As one of the important parts of the extrusion system o […]
As one of the important parts of the extrusion system of the plastic extruder, the screw not only plays a role in conveying plastics, but also plays an extremely important role in the extrusion, plasticization and molding of plastics. Reasonable selection of screw structure and parameters is an important part of obtaining ideal product quality and output.
In order to meet the needs of different plastic processing, there are many types of screws. The common ones are as follows: gradient type (equal distance is not equal), gradient type (equal depth is not equal), mutant type, * head type, etc.
The selection of the screw type is mainly determined by the physical properties of the plastic and the production specifications of the extruder.
(1) The softening of the amorphous polymer is carried out at a relatively wide temperature, and an equidistant gradient screw is generally used. The temperature range in which the crystalline polymer is melted is relatively narrow, and an isometric mutant screw is generally used.
(2) On small plastic extruders, such as φ45 extruder screw, the full-thread type with equal distance and unequal depth, the long diameter of the screw is relatively small, mainly used for extruding small-section insulating layer and sheath layer. The extrusion speed is faster.
(3) The medium-sized screw adopts a full-thread type with equidistant and thread depth gradient. Its length-to-diameter ratio is larger than that of the small screw, and the pitch of the threads is equal, from shallow to deep from the root. The thread at the end of the thread is deeper, and the thread at the root is shallower, so that the plastic extrusion amount is more, the screw strength is not affected, the extrusion speed is fast, and the plastic plasticization is good. It is a general small and medium-sized extruder to produce insulation layer and protect The ideal screw for the jacket.