What is Insert Molding? Benefits, Process, and Applications

Ever thought about the days when producing multiple parts and then assembling them into one product was the norm? Imagine if you could streamline that entire process into a single step. That’s where insert molding comes in.

It merges the strengths of different materials into one seamless part, providing unmatched durability and precision. At Precikam, I’ve seen how this process revolutionizes product design and production efficiency.

But how exactly does insert injection molding achieve this, and why are more industries turning to it? Stick with me, as I will answer all your questions in this blog post – purely based on my experience and knowledge!

What is Insert Molding?

Insert molding is a specialized precision plastic injection molding technique that involves incorporating a preformed insert into the mold before injecting molten plastic. This process allows the plastic to bond with the insert, creating a single, integrated component. Insert molding enhances the durability and functionality of parts, making it widely used in various industries, including automotive, electronics, and medical devices.

Now let’s explore various insert types, materials used for inserts, and precise tolerances in insert molding to achieve high-quality results.

Types of Inserts in Insert Molding

The inserts used in insert molding are generally classified into two groups: part inserts and mold inserts.

Part Inserts
Part inserts are components placed into the mold before the injection phase. They are ejected along with the finished part. Part inserts can be made of metal or plastic. Each new shot assumes a new part insert. You can specify the initial temperature and contact time with the mold before injection. Common examples include threaded inserts, pins, and bushings.

Mold Inserts
Mold inserts are usually made of metal and are attached to the mold. These inserts can be made from high-conductivity metals. This can affect the temperature during the injection process. A specific type of mold insert is the core. Core mold elements are considered in core shift analysis. This means we can simulate how mold cores shift and affect the thickness of the molded part. Common mold inserts include cores, ejector pins, and cooling channels.

Materials Used as Inserts

The materials used as inserts in insert molding are chosen based on the application’s specific requirements. Common materials include metals like brass, stainless steel, and aluminum for their strength and durability. Plastics compatible with the injection molding process, ceramics for high heat resistance, and electronic components like sensors and connectors are also used as inserts.

Selecting appropriate materials is crucial. For insights into material selection and other vital factors, see our article on six key insert molding considerations.

Tolerances Achieved with Insert Molding

Insert molding can achieve high tolerances, often in the range of ±0.001 inches (±0.025 mm). This precision is crucial for applications requiring tight dimensional control and reliable performance. The process ensures that inserts are accurately positioned and bonded within the plastic, reducing the risk of misalignment and enhancing the overall quality of the final product.

In my opinion, insert molding is a game-changer. It allows for the integration of multiple parts into a single piece, reducing assembly time and improving product reliability.

What industries commonly use insert molding?

Insert molding is widely used across various industries because it can create complex parts by integrating different materials. Here are some key industries that utilize insert injection molding:

• Aerospace: In the aerospace industry, insert molding helps create lightweight and durable components. Examples of aerospace plastic injection molded parts include aircraft seating brackets, stowage bin latches, and user interface switches. 
• Automotive: The automotive sector benefits from insert injection molding by replacing metal parts with lighter and more durable plastic components. Common insert molded parts in this industry include electrical connectors, sensor housings, threaded inserts for fasteners, etc.
• Medical: The medical field relies heavily on insert injection molding to produce precise and sterile components. Clean room injection molding is often used to maintain high hygiene standards. ISO 13485 certification ensures that the medical insert molding process meets stringent quality management standards. Examples of inserted molded medical parts include catheters, surgical instruments, pacemaker components, and implantable devices. 
• Security: In the defense and security sector, insert molding produces robust and highly reliable components. Common applications include creating durable and tamper-resistant enclosures for secure communication devices, housings for weapons, and connectors used in military equipment. The process ensures that these components can withstand extreme conditions. 
• Machinery and Industrial Parts: Insert molding in machinery and industrial applications involves producing components that require high strength and durability. Some common insert molded parts for the industrial sector include tool handles, industrial gears, and connectors. 

At Precikam, we excel in creating injection-molded precision plastic components for the above-mentioned sectors. We also specialize in producing custom insert-molded parts that provide tailored solutions to each industry’s unique needs.

What is the insert molding process?

Let me walk you through the basics of the insert molding process as we follow it in our facility. It will help you better understand the whole process.

1. Mold Design

The first step is mold design. Our experts in precision plastic injection molding develop the mold to meet the specific requirements of insert molding. They ensure the mold is designed accurately to hold the insert in place during injection. Ensuring the plastic flows properly around the insert creates a solid bond.

2. Insert Placement

Next, we move to insert placement. Skilled operators can do this manually or automatically using precision robots. Manual placement is perfect for smaller production runs, while automated placement is ideal for larger runs, ensuring consistency and speed.

3. Plastic Injection

Then comes the plastic injection. The molten plastic is injected into the mold. It flows around the insert, filling the entire cavity. As the plastic cools and solidifies, it forms a strong bond with the insert, creating a durable part.

4. Removing the Molded Part

After the molding process, the operator removes the molded part. This step requires careful handling to avoid any damage. Precision is key here to maintain the integrity of the part.

5. Post-Molding Operations

Finally, we carry out post-molding operations. This includes trimming extra material and deburring any sharp edges. If required, several surface treatment processes are also performed to enhance the part’s appearance and performance. The inspection team performs several quality checks to ensure each molded precision plastic part meets the highest standards.

This is the entire insert injection molding process. Engineers and product manufacturers should understand these steps to improve product quality and manufacturing efficiency.

How does insert molding differ from other plastic injection molding techniques?

At a glance, insert molding, injection molding, and overmolding might seem similar because they all involve injecting molten plastic to create parts. However, these three processes are different from one another. Let me explain.

Insert Molding vs. Basic Injection Molding

Insert molding involves placing metal or plastic inserts into the mold before injection. Basic injection molding only uses plastic without any pre-placed inserts. This key difference allows insert molding to create integrated parts, while basic injection molding produces standalone plastic components.

Insert Molding vs. Overmolding

Insert molding places inserts into the mold before injecting plastic. Plastic overmolding involves molding plastic over an existing part to create a layered structure. Insert molding integrates inserts into the part, while overmolding adds an additional layer to the existing part. Both techniques offer unique advantages for different applications.

See our article “Understanding plastic overmolding in plastic injection molding” to learn more about overmolding.

Comparison table between insert molding, injection molding, and overmolding.

What are the benefits of insert molding?

Insert molded parts produced by a reliable injection molding service provider can bring many benefits to the table. Here are some of them:

• Enhanced Durability & Strength: Insert molding combines plastic resin with sturdy inserts to create durable parts. The metal insert provides rigidity, while the plastic offers damping capabilities. This results in a product that withstands higher stress and reduces friction with surrounding components.
• Size and Weight Reduction: This technique helps to reduce the size and weight of components. This is because manufacturing parts with integrated inserts eliminates the need for additional fastening elements. This results in up to 50 times lighter and more compact parts, which is beneficial for many applications like aerospace and automotive.
• Time and Cost-Effective: Insert molding significantly reduces overall costs by integrating inserts directly during the molding process, which eliminates the need for separate assembly steps. This method reduces labour costs and assembly time while minimizing the risk of errors. Moreover, combining multiple parts into a single molded component enhances production efficiency and leads to substantial cost savings.
• Added Precision and Functionality: This process provides precise placement of inserts, which ensures consistent quality. This precision is crucial for parts requiring tight tolerances and reliable performance. For instance, electronic components benefit from accurately placing metal inserts, ensuring reliable connections.
• Improved Design Flexibility: Insert molding eases the work of design engineers and manufacturers by allowing them to create various shapes and designs that they cannot achieve with metals alone.
• Better Sealing and Waterproofing: Insert molding enhances sealing and waterproofing by embedding inserts into the plastic. This creates a tight seal around the insert, which is crucial for water- and fluid-resistant applications. For example, the automotive industry ensures that engine components and electrical systems are protected from moisture and other environmental factors.

Understanding these advantages will help you make informed design and production decisions.

Maximizing Efficiency and Quality with Insert Molding

Now you know how insert molding is transforming the manufacturing process. Its ability to combine the strengths of different materials results in products with enhanced durability, precision, and functionality. In North America, this process is widely adopted by manufacturers across the aerospace, automotive, security, and medical sectors. The reason behind this adoption is its significant benefits, which include reduced assembly time, improved product reliability, and cost efficiency. Consider insert molded parts for your next project to achieve superior strength and improved design flexibility.

Ready to take your manufacturing process to the next level with precision insert molding?

At PreciKam, we specialize in delivering high-quality, high-precision insert-molded parts tailored to meet the demanding needs of the medical, aerospace, automotive, and military industries in Canada, the USA, Maxico, and worldwide. With over 50 years of precision plastic injection molding expertise and a commitment to rigorous quality management, we ensure your parts are produced to the highest standards.

Contact us today to discuss your project requirements and discover how our advanced insert molding capabilities can enhance your product performance and reliability.