Overmolding and insert molding are two injection molding processes used in the manufacture of commercial and industrial products. Both use the same concept, that is, a plastic part is molded onto another part. However, both differ in terms of the properties and functions of the “other party”. Therefore, they have different areas of application.
Using any of the methods without proper understanding can lead to several adverse effects. Common consequences include product defects, wasted time and materials, and increased production costs. That's why this article compares insert molding to overmolding to help you choose the right process for your project.
Insert Molding Overview
What is insert molding?
Insert molding is a manufacturing process that involves pouring plastic over a non-plastic part (usually metal, also known as inserts). The process follows the normal injection molding process with the addition of an insert. An insert is placed in a mold and molten plastic is injected into the mold. This means that the insert is covered with plastic material. Ejection then occurs.
Insert molding can be done in two ways: manual and automated. On the one hand, a manual process is less expensive and provides easier control for the operator. On the other hand, the automatic process guarantees repeatability, error reduction and overall production efficiency.
Insert Molding Applications
Inset molding is widely used in the aerospace, medical, electronics and defense industries. Common examples of insert molding include products such as screwdrivers, spring contacts, clips, and pins.
Advantages of Insert Molding
Due to their advantages, embedded molds can be used in a variety of ways. Below are some reasons why you should consider this process in your project.
- Insert molding is suitable for creating strong, reusable connections.
- It's profitable.
- Suitable for producing thin-walled non-weldable boxes
- The need for assembly of parts is reduced.
- Improves the combination of plastic and metal parts, increasing the performance of the parts.
- Suitable for making anti-traction, anti-vibration, anti-moisture and anti-dust products.
Disadvantages of Insert Molding
- The insert mold is suitable for various products. However, it is not suitable for others. Use the following. Below are some disadvantages of the procedure.
- Resin may shrink or penetrate the insert, causing functional problems.
- Requires a high level of technical knowledge for complex parts.
- It requires multiple manufacturing technologies, i.e. metal and plastic.
Overmolding Overview
What is overmolding?
Overmolding is another common injection molding process that involves molding one plastic material over another plastic material. It is a double injection molding process. Therefore, it is also called two-component injection molding.
Overmolding involves injecting plastic into a mold to form the first plastic part (also called the substrate). After solidification, the substrate is placed in another mold and the second plastic material is injected (overmolding). Finally, the substrate is covered with the overmolding. Ejection then occurs.
Important: Both processes occur simultaneously, that is, substrate formation and overmolding do not occur separately. This ensures that both plastic materials fuse together.
Overmolding Applications
Overmolding of injection molded parts is widely used in many industrial and commercial sectors (even synonymous with insert molding). Overmolded parts can be used in the following ways:
- Products that require a comfortable grip, e.g. B. Plastic handles.
- Parts used in environments subject to vibrations, heat and electric shocks.
- To create more aesthetically pleasing products by casting complementary or contrasting colors.
- Products with raised or recessed areas that display the company name or logo.
Advantages of overmolding
Due to its advantages, overmolding can be used in various applications. Below are some reasons why you should consider this process in your project.
- Increasing the flexibility of the material through the use of different plastic parts.
- Plastic welding or other connection mechanisms such as gluing are not required.
- Improve product performance by increasing product durability.
- A firm connection is created between the two plastic materials.
Disadvantages of overmolding
Overmolding is suitable for some products. However, it is not suitable for others. Below are some disadvantages of the procedure.
- Multiple injection molding operations are required, increasing cycle time and production costs.
- The two-step process requires more tooling than a single injection molding process, increasing development costs.
- Delamination can occur due to fluctuations in the ideal temperature range.
- Additionally, special tools may be required, which also increases development costs as suppliers may not have them and charge higher fees to produce them.
- Not all plastic materials are compatible with each other. Therefore, you should work with your injection molding service provider to find the best material.
Differences between insert molding and overmolding
Both procedures are similar. However, there are many differences you need to consider before choosing the right process for your project. The difference between overmolding and insert molding includes the following:
Insert Molding vs. overmolding: process
The main difference between insert molding and overmolding is the molding process. On the one hand, overmolding is a two-step manufacturing process (hence the name two-component molding) in which one plastic (overmolding) is cast into another plastic (substrate). Insert molding, on the other hand, involves pouring plastic over a non-plastic material. Unlike the overmolding process, this is a single-step manufacturing process (the insert is manufactured separately).
Insert Molding vs. overmolding: production speed
Both procedures are time-consuming. However, insert molding is relatively time-consuming due to the application of an additional layer to the product, that is, the complete product surrounding the insert. In contrast, overmolding requires partial coating. Furthermore, insert molding does not require separate production of the two plastic parts, unlike overmolding, which involves a substrate and a forming process.
Insert Molding vs. overmolding: material selection
For one, overmolded parts consist of plastic parts that can form chemical bonds with each other. However, not all plastic materials are compatible with each other. For example, ABS is compatible with ABS, polycarbonate and polyethylene, but not with POM. On the other hand, most plastic materials are compatible with non-plastic parts. Therefore, insert molding has wider material compatibility.
Important Note: Familiarize yourself with the different injection molding materials before choosing a process. It is best to seek advice from an injection molding service provider when choosing the right material.
Insert Molding vs. overmolding: costs
Overmolding is a more expensive project due to the two spraying processes. Additionally, insert molding reduces assembly costs and improves project productivity, especially in high-volume production. However, it is more expensive than injection molding.
Should I choose insertion or overmolding?
The correct process between insert molding and overmolding depends on the application. However, it is impossible to choose one for your project. However, you can determine the correct process based on the variety of insert molded and overmolded parts. Consider the following factors:
When is insert molding used?
Consider insert molding when producing products with the following properties or applications:
- When working with prefabricated substrates.
- If the substrate contains computer-controlled parts, metals, or wires.
- The final piece must be a solid piece.
- Coat metal parts or other non-plastic parts with a plastic polymer or resin, such as: B. a screwdriver.
When is overmolding used?
Consider overmolding when manufacturing products with the following properties or applications:
- The finished product can be made from rubber or thermoplastic.
- Finished products have multiple layers of color.
- In the production of the second layer and the substrate, this occurs simultaneously.
- No need to disassemble the final part
- If you want to improve the feel and texture of a piece
- If you want to add padding and shock absorption to your household items.
University Degree
Overmolding and insertion molding are injection molding processes that use the same concept, that is, overmolding one plastic part over another. However, they differ in process, cost, speed, and material selection. Before deciding on any of the procedures, you must understand it completely. That's why this article did a comparison between insert molding and overmolding to help you decide.
Common questions
What is two component injection molding?
Two-component casting is another name for overmolding. Also known as double-shot, multiple-shot, or dual-shot injection molding, it simply involves injecting one plastic part (overmolding) into another plastic part (substrate) at the same time. The process occurs simultaneously and allows engineers to produce parts from different materials or in different colors without assembly.
What are inserts in injection molding?
Inserts are non-plastic parts that play an important role in insert molding. They are placed in the mold and injected with plastic material. Most often these are simple objects, e.g. B. wires or rods. However, they can also be complex, e.g. B. a battery.
