What is the difference between a two-color mold and an overmolded mold?


Two-color mold: a mold in which two plastic materials a […]

Two-color mold: 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 released once. Generally, this molding process is also called two-component injection molding, which is usually completed by a set of molds and requires a special two-color injection molding machine.

Overmolding mold (secondary molding): The two plastic materials are not necessarily injected on the same injection molding machine, and are molded in two times; after the product is taken out from one set of molds, it is put into another set of molds for second Injection molding. Therefore, in general, this molding process is usually completed by 2 sets of molds, without the need for a special two-color injection molding machine.

Overview of the two-color mold and the overmolding mold: The overmolding mold should pay attention to the positioning of the hard plastic parts in the design, and it is necessary to achieve a reliable seal and have a reverse slope hole on the plastic part to prevent the deformation of the rubber. Two-color molds are increasingly popular in the market. This process can make the appearance of the product more beautiful, and it is easy to change the color without spraying, but the cost is expensive and the technical requirements are high.

1. The two shapes of Cavity are different, and one product is formed separately. The Core's two shapes are the same.

2. After the front and rear molds of the mold are rotated 180o from the center, they must be matched. This check action must be done at design time.

3. Pay attention to the position of the thimble hole, the minimum distance is 210mm. For large molds, the number of top stick holes must be appropriately increased. In addition, since the thimble attached to the injection molding machine itself is not long enough, we must design a longer thimble in our mold, and the thimble grows out of the bottom plate of the mold base by about 150mm. Two positioning rings must be designed on the bottom plate of the rear mold.

4. The total thickness of the front mold panel plus the A board should not be less than 170mm. Please carefully check other reference data of this type of injection molding machine, such as the maximum die thickness, the minimum die thickness, the distance of the top bar hole, etc.

5. The nozzle of the three-plate mold can be designed to automatically release the mold. Pay special attention to whether the release action of the soft glue nozzle is safe.

6. The depth of the front SPRUE should not exceed 65mm. The distance from the top of the upper side (large nozzle) SPRUE to the center of the mold base is not less than 150mm.

7. When designing the CAVITY for the second injection, in order to prevent the CAVITY from inserting (or scratching) the glue position of the product that has been molded for the first time, a part of the cavity can be designed. However, the strength of each sealing position must be carefully considered, that is: in the injection molding, is there a possibility that the plastic will be deformed under the large injection pressure, which may lead to the possibility of a sharp edge in the second injection molding?

8. During injection molding, the product size of the first injection molding can be slightly larger, so that it can be pressed more tightly with another CAVITY during the second molding, so as to achieve the effect of sealing.

9. Note that during the second injection, will the flow of plastic impinge on the product that has been molded for the first time, causing its glue position to be deformed? If this is possible, there must be a way to improve it.

10. Before the molds of the A and B plates are closed, pay attention to whether the front mold Slider or Lifter will reset and crush the product first? In this way, we must find a way to make the A and B plates to close the mold first, and then the SLIDER or LIFET of the front mold can be reset.

11. The water transport arrangement of the two CAVITY and CORE should be as full as possible, balanced and the same.

In 12.99% of cases, the hard rubber part of the product is injected first, and then the soft rubber part of the product is injected. Because the soft rubber is easily deformed.