Bi-Injection is one of the variants producing a two-color / material part without using the two-stage rotation molding method. Two materials are injected independently via two independent gates into a single cavity in a more or less defined configuration. Except for the reduced cycle time, another benefit of using Bi-Injection molding is the better adhesion of the two materials at the junction, mostly due to the better molecular penetration at higher temperature.
The challenge of designing the Co-Injection process is the selection of gate location, and the processing condition. This is because the material interface of the two materials is solely governed by the melt flow pattern. Achieving a desired material interface requires an understanding of the flow and this is where Moldex3D can benefit the design process.
Bi-Injection Molding showing two melts (Blue, Yellow) flowing simultaneously inside the cavity
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