Identification of Mixing Ratios of Metallic Flakes in Metallic Color Products Injection-Molded by Image Analysis

Suda Takashi, Kuroiwa Hiroki, Fukushima Yoshio, Oyake Masaru, Takaoka Toshihito, Terauchi Fumio

doi:10.4325/seikeikakou.27.109

The exterior components are often painted with metallic color. However, painting increases the cost and environmental impact. So, manufacturing technology that makes metallic-colored plastic parts by injection molding without painting is being developed by many companies. But color unevenness hinders commercialization. In this study, we focused on the dispersion of metallic flakes that cause uneven color in metallic molding and investigated in order to evaluate the dispersion. We made test pieces with different sizes of metallic flakes by injection-molding and evaluated influence of proportion of metallic flakes on the qualities of plastic parts. We took the test pieces using a CCD microscope and compared the results of image analysis. We selected skewness (SKEW),angular second moment (ASM) and entropy (ENT) as values that indicate the features of the image. The following conclusions were obtained. (1) When the ratio of metallic flakes increased, flakes that are present at a position near surface increased. In the gray level histogram, SKEW decreased. The results of the analysis by co-occurrence matrix, ENT increased. (2) When the size of metallic flakes increased, SKEW increased. The results of the analysis by co-occurrence matrix, ASM increased. (3) It was considered that the difference of the ratio and the size of metallic flakes affected the results of image analysis. (4) It was suggested that gray level histogram and co-occurrence matrix were useful for evaluating the dispersion of metallic flakes.

Identification of Mixing Ratios of Metallic Flakes in Metallic Color Products Injection-Molded by Image Analysis

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