Additionally, it would be difficult to obtain reliable numerical predictions when the rheology, the thermal properties, and the solidification conditions are not properly known.ĭuring the last decades, several attempts were carried out to predict the flow length, viscosity, and the pressure drop during the injection molding process by simplified strategies. The simulation by commercial software of the injection molding process, usually adopted for the determination of the flow length, involves considerable amount of interactions, costs, and computation time. The simplified strategies are especially required when incomplete material characterizations, in terms of rheology and thermal properties, are available. Thus, there is a need for simplified strategies that allow determining the capability of a melt to advance inside a cavity with at least one micrometrical dimension. It is not easy to determine the conditions that allow the complete filling of the cavity during the micro-injection molding, mainly because the fast cooling occurring during the filling can cause a premature solidification. Micro-injection molding process is widely diffused because of an increasing demand for miniaturized parts that are adopted in many fields, from the electronic to the biomedical sector. In this work, with reference to an isotactic polypropylene, some spiral flow tests obtained with different mold temperatures and injection pressures are analyzed with a twofold goal: on one side, to obtain from a few simple tests the basic rheological parameters of the material on the other side, to suggest a method for a quick prediction of the final flow length. The so-called spiral flow test, consisting of measuring the length reached by a polymer in a long cavity under different molding conditions, is a method of this kind. A simple test aimed at obtaining the required parameters is then highly advantageous.
These parameters are not always easily reachable. However, this simulation requires a complete characterization of the material for what concerns the rheological and thermal parameters, and also a suitable criterion for solidification. Obviously, modern computational methods allow the simulation of the injection molding process for any material and any cavity geometry. in micro-injection molding), is the determination of the conditions of pressure, mold temperature, and injection temperature to adopt to completely fill the cavity.
One of the most significant issues, when thin parts have to be obtained by injection molding (i.e.
0 kommentar(er)
