Working principle and selection points of SHJ series twin-screw extruder

2024-10-29

When choosing an SHJ series twin-screw extruder, you should pay attention to whether the composition of each part is scientific and reasonable and whether the outer surface of the twin-screw extruder is finely made. From many aspects, we can see whether the technical situation and comprehensive strength of plastic extruder manufacturers can meet the requirements for providing services for our subsequent production.

Twin-screw extruder according to the type of extruded products and materials are different then the extruder screw design and subsequent configuration of the equipment design is also different. We need to select the right twin-screw extruder for our products according to our own use. For example, if we just use it for pelletising, then we need to purchase a plastic pelletising machine, while if we use it for plastic pipe extrusion, then we must select the appropriate type and configuration of the twin-screw extruder for the production of plastic hoses.

Therefore, when we choose a twin-screw extruder, we must choose it according to the actual purpose. If we don’t know much about the twin-screw extruder, we can ask the twin-screw extruder manufacturer to make an equipment feasibility plan for us. Let’s learn about the configuration and functions of the extruder.

Finally, we will also conduct on-site visits from actual users of twin-screw extruders, and learn about the use of the equipment and the reputation of the manufacturer. When we choose a twin-screw extruder, we need to choose a cost-effective equipment for extrusion production that can meet the long-term supply of equipment accessories.

Working principle of SHJ series twin-screw extruder:

From the perspective of motion principles, twin-screw extruders include co-meshing, counter-meshing and non-meshing types.

There are two types of co-rotating twin-screw extruders: low speed and high speed. The difference lies in the design, operating characteristics and application fields of the two extruders. The former is mainly used for profile extrusion, while the latter is used for special polymer processing.

Close-meshing extruders are low-speed extruders with close-meshing screw geometries in which the profile of the ribs of one screw closely matches the profile of the groove of the other.

The close-meshing co-rotating profile seems to show a good seal between the two screws, and the cross-section of the meshing area shows a large gap between the grooves of the two screws. Therefore, the conveying characteristics of a closely meshed co-rotating twin-screw extruder are not as positive as those of a closely meshed counter-rotating extruder.

Theoretically, the tightly meshed co-rotating twin-screw extruder can be designed so that the screws are fully meshed and sealed laterally, but they cannot be sealed longitudinally and must be released, otherwise the screws will not mesh. The width of the screw groove must be designed to be larger than the width of the screw rib, so the co-rotating twin-screw extruder has a sliding engagement.

When the material is added to a screw from the feeding port, it is transported forward along the groove of the screw under friction and drag, and is compressed to a certain extent. If the screw belly gap is large, the spiral edge of the other screw will not block the path forward for the material. Since the two screws have an equal and opposite speed gradient in the wedge area, the material will not enter the meshing area and continue to move around the same screw. Instead, it will be lifted up by the other screw and dragged by friction on the barrel surface. The material is conveyed forward along the groove of the other screw. When the material advances to the wedge-shaped area above, the process is repeated. From a macro perspective, the material moves in an ∞ shape and moves in the axis direction at the same time.