insert
This process starts with forming an insert, which can be made of any material. The insert is the part you want to use as a starting material. Imagine you want to get a plastic handle on the screwdriver. The initial raw screwdriver without a handle will be inserted in such a case. You can use any material, e.g., steel or brass, to make this insert.
Quick Highlight: In this explaination, I am using the example of the formation of a screwdriver with a plastic handle. We will create a screwdriver handle with a metal thread inside it. This will help you better understand how this process works. The working process of this insert molding will be the same for every product.
2- Mold Creation with Insert Placement
The second step is to create a mold. Mold creation is standard in both insert and regular injection molding processes. The cavity of the mold must have an insert placement position. This is where you’ll position the insert. The insert shape should be accurate to fit this position perfectly. A clamp must be inside the cavity to keep the insert in one position. Remember, if the insert (premade) material moves, it will affect the precision.
3- Injection of Molten Materials
Generally, molding machines come with an injection unit. This unit injects molten material inside the mold’s cavity. Let’s continue discussing our example, which is the creation of a screwdriver handle. We will use a screwdriver as an insert. Remember, the mold cavity consists of an insert placement position.
In your case, the insert can be anything on which you want plastic material to make a bond. We will have the screwdrivers (insert) in the mold. After that, the injection unit will inject the molten plastic inside the mold. Once the mold is filled, you will have to close the mold perfectly to avoid any leakage of molten plastic.
Remember, the insert inside the mold must be stable and should not move. For this purpose, the mold cavity has clamps that stabilize the insert. Moreover, the injection of molten materials into the mold happens at high pressure. Any mistake in this step would affect the final product. The molten material will join the insert present inside the cavity and make the bond with it.
4- Solidification of Molten Materials
After injection, the solidification of molten material starts. In this step, the temperature inside the mold reduces, causing the molten plastics to solidify. As you know, the molten material will begin to solidify on the surface of the insert, making a strong mechanical bond with the insert surface.
In our case, the insert (screwdriver thread) will get embedded in the plastics. As a result, the screwdriver thread will get a plastic handle. Once molten plastics solidify completely, the ejection process is carried out. This process ejects the insert from the mold using plastic material. We will have a screwdriver with a plastic cover on its thread.
5- Trimming & Finishing
After ejection, you’ll have the insert embedded perfectly with plastic material. However, the plastic part will require additional trimming and finishing to create a refined shape.
In our case, we will get a screwdriver with one thread covered with plastics. This plastic cover will give us grip. However, the plastic cover can have a rough surface. Therefore, additional trimming will remove surface roughness. As a result, you will get a perfect surface that offers ideal gripping.
Quick Highlight: This insert molding ensures the molten material creates a strong bond with the insert. You can join any two materials with ease and get your final product. This joining does not require any additional gluing or joints. Moreover, it is not only limited to screwdrivers. I used a screwdriver example to make it easy for you to understand this process.
Key Considerations & Factors to Consider for Insert Molding
The insert molding process is not very complex. However, there are a few things that you must consider when using this method. It will help you create products of the highest quality. Here is the list of those key considerations:
- First, you should carefully analyze the insert material. It will help you choose the right type of plastic. As a result, the bond between the insert and the plastic will be strong and durable.
- Don’t keep the temperature high when you inject molten material into the mold. This will make the material extremely molten. It will increase the chances of leakage.
- The mold shape plays a key role in the insert molding process. Therefore, I recommend hiring an expert to design the mold cavity. Moreover, you should ensure the proper insert placement in the mold.
- Last but not least, the insert’s stability in the mold is crucial. You should make sure that the insert does not move during molding. Slight movement will result in inaccurate products.
Advantages & Disadvantages of Insert Molding
It will be unfair if I don’t discuss the pros and cons of this molding method. No doubt this insert molding is an excellent process. However, its pros and cons go hand in hand. You must understand both to get an idea if this process is suitable for you or not.
Advantages of Insert Molding
- Insert molding helps join two different materials securely. The bond between two materials will last for many years.
- This molding method does not require any fastener or screws to join two different materials. The bond between the insert and the material does not need anything like glue.
- This manufacturing method is very reliable in the long term. The reason is that it does not use screws or adhesion that could get loose over time. This ensures the reliability of the products in the long run.
- This process has no bolts or fasteners to create joints between two materials. So, the final product remains very lightweight. There is no additional weight on those fasteners.
- This process is rapid. The solidification process quickly completes once you inject molten material into the mold. As a result, you get the final product with less time consumption.
- This insert molding method gives you more control. For example, you can use a complex-shaped design when creating mold. As you know, the final product you get is similar to the shape of the mold. So, it becomes easier to make products of complex shapes.
- It gives excellent repeatability. All you have to do is to create the mold. Once done, you can use it to create thousands of products of the same shape and size. This is particularly more beneficial when you need a product in bulk quantity.
Disadvantages of Insert Molding
- The insert molding uses a dedicated machine, which is very expensive. If you need a product in small quantities, this process may not be cost-effective.
- This method also needs some additional tools. The cost of tooling can further be a hindrance for those who have tight budgets.
- Material compatibility is crucial. The insert and molten material you use must form bonds with each other. Before starting, you’ll have to analyze the materials. Misfit materials will result in low-quality products.
- It requires a high level of attention, especially during insert placement. Remember, the insert can move during the process. If it moves, you might get faulty end products.
Applications of Insert Molding
Insert molding is a very versatile manufacturing process. Various industries use this to enhance their productivity. In the section below, I am giving you a table indicating applications of this process:
| Industry | Application of Insert Molding |
| Automotive | Car door handles, engine components, battery terminals. |
| Electronics | USB ports, laptop hinges, charging cables |
| Medical | Surgical instruments, hearing aids, pacemaker housings |
| Aerospace | Control panel buttons, insulated wiring, cabin components (seats, handles). |
| Consumer Products | Power tool handles, kitchen utensils, electric toothbrushes |
| Industrial Equipment | Gears & bearings, hydraulic fittings, electrical enclosures. |
| Telecommunications | Antenna components, fiber optic connectors, cell phone housings. |
Conclusion
The insert molding process is handy in making products of two different materials. Many industries use this molding type to create complex-shaped products. In this article, I’ve discussed all the ins and outs of insert molding. Remember, this is a process that uses insert or pre-made products. It adds plastic or rubber material to the existing product. For example, you can create door knobs, knife handles, and the list goes on.