Study On The Balance Of The Unbalanced Plastic Injection System

The balance of the multicavity unbalancing injection system has great influence on the quality of the parts. If the plastic melt cannot reach each gate and fulfill each cavity in the same time, it will cause the heterogeneity of the pressure arrangement, which could lead to bad quality, or short shot. In order to keep this kind of injection system in balance, the normal way is to use the tranditional formulas to keep the runner system and the gate in balance. But the traditional method does not take the rheologic characteristic into account, we have to use trial and error method to modify the mold before it put into formal production. The researchers have found some methods to improve the balancing state of the injection system. The calculation of the methods is complicated, so most of them need the computer programme to finish the calculation. That means different mold needs different programme. Therefore, we should find a way to make up the shot of the tranditional method without computer programme help With the development of computer technology and finite element theory, FEM is widely use in plastic injection analysis. FEM takes account of rheology, mold temperature, injection pressure, etc., with the method we can get an accurate analysis result. This research studies the balance theory of the unbalancing injection system, select simple runner balance method and gate balance method in all the methods, which have been proposed by the researchers. We use the mold CAD technology to build the three-dimensional model, which has eight unbalancing cavities, and use Moldflow to analyse the fill processs. With the result of the analysis, we optimize the runner balance method by propose two auxiliary values: m and n. then we proof the feasibility of the auxiliary values by the analysises using different length of runners and different material. Finaly, we get new formulae of runner balance. Still, by analyzing the simulation results, we can know that the balance of the injection system is not a simple combination of the runner balance and gate balance. In this study, it's a pity that there is no experiment to support the derived result. This study closely combines the injection system balance theory and the numeric emulsion technique, to improve the productive efficiency, shorten the product exploitation period, and save the cost of production. In the same time, it provides the good academic evidence for the manufacture and engineering practice.