Two-color Injection Molding Machine: You Need to Know

SS Machinery

The two-color injection molding machine uses the two-color molding process to manage product molding with two different materials and colors. Two-color molding is now widely used in electronic parts, power tools, medical parts, household appliances, toys, and almost all plastic products. Next, I will take you to know the information about the two-color injection molding machine you want to know.

What is a two-color injection molding machine

We introduce from two aspects of machine and molding.

What is a two-color injection molding machine

As the name suggests, it is an injection molding machine that can process two colors of plastic materials at the same time. It usually has 2 injection units, processing one material at a time. These two materials can be injected at the same time or at different times according to product requirements.

Toothbrushes are a good example of parts made using these machines.

What is two-color injection molding

The so-called two-color injection molding refers to the molding method of injecting two different colors of plastic into the same mold. The two thermoplastic resins are sequentially injected into the mold through different methods. The plastic parts can be made into two different colors , and the plastic parts can be made into regular patterns or irregular moire colors to improve the practicability and aesthetics of the plastic parts.

In order to actually use the two-shot injection molding method, a dedicated injection molding machine is usually required. In the two-color injection molding method, since beautiful multifunctional molded products can be produced in one step, molded products with high added value can be produced.

Features of two-color injection molding machine

We introduce from two aspects of process and design.

Characteristics of two-color injection molding process

  • Two-color injection molding machine configuration

    Considering the molding effect, the same injection molding machine needs to be equipped with two sets of matching plasticizer injection devices, not only for process requirements, but also for the purpose of modification. Except for the structure, the specifications of the two injection devices need to have the same functions. In the injection molding process, the material temperature, injection pressure, and injection speed of the two sets of equipment need to be adjusted consistently to ensure that the performance of the final molded part is at the same level, and then related fusion and integration work is carried out. If there is an inconsistency between the two injection devices, please pay attention to the alignment parameters.

  • The structure difference between two-color injection molded parts and ordinary injection molded parts

    due to the uniqueness of two-color injection molded parts, there are some obvious differences in the machine mechanism setting compared with ordinary injection molding machines. First, the two- color injection molding component uses a higher melt temperature, which requires high temperature to maintain the flow ability; secondly, it requires a larger injection pressure, not only because of the use of two different plastic materials, but also the pressing requires a strong fusion pressure . It is designed to overcome the huge resistance of the melt flowing through the mold and ensure smooth filling.

  • Two-color injection molding technology material parameter setting

    Two-color injection molding technology uses two different materials for the production of plastic products, so materials must be carefully considered before injection molding. Not only must the material quality standards be considered, but also the temperature, pressure and related parameters in the molding process must be controlled. Since the two-color injection molding process is different from the general injection molding process, the material used in the two-color injection molding process requires a higher melting temperature parameter to ensure that the material does not solidify before the filling is completed. Please ensure that you use the injection device to control the pressure of the material so that it reaches the mold Each area achieves the purpose of injection molding.

Design features of two-color injection molding machine

Two-color molding machines are becoming more and more popular in the market, but it puts forward higher requirements for mold design, mold manufacturing and injection molding.

  • Molding

    Two-color mold molding is almost the same as other ordinary injection molding. The difference is that the convex/core side of the injection mold at the two positions should be regarded as the same, and the concave/cavity side should fit well with the convex/core side. Such molded parts are small.

  • Demoulding

    Since the two-color molded part can only be demolded after the second injection, the demolding system will be invalid during the first injection. For parallel turntable injection machines, the ejector system in the injection machine can be used for parts release.

  • Gate system

    Because it is two-color molding, there are a first gate system and a second gate system from two different injection devices.

  • Mold

    Because the two-color molding method is special and needs to be coordinated with each other, the size and accuracy of the guide devices of the two molds must be consistent. The clamping height of the parallel turntable injection machine must be the same, and the centers of the two molds should be on the same radius of rotation, with a difference of only 180°. For vertical turntable injection molding machines, the two molds should be on the same axis.

Advantages of two-color injection molding machine

Compared with traditional injection molding, two-component injection molding machine has the following advantages:

The two-color mold can inject two resins with different characteristics and colors into a single two-color product, reducing the assembly and post-processing of the molded product.

It saves printing cost and increases the beautiful visual effect of the product.

Two-color injection molding not only has the functions of anti-skid and increased friction, but the flexible resin material is more ergonomic and feels better.

Two-color injection products are of high quality; product deformation is easy to control, and the molding cycle is short.

Save materials and reduce costs. The loss is 7% lower than that of insert molding, and the product manufacturing cost is 20%-30% lower than that of package injection molding.

Technical requirements for two-color injection molding machine

We introduce from two aspects of design and grinding tools.

Soft and hard rubber double fire design

There must be a certain temperature difference between the two materials, generally 60 degrees Celsius is recommended, and at least 30 degrees Celsius is recommended. The first material has a high melting point, the first is PC or PC/ABS, the second is TPU or TPE, and the thickness of PC is 0.6 -0.7mm, above 0.4mm by software.

Try to widen the contact area, make grooves, etc. to increase adhesion, or use the core for the first injection, and the material from the second injection part is injected into the first, and the first side of the mold is as rough as possible.

The mold of the two-color molding machine generally has the following requirements

  1. The two shapes of the female mold must be different, forming a product separately, while the two shapes of the male mold must be exactly the same.
  2. After the center of the mold is rotated 180 degrees, the mold must be consistent.
  3. The total thickness of the front panel plus A board should not be less than 170mm. The maximum thickness of the mold, the minimum thickness of the mold and the distance of the KO hole should be carefully studied.
  4. The water outlet of the three-plate mold can be designed with automatic demoulding.
  5. When designing the master mold for two-shot injection, in order to avoid the second master mold from scratching the glue surface of the first molded product, a part of it can be designed to avoid voids. However, it is necessary to carefully consider the strength of each sealing part (that is, whether there is plastic deformation under high injection pressure during injection molding, which may lead to the possibility of cracking in the second injection molding).;
  6. Injection molding, the product size of the first injection molding can be slightly larger, so that it can be tighter with others in the second molding to meet the sealing effect;
  7. Pay attention to the second injection, the plastic flow will impact the first molded product and deform the glue;
  8. Before closing the mold of A board or B board, pay attention to whether the front mold slider or inclined top will reset and crush the product first.
  9. The water distribution of the two female molds and the male mold should be used as much as possible and balanced;
  10. In 99% of cases, the hard rubber part of the product is injected first, and then the soft rubber part of the injection product, because the soft rubber is easily deformed.


From the characteristics and applications of multi-color molding and two-color molding, it can be seen that the development prospects of two-color injection molding machines are quite broad. The innovation of two-color injection molding machine and multi-color injection molding machine not only improves the precision of the molding process, provides technical and equipment support for difficult processes, but also opens up a new molding range.

Excellent two-color and multi-color injection molding machines can handle and produce diversified, high-quality, and high-value-added products. If you need to buy a two-component injection molding machine, you can browse Shuangsheng's products. Shuangsheng is an injection molding machine company from China, one of the scientific research and production enterprises with full experience and strength in precise medium and small injection molding machines.We believe that we can be your trusted partner.

Contact us now to get the latest quotation and product consultation.

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