Tool Design -Bi-injection mould design Techniques...

              Bi-injection moulding or called as two color injection molding

Bi-injection mould design: injection is carried out with two plastic materials in one injection machine, so the production is shaped at twice but demoulded once only.

bi-injection-mould-design-1

Bi-injection mould design tips:

1. Bi-injection mould with two different cavities but with the same cores.

2. The front and rear moulds must match each other after 180º rotation, which must be checked while designing.

3. The minimum distance of the ejection rod hole is 210mm. And the large mould should properly add the number of ejection rod hole. The ejection rod in bi-injection mould should be designed to be longer than mould floor about 150mm. Meanwhile, two locating rings should be designed on the rear mould floor.

4. The total thickness of Front mould plate and A plate should not be less than 170mm.

5. The gate on 3-plate mould in bi-injection mould can be designed with automatic ejection. Particularly pay attention to the reliableness of gate ejection.

6. The depth of front-side sprue should not be more than 65mm. The distance from the top of  upper-side sprue to the center of mould base should not be less than 150mm.

7. Pay more attention to the strength of every molding place.

8. The size of the first injection shaped production can be more bigger so that it can be pressed to the other cavity tightly in second formation in order to reach the sealing function.

9. Ameliorate the deformation in second injection.

10. Before the clamping, take care that whether the slider or lifter in front mould will reset   first to crush the production or not? So, we must find ways to make the A and B mold plates clamping, then the slider or lifter on front mould can reset.

11. The cooling system arrangement in cavity and core should be abundant and balanced.

12. In 99% situation, the PS parts of production are injected first, then it comes to the PE parts for its easiness to deform.

13. Take the roughness of bi-injection mould surface into consideration. Bi-injection mould usually has specialized TPU. More smooth the surface is, more tight the two kind of plastic rubber stick to each other.

14. Pay attention to the location of front and rear mould. The slope drop should be above 0.1mm.

two colors injection mold design

bi injection molds design