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Design and injection molding of two-color molds-1

A two-color mold refers to a mold in which two plastic materials are injected on the same injection molding machine and molded in two times, but the product is only ejected once. Generally, this molding process is also called double-material injection molding, which is usually completed by a set of molds and requires a specialized two-color injection molding machine. Two-color molds are becoming increasingly popular in the market. This process can make the appearance of the product more beautiful, and it is easy to change colors without spraying. However, it has high requirements for design and injection molding.

[Dry information] Technical key points of two-color design process

  1. Basic principles of two-color mold design
    (1) Do it once for hard glue and twice for soft glue;
    (2) Do it once for transparent and twice for non-transparent;
    (3) Do it once for plastics with high molding temperature and twice for plastics with low molding temperature;
    The above are the basic principles for making two-color molds, otherwise the mold will be made in vain; in addition, when sealing, try to use break-in sealant instead of inserting break-in sealant. Even if the customer is advised to modify the product, try to use break-through sealant.
  2. The mold base guide posts and guide sleeves must be symmetrical up, down, left, and right, and the front and rear molds must be symmetrical.​
  3. The rear mold should be rotated 180 degrees and the front mold should not move.
  4. The spacing between products must be based on the spacing between the nozzles of the injection molding machine. The nozzle spacing of some foreign two-color injection molding machines is adjustable, some are not adjustable, and the domestic ones are not adjustable.
  5. Two independent ejection systems, including two ejection sticks. The two rear mold products are the same, and the ejectors are the same. They are in a rotational relationship and must not be made into a translational relationship.
  6. The ejector plate can only be reset by spring, and cannot be forced to reset by screws, because the rear mold needs to rotate.
  7. The side locks must be on the four sides of the center of the mold, and the front and rear molds are symmetrical, otherwise the rear mold will not align with the front mold when rotated 180 degrees.
  8. If the distance between the glue inlet points and the distance between the nozzles of the injection molding machine are different, the ejector pin hole must be made into a waist shape, because the distance between the ejector pins of the injection molding machine cannot be adjusted. Note that most injection nozzles of domestic 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 product ranking.​
  10. The direction of transporting water in and out must be on the sky and earth side, and the inlet and outlet of each circulating water must be on the same surface. Water cannot enter in the sky and water should exit on the ground side, because the rear mold needs to be rotated 180 degrees, so pay attention to the mold base The size should not exceed the height of the outlet water tank of the injection molding machine, otherwise it will not be able to receive and transport water.​
  11. The first injection molded product should be placed on the non-operation side, because after the first injection molding, the product needs to be rotated 180 degrees for the second injection molding, just to the operation side, making it easier to take out the product.​
  12. The code mold position of the export mold must be on the operating side and the non-operating side, not on the heaven and earth side, because their products must be fully automatic.
  13. Precautions for the parting surface: The parting surface of the rear mold should be obtained by merging the two products. The parting surface obtained by combining the two products should be that of the rear mold; the parting surface of the front mold should be that of a single product, and the merged product is not acceptable. Parting surface.
  14. The tolerance of the front and rear flanges is minus 0.05mm, the tolerance of the spacing between the two flanges is plus or minus 0.02mm, the clearance between the ejector pin and the ejector pin hole is 0.1mm on one side, and the tolerance of the center distance of the front and rear mold guide sleeves and guide posts is plus or minus 0.02mm. 0.01mm, tolerances must be added to the four sides and depth of the mold frame, otherwise when the back mold is rotated 180 degrees, there will be a sharp edge due to inconsistent height. The frame depth tolerance is minus 0.02mm.
  15. If the mold base has been processed in the mold base factory, when the factory wants to process the nozzle and ejector pin hole, the number should be taken based on the center of the distance between the four guide posts and guide bushing holes. Otherwise, there will be too much deviation and it will be easy to get stuck. Dead model. When ordering the mold base, please indicate that it is a two-color mold base. The four guide posts, guide sleeves and frame are symmetrical. The rear mold can be matched with the front mold after being rotated 180 degrees.
  16. If it is a double color with the rear mold rotating, it will be much simpler. The two front mold cores are the same… After injecting the hard glue on one side, rotate it 180 degrees (note that the product cannot fall when rotating, and the gate can automatically Separate), turn to the other side and then inject soft rubber… There is no need to arrange the ejector pin when injecting hard rubber… Just arrange it in the core of the soft rubber side… In addition, pay attention to shrinkage… If the soft rubber is completely Wrap the hard glue… Then you only need to shrink the hard glue… If the contours are connected, then both the hard glue and the soft glue need to be shrunk.
  17. If it is a set of two-color molds, it has a straight barrel and a 90-degree barrel to shoot glue. It does not need to be rotated. It only needs one mold core. The separation method of soft glue and hard glue relies on row position sealing. glue.
  18. The two shapes of Cavity are different, and one product is formed respectively. The appearance of the two Cores is exactly the same.
  19. The front and rear molds of the mold must be aligned after they are rotated 180° from the center. This check must be done during design.
  20. Pay attention to the position of the thimble holes, the minimum distance is 210mm. For large molds, the number of ejector pin holes must be appropriately increased. Moreover, since the ejector pins attached to the injection molding machine are not long enough, our mold must be designed with an extended ejector pin that extends about 150mm beyond the bottom plate of the mold base.
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