What is Insert Molding: Applications & Considerations

Manufacturing components that consist of plastics and metals at the same time uses the process of insert molding. Such components are widely used in many applications, and the guide below provides detailed insight into the process of insert molding.

So, if you want to know what insert molding is, where it is used, and how you can achieve the best out of it, read below.

What is Insert Molding?

Insert molding is a method in which plastic injection molding is used to merge metal inserts with plastic injection molded components. An insert is positioned in the cavity before the molten plastic is poured. When the molten plastic is poured using high pressure, the insert solidifies with plastic when cooled.

Metal insert molding allows the manufacturing of plastic and metal components that are durable, lightweight, and strong. It is used in many applications due to its effectiveness and compatibility.

How Insert Molding Works？

The process of insert molding is discussed below.

Step 1: Load Inserts into the Mold

The first step is loading the inserts into the mold, and for this, you have to ensure that the position of the insert is maintained throughout the molding process. There are two ways the inserts are loaded into the molds.

Automatic insertion is a consistent, efficient, and precise method that uses robots to insert components into the molds. This method offers a quick manufacturing process. The other method is suitable for low-volume production in which manual insertion is done, and the inserts are loaded by hand.

Step 2: Inject the Molten Plastic into the Mold

Once the insert is set, the molten plastic is inserted into the mold using high pressure. The plastic is filled into the mold uniformly so that the mold binds with the insert properly.

Step 3: Open the Mold and Remove the Molded Part

The molten plastic is filled in the mold evenly and is left for solidification. The mold is kept closed. When cooled down, it is opened, and the molded part is manufactured.

Step 4: Separate the Molded Part from the Sprues

The molded components get attached to the spruces, which helps them form. These spruces are like frames which ensure that the molded parts are properly made.

The molded part needs to be detached from the spruce so that it can be used. The separation from the spruce should be very carefully done to avoid damaging the component.

Step 5: Post-Molding Operations

The plastic components, once molded, may need some post-processing using different methods as given below:

• The burrs from the molded parts are removed so that any excessive material is removed from the past.
• Heat treatment is applied to enhance the quality of the component.
• Molded components are also bathed in hot water, which enhances their moisture absorption and prevents oxidation.

Pros and Cons of Injection Molding Insert

Injection molding inserts have some pros and cons, and this section highlights both of them.

Prós

• Injection molding insert reduces the cost of assembly and labor, and the need for post-molding assembly may be avoided.
• The sizes and weights of the products are reduced by using the inserts.
• It offers design flexibility and creates unique components.
• The insertion of metals in the injection molded components improves the mechanical properties of the parts.

Cons

• The process of designing molds with inserts is expensive and complex.
• The insert material may be incompatible with the process of molding in many cases.
• If the injection molding insert is not properly inserted, defects can be observed in the molded components.
• The cycle time increases when inserts are used due to the positioning process.

Common Insert Molding Materials

Injection molding is a versatile method that can be carried out using various materials. However, thermosets and thermoplastics are widely adopted. Some of the materials commonly chosen for insert molding are as follows:

Thermosets: Urea-formaldehyde resins, melamine-formaldehyde resins, and epoxy.

Thermoplastics: Nylons, polycarbonates, polypropylene, polyethylene, ABS, and acetal.

Elastomers: Natural rubber, polyurethane.

Applications of Insert Molding Parts

The applications of insert molding components are observed in many industries, and some of these are as follows:

Automóvel

In the automobile industry, the insert molding components are used instead of the metal parts. These components are lightweight and more durable, which enhances the efficiency of vehicles. Threaded fasteners, electrical sensors, and gears are manufactured using this process.

Médico

O sector médico uses injection molding components to sterilize. These components are tubes, prosthetics, medical knobs, dental tools, and surgical instruments.

Eletrónica

The electronics industry uses insert molding for fastening and soldering components. Some of the applications of insert molding can be seen in the form of knobs for machinery and wires covered in rubber.

Design Considerations for Insert Injection Molding

To ensure success in insert injection molding, some of the design considerations to have in mind are as follows:

Types of Inserts

The type of insert is a very important factor, and you should choose the one that is capable of withstanding the temperature and pressure during the process.

Insert Location

Insert location is very important to keep it in place firmly. Hence, when choosing the location of an insert, make sure to consider the function it has to perform and the plastic required to keep it in place.

Narrow Gap between Metal Inserts

The gap between the molten plastic and insert is a critical factor to consider because a narrow gap can offer a reliable insert molded component.

Choose the Appropriate Material

The right type of material that can hold the insert metal properly is important, and it should also have the ability to withstand the application requirements.

Use the Right Mold

The type of mold selection plays a vital role in keeping the insert at the required place and ensuring high-quality component manufacturing.

The Cost

Components that are cost-sensitive must be manufactured with the cost of inserts and the cost of the process in mind.

Volume de produção

The production volume will help determine whether you should go for the manual or the automated process of insert molding. It also considers the cost-benefit analysis so that you can choose the method.

Insert Molding vs. Overmolding Comparison

Insert molding and overmolding are both injection molding processes, but their techniques differ. Insert molding is a process wherein molten plastic is poured into a mold that has an insert. The plastic creates a bond with an insert and combines to form one component.

The overmolding process involves molding plastic in the form of rubber over another plastic. It is a double molding process, which is expensive and uses more material.

Insert molding offers to produce components with improved structural integrity and strength, whereas over-molding adds more layers of protection and aesthetic finish.

Get Insert Molding and Overmolding Parts with DEK

If you are planning to start a new project and want to have some components manufactured through insert molding or over-molding, you can get in touch with us. We at DEK have specialized and automated methods to help you achieve high-quality components.

Conclusão

Understanding the entire process of insert molding is very important before you implement it in your applications. As the guide above has highlighted the details of the process of insert molding, you can now make informed decisions regarding your projects.

FAQs

What are the common inserts used in insert injection molding?

The inserts commonly used in insert section molding are screws, studs, switches, terminals, connectors, and some other plastic parts.

Why are inserts important in injection molding?

Inserts improve the strength of components as they are usually made using metals and, hence, are durable.

Is insert injection molding compatible with large parts?

The insert molding process helps create components of small or medium size, as opting for larger parts can be complex and requires increased tooling.

What are the rules for insert molding?

It is important to maintain consistency in the thickness of the wall, eliminate undercuts, and maintain the appropriate draft angles.