Two color(2-K) mold refers to a mold in which two types of resin materials are injection molded on the same injection molding machine in two stages, but the part is only molded once. This type of molding process is also known as dual material injection molding, which is usually completed by a set of molds and requires specialized two-color injection molding machines. Some two materials are of different colors, while others are of different hardness, in order to improve the aesthetics and assembly performance of the part.

Compared to traditional injection molding, the dual material co injection molding process has the following advantages:
1. Low viscosity materials can be used as core materials to reduce injection pressure.
2. From an environmental perspective, recycled secondary materials can be used as core materials.
3. According to different usage characteristics, such as using soft materials for the outer layer of thick finished products, hard materials for the core material, or foam plastics for the core material to reduce weight.
4. Lower quality core materials can be utilized to reduce costs.
5. Cortical or core materials can use expensive and special surface properties, such as anti electromagnetic interference, high conductivity, etc., to increase product performance.
6. The appropriate combination of skin material and core material can reduce residual stress in the molded product, increase mechanical strength or surface properties of the product.
7. Produce products with marble like patterns.

Development and Application:
The characteristics and applications of multi-color injection molding and dual material co injection molding indicate a trend towards gradually replacing traditional injection molding processes in the future. The innovative injection molding technology not only improves the precision of the injection molding process and provides high difficulty process technology, but also expands the scope of the injection molding process field. Innovative injection equipment and processes are sufficient to meet the increasingly diverse, high-quality, and high value-added product demands.
Two color injection molding has been widely used in almost all plastic fields such as electronic products, power tools, medical products, home appliances, toys, etc. The production and molding of two-color molds, as well as the research and development of two-color and multi-color injection molding machines and raw materials for two-color injection molding, have also made rapid progress.