The conveying element is threaded, and its function is to convey materials (including liquid materials). The shape of the screw groove can be rectangular or a special shape (meshing type) generated according to the principle of relative motion. The threaded components are divided into two types, forward and reverse, and can be divided into single-head, double-head and three-head threaded components.
Single threaded element
The solid conveying capacity is generally used in the feeding section to improve the extrusion volume that is limited by the feeding volume and to convey materials with poor fluidity, such as low-density materials. It is generally used to transport materials with a particle size similar to water during the reaction process, and can also be used in the discharge section. The output capacity of single-threaded threads is greater than that of multi-threaded threads, and the torque is also greater than that of multi-threaded threads, and its mixing characteristics are more than that of multi-threaded threads.
Compared with double-threaded and triple-threaded
Under the same central moment, D/D. It is relatively large and the groove is deeper, so it can provide a lower shear rate under the same screw speed, which is more suitable for processing powder materials, especially low bulk powder, glass fiber and other materials that are sensitive to shear . Compared with three-threaded components, under the same shear stress and torque, two-threaded components can work at a higher speed and have higher productivity. Under the same screw speed, the three-threaded element can apply a higher average shear rate and shear force to the material. In addition, due to the shallow screw groove, the material layer becomes thinner, and the three-threaded component has better heat transfer performance than the two-threaded thread. Material is plasticized and melted. However, because of the strong shearing, it is generally not easy to use in the processing of shear-sensitive materials, such as glass fiber and PVC.
Lead changes and characteristics:
In the screw combination, for output-oriented occasions, choosing a larger lead thread is beneficial to increase the output. For the extrusion of heat-sensitive polymers, choosing a larger lead can shorten the residence time of the material and reduce the thermal degradation of the material . The thread lead has a great influence on the extrusion volume, mixing characteristics, and torque. Generally speaking, as the thread lead increases, the screw extrusion volume increases, the residence time of the material decreases, and the mixing effect of the material is relatively reduced, and the torque also decreases. Become smaller. For mixing-oriented occasions, choose the medium-lead thread, and for the threads in different working areas of the screw, the lead is gradually reduced. It is mainly used for the output and pressurization of solid materials to increase the melting speed or mixture. Speed and extrusion stability.