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Unformatted text preview: . With this understanding, several researchers have applied genetic algorithm in statistic tolerancing [Shan et al., 2003]. In this paper, genetic algorithm is adopted as optimization technique with sets of tolerance assignment plans as a population. 3. INITIALIZATION OF TOLERANCE ASSIGNMENT Assuming that the operation type information is available based on best practice and/or existing manufacturing resources, a tolerance assignment plan dictate how accurate each process should be and what range of the process error and locator error can ensure that accuracy. To comply with industrial standards, the international tolerance (IT) grade is utilized in this paper to depict the accuracy level of each process. In the ISO standard, international tolerance grades are numbers which for a particular IT number have the same relative level of accuracy but vary depending upon the nominal or basic size. There are 18 defined tolerance grade bands for each size group. Smaller grade numbers 216 H. Song et al. indicate smaller tolerance zones. Table I and II illustrate IT grades and corresponding accuracies for typical processes. Dif...
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