Numerical Prediction of Bubble Growth in the Microcellular Injection Molding Process Assisted with Counter Pressure Filling of Gas

• Main Authors: Chih-Wei Chang, 張智韋
• Other Authors: Shiu-Wu Chau
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/27032893098910445779

碩士 === 國立臺灣科技大學 === 機械工程系 === 101 === This study proposes a numerical model to simulate the bubble growth in the microcellular injection molding process assisted with counter pressure filling of gas, where various conditions is employed to investigate the effects of processing parameters on the bubble size. The microcellular injection molding process is described by the continuity equation, the momentum equation, the energy equation, and the front transport equation. The govern equations are discretized by a finite volume approach, while the volume-of-fluid method is employed to calculate the location of melt front. The non-Newtonian rheological behavior of polymer is described by the modified Cross-WLF model. The proposed numerical model is proven to give both qualitative and quantitative agreement with corresponding experiments. The results of this study reveal that the size of bubble decreases with the holding time and the weight percent of supercritical fluid, as well as the counter pressure. The size of bubble grows as the location of bubble moves away from the mold surface. Better agreement between numerical simulations and experimental results is found for the case with counter pressure of 150 bar, where the bubble size is about 25 μm at the reference point in the experiment