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?