Bi-injection Molding

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.


  • 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.



  • 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.