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Introduction to two-color injection molding technology and mold characteristics

Two-color injection molding technology is also called double-material injection molding technology. This is a technology that uses two plastic materials to be mixed and injection molded to form plastic products. Its technical connotation is actually to use a mold component to shape the shape and mold it in the mold. Welding work, so the basic principle is to plasticize two different plastic raw materials, and then use the mold for welding and installation to achieve the purpose of two-color injection molding.two-color injection molding technology and mold characteristics

  1. Two-color injection molding technology type

1.1 Core rotation two-color injection molding technology
This technology is also called rotary core two-color injection molding technology. Its technical principle is to first use injection equipment to inject the first raw material plastic into the small hole of the mold. After it is molded, it becomes the first plastic. , then rotate the mold 180°, use the same injection equipment to inject the second raw material plastic, wait until the second plastic is formed, and then perform the final encapsulation work. A basic two-color injection molding work is completed.

The use and operation of this technology are relatively simple. Generally, workers with a little training can operate it freely. It can greatly increase the design freedom of plastic products and can be processed with simple tools.

1.2 Shrink mold core two-color injection molding technology
Shrink mold core two-color injection molding technology mainly uses a hydraulic device to compress the mold. First, under the control of the hydraulic device, the core that can move up and down is pushed to the top rising position like a piston, and the plastic raw material is injected. After the first raw material solidifies, the movable core is controlled to fall, and then Inject another plastic raw material, then control the hydraulic device to raise the core and press it until it solidifies.

The plastic products pressed by this technology are initially produced, and then the formed plastic parts are taken out for subsequent processing. This technical operation is also relatively simple, and the timing of the movement of the hydraulic device must be controlled.

1.3 Principle of two-color injection technology with stripping plate rotation
Before working with this technology, the first raw material must be injected. During injection, other parts of the mold are clamped, and they are gradually cut and separated during the injection mold. The rear part of the insert will gradually retreat, but still exists on the stripping plate part, and the mold will retreat dynamically. , after passing through the entire injection molding machine’s ejector and pellet rod parts, they are cooled and dropped off, and the first part is completed;

The next step is to perform the injection molding operation of the second part, which is roughly the same as the first part, but the second injection molding uses two nozzles to inject at the same time. After waiting for it to solidify, the two parts are ejected together to complete an injection molding cycle.

1.4 Core sliding two-color injection technology
The working principle of the core sliding two-color injection technology is to classify the core into two times for use. During the first injection molding, the core used is slid to the designated position to perform the mold closing injection molding work. The first raw material is The plastic is injected into the mold, and after cooling, the mold is opened once.

The transmission device slides the first core out, slides the second core to the cavity, and then injects the plastic for the second time. After it cools and molds, an injection molding cycle is completed, and the two are synthesized. The finished product slides out. This technical model is more suitable for the needs of large-scale two-color injection molded plastic parts.https://doi.org/10.1533/9780857096234.3.338

  1. Introduction to the characteristics of two-color injection molding process

2.1 Two sets of structures of the two-color injection machine
Due to the purpose of making products, the two-color injection molding machine needs to be equipped with two identical plastic injection devices. This is not only a requirement for its process, but also requires the ability to perform rotational transformations.

These two sets of injection devices with the same specifications need to have the same function in addition to the same structure. When performing injection molding, the raw material temperature, injection pressure and injection rate in the two sets of equipment can be adjusted consistently to ensure that the injection molded plastic products The various indicators are kept at a consistent level, and then related fusion and welding work is carried out. If the parameters of the two sets of equipment are inconsistent, try to adjust them to the same level.

2.2 Differences in machine structure between two-color injection molding components and ordinary injection molding components
Due to the unique characteristics of plastic products produced by two-color injection molding components, there are some obvious differences between the machine’s mechanism settings and ordinary injection molding material machines.

First of all, the melt temperature used in two-color injection molding components is relatively high, which is somewhat different from ordinary injection molding components. High temperature is required to maintain the ability to operate and flow in the mold; secondly, the injection pressure is also relatively high, not only because of the They are two different plastic raw materials. To press and weld them, they need to be fused using strong pressure. They are also designed to overcome the huge resistance of the molten material flowing in the mold to ensure smooth injection molding.

2.3 Material parameter settings for two-color injection molding technology
Two-color injection molding technology uses two different materials to make plastic products. Therefore, the materials need to be considered before injection molding. Not only should the quality standards of the selected materials be considered, but also the temperature, pressure and other parameters of the materials during injection molding should be paid attention to. control.

Since the mold used in the two-color injection molding technology is different from the mold used in ordinary injection molding, this requires the material usage parameters of the two-color injection molding technology to have a higher melt temperature to ensure that the melt does not solidify in advance before the injection molding is completed. At the same time, the injection device must be used to control the pressure of the raw material so that it can smoothly reach all parts of the mold, thereby achieving the purpose of injection molding.https://solidcomould.com/product/fitting-pipe-mould8/

  1. Key points of two-color injection molding products and mold design

3.1 Structural characteristics of two-color injection molded products
The structure of two-color injection molded products is very different from that of ordinary plastic products. Since two different materials are used for injection molding, the products have two different properties and characteristics, which are fundamentally different from ordinary injection molded products; at the same time, Before injection molding, careful structural design of two-color injection molded products is required, and the compatibility characteristics of the two materials should be fully considered.

Design the mixing ratio and connection method of the two materials based on the functions and usage environment of the plastic product, and analyze the complexity of the process in detail. At the same time, the strength of use must be considered in the design so that the two-color injection molded product can meet the relevant material standards. and requirements.

3.1.1 Selection of two materials
Two-color injection molding technology uses two different materials for injection molding, so the selection of two different materials is also an important process. Generally, two plastics with different colors are used, which can greatly improve the strength and durability of the injection molded product. It also makes it easier to fuse and shape. However, products with special uses may need to take advantage of the situation where the properties of two materials are very different, which requires solving the problem of difficulty in fusion of two materials with large differences.

The main problems are delamination and shedding, which are fatal blows to injection molded products. Therefore, careful consideration is needed for the shrinkage rate and different interface conditions, and the proportion of materials must be adjusted.

3.1.2 Design of internal structure and shape of product
The design of the product structure and shape must first consider the purpose and use of the product, and conduct detailed research on the size and internal structure.

Generally, it is necessary to increase the contact area of the two raw materials to enhance the firmness. Here, many small grooves and convex grooves can be designed inside the product for inlaying and stitching. This achieves the purpose of increasing the contact area of the two materials. , when performing injection molding, the strength and service life of the product can be better improved and the practicality enhanced.

3.2 Rotary mold two-speed injection mold
This kind of mold requires different considerations in the molding part. First, the concave and convex grooves of the two injection molds need to be carefully designed to ensure a tight fit during docking. At the same time, when designing the demoulding mechanism, a second injection is required before demoulding can be carried out. Different injection molding methods need to be differentiated in different details. After the vertical rotation injection machine is ejected from the mold, the product is ejected to complete the relevant operations. In the demoulding situation where the injection machine cannot be ejected, a hydraulic device is required for ejection. mold.

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