Research On Efficient Plasticizing Method In Injection Molding Machine

Efficient plasticizing technology is of Energy saving and high-yield in injection molding as one part of the global theme of energy saving. The present thesis conducted theoretical and experimental study for analyzing the heating efficiency of new heating methods and the effect of grooved barrel on transportation efficiency of materials, in which the latter is also simulated. The main results are as follows.1. Plasticizing process in the injection was approximatively described when dividing the whole process as discrete extrusion plasticizing stage with different axial lengths, which was followed by simulation using plastics analysis program corresponding to three phase stages into seven zones. The results showed that non-plug zone and plug zone have not been varied while the other zones appear earlier. The length of delay zone, circulation zone and melt conveying zone reduced while the length of plug zone increased. Melt proportion in solid bed reduced when it broke. At the same time, its width increased and the thickness reduced.2. The new heating methods which can improve the heating efficiency were used to achieve efficient plasticizing. Three kinds of heating ways were analyzed including resistive heating, infrared heating and electromagnetic induction heating. Simulation was conducted for studying radial temperature rise and its distribution in the barrel wall using ANSYS software. The latter was treated as the boundary conditions in simulating the effects of different heating ways on plasticizing process. The results showed that the barrel temperature was initially increased more rapidly by infrared heating and electromagnetic induction heating than by conventional resistance heating. In the preheating process, the radial temperature difference in barrel was smaller by electromagnetic induction heating than by infrared heating when it was largest by resistance heating. Plasticizing simulation showed electromagnetic induction heating put the delay zone, circulation zone and solid bed-breaking zone ahead when increasing melt proportion in solid bed. In contrast, axial force and torque of screw reduced. Experimental results showed that the efficiency of the infrared heating and electromagnetic induction heating are higher than the resistance heating while the consumed heating energy and plasticizing energy were lower than the resistance heating.3. Barrel was grooved in reciprocating injection molding machine here to improve solid conveying capacity as in screw extruder, which can achieve efficient plasticizing by improving transmission efficiency of material. Six groove barrels were designed with different sizes (four straight groove barrels and two spiral groove barrels) for studying their effects on the plasticizing performance combining injection molding process. The experimental data confirmed the theoretically predicted results. The solids can be conveyed by both positive displacements conveying mechanism and friction drag conveying mechanism in spiral groove injection barrel. The contributed proportion of the former reduced when increasing screw retraction speed. With the same process conditions and other structure sizes, spiral groove barrel can significantly improve the plasticizing capacity than straight groove barrel. The situation turned around when the back pressure is high. It should be noted that groove barrel can reduce the molding weight repeatability when increasing conveying efficiency.