At the feature level the cost depends on material

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Unformatted text preview: where, USL = Upper Specification Limit LSL = Lower Specification Limit x = mean value of the process variation σ = standard deviation of the process variation For tolerance assignment purpose, we name the median level of IT grades a machining process can achieve ‘economic IT grade’ for that process. Table I and II illustrate IT grade ranges and corresponding tolerance zones for typical processes. IT Grade Lapping Honing Superfinishing Cylinderical grinding Plan grinding, Broaching, Reaming Boring, Turning Milling Shaping, Cold Rolling, Drawing Drilling Die Casting Forging Sand Casting Hot rolling, Flame cutting 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Table I; Machining process associated with ISO tolerance grade. To initialize a tolerance assignment plan, the economic IT grade is assigned to each process. At this stage, it is roughly estimated that locator error is accountable for 20 percent of the tolerance under economic IT. With this initial tolerance assignment plan, Tolerance Assignment for Production Planning 217 the Monte Carlo simulation can be performed to verify the satisfa...
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This note was uploaded on 08/03/2010 for the course DD 1234 taught by Professor Zczxc during the Spring '10 term at Magnolia Bible.

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