One. Two-color injection molding advantages:
The two-color mold can convert two different resins and colors into a single two-color product, which can reduce the assembly and post-processing processes of the molded product. Save the cost of melting and printing, increase the beautiful visual effect of the product, and improve the grade and added value of the product. Not only has the function of anti-slip and increasing friction, the flexible resin material makes it more ergonomic and feel better. Two-color injection molded products have high quality stability, easy to control product deformation, short molding cycle, high output, loss can be 7% lower than plastic injection molding, and product manufacturing costs can be 20% -30% lower than plastic injection.
two. Two-color molding principle
Two-color injection molding generally refers to the molding of two colors or different types of plastics. Because the two groups of injection units and nozzles of the two-color machine are independently separated, the color of the finished product is mostly two-colored and not mixed. The biggest difference between the two-color injection molding machine and the ordinary injection molding machine is the design of the movable template of the injection unit. Generally speaking, a two-color machine has two sets of injection units that are separate and separate. Generally, there is only one set of injection units for an injection machine. The configuration of two sets of injection units varies with the design of each manufacturer. As for the design of the movable template, it is necessary to provide a rotation mechanism. Generally common designs such as adding a turntable or a shaft mechanism to provide 180 ° reciprocation The rotation function causes the mold to generate cyclic and alternating actions. Other special two-color molds do not require a turntable or a shaft mechanism, and the molds perform sliding alternate or horizontal rotation.
Third, the production process characteristics of injection molding two-color products
1. The two-color injection molding machine consists of two sets of plasticizing injection devices with the same structure and specifications. According to the production mode, the nozzle should have a special structure or be equipped with two sets of forming dies with the same structure that can be rotated and transposed. When plasticizing and injecting, process parameters such as melt temperature, injection pressure, and melt volume in the two sets of plastic injection devices are required to be the same. It is necessary to minimize the fluctuation of process parameters in the two sets of devices.
2. Compared with two-color injection molded plastic products, the melt temperature and injection pressure of the two-color injection molded plastic products must adopt higher parameter values. The main reason is that the mold runner in the two-color injection molding is relatively long, the structure is complicated, and the resistance to injection melt flow is large.
3． Two-color injection molded plastic products should use raw materials with good thermal stability and low melt viscosity to avoid decomposition due to high melt temperature and long residence time in the flow channel. The most commonly used plastics are polyolefin resins, polystyrene, and ABS materials.
4． When two-color plastic products are injection-molded, in order to make two different colors of molten material weld well in the mold during molding to ensure the molding quality of injection-molded products, higher melt temperature and higher mold temperature , Higher injection pressure and injection rate.
Fourth, two-color mold structure
The traditional two-color injection mold has two forms of "convex die translation" and "convex die rotation".
① The die of "convex die translation" has two concave dies and one convex die. When the first barrel is shot, the convex mold is closed with the first concave mold. Complete the first plastic injection. After the first plastic is solidified, the concave and convex molds are separated. The semi-finished product formed by the first plastic stays in the convex mold, and moves with the convex mold to the position aligned with the second concave mold. After the injection molding machine is closed, a second barrel is injected with a second plastic. After the second plastic has solidified, the injection molding machine opens the mold and takes out the complete product.
② The two-color die in the form of a "rotating die" has two concave dies and two convex dies combined back-to-back. The two-side injection molding machine equipped with two barrels, the second barrel is preferably designed in the vertical direction of the injection molding machine movement direction. Two different plastics can be injected at the same time. When the two plastics injected are solidified, the injection molding machine opens and ejects the complete product automatically. After the product is taken out, the "rotatable punch" is turned through 180 degrees. The injection molding machine is closed and the next cycle is performed.
Because the first and second barrels of the "die transfer" mode are injected in turn, the first and second barrels of the "die rotation" mode are injected simultaneously. Therefore, for the same product, the production efficiency of the "embossed die rotation" mode is twice as high as that of the "embossed die translation" mode.
Five, two-color mold new technology
The two-color injection molding machine is equipped with two barrels. The mold is single cavity and has the common cavity required for the first plastic ("hard glue") and the second plastic ("soft glue"). This technology requires a single die and punch, which is fundamentally different from the previous two production models. After the first barrel is injected with the first plastic, wait for the first plastic to partially solidify or solidify. The power cylinder controlled at the beginning drives the blade, which acts as an isolation, back to the level of the profile of the punch. The second cartridge is then injected with a second plastic. After the second plastic has completely solidified, the injection molding machine is turned on and the complete product is taken out. The injection molding machine is then switched off and the next cycle is performed. The obvious advantage of this technology is that it simplifies the mold and reduces the need for injection molding machine working space (smaller two-color injection molding machines can be used to reduce investment and energy consumption). And it can increase the yield by a factor of two compared with the previous "encapsulation method", and fundamentally avoid the defective products caused by re-entering the "hard rubber" that has been shrunk and deformed into the cavity.
Six, the difference between plastic mold and two-color mold:
1. Two-color mold: A mold in which two plastic materials are injected on the same injection molding machine and molded twice, but the product is only ejected 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. The two-color mold can convert two different resins and colors into a single two-color product, which can reduce the assembly and post-processing processes of the molded product. Save the cost of melting and printing, increase the beautiful visual effect of the product, and improve the grade and added value of the product. Not only has the function of anti-slip and increasing friction, the flexible resin material makes it more ergonomic and feel better. Two-color injection molded products have high quality stability, easy control of product deformation, short molding cycle, high output, loss can be 7% lower than plastic injection molding, and product manufacturing costs can be 20% -30% lower than plastic injection molding.
2. Overmolding mold (secondary molding): two plastic materials may not be injected on the same injection molding machine and divided into two moldings; the product is taken out of one mold and then placed in another mold. The second injection molding. Therefore, this molding process is usually completed by two sets of molds, without the need for a special two-color injection molding machine. The mold is the same as the mold structure for single-color injection. Of the junction. The rubber mold is mainly soft rubber and hard rubber. Among them, soft rubber is commonly used in artificial rubber, TPU, TPR and other rubber materials. Hard rubber can be ABS, PC, PP, etc.
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