What are the experiences of the design process of two-color injection moulds?

Fri May 12 15:44:08 CST 2023

1. The basic principles of two-color injection mold design:

(1) Hard rubber do 1 time, soft rubber do 2 times.

(2) transparent do 1 time, non-transparent do 2 times.

(3)Do 1 time for plastic with high injection molding temperature and 2 times for low molding temperature.

2. The mold embryo guide pillar and guide sleeve must be symmetrical up and down, left and right, and symmetrical front and rear mold.

3. The rear mold should be rotated 180 degrees and the front mold should not move.

4. The product spacing must be based on the spacing of the injection molding machine nozzle, some foreign two-color injection molding machine nozzle spacing is adjustable, some are not adjustable, the domestic non-adjustable.

5. Two independent ejector system, the top stick is also two. After the mold two products are the same, the ejector pin are the same, is a rotary relationship, do not make a translation relationship.

6. The ejector plate can only be reset by spring, not by screw forced reset, because the back mold to rotate.

7. The side lock must be on the four sides of the center of the mold, and the front and rear mold symmetry, otherwise, when the rear mold rotates 180 degrees, and the front mold can not be right, it is not good.

8. If the spacing of the feeding point and the injection molding machine nozzle spacing is different, the top stick hole should be made waist-shaped, because the top stick spacing of the injection molding machine is not adjustable. Note: Most of the domestic two-color injection molding machine injection nozzle is not adjustable.

9. Pay attention to the direction of the parallel nozzle of the injection molding machine provided by the customer, is the X-axis or Y-axis, so as to determine the layout of product placement.

10. The direction of water transportation in and out of the water must be in the heaven and earth side, and each cycle of water in and out must be on the same surface, not into the water in the sky, out of the water in the ground side, because the rear mold to rotate 180 degrees, pay attention to the size of the mold embryo can not exceed the height of the injection molding machine out of the water tank, otherwise, can not receive water transportation.

11. The products of the first injection should be put on the non-operating side, because after the first injection, the products should be rotated 180 degrees for the second injection, just turn to the operating side, which is convenient to take the products.

12. The code mold position of the export mold should be on the operation side and non-operation side, not on the heaven and earth side, because they products should be fully automatic.

13. Notes on the parting surface: the parting surface of the rear mold should be obtained after the merger of two products for the rear mold; the parting surface of the front mold should be taken for a single product, not the combined product parting surface.two-color injection mold

The tolerance of front and rear flange is minus 0.05mm, the tolerance of spacing between two flanges is plus or minus 0.02mm, the gap between top stick and top stick hole is 0.1mm on one side, the tolerance of center distance between front and rear die guide bush and guide column is plus or minus 0.01, the tolerance of four sides and depth of die frame should be added, otherwise, when the rear die rotates 180 degrees, the batch front will be produced because of the inconsistent height; the tolerance of frame depth is minus 0.02mm.

15. If the mold embryo has been processed in the mold embryo factory, when the factory wants to process the nozzle and the top stick hole, it should take the spacing center of the 4 guide pillars and guide bush holes as the base, otherwise the deviation is too much and it is easy to jam the mold. When ordering mold embryo, it should be indicated that it is a two-color mold embryo, the four guide pillar guide bush and frame are symmetrical, and the rear mold can match with the front mold after rotating 180 degrees.

16. If it is a set of mold of two-color mold, then it is a straight barrel, a 90-degree barrel shot glue, no need to rotate, only a mold core, the separation method of soft glue and hard glue rely on line position seal glue.

17. The two shapes of the cavity are different, molding a product respectively, while the two shapes of the core are intact and the same.

18. The front and back of the mold must match after rotating 180° with the center. When designing, it is necessary to do this check action.

19. pay attention to the location of the ejector hole, the minimum interval 210mm. large mold must be appropriate to increase the number of ejector stick hole, and, because the injection molding machine itself comes with the ejector is not long enough, so, our mold must be designed to extend the ejector, ejector long out of the mold embryo bottom plate about 150mm.

20. Two positioning rings must be designed on the base plate of the rear mold.

21.The total thickness of the front mold panel plus A plate should not be less than 170mm, please check the other reference data of this type of injection molding machine carefully, such as the maximum mold thickness, minimum mold thickness, and the spacing of the top stick hole.

22. The depth of the front side SPRUE should not exceed 65mm, and the distance from the top of the upper side (large water outlet) SPRUE to the center of the mold embryo should not be less than 150mm.

23. When designing the cavity for the second injection, in order to prevent the cavity from inserting (or rubbing) the glue position of the product that was molded for the first time, a part can be designed to avoid emptying.

24. When injection molding, the size of the first injection molding product can be slightly larger, so that it can be pressed more tightly with another cavity in the second molding, in order to reach the role of sealing glue.

25. The water transportation arrangement of the two cavities and cores should be as full as possible, and balanced and the same.

26. Two-color injection mold, must be careful to choose the location of the gate. It is better to choose submerged gluing for one product, so that the product and the runner can be cut off automatically. When it is not possible to use latent feeding, you can consider three-plate mold or hot runner mold. If the primary material is a point gate, make a wave boy to avoid touching through the secondary material due to the residue of the primary feeding point.

27. Two-color injection molds often use rotary injection molds. The size and precision of the convex/concave mold in the two positions of the rotary injection mold should be the same, and it should be well matched with the concave/convex mold. When it is not possible to use the ejector and release mechanism on the two-color injection molding machine, a hydraulic ejector and release mechanism must be set on the rotary table.

28. For two-color injection molding, the same plastic of different colors is usually used, or two different plastic materials, which should be considered in terms of the interface effect of the two materials, the difference of shrinkage rate, processing parameters, etc.

29. Generally speaking, the shrinkage rate of two-color molds depends on the primary material. Because the primary material has already held the outline of the plastic product, the secondary material will not shrink more. As for how to determine the primary and secondary materials, there are many factors to be taken into account, such as raw material fluidity, plastic product shape, etc.

30. Pay attention to the positioning of the front and rear mold, all insertion through, against the broken surface of the slope of the fall as large as possible, to 0.1mm or more.