Injection molding two-color or mixed-color plastic products are prepared by mixing the same raw materials into two different colors, and plasticizing two kinds of color melts by two injection molding machines of the same structure and the same specifications, and then injecting them through a nozzle. Inside the mold. The molded plastic products are color-separated, mixed or irregular, and the appearance effect is not obtained by ordinary injection molding and surface modification. The alternating plasticizing melts in the two injection molding machines of the same specification are completed by nozzle injection, and are controlled by the program control valve between the plasticizing cylinder and the nozzle. The structure of this two-color injection molding machine is shown in Figure 2-3. If a rotatable mandrel is added to the nozzle of the injection molding machine shown in Figure 2-3, when plasticizing the injection, the two plasticizing injection devices can simultaneously and simultaneously, the same amount, the same pressure, and the same injection speed. Melts of different colors are injected into the forming mold through the same rotating mandrel nozzle, so that injection molded articles of different pattern patterns can be produced. Figure 2-4 is a schematic view of the construction of an injection molding machine in which a forming mold can be rotated and displaced about a central axis. It consists of two sets of plastic injection devices and mold devices of the same specifications and the same structural form. The working method of this type of injection molding machine is as follows. After the two plasticizing injection devices complete the first injection at the same time, two sets of molding molds of the same structure are rotated around the central axis by 180 ° C, and then two sets of injection devices are injected into the forming mold by two sets of injection devices. . By performing the action of injecting different colors of molten material into the same molding die in two steps, a two-color injection molded article can be obtained. The production process characteristics of injection molding two-color products are as follows.
The 1 two-color injection molding machine consists of two sets of plastic injection devices with the same structure and specifications. The nozzles should have a special structure according to the production method, or two sets of molding dies with the same structure that can be rotated and transposed. When plasticizing injection, the process parameters such as melt temperature, injection pressure and injection melt amount in the two sets of plasticizing injection devices are required to be the same, and the fluctuation of process parameters in the two sets of devices should be minimized.
2 Two-color injection molded plastic products have higher parameter values ​​for the melt temperature and injection pressure at the time of injection compared with ordinary injection molded plastic products. The main reason is that the mold flow path in the two-color injection molding is relatively long, the structure is relatively complicated, and the flow resistance of the injection melt is large.
3 Two-color injection molding plastic products should use raw materials with good thermal stability and low melt viscosity to avoid decomposition due to high temperature of the melt and long residence time in the flow channel. The plastics used in many applications are polyolefin resins, polystyrene and aBS materials.
4 In the injection molding, in order to make the melt of two different colors melt well in the mold during molding, and to ensure the molding quality of the injection molded product, a higher melt temperature and a higher mold should be used. Temperature, higher injection pressure and injection rate.
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