Structure of ordinary screw of extruder equipment

Conventional fully threaded three-section screws can be divided into three forms according to changes in thread lift and groove depth:
(1) Equally spaced depth screw
The speed of the equidistant depth-changing screw from the groove depth can be divided into two forms:
① Equidistant gradient screw: A screw whose depth gradually becomes shallower from the feeding section to the last screw groove in the homogenizing section. Over the longer melting section, the groove depth gradually becomes shallower.
② Isometric mutation screw: that is, the screw groove depth in the feeding section and homogenization section remains unchanged, but the groove depth in the melting section suddenly becomes shallower.
(2) Constant depth variable pitch screw
The constant depth variable pitch screw means that the depth of the screw groove remains unchanged, and the screw pitch gradually becomes narrower from the first screw groove in the feeding section to the end of the homogenization section.
The characteristic of the constant-depth variable pitch screw is that due to the constant depth of the screw groove, the cross-sectional area of the screw at the feeding port is larger and has sufficient strength, which is conducive to increasing the rotation speed, thereby improving productivity. However, screw processing is difficult, the flow of molten material backflow is large, and the homogenization effect is poor, so it is rarely used.
(3) Variable depth and variable pitch screw
The variable depth and variable pitch screw refers to a screw whose groove depth and thread lift angle gradually change from the beginning of the feeding section to the end of the homogenization, that is, the thread lift gradually becomes narrower from wider, and the screw groove depth gradually becomes shallower from deeper. This screw has the characteristics of the previous two screws, but it is difficult to machine and is rarely used.