Experimental And Simulation Research On Rapid Heating Cycle Injection Molding Process

Injection molding is one of the most important methods to produce plastic products due to its advantages. Conventional injection molding makes the mold temperature stay at low level to guarantee the production efficiency. For this, the polymer melt will cool rapidly when it touches the cold mold surface during filling stage, which will low the fluidity of the melt and have negative effects on the surface quality of the products. To satisfy the requirements of higher precision, mechanical properties and surface appearance, rapid heat cycle molding (RHCM) technology is developed in recent years.The molding temperature of RHCM is changing during all the production period. Before the filling stage, the mold is heated by some methods over the glass transition temperatures of the materials. After the filling stage, the mold is cooled rapidly to guarantee the productivity. High-quality plastic parts with excellent appearance and no weld marks can be produced by this and the subsequent processing processes, such as spraying and coating which seriously pollute the environment can be eliminated. Process features and process theory are studied based on the methods of simulation and experiment. For the cooling stage, the influences of cooling occasion and cooling rate on the quality of the plastic products are researched. The applications of RHCM to amorphous and crystalline polymers are also studied in this work.Based on the principles of the rapid heat cycle molding technology, the filling stage of RHCM is researched by simulation. The features of filling stage for RHCM are studied by analyzing the relationships between mold surface temperature and injection pressure, clamp force, frozen index and wall residual stress. And also, the differences between RHCM and conventional injection molding are studied by analyzing the simulation results of residual stress, warp, and sink mark and volume shrinkage.The cooling occasion and cooling rate are studied by simulation. Cooling is an important stage for injection molding both for production efficiency and the quality of plastic parts. A better strategy of cooling is got by compared the results of different cooling occasions and cooling rates.Experimental and simulation study of RHCM for amorphous and crystalline polymers. Utilizing the electricity RHCM experimental line set up by our group to conduct the experiments. Mold temperature is controlled by changing the heating time. The applications of RHCM to amorphous and crystalline polymers are researched by analyzing the mechanical properties and surface qualities of the PS and PP parts produced under different mold temperatures. The contributions of melt temperature, injection pressure, injection rate and mold temperature to the filling ability of PS and PP melts are studied by orthogonal experiments. Filling ability is indicated by the weights of the plastic parts. The influence of mold temperature is also studied using single factor experiment method to get the exact results.