Two-Color Injection Molding Machines: How They Work and Main Types

A two-color injection molding machine has two injection units (two barrels), usually each with its own dryer, and a mold with two moving halves and two fixed halves of essentially the same structure. It injects two different materials or colors into the same mold to produce one finished part.

Both materials are molded on the same machine in two shots, but the part comes out of a single mold. The result is a part with two colors or two materials, improving both appearance and feel. Two-color molds are more complex than single-color molds and have their own design rules.

Main types

By structure, two-color molding systems can be divided into core-rotating, core-retracting and sliding-plate rotating types. Core rotation is currently the most widely used, in two forms:

• Split type: two separate molds on one machine rotate alternately to produce the two-color part.
• Integrated type: both shots are molded within a single mold set.

Design tip

To prevent the second-shot cavity from damaging the first-shot part, provide clearance in suitable areas and control the shut-off (sealing) force so the part does not deform under impact.

Two-color molding is widely used for electronics, toys and medical products, and multi-color machines are developing quickly as well.