During the last decade, injection molding has been required to be more accurate in order to be able to produce products of high-dimensional accuracy. Precision in injection molding requires dimensional accuracy and stability in time, which are related to the distribution of a number of thermomechanical properties across the material. This study focuses on the identification and visualization of the problems during injection molding process to help to understand the cause of the problems and thus find the solution through simulation techniques. Through animated results, which show the flow pattern of the polymer as it fills the cavity, the details of the weld line and the subsequent bubble formation (which may not be captured with static graphics) will be highlighted.