Experimental Investigation of Designed Parameters on Dimension Shrinkage of Injection Molded Thin-Wall Part by Integrated Response Surface Methodology and Genetic Algorithm: A Case Study

Shrinkage plays an important role to evaluate the quality of molded plastics. In this article, dimension shrinkages of thin-wall molded part are investigated through experiments in the transverse and the longitudinal direction, simultaneously. Injection velocity, packing pressure, mold temperature and melt temperature are designed as processing parameters. Response surface methodology is adopted to develop the statistical models of dimension shrinkage. Results show that packing pressure is the most influential factor on the shrinkage variation in both directions, followed by mould temperature, injection velocity, and melt temperature. Based on the genetic algorithm technique, the optimal conditions of injection velocity, packing pressure, mold temperature, and melt temperature for minimum overall dimension shrinkage variations are 398.2mm/s, 39.7kgf/cm2, 69.8 degrees C, and 239.9 degrees C, respectively. Moreover, the error of overall dimension shrinkage between the predicted value and experimental measurement is about 7%. Through verification tests, the shrinkages are obviously improved about 85% and 63% in the transverse direction and the longitudinal direction, respectively.