Leverage the Many Advantages of Insert Molding
Are you looking for ways to decrease the weight, complexity and cost of your parts? Is replacing metal components with high-performance plastic parts a priority? Injection molding inserts can address these challenges and give you greater design freedom.
What are Injection Molding Inserts?
Insert injection molding is the process of forming a plastic part around a different type of material. This is typically done with simple metal objects like a threaded rod. However, this process can be used to place a wide variety of other elements into injection-molded parts, including other plastic parts, threaded bushings, electrical connectors, magnets and RFID tags.
Applications of Injection Molding Inserts
There are many applications of insert molding, including:
- Auto industry components
- Industrial equipment components
- Medical devices
- Couplings
- Threaded fasteners
- Electrical connectors
- Knobs
Industries where threaded inserts are used include:
- Automotive and transportation
- Aerospace
- Medical instruments and devices
- Defense
- Electronics
- Industrial products
- Consumer products
What Do Injection Molding Inserts Make Possible?
Insert molding is an excellent way to replace metal parts with lighter-weight plastic versions that are just as strong. Threaded injection molding inserts enable them to be attached to other components without cracking or damaging the plastic.
Inserts enable you to design lighter parts with thinner walls and less complex geometries. In many cases, plastic parts are up to 50% less expensive than their metal counterparts.
In addition, it enables you to design parts that wouldn’t be possible using either metal or plastic alone. It combines the best characteristics of both materials in an affordable, high-performance package.
Benefits of Injection Molding Inserts
Inserts Are Fully Anchored Into the Plastic: With heat staking, the plastic adjacent to the hole may not fully encapsulate the insert, causing to not be fully anchored to the plastic. With insert molding, the molten plastic flows around the insert, fully anchoring it for maximum holding power.
Consistently Correct Orientation: With insert molding, the insert is placed in a pocket of the mold cavity, which holds it in the correct orientation as the plastic is molded around it. With heat staking, there may be some variation in the depth and orientation of the inserts relative to the surface of the part.
Robust Assembly and Disassembly: For products that need to be serviced repeatedly, threaded injection molding inserts enable components to be easily disassembled and reassembled multiple times without causing degradation of the hole, which can happen when screws are fastened directly into the plastic.
Forms a Stronger Connection Between Parts: A threaded metal insert provides greater assembly strength between connected parts than other forms of fastening, such as inserting a screw directly into plastic or gluing the parts together.
Special Considerations for Injection Molding Inserts
What’s Your Design Objective? Insert selection is usually based on two factors: How much torque must the insert withstand before it breaks free and spins within the plastic part and how much pullout force does it need to withstand before it breaks free and can be pulled out of the plastic? A variety of insert designs are available that can meet the needs of your application or they can be custom manufactured as needed. An insert molding expert can help you select the best insert design for your specific needs.
Optimizing the Part Design for Inserts: Can the part design support the insert? The part must have enough material around to insert to hold it securely in place. A common mistake is to design a part with inserts located too close to the outer wall of the part. That can cause cracks and cosmetic defects. Bosses, which are internal structures that will hold the inserts in place, must be designed in certain ways to prevent cosmetic or structural defects.
Heat Pressing vs. Molded-in Inserts: Heat-pressed inserts are either manually or automatically inserted into the plastic after the part has been molded. The insert is heated to partially melt the plastic so it can be placed to the required depth and orientation. Molded-in inserts are placed in the mold cavity before the shot. The molten plastic flows around them and holds them in place. Each approach has its pros and cons. Ask your injection molder which one is best for your application.
Off-the-Shelf vs. Custom Inserts: In the U.S., standard-size inserts are fairly inexpensive and custom inserts tend to be more expensive. That’s why most molders and OEMs specify off-the-shelf insert designs and sizes. When molding overseas, however, the opposite is true. Custom inserts are significantly more affordable. Working with your molder to source a custom insert can enable you to optimize your part and insert designs around your needs, instead of choosing from “best-fit” options that may be less than optimal.
Advantages/Disadvantages
Advantages
Weight Reduction: Injection molding with inserts can produce a part with similar functionality as an all-metal version but which weighs less. Weight reduction is critical in industries like automotive and aerospace.
The Potential to Reduce Post-Processing needs: Threaded inserts can eliminate the need for other methods of fastening parts together, such as snap fitting or gluing them. If they are properly engineered into the part design, inserts can prevent loosening and can help protect assemblies against vibration and shock.
Disadvantages
Optimizing Part Designs for Inserts Requires Special Expertise: The placement of inserts and the bosses that hold them must be done properly to avoid cosmetic and structural defects. For best results, consult a supplier with deep insert molding expertise.
Designing Molding Processes for Automated Insertion can be Challenging: Picking, holding and loading inserts into a mold tool can be complex, depending on the geometry of the part and other factors. A partner with extensive insert molding expertise can help you design the best approach to automated insertion.
Why Choose ICOMold for Insert Molding?
When designing a part to incorporate inserts, there are many combinations of potential options you need to consider, including:
- Insert material, size and configuration,
- Optimizing part geometry and molding processes for inserts,
- Plastic material selection,
- And more.
ICOMold’s engineering and manufacturing experts have extensive insert molding experience and expertise. We can help you navigate the options and trade-offs to arrive at the best possible solution for your part designs.
