Injection of different materials or colours 

Bi-Injection Molding is the injection of two different colors of the same material or two different thermoplastic materials, at separate injection locations, with independent process controls, for the production of a plastic part.

As is the case in traditional injection moulding, bi-injection moulding uses materials that are at their melting point, so that the viscous material can fill the cavities of a mould.

In general, advantages of bi-injection include creating a single-structure part with different regional materials and also creating a single part with multiple independent polymer colors.

Process Steps

• The two materials are melted at their viscosity temperature.
  
  
• The melted materials are injected, at separate injection locations, with independent process controls.
  
  
• When the mold closes, both unites start filling the cavities.

Advantages

• Can incorporate 2 different colors or join different materials like rubber and plastic.
• Reduces the production phases, optimizing time and energy cost.
• Complex geometry of the molded parts.

Disadvantages

• Big tonnage machine is required.
• Tooling is more complex and more expensive.
• Long cycle time.

Examples of applications

Applications range from simple household items like a toothbrush to construction of items like power tools. More and more applications are met in the automotive industry as well.