In the plastic extrusion molding equipment, the plastic extruder is usually called the main machine, and the supporting equipment plastic extrusion molding machine is called the auxiliary machine. After more than 100 years of development, the plastic extruder has been derived from the original single screw, such as twin screw, multi-screw, and even no screw. Plastic extruder (main machine) can be used with various plastic molding auxiliary machines such as pipes, films, holding materials, monofilaments, flat filaments, packing belts, extruded nets, plates (sheets), profiles, granulation, and cable coating. Match and form various plastic extrusion molding production lines to produce various plastic products. Therefore, plastic extrusion molding machinery is one of the widely used machines in the plastic processing industry, now and in the future.

The main machine of a plastic extrusion machine is an extruder, which is composed of an extrusion system, a transmission system and a heating and cooling system.

The extrusion system includes a screw, a barrel, a hopper, a head, and a die. The plastic is plasticized into a uniform melt through the extrusion system, and is continuously extruded by the screw under the pressure established in the process.

In the mold sleeve, the plastic is given the necessary forming pressure. The plastic is plasticized and compacted in the barrel, and passes through the porous filter plate along a certain flow path through the neck of the head and flows into the head forming mold. The core mold sleeve is properly matched to form a circular gap with a decreasing cross-section, so that the plastic melt is in the A continuous and dense tubular coating is formed around the core wire.

In order to ensure that the plastic flow path in the machine head is reasonable and eliminate the dead angle of the accumulated plastic, a shunt sleeve is often installed. In order to eliminate the pressure fluctuation when the plastic is extruded, there is also a pressure equalizing ring. The head is also equipped with a mold correction and adjustment device, which is convenient for adjusting and correcting the concentricity of the mold core and the mold sleeve.

The extruder divides the machine head into a beveled machine head (with an included angle of 120o) and a right-angle machine head according to the angle between the head material flow direction and the centerline of the screw. The shell of the machine head is fixed to the fuselage with bolts. The die in the machine head has a core seat and is fixed to the wire inlet port of the head with a nut. The front of the core seat is equipped with the core, the core and the core seat. There is a hole in the center for passing the core wire. There is a pressure equalizing ring on the front of the machine head for equalizing pressure. The extrusion molding part is composed of a die sleeve and a die sleeve. The position of the die sleeve can be adjusted by the bolt through the support In order to adjust the relative position of the mold sleeve to the mold core, it is easy to adjust the uniformity of the thickness of the cladding layer. The head is equipped with a heating device and a temperature measuring device.

The function of the drive system is to drive the screw and supply the torque and speed required by the screw in the extrusion process. It usually consists of a motor, a reducer and a bearing.

Under the premise that the structure is basically the same, the manufacturing cost of the reducer is roughly proportional to its external dimensions and weight. Because the shape and weight of the reducer are large, it means that more materials are consumed during manufacture, and the bearings used are also relatively large, which increases the manufacturing cost.

For the extruder with the same screw diameter, the high-speed and high-efficiency extruder consumes more energy than the conventional extruder, doubles the motor power, and the size of the reducer must be increased accordingly. But high screw speeds mean low reduction ratios. For gearboxes of the same size, compared with gearboxes with low reduction ratios, the gear modulus increases, and the capacity of the gearboxes to withstand load increases. Therefore, the increase in volume and weight of the reducer is not linearly proportional to the increase in motor power. If the amount of extrusion is used as the denominator, divided by the weight of the reducer, the number of high-speed and efficient extruders is small, and the number of ordinary extruders is large.

In terms of unit output, the motor power of the high-speed and high-efficiency extruder is small and the weight of the reducer is small, which means that the unit production cost of the high-speed and high-efficiency extruder is lower than that of ordinary extruders.

Heating and cooling are necessary conditions for the plastic extrusion process to take place.

1.The extruder usually uses electric heating, which is divided into resistance heating and induction heating. The heating sheet is installed in the body, neck and head. The heating device heats the plastic in the cylinder externally to increase the temperature to reach the temperature required for the process operation.

2.The cooling device is set to ensure that the plastic is in the temperature range required by the process. Specifically, it is to exclude the excess heat generated by the shear friction caused by screw rotation, so as to avoid the temperature being too high to make the plastic decompose, scorch, or shape difficult. The barrel cooling is divided into two types: water cooling and air cooling. Generally, small and medium-sized extruders are more suitable for air cooling, and large-sized ones are mostly water-cooled or combined with two forms of cooling. To stabilize the amount of glue and improve product quality; but the cooling at the hopper is to strengthen the transport of solid materials, to prevent plastic particles from sticking due to temperature rise, and to ensure the normal operation of the transmission part.

Plastic extruder can be divided into single screw extruder, twin screw extruder and multi-screw extruder according to the number of screws. At present, single screw extruder is the most widely used and suitable for extrusion processing of general materials. The twin-screw extruder has less heat generated by friction, more uniform shearing of the material, larger screw conveying capacity, more stable extrusion capacity, longer material stay in the barrel and uniform mixing.

The single-screw extruder occupies an important position whether it is a plasticizing granulation machine or a molding processing machine. In recent years, the single-screw extruder has developed greatly.

The twin screw extruder has good feeding characteristics, is suitable for powder processing, and has better mixing, venting, reaction and self-cleaning functions than the single screw extruder. It is characterized by processing plastics and blends with poor thermal stability. Shows its superiority when the material. On the basis of twin-screw extruders, in order to more easily process blends with poor thermal stability, multi-screw extruders, such as Guanghua Plastic Extruder, have been developed.