通電式塗膜評価における指標について(商船・理工論)

概要

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The inside of a metallic can filled with some drink is usually coated with a macro-molecular film to suppress the progress of corrosion. The degree of its coating is evaluated by so-called Enamel Rater Value (shortly, ERV) of a quick electrical stress test. ERV is nonnegative-valued, and its small value is desirable for coating. A distributional shape of ERV data, coming from typical manufacturing processes of aluminium cans under control, is usually left-censored and anti J-shaped with a very high peak near the origin and also an extremely spread tail. Thus, theoretical distributions for ERV data have never been considered for a long time, and a process capability for a coating process has been evaluated only through nonparametric methods such as histograms. Recently, a theoretical distribution for ERV data (shortly, ERV distribution) has been introduced by Isogai et al. [7] and also, instead of an usual Cp, an Index of Good Coating (shortly, IGC) has been introduced at the same time. Our objective here is to examine behaviors of IGC for several theoretical distributions for ERV data. Four statistical distributions, including the above ERV distribution, have been adopted to fit six ERV data sets to examine their IGC. Good performance of IGC has appeared in dealing with ERV distribution and a new power normal family (Isogai [4]).