After more than 100 years of development, plastic pelletizing extruders have been derived from the original single screw, such as twin screw, multi screw, and even screwless models. Plastic pelletizing extruder (main machine) can be formed with various plastics such as pipes, films, holding materials, monofilaments, flat filaments, packing tapes, extruded nets, plates (sheets), profiles, pellets, and cable coatings. Auxiliary machines are matched to 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 development trend of plastic pelletizing extruder is as follows:
(1) Extruders are developing towards large-scale, high-speed, and high-efficiency. Plastic pelletizing extruders with screw diameters of 200-250mm are very common. Special extruders with screw diameters greater than 400mm are not uncommon. Increasing the diameter of the screw can increase the production capacity of the extruder. When the diameter of the screw is doubled, the production capacity of the extruder can be increased several times.
Another effective method to increase production capacity is to increase the speed of the screw. High-speed and ultra-high-speed extruders with speeds above 300 r / min have appeared abroad, thereby greatly improving the production capacity of the extruder. However, problems such as poor plasticization will be brought about after the increase of the rotation speed, which urges people to study and test the extrusion theory and screw structure. As a result, many new types of screws have appeared, such as separation type, mixing type, barrier type, and shunt type , Combination, etc. The aspect ratio of the screw has also developed from 20: 1 to 36: 1, some as high as 43: 1. This is very effective for improving the plasticizing quality and efficiency.
(2) The auxiliary equipment of the extruder has also been perfected and standardized to meet the requirements of different plastic products.
(3) Extrusion automation, using microcomputer to detect and control the extruder process parameters, the temperature difference can be controlled within ± 1 ℃. The extrusion equipment adopts microelectronic technology to make the plastic extrusion molding process develop in the direction of accuracy, precision, energy saving and automation.
(4) In order to meet the requirements of new materials and new processes, new or dedicated extruders are constantly appearing. Such as three-screw extruder and planetary multi-screw, screw-free extruder, reactive extruder, two-color extruder, foaming extruder, etc.
Nowadays, modern plastic pelletizing extruders have generally adopted modern electronic and computer control technology to carry out on-line inspection of the entire extrusion process, and adopt microcomputer closed-loop control. In order to meet the diversified needs of production development, plastic molding technology has flourished towards modern efficient large-scale production and intelligent control.