You work for
Harley-Davidson, manufacturer of popular a motorcycle in the U.S. You
have been assigned to a corporate cross-functional team tasked with finding the
best supplier of metal stampings to ensure a quality product. Your
engineering department has provided specifications on a piston ring produced by
suppliers, such that the USL = 82.9500 mm and the LSL = 82.8900 mm. The
design center target is 82.9200 mm.
One supplier, Metals
Inc., has provided SPC charts of their manufacturing process, and you have
determined from studying them that the estimated standard deviation is 0.006
mm, while the process mean is 82.9110 mm. Another supplier, Rings Inc.,
also wants to supply the product. Rings, Inc. representatives have
provided detailed process data showing their process capability indexes to be
Cp = 1.00 and their Cpk to be 0.50.
1 Determine the process capability for Metals Inc., i.e.,
determine Cp and Cpk. Show your computations for full credit.
2 Based on your results in question 1, how can you interpret Cp
and Cpk for Metal Inc and for Ring Inc.?
3 How many defective parts per million is each supplier capable
of? Given the results of your calculations in 1, 2 and 3, which supplier
would you choose for this contract? What request would you have for the
selected supplier?
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