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Screw Design Principles

The main part of the pin screw is a common screw, and the locking pin can be set in the groove of the melting section or metering section of the screw, or on the smooth cylindrical surface at the end of the metering section without a screw groove.

The locking pins are arranged in a certain way with varying density and quantity. The cylindrical locking pins are assembled into the holes of the screw, while the square or diamond-shaped locking pins are directly milled onto the screw. If these locking pins are set in the melting zone, they can crush the solid bed, disrupt the two-phase flow, and mix the solid and liquid phases together, increasing the contact area between the fragmented solid phase and the already molten material, promoting melting. If the locking pins are set in the melt conveying zone, their main function is to divide the material flow, increase the interface, change the direction of the material flow, and rearrange the flow beam. By repeatedly dividing and merging, changing the flow direction, the melt components and temperature can be homogenized. The mixing section is a slotted structure that opens inward, set at the end of the ordinary screw homogenization section, and its outer diameter is equal to the outer diameter of the screw. The grooves are divided into several groups, and the convergence zone of the material is between each group. The material is divided by the grooves, converged in the convergence zone, and then divided and converged again. The principle is similar to that of the locking pins.

The characteristic of a separable screw is that, in addition to the original single screw thread (called the main screw), an additional screw thread (called the sub-thread) is added on the melting section. The outer diameter of the sub-thread is slightly smaller than that of the main thread, and the pitch of the main and sub-threads is different. The sub-thread starts from the end of the feeding section (and is connected to the feeding section), passes through several threads, and gradually intersects with the main thread in the homogenization section. The groove depth and thread pitch of this screw gradually change from the beginning of the feeding section to the end of the homogenization section, with the thread pitch gradually narrowing and the groove depth gradually becoming shallower, which can compress the material to the maximum.