Study On The Packing Effects On The Shrinkage Of Injection Molded Thick Wall Products

For thick-walled injection molding products, non-uniform thickness due to uneven shrinkage is a major flaw. In injection molding, due to the frozen time of thick-walled products is relatively long, holding time is longer than thin walled products. The quality of thick-walled products are significantly impacted by packing process. Constant holding pressure is still commonly used in industrial now, conversely, the quality of thick-wall molding can be improved by variable pressure packing process. In this thesis, Moldflow Palstic Insight(?) simulation and injection molding experiments are used in the study on the packing effects on the shrinkage of injection molded thick wall products.Firstly,for example with flanges,the effects of injection molding process parameters on the shrinkage of thick-walled products was studied by the orthogonal test using. The results showed that the impact of packing pressure on the shrinkage of thick walled products is significant.The relationship between packing pressure and the frozen time of gate was studied by using Moldflow Plastic Insight simulation. The results showed that the packing pressure have little effect on the frozen time of gate. The packing time can be set to a given value.The relationship variable pressure packing process and the uniformity of the shrinkage was studied by constrasting data from Moldflow Plastic Insight simulation and collected by data acquisition system.The result showed that:Compared to constant pressure packing process, variable pressure packing process can improve the uniformity of thick-walled products of contraction. The shrinkage of plastic parts can be uniform when improved holding pressure curves was used.At last, the packing curves were optimzated by using artificial neural networks combined with genetic algorithms.The result is that the uniformly of shrinkage of thick-walled products was improved.