Computer simulation of weld lines in injection molded poly(methyl methacrylate)

Abstract

Abstract Computer simulation packages have had success in predicting filling behavior in extremely complicated geometries. However, few packages offer the possibility of predicting the location and strength of weld lines. This work examines the sensitivity of Moldflow's weld‐line prediction algorithm to variations in material properties and processing conditions. Qualitatively, the algorithm correctly predicted the effects of changes in viscosity, density, and PVT relationship on weld‐line strength of a poly(methyl methacrylate). The algorithm is also successful in predicting the influence of variations in the injection time on weld line strength. However, the algorithm predictions for changes in the mold and die temperatures were at odds with the experiment. An attempt was made to correlate Moldflow's computed viscosities with the experimentally measured reduction in the strength in the weld‐line area. It was shown that a one‐to‐one relationship existed between these two quantities. Whereas the potential of using the viscosity to predict weld‐line strength has been demonstrated, further refinement of this new concept is needed and its validity for other systems has to be established.