Considerations for two-color plastic housing mold design and injection molding

1. Basic principles of two-color plastic shell mold design:

a.      Hard material is first shot, and soft material is second shot;

b.      Transparent part is first shot, and non-transparent is second shot;

c.      Part with high molding temperature plastic raw materials is first shot, and plastic parts with low molding temperature material is second shot; 

2.The mold base guide pin and guide sleeve must be symmetrical up and down, left and right, and the front and back molds must be symmetrical.

3.The core side mold must be rotated 180 degrees, and the mold cavity side does not move.

4.The spacing of the plastic shell must be based on the spacing of the nozzle of the injection molding machine. The nozzle spacing of some two-color injection molding machines is adjustable, some is not adjustable.

5. Two independent ejector systems, and there are also two ejector rods. The two products of the mold core are the same, and the ejector pins are the same. It is a rotation relationship, and it must not be made into a translation relationship.

6. The ejector plate can only be reset by springs, not by screws, because the mold core side needs to rotate.

7. The side locks must be on the four sides of the center of the plastic shell mold, and the mold cavity and core side must be symmetrical, otherwise the core will not match the cavity after rotating 180 degrees.

8. If the distance between the injection points and the injection molding machine nozzles is different, the ejector hole must be made into a waist shape, because the distance between the ejector nozzles of the injection molding machine is not adjustable. Note that most of the injection nozzles of China two-color injection molding machines are not adjustable.

9. Pay attention to the direction of the parallel nozzle of the injection molding machine provided by the customer, whether it is the x-axis or the y-axis, to determine the layout of the plastic shell arrangement.

10. The direction of water inlet and outlet must be on the top and bottom sides, and each circulating water inlet and outlet must be on the same side. The water inlet cannot be on the top and the water outlet cannot be on the bottom side. Because the rear mold needs to be rotated 180 degrees, it should be noted that the size of the mold base cannot exceed the height of the water outlet tank of the injection molding machine, otherwise the cooling cannot be connected.

11. The plastic shell of the first injection molding shot should be placed on the non-operating side, because after the first injection molding, the plastic shell needs to be rotated 180 degrees for the second injection molding, just to the operating side, which is convenient for taking the plastic shell.

12. Notes on the parting surface: The parting surface of the core should be the parting surface obtained by merging the two plastic shells; the parting surface of the cavity can be taken from a single plastic shell, and the parting surface of the merged plastic shells cannot be taken.

13. The tolerance of the front and rear flanges is minus 0.05mm, the tolerance of the distance between the two flanges is plus or minus 0.02mm, the gap between the ejector pin and the ejector pin hole is 0.1mm on one side, the center distance tolerance of the front and rear mold guide sleeves and guide pins is plus or minus 0.01, and the four sides and depth of the mold frame must be added with tolerances, otherwise when the core is rotated 180 degrees, the height will be inconsistent and the punch will be produced. The frame depth tolerance is minus 0.02mm.

14. If the mold base has been processed in the mold base factory, when injection mold making factory processes the nozzle and ejector rod holes, the numbers should be taken based on the center of the spacing between the four guide pins and guide sleeve holes. Otherwise, the deviation will be too large and the plastic shell mold will be easily stuck.

15. If it is a two-color mold with core side rotation, it is much simpler. The two mold cavities are the same. After the hard material is injected on one side, it is rotated 180 degrees, but the plastic shell cannot fall when rotating. The gate can be automatically separated. After rotating to the other side, the soft material is injected. There is no need to arrange ejectors for hard material injection. It only needs to be arranged on the mold core on the soft material side. In addition, attention should be paid to shrinkage. If the soft material completely entangles the hard material, only the hard material needs to be shrunk. If the contours are connected, both the hard and the soft material need to be shrunk.

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