The main body of the plastic extruder is an extruder consisting of an extrusion system, a transmission system and a heating and cooling system.
The focus here is on the extrusion system:
The extrusion system includes a screw, a barrel, a hopper, a handpiece, and a mold. The plastic is plasticized into a uniform melt by an extrusion system, and is continuously extruded by the screw under the pressure established in the process.
(1) Screw: It is the most important part of the extruder. It is directly related to the application range and productivity of the extruder. It is made of high strength and corrosion resistant alloy steel.
(2) Barrel: It is a metal cylinder, which is generally made of alloy steel with high heat resistance, high compressive strength, strong wear resistance and corrosion resistance or composite steel pipe lined with alloy steel. The barrel is matched with the screw to achieve pulverization, softening, melting, plasticizing, venting and compacting of the plastic, and continuously and uniformly conveying the rubber to the molding system. The length of the general barrel is 15 to 30 times its diameter, so that the plastic is fully heated and fully plasticized.
(3) Hopper: The bottom of the hopper is equipped with a cutting device to adjust and cut the flow. The side of the hopper is equipped with a sight hole and a calibration metering device.
Advantages: The single-screw extruder is simple in design and inexpensive, so it is widely used.
Disadvantages: (1) The material conveying of the single-screw extruder is mainly based on friction, which limits the feeding performance. Powder, paste, glass fiber and inorganic filler are difficult to join.
(2) When the head pressure is high, the countercurrent is increased to lower the productivity.
(3) The material of the single-screw exhaust extruder has a small surface renewal effect in the exhaust zone, and thus the exhaust effect is poor.
(4) Single-screw extruders are not suitable for certain processes, such as polymer coloring, processing of thermosetting powders, and the like.
Extrusion is also known as extrusion in plastic processing, and is used in the processing of non-rubber extruders by using hydraulic press pressure to extrude the extrusion of the mold itself. It refers to a processing method in which the material passes through the action between the barrel and the screw of the extruder, is plasticized while being pushed forward by the screw, and continuously passes through the machine head to make various cross-section products or semi-products.