Introduction to the working principle of screw plastic pelletizing recycling line machine

Screw plastic granulator extruder is one of the most important equipment for plastic molding processing. It uses solid power transportation, compaction, melting and shear mixing extrusion molding of plastics through external power transmission and heat transfer from external heating elements. Since the birth of screw extruder, after nearly a century of development, it has developed from a common screw extruder to a new type of screw plastic pelletizing extruder. Although there are many types of new screw extruders, they are basically the same in terms of the extrusion mechanism. The extrusion process of the traditional screw plastic pelletizing extruder is realized by external heating of the barrel, friction between solid materials and the barrel, screw friction and melt shearing force. "Friction coefficient" and "friction", "viscosity" and "shear stress" are the main factors affecting the working performance of traditional screw extruders. Because the factors affecting "friction" and "viscosity" are very complex, therefore The extruder extrusion process is an unstable state and difficult to control. It is particularly prominent for some thermally sensitive plastics with poor thermal stability and high viscosity. Since the 1960s, scholars from various countries around the world have done a lot of research on the screw extrusion mechanism and have made significant achievements, but because their research is mostly limited to traditional plastic extrusion molding mechanisms, mechanical structure forms and energy conversion methods, There has been no major breakthrough. A series of shortcomings of the traditional screw extruder, such as large volume, high energy consumption, high noise, and difficult to improve product quality, have not been fundamentally solved.

In 1979, after many years of teaching and scientific research, Professor Qu Jinping, after long-term observation and thinking, and theoretical research, on the basis of summing up previous studies, he boldly proposed the concept of introducing vibration fields into the entire process of extrusion molding. The structure of the screw extruder is completely changed. After two years of hard work, the first prototype of a plastic electromagnetic dynamic plasticizing extruder was finally developed in 1990. The principle prototype uses a direct energy conversion method to introduce the vibration field into the entire process of plasticizing extrusion, from principle to mechanical structure. They are completely different from traditional screw extruders and overcome many of the shortcomings of traditional equipment. They have the advantages of small size, light weight, low manufacturing cost, low energy consumption, low noise, and good plasticizing effect. At the end of 1990, experts from the Torch High-tech Industrial Development Center of the National Science and Technology Commission, after inspection and defense, included them in the 1991 National Torch Plan Preparation Project for research and development. In July 1991, one of the series of research, "Mechanical and Electromagnetic Integration Research of Plastic Blending Extrusion Equipment" was supported by "Huo Yingdong Youth Education Fund". With the support of this fund, the in-depth study of the coextrusion and compounding mechanism of electromagnetic dynamic plasticization and extrusion of plastics was conducted. For the first time at home and abroad, the principle of polymer electromagnetic dynamic plasticization and extrusion engineering was proposed, and a relatively complete polymer dynamic solid The mathematical model of conveying, melting and melt conveying clarifies and quantitatively describes the basic laws of dynamic plasticization and extrusion of polymers. Based on the new principle, the "electromagnetic dynamic plasticizing and extruding equipment for plastics", which was pioneered at home and abroad, was developed.

Innovative technology trend of the twin screw market: Twin screw processing technology has become a very common processing method used in the plastic processing industry, and the corresponding competition is extremely fierce. How to be invincible in the fierce competition? Different suppliers have launched their own innovative technologies to win the market. High-speed, high-output High-speed, high-efficiency, energy-saving has been the main theme of continuous improvement of international plastic machinery in recent years. The high speed and high output allow investors to obtain high returns with lower investment. However, the high speed of the screw speed brings a series of problems that need to be solved: if the material stays in the screw for a short time, it is easy to cause uneven mixing and plasticization of the material; excessively high shear may cause the material to rise rapidly and thermally decompose; Extrusion stability issues; the need for high-performance auxiliary machines and precision control systems to support them; wear problems of screws and barrels; and design issues of reduction gearboxes. Therefore, it is one of the important directions for the technical innovation of twin screw suppliers to provide solutions to the problems that high speed may bring.

In order to meet the needs of high speed and high output, the plastic pelletizing extruder needs to have multiple improvements. Equipped with a barrel heater, which can complete the extruder's heating in a very short time, the maximum heating temperature can reach 450 ℃; the cooling channel design truly realizes reverse flow cooling, and optimizes the cooling system; "Tightening device", the replacement time of the barrel can be faster than the traditional bolt connection type; the barrel uses a patented high-frequency quench hardening process, which imparts excellent wear resistance, thereby eliminating expensive wear-resistant bushings; It is also equipped with the company's advanced process control system. In terms of function, the twin-screw extruder is no longer limited to the molding and mixing of high-molecular materials, and its uses have been extended to the fields of food, feed, explosives, building materials, packaging, pulp and ceramics. In addition, the "one-step direct extrusion process", which combines kneading and granulation with extrusion molding, is also very attractive.