The number of draws is based on the ratio of height and diameter of the cup as given in Table 21.1.
Table 21.1 Number of Draws in Deep Drawing
where h, depth of cup; d, shell diameter; D, blank diameter.
Both the factors limit the reduction percentage; top limit for the first draw is in between 45 and 48% reduction. It is 30% for the second draw and is 20% for the third and subsequent draws. Total reduction should not be increased beyond 70–75%; it should be annealed and reduction may again start at the maximum percentage, number of draws does not exceed 3–4 in this way.
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