Study of Variable Mold Temperature to Improve the Surface Quality of Microcellular Injection Molded Parts

• Main Authors: Ho-Hsiang Wang, 王荷翔
• Other Authors: Shia-Chung Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/87671074982504289660

碩士 === 中原大學 === 機械工程研究所 === 95 === Microcellular injection molding process is one of the new technologies in polymer process. Benefits associated with microcellular foaming process including significant reductions in part weight, processing temperature and pressure, clamping force, shrinkage and warpage, cycle time and increase dimensional stability. But the sliver streaks and swirl marks on the product surface is the most disadvantage to microcellular foamed products. In this study, we built a rapidly temperature control system. First stage, we varied the mold temperature which was heated by induction heating, melt temperature and injection rate to mold. Then we measured the surface roughness and the appearance of products. Second stage, we used two thickness of membranes and set it upon core mold surface. Then study on the melt contact temperature during filling stage and the surface quality of microcellular foamed products. As a result, the surface roughness decreases from 25 to 5 μm when mold temperature increase from 100 to 220℃, and surface roughness decrease from 8 to 5 μm with the increasing of melt temperature from 280 to 320℃ and injection rate from 40 to 140cm3/s. Sliver streaks and swirl marks will be eliminated with higher mold temperature, melt temperature and injection rate. We also find sliver streaks and swirl marks can be improved with the increasing thickness of membrane. Besides, the melt contact temperature is 156℃ when there is a 0.125mm membrane on the mold surface, and melt contact temperature is 160℃ when the membrane is 0.188mm thick. In this study, we use the rapidly temperature control on microcellular injection molding successfully, and we prove that it can improve the surface quality of microcellular foamed products.