Evaluation of polymer injection molded parts via density-based magnetic levitation

The quality of polymer injection molded parts is definitely related to the molding process. Polymer injection molded parts with different properties differ in density and internal density distribution. This paper proposes a novel evaluation method for polymer injection molded parts through magnetic levitation (MagLev) to detect the differences among products by means of their densities and density distributions. Three cases of polycarbonate lenses are employed as samples in the experiments: lenses produced at different processing parameters, lenses obtained from different cavities in one mold, and those with different interior defects. The lenses obtained at different processing parameters differ in density, and those with different defects exhibit different behaviors during the levitation. The MagLev testing method shows its capability in distinguishing minute differences among the densities (< 0.0005 g cm-3) that even the subtle distinctions among the lenses formed from different cavities in one mold can be detected. Further analysis demonstrates that minute changes in thickness (2.5 mu m) can also be detected. The theoretical analysis and experimental results indicate that the MagLev testing method is applicable to the evaluation of polymer injection molded parts. Moreover, the method affords advantages, such as high accuracy, high sensitivity, and convenience. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48431.