Optimization Of Runner System In Multi-cavity Injection Molding Based On CAE

For maximizing productivity and minimizing cost, multi-cavity injection moldshave been applied widely. The type of runner layouts in multi-cavity injection moldsis divided into the non-balanced and the balanced. When the two layouts are used,various kinds of flow imbalance phenomenon can be occurred in the practicalproduction processing. The cause and solution to imbalances which occur in thevarious layouts are also different. On the basis of the engineering practices, thepaper is exemplified by the processing of selenium drum cleaning slice and printercartridges cover, and the injection mold CAE software Moldflow is used to simulateand resolve the issue of flow imbalance which occurred in the practical production.1、As for the case of selenium drum cleaning slice, the issue of flow imbalanceis discussed respectively from the aspects of the different runner layouts.When the non-balanced runner layout was used, the traditional artificialequilibrium method which included the two aspects of geometrical parameters andprocessing parameters was used to optimize the flow imbalance issue. In the methodof geometrical parameters, the filling imbalance rate can be decreased by adjustingthe size of gate and runner, so as to realize the balance of every cavity in the fillingprocess. Then, based on the optimized results of the geometrical parameters, theorthogonal test was utilized to discuss the influence how the three factors affect thefill balance in the optimization process of processing parameters. The results showthat the injection rate has the maximum influence on the fill balance of seleniumdrum cleaning slice, next is the mold temperature, the last is the melt temperature.The best optimization level combination was gotten, which is the injection rate(10cm3·s-1), mold temperature (90℃) and melt temperature (210℃),.After achieving the filling balance, the flow balance in packing process shouldbe taken into account. Then, using the constant packing pressure and variablepacking pressure separately, the relationship between the packing methods andvolumetric shrinkage was investigated. The simulation analyses show that constantpacking pressure has little influence for volumetric shrinkage of the parts, andvolumetric shrinkage of the parts can be decreased by using variable packing pressure.When the balanced runner layout was used, the issue of flow imbalance amongthe cavities can be resolved from the root of shear effect. Then, the truly flowbalance can be achieved by changing the non-symmetrical shear distribution in therunner by means of the runner design of melt rotation.2、As for the case of printer cartridges cover, it was optimized by the artificialequilibrium when the non-balanced runner layout was used. The rate of fillingimbalance among the cavities can be decreased by adjusting the section size ofrunner. The results of the orthogonal test show that the injection time has themaximum influence for the fill balance of printer cartridges cover, next is the moldtemperature, the last is the melt temperature, and the best optimization levelcombination was the injection time(2s), mold temperature (50℃) and melttemperature (230℃).