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With China Plastic Machinery
With China Plastic Machinery
Double-color injection molding refers to the process of injecting two different materials into the same mold, so that the molded parts are formed by two materials. Some of the two materials are different colors, and some are different in hardness and softness, so as to improve the aesthetics and assembly performance of the product.
Double-color injection molding is an operation method in which two different colors of the same plastic are plasticized through two barrels and then injected through the same nozzle at the same time or successively. Using two injection molding machines or two-color injection molding machines to form, a variety of mixed-color pattern products can be produced, and products with obvious color separation can also be produced.
Compared with traditional injection molding, the double-material co-injection molding process has the following advantages:
1. The core material can use low-viscosity materials to reduce the injection pressure.
2. From the perspective of environmental protection, the core material can use recycled secondary materials.
3. According to different usage characteristics, such as using soft materials for the skin material of thick finished products, using hard materials for the core material, or using foamed plastics for the core material to reduce weight.
4. You can use lower quality core materials to reduce costs.
5. Expensive materials with special surface properties, such as anti-electromagnetic interference, high conductivity, etc., can be used for the skin material or core material to increase product performance.
6. Appropriate combination of skin material and core material can reduce the residual stress of the molded product, increase the mechanical strength or surface properties of the product.
7. Produce products with marble patterns.
Plastic products that use two different types of plastics and can be clearly distinguished on the product are called two-color products. A mold installed on the same injection molding machine with two sets of injection molding devices (i.e., two-color injection molding machine) that injects two plastics in sequence and produces two-color products is called a two-color mold.
Two-color injection molding machines are usually of two types, parallel injection molding machines and vertical injection molding machines.
1. Parallel type
The injection molding screws are arranged in parallel and can act independently or simultaneously. There are two sets of independently acting ejector mechanisms as shown in the figure below.
2. Vertical type
The injection molding screws are arranged vertically in a plane, as shown in the figure below. They can also act independently or simultaneously, but there is only one set of ejector mechanisms.
Two-color molds can be divided into core rotation type, core retreat type, and push plate rotation type according to their structure. Among them, the core rotation type can be divided into two types: split type and one-piece type. The so-called split type is to use two pairs of molds installed on one injection molding machine to complete the injection molding of two-color products. The one-piece type is to complete the injection molding of two-color products in one mold. Among them, the core rotation split type is more widely used.
1. Molding part
The molding part of two-color injection mold is basically the same as that of general injection mold. The difference is that the punch of the injection mold at two positions should be consistent, and the concave mold should cooperate well with the two punches. Generally, the plastic parts molded in this way are smaller.
2. Demolding mechanism
Since two-color plastic parts can be demolded only after two injections, the demolding mechanism on the one-shot injection device will not work. For horizontally rotating injection molding machines, the ejection mechanism of the injection molding machine can be used for demolding, while for vertically rotating injection molding machines, the ejection demolding mechanism of the injection molding machine cannot be used. In this case, a hydraulic ejection demolding mechanism can be set on the rotary table.
3. Casting system
Since it is two-color injection molding, the casting system is divided into the casting system of one injection and the casting system of two injections, which come from two injection molding devices respectively.
4. Mold
Due to the special molding method of two-color injection molding, it requires mutual cooperation and coordination, so the size and precision of the two mold guide devices must be consistent. For horizontally rotating injection molding machines, the closing height of the molds must be consistent, and the centers of the two molds should be on the same rotation radius and 180 degrees apart. For vertically rotating injection molding machines, the two molds must be on the same axis.
From the characteristics and applications of multi-color injection molding and double-material co-injection molding, it can be seen that there is a trend of gradually replacing traditional injection molding processes in the future. Innovative injection molding technology not only improves the precision of the injection molding process and provides high-difficulty process technology, but also expands the scope of the injection molding process. Innovative injection equipment and processes are sufficient to meet the needs of more and more diversified, high-quality, and high-value-added products.
Two-color injection molding is now widely used in almost all plastic fields such as electronic products, power tools, medical products, home appliances, toys, etc. The production and molding of two-color molds, as well as the research and development of two-color and multi-color injection molding machines and two-color injection molding raw materials have also developed rapidly.
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