For the search zones used to determine repeatability and re- producibility, the percentage of elements matched reached a maximum as the search zone coefficient increased (see Fig- ure 15.) Based on these observations, the search zone sizes were considered appropriate.
Conclusions and Future Work
This study introduces an approach to assess measurement error for visual inspection processes. This method deter- mines the amount of measurement error when the location of the defect regions are not defined a priori. This method also handles instances where two or more defects from one trial could overlap only one larger defect of another trial. The applications of this methodology, however, are not limited to the steel casting industry. If utilized, it could prove useful in other fields where subjective evaluations are used, such as medical image analyses, nondestructive evaluation techniques, and meat carcass inspections.
The results of the application showed that there was signifi- cant variation in both repeatability and reproducibility mea- surements of casting surface inspections. Although the re- peatability measurements were somewhat consistent within the companies, the reproducibility measurements exhibited considerably more variation.
Propelled by the need shown here, current efforts are striv- ing to improve the visual inspection process. Better control over the process in terms of the environmental conditions as well as limiting the expected inspection speed based on the quantity of surface information that a human operator is able to accomplish is being investigated. In addition, better train- ing tools for the initial as well as ongoing training periods is being researched.
Acknowledgements
We would like to thank the Department of Energy (DOE) Office of Industrial Technology, which provided funding via grant No. DE-FC07-02ID14228. However, any opin- ions, findings, conclusions, or recommendations expressed herein are those of the author and do not necessarily reflect the views of the DOE.
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