What Is Injection Molding?

Injection molding is a process where molten plastic resin is injected into a custom-designed mold to create the product. Insert molding differs from over-molding, in which a secondary shot is used to coat the plastic over a preformed metal part. Instead, the metal is inserted into a customized insert mold and encased in the molten plastic prior to closing the mold. This allows for a seamless transition from the metal to the plastic without a noticeable seam. The insert can be any type of metal or solid component that needs to be incorporated into the final product. Inserts are commonly used to reduce assembly time and cost, and enhance design strength and durability. Insert molding is particularly effective for products that require a comfortable grip or are designed to accommodate a hand. Some common examples include medical implements, handles, electrical sockets and wires, dash panels, and remote control coverings.

The benefits of using insert molding over traditional methods for manufacturing products that contain metal components include decreased assembly and labor costs, reduced component size and weight, increased mechanical integrity, improved aesthetics and design flexibility, as well as enhanced corrosion resistance. In addition, insert molding provides greater manufacturability compared to traditional methods like heat staking and ultrasonic inserting.

For insert molding, the first step is to build a custom-designed mold that will accept a metal insert. The inserts are loaded into the mold, either manually or robotically. The insertion process is done at the optimal temperature to ensure that the insert will mate with the molten plastic resin and become fully integrated into the product after it cools down.

A key factor in insert molding is determining the best location for each metal component and how it will be subjected to the forces that are likely to be exerted on it. Insert locations are often positioned to withstand the greatest stresses such as torque, tensile force and shear force. When properly paired with the right type of insert, insert molding can provide an extremely strong mechanical bond between metal and plastic.

During the molding process, a solid insert is placed into the mold and then covered with a smooth layer of plastic resin to form the desired finished product. The plastic encapsulates the metal and provides a soft grip, which can make handling the product more ergonomic and comfortable for users. Once the product has cooled, it is removed from the mold and can be inspected for quality.

Insert molding is a popular choice for connecting and reinforcing parts in consumer goods, automotive, and industrial manufacturing. It is also widely used for medical devices such as surgical tools and instrument handles, syringes and catheters. It can be a more economical and efficient option than traditional methods like screw assemblies, gluing or welding, as the inserts can be securely bonded to the plastic using the injection molding process. Moreover, the inserts can be made of metal or other materials to suit different applications and needs.insert molding