Insert molding allows you to combine the strength and rigidity of metal components with the flexibility and design freedom of plastic, in a single molded part. It is a great choice for applications where the mechanical properties of both materials are required, such as threaded inserts or metal-to-plastic bearing surfaces. This method is also commonly used to make parts that require a soft grip or a durable covering, such as remote control covers or handles.
The process is similar to overmolding, but instead of creating a finished product using two separate shots like overmolding, insert molding involves a preformed component (often a metal) being loaded into an injection mold and then overmolded with a thermoplastic resin to create a finished component. This makes it an ideal option for manufacturing consumer and industrial goods where the inclusion of a metal component would otherwise increase production costs through the use of expensive, multi-part tooling.
An important factor to consider when designing for insert molding is the need for sufficient mechanical bonding between overmolded materials. For this reason, it is important to choose an insert material that provides a good mechanical bond with the resin you are using and ensure that the overmolded plastic is designed with enough clearance for the intended location of the insert.
Similarly, the injection mold must be designed to prevent the plastic from covering areas of the insert or substrate that should remain exposed and functional. The insert should also be designed in a way that offers protection from the temperatures and pressures of the injection molding process. This can be accomplished in a number of ways, such as through undercut features or the use of a metal insert with threads to allow for pipe or screw attachment to the final molded part.
Another benefit of insert molding is the ability to reduce assembly time for a final product. Since insert molded components can be made in the same injection molding process as a completely plastic part, this eliminates the need for secondary processes such as soldering, adhesives or gluing, and can help to improve product reliability. Insert molded components can also be manufactured faster than traditional metal forming techniques, such as CNC machining, and at a lower cost per unit.
Whether your project requires a simple metal-to-plastic connection or you need to encapsulate an electronic sensor, insert molding is a highly flexible and cost-effective solution. Combined with sound design for manufacturability, it is an excellent choice for the production of many different types of consumer and industrial goods. Contact a Protolabs team member to discuss the potential benefits of insert molding for your next project.