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Screw is the core part of Extruder. Not only essential, but especially important.
Today I would like to introduce you to the general screw extruder three kinds of structural forms:
According to the change of the thread lift and the depth of the screw groove, the conventional full thread three-section screw can be divided into three kinds of forms:
(1) Isometric variable depth Screw
The speed of the variation of the distance from the spiral groove of the isometric variable depth screw can be divided into two types: ① Equidistant Tapered Screw: The depth of the last spiral groove from the feeding section to the homogenization section is a tapered screw.
The depth of the spiral groove is gradually shallower on the longer melting section.
② Equidistant mutant Screw: The screw groove depth of the feeding section and the homogenization section is unchanged, and the screw groove depth suddenly becomes lighter at the melting section.
(2) Equal depth variable pitch screw
Constant depth variable pitch screw is the same as the depth of the spiral groove, the pitch from the feeding section of the first spiral groove to the end of the homogenization section is a lenient gradient narrow. The characteristic of constant depth variable pitch screw is that the screw groove is deep, the screw section area at the feeding port is larger, has enough strength, it is advantageous to increase the rotational speed, thus can increase the productivity.
But the screw processing is more difficult, the melt flow is bigger, the homogenization effect is poor, less use
(3) Variable depth variable pitch screw Variable-depth variable-pitch screw refers to the depth of the spiral groove and the thread rise angle from the feeding section to the end of the homogenization is gradually changing, that is, the thread lift leniency gradually narrowed, the depth of the spiral groove from deep gradually to shallow screw. The screw has the characteristics of two kinds of screw in the front, but the machining is difficult and less used.