With the manufacturing process of twin-screw extruders becoming better and better, it not only needs to perform tasks such as feeding and plasticizing but also has requirements for dehydration, drying, etc. In order to better meet users' different needs, the twin-screw extruder must continuously improve its work efficiency and find ways to improve the quality of the products produced. So, how should we do it?
Improving work efficiency is one of the critical goals in the development and design of new co-rotating twin-screw extruders. This can be achieved by increasing the screw speed and enhancing plasticization and mixing levels. At the same screw speed, increasing the depth of the screw groove can greatly increase the throughput. Correspondingly, the plasticization and mixing levels of the screw must also increase, which requires the screw to withstand higher torque.
At high screw speeds, the residence time of the material inside the extruder decreases, potentially causing the material to not be plastified and melted, or mixed sufficiently.
Therefore, it is necessary to appropriately increase the screw length, which will inevitably result in an increase in the torque and power that the twin-screw extruder actually bears.
Increasing the free volume of the screw groove is also an important factor. In the feeding section and devolatilization section, the threaded elements need to have a large free volume. For materials with low bulk density, increasing the free volume of the feeding section and the degree of filling of the material in the screw groove can greatly improve the processing capacity of the extruder.
Increasing torque and speed requires careful design of the gearbox. Significantly increasing the torque index of the equipment will inevitably raise higher requirements for the design and manufacturing level of the gearbox.
The higher the torque, the higher the requirements for the design, manufacturing accuracy, material strength, and heat treatment of parts such as gears, output shafts, and bearings in the transmission box. At the same time, higher requirements are also placed on the design and manufacturing accuracy of parts such as the core shaft of the screw, threaded elements, and kneading discs.
Because it is necessary to increase the free volume of the threaded elements, when the outer diameter of the screw remains unchanged, the center distance between the two screws will decrease. This will inevitably make the installation space problems of gears and thrust bearings more prominent.
To obtain high product quality, the design of the core component of the extruder—the plasticizing system—is crucial.
The plasticizing system mainly includes the screw and barrel. To meet various processing requirements, the screw and barrel are generally designed as modular structures. According to the function of each section, the screw can be divided into the feeding section, plasticizing section, mixing section, exhaust section, and extrusion section. These sections have different functions during the extrusion process, their structures are not the same, and the geometric parameters of the corresponding screw elements are also different. Therefore, determining the geometric parameters of the threaded elements becomes the key to the design of the plasticizing system.
For co-rotating twin-screws, there is a certain relationship between the diameter ratio (the ratio of the center distance of the two screws to the screw radius), the number of threads, and the thread apex angle. They cannot be designed arbitrarily; otherwise, interference may occur between the two screws. For companies looking for a twin screw extruder for sale, or those evaluating solutions from reliable twin screw extruder machine manufacturers, understanding these design principles is essential to ensure efficiency and quality.
In addition, combined with practical projects and with the help of computers, three-dimensional solid modeling of twin screws with gaps can be completed. This can be used to check whether the gaps between the two screws are uniform to ensure that there are no dead corners in the movement of the material in the screw, thus ensuring that the screw has a strong self-cleaning ability and can effectively prevent the material from staying too long in the machine and degrading. This undoubtedly provides excellent processing means for the production of high-end and high-quality plastic products.
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