Two-stage injection molding, also known as bi-injection molding or co-injection molding, is a process used to manufacture plastic parts by injecting two different types of polymer into a single mold. In the first stage of the process, a base polymer is injected into the mold to form the core of the part. In the second stage, a second polymer, known as the skin polymer, is injected around the core to form the outer layer of the part.
Two-stage injection molding allows for the production of parts with complex geometries and multiple materials, as the two polymers can be injected into the mold in different patterns and at different pressures to create the desired shape and properties. It also allows for the use of different polymers to achieve specific properties in different parts of the same part, such as improved strength or aesthetics.
Two-stage injection molding machines are specifically designed to carry out the two-stage injection molding process. They typically consist of two injection units, a control system, and a clamping system. The two injection units are used to inject the base and skin polymers into the mold, while the control system is used to monitor and control the various processes involved in the molding process. The clamping system is used to hold the mold in place during the injection process.
Two-stage injection molding is widely used in the production of a variety of plastic parts, including automotive parts, medical devices, and consumer goods. It offers a number of advantages over traditional injection molding, including the ability to produce parts with complex geometries and multiple materials, and the ability to achieve specific properties in different parts of the same part.
