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. The industry standard for Cp is 1.33 or higher.
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.
What is your interpretation of Cp and Cpk for the other supplier, Ring Inc?
How many defects per million is Metal Inc capable of?
How many defects per million is Ring Inc. capable of?