1. Definition of plastic extruder

In plastic extrusion molding equipment, twin-screw plastic extruder are often referred to as main engines, and the subsequent equipment plastic extrusion molding machines are called auxiliary machines. After more than 100 years of development, plastic extruders have been derived from the original single screw twin screw, multi-screw, and even no screw. Plastic extruder (main machine) can be used with pipes, films, materials, monofilaments, flat yarns, packing belts, extruded nets, plates (sheets), profiles, granulation, cable coating, etc. Matching, forming a variety of plastic extrusion molding lines to produce a variety of plastic products. Therefore, plastic extrusion molding machines are one of the most widely used models in the plastics processing industry, now or in the future.

 

  1. Composition of plastic extruder

The main body of the twin-screw plastic extruder is an extruder consisting of an extrusion system, a transmission system and a heating and cooling system.

  1. 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.

 twin-screw plastic extruder
twin-screw plastic extruder

twin-screw plastic extruder

(1) Screw: It is the most important part of the twin-screw plastic 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.

(4) Handpiece and mold: The machine head is composed of an alloy steel inner sleeve and a carbon steel jacket, and a molding die is arranged in the machine head.

  1. Transmission system

     The function of the drive system is to drive the screw, which supplies the torque and speed required by the screw during the extrusion process, usually consisting of a motor, a reducer and a bearing.

  1. Heating and cooling device

 Heating and cooling are essential for the plastic extrusion process.

 twin-screw plastic extruder
twin-screw plastic extruder

(1) Nowadays, twin-screw plastic extruder usually use electric heating, which is divided into resistance heating and induction heating. The heating sheets are installed in the fuselage, neck and nose parts. The heating device heats the plastic in the cylinder from the outside to raise the temperature to achieve 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 eliminate the excess heat generated by the shear friction of the screw rotation, so as to avoid the decomposition of the plastic, the scorch or the setting of the plastic is difficult. The barrel cooling is divided into two types: water cooling and air cooling. Generally, small and medium-sized twin-screw plastic extruder are suitable for air cooling, while large ones are mostly water-cooled or combined with two types of cooling. The screw cooling mainly uses central water cooling to increase the material solids conveying rate. Stabilize the amount of glue and improve the quality of the product; however, the cooling at the hopper is to strengthen the conveying effect on the solid material, prevent the plastic particles from sticking to the material block due to the temperature rise, and the second is to ensure the normal operation of the transmission part.

 

With Best Regards,

Lee ( Sales Department; Miss. )         
NER GROUP CO.,LIMITED                            
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