It is well known that in recent years, with the rapid development of my country's plastics industry, the use of plastics has become more and more extensive, and the requirements for plastic products have become higher and higher. For the injection molding machine industry, there are more and more studies on the screw used to form various products. In fact, using the traditional three-stage general-purpose screw is difficult to meet the molding requirements of blending, coloring, mixing and homogenization of different raw materials. In order to meet the market requirements, according to the technological characteristics and formula requirements of some raw materials in the processing process, our company has designed several new types of screws, which better solve the shortcomings of ordinary screws in the injection process and achieve good results.
haitian alloy material tube group1. Structure and application of mixing ring screw
The feature of the on-machine mixing ring
single screw barrel is that the mixing element is set at the position of the metering section, which mainly plays the role of mixing and homogenization. Based on the consideration of mechanical manufacturing process, there are generally two forms in structure, namely pin type and barrier type.
During the plasticizing process, the pin-type mixing element makes full use of the diversion effect of the pin. During the diversion process, the unplasticized small pieces in the front section will continuously absorb heat from the molten material, so that the entire molten material will be absorbed. temperature decreased. When the plastic passes through the pin, the solid phase in the material is crushed and refined, and the melting time is shortened. And due to multiple mixing, a good plasticized melt can be obtained. With this structure, it is more suitable for raw materials with high requirements on temperature control and small temperature rise during processing. Such as HPVC, PET transparent material, etc. In the design, attention should be paid to the selection of parameters such as the position, number and circulation area of the pins.
During the plasticization process of the barrier type mixing element, the shearing effect of the barrier edge between the feeding chute and the discharging chute on the material can be used to further homogenize the remaining unplasticized small fragments, and at the same time the material can be further homogenized. can also be mixed. With this structure, the material should contain a certain amount of solid phase material before entering the mixing section to maximize the efficiency of this element. Its color mixing and plasticizing effects are relatively good, but for some products with high transparency or raw materials with poor thermal stability, attention should be paid to the parameter selection of mixing elements.
2.The structure and application of the separation screw
The structure of the separation screw is that a secondary screw is added in the melting section, and the main thread groove is divided into two parts. The gas in the phase groove is discharged backward from the material under the action of pressure, which reduces the bubbles in the product. At the same time, the heat exchange area between the solid phase material and the inner wall of the barrel is increased.
There are many types of separate screw structures. In the actual design and test, the company believes that in terms of the convenience of machining and the effect of use, the main and auxiliary threads have the same lift, the liquid phase groove and the solid phase groove width of the screw groove. Remaining unchanged, the depth of the solid phase tank gradually becomes shallower from the beginning of the compression section, while the depth of the liquid phase tank gradually becomes deeper to the end of the homogenization section. This structure is beneficial to products with high transparency and raw materials with poor thermal stability. And it has strong adaptability to raw materials.
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