1、 Advantages of two-color injection molding:

The two-color mold can turn two resins and colors with different characteristics into a single two-color product, which can reduce the assembly and post-treatment engineering of molded products. Save the cost of dissolving and printing, increase the beautiful visual effect of products, and improve the grade and added value of products. It not only has the function of anti-skid and increasing friction, but also the flexible resin material makes it more ergonomic and feel better. The two-color injection molding product has high quality stability, easy control of product deformation, short molding cycle, high output, 7% lower loss than the plastic coated injection molding, and 20%-30% lower product manufacturing cost than the plastic coated injection molding

2、 Principle of two-color molding

Two color injection molding usually refers to the molding of two colors or different kinds of plastics. Because the two groups of injection units and nozzles of the two-color machine are independent and separated, the colors of the finished products are mostly two-color distinct and not mixed together. The biggest difference between the two-color injection molding machine and the general injection molding machine is the design of the movable template of the injection unit machine. Generally speaking, a two-color machine has two separate injection units, while a general injection machine has only one group of injection units. The configuration mode of two groups of injection units has various forms according to the design of each manufacturer. As for the design of movable template, it must provide rotation mechanism. Generally, common designs such as adding rotary table or rotating shaft mechanism to provide 180 ° reciprocating rotation function and make the mold produce cyclic alternating action. Other special two-color molds do not need a rotary table or rotating shaft mechanism, but slide alternately or rotate horizontally by the mold.

3、 Production process characteristics of injection molding two-color products

1. The two-color injection molding machine is composed 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 groups of forming molds with the same structure that can rotate and transpose. During plasticizing injection, the melt temperature, injection pressure, injection melt volume and other process parameters in the two sets of plasticizing injection devices are required to be the same, and the fluctuation difference of process parameters in the two sets of devices should be minimized.

2. Compared with ordinary injection molded plastic products, the melt temperature and injection pressure of two-color injection molded plastic products should adopt higher parameter values during injection. The main reason is that the mold runner in two-color injection molding is relatively long, the structure is relatively complex, and the flow resistance of injection melt is large.

3. Materials with good thermal stability and low melt viscosity should be selected for two-color injection molding plastic products to avoid decomposition due to high melt temperature and long residence time in the runner. The most widely used plastics are polyolefin resins, polystyrene and ABS materials.

4. During the injection molding of two-color plastic products, in order to make the molten materials of two different colors weld well in the mold and ensure the molding quality of the injection molded products, higher melt temperature, higher mold temperature, higher injection pressure and injection rate should be adopted.

4、 Two color mold structure

The traditional two-color injection mold has two forms: "punch translation" and "punch rotation".

① The die of "punch translation" has two female dies and one male die. When the first barrel is sprayed with glue, the punch and the first concave die are closed. Complete the injection of the first plastic. After the first kind of plastic solidifies, the concave and convex dies are separated, and the semi-finished product formed by the first kind of plastic stays on the convex die and moves with the convex die to the position aligned with the second concave die. After the injection molding machine is closed, the second barrel carries out the injection of the second kind of plastic. After the second kind of plastic solidifies, the injection molding machine opens the mold and takes out the complete product.

② The two-color die in the form of "punch rotation" has two female dies and a punch composed of two back-to-back groups. This punch can rotate. The injection molding machines equipped with both sides have two barrels, and the second barrel is preferably designed in the vertical direction of the movement direction of the injection molding machine. Two different plastics can be injected at the same time. When the injected two kinds of plastic solidify, the injection molding machine opens and automatically ejects the complete product. After taking out the product, the "rotatable punch" rotates 180 degrees. The injection molding machine is closed for the next cycle.

Because the first and second barrels in the "punch translation" mode are injected in turn, while the first and second barrels in the "punch rotation" mode are injected at the same time. Therefore, for the same product, the production efficiency of "punch rotation" mode is twice that of "punch translation" mode.

5、 New technology of two-color mold

The two-color injection molding machine is equipped with two barrels. The mold is single cavity and has the common cavity required by the first kind of plastic ("hard glue") and the second kind of plastic ("soft glue"). This technology requires a single die and punch, which is fundamentally different from the first two production modes. When the first plastic is injected into the first barrel, wait until the first plastic has partially solidified or solidified. The power cylinder at the beginning of the control drives the blade that plays an isolating role to retreat to be level with the profile of the punch. At this time, the second plastic is injected into the second barrel. After the second kind of plastic is completely solidified, the injection molding machine is opened and the complete product is taken out. Then the injection molding machine is shut down for the next cycle. The obvious advantage of this technology is that it simplifies the mold and reduces the need for the working space of the injection molding machine (a smaller two-color injection molding machine can be used to reduce investment and energy consumption). And it can double the output of the previous "glue wrapping method", and fundamentally avoid the defective products caused by putting the shrinkage and deformation "hard glue" back into the mold cavity.

6、 The difference between rubber coated 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 in two times, but the product is molded only once. Generally, this molding process is also called double material 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 turn two resins and colors with different characteristics into a single two-color product, which can reduce the assembly and post-treatment engineering of molded products. Save the cost of dissolving and printing, increase the beautiful visual effect of products, and improve the grade and added value of products. It not only has the function of anti-skid and increasing friction, but also the flexible resin material makes it more ergonomic and feel better. The two-color injection molding products have high quality stability, easy control of product deformation, short molding cycle, high output, 7% lower loss than the plastic coated injection molding, and 20% - 30% lower product manufacturing cost than the plastic coated injection molding.

2. Plastic wrapping mold (secondary molding): two kinds of plastic materials may not be injected on the same injection molding machine, but are molded in two times; After the product is taken out of one set of mold, it is put into another set of mold for the second injection molding. Therefore, generally, this molding process is usually completed by two sets of molds, without the need for a special two-color injection molding machine. The mold structure is the same as that of the monochrome injection mold, which mainly depends on adjusting the flow rate of the injection parameters to control the combination point of seed materials. The rubber covering mold is mainly composed of soft rubber covering hard rubber, of which soft rubber is commonly used as artificial rubber, TPU, TPR and other rubber materials, and hard rubber can be ABS, PC, PP, etc.

Comparison of structural differences between two-color mold and rubber coated mold