It can be seen from the extrusion process that the scre […]
It can be seen from the extrusion process that the screw works under high temperature, certain corrosion, strong wear and high torque. Therefore, the screw must:
(1) High temperature resistance, no deformation under high temperature;
(2) wear resistance and long life;
(3) Corrosion resistant, the material is corrosive;
(4) High strength, can withstand high torque, high speed;
(5) has good cutting performance;
(6) The residual stress is small after heat treatment, and the thermal deformation is small.
The main part of the screw is a conventional screw which can be placed in the groove of the melting section or the metering section of the screw or the smooth cylindrical surface without the groove at the end of the metering section. The pins are arranged in a certain arrangement, and the density can vary from one to another. The cylindrical pin is formed by fitting the pin into the hole of the screw; the square or diamond pin is formed by milling the pin directly on the screw.
If the pins are arranged in the melting zone, the pin can break the solid bed, destroy the two-phase flow, stir the solid and liquid phases together, and increase the contact area between the final dissolved solid phase fragments and the contained materials, and promote Melt. If the pin is placed in the melt transfer zone, its primary function is to split the flow, increase the interface, change the direction of the flow, and rearrange the flow. Dividing and converging multiple times, changing the flow direction to homogenize the melt composition and temperature.
The mixing section is an inwardly slotted structure disposed at the end of the normal screw homogenization section, and the outer diameter is equal to the outer diameter of the screw. The grooves are divided into groups, each of which is a confluence area of materials. The material is divided by the groove, merged into the confluence area, and then divided and merged. The principle is similar to the pin type.
The separation type screw is characterized in that in addition to the original one screw thread (called the main screw), a thread is added to the melting section (referred to as an additional thread), and the outer diameter is slightly smaller than the outer diameter of the main thread, and the main and auxiliary lines are The lead is different from the end of the feed section (and here associated with the feed section), after a few threads, gradually intersects the main thread of the homogenization section.
The screw groove depth and thread lead of the screw are gradually changed from the feeding section to the homogenizing end, and the thread lead is gradually narrowed from the width, and the groove depth is gradually shallowened from the depth, so that the material can be greatly compressed.