The percentage matches for repeatability and reproducibility was also carried out via macros programmed in the spread- sheet. The radius of the search zone was increased from 1.5 to 1.8 times the element radius because of the image quality.


The results showed that there is a significant amount of repeat- ability and reproducibility error in the visual casting surface inspection process. The repeatability and reproducibility val- ues are shown in Figure 12 and 13, respectively. On average, the repeatability was better than the reproducibility measure- ments, and the master cluster match percentages were lower than the element match percentages for the same operator.


Sensitivity Analysis for Search Zone Coefficients


A sensitivity analysis was conducted to examine the ef- fects of varying the size of the search zone coefficients on the total number of master clusters as well as repeatabil- ity and reproducibility percentages using the data from Company 1. For the search zones used for establishing the master clusters, the number of master clusters approached a minimum as the search zone coefficient was increased (see Figure 14.) As the search zone approached zero, the number of master clusters approached the number of ele- ments, as expected.


(a)


(b) Figure 12. Repeatability results for percent master cluster match (a) and percent element match (b).


(a)


(b) Figure 13. Reproducibility results for percent master cluster match (a) and percent element match (b).


Figure 14. Effects of search zone coefficients on the total number of master clusters.


International Journal of Metalcasting/Summer 2011


Figure 15. Effects of search zone coefficients on the repeatability of one operator and reproducibility.


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