Course: Lean Six Sigma

Case study from Minitab's database: An engine manufacturer uses a forging process to make piston rings. The quality engineers want to assess the process capability. They collect 25 subgroups of five piston rings and measure the diameters. The specification limits for piston ring diameter are 74,0 mm 0.05 mm. Process Capability Sixpack Report for Diameter Capability Histogram Xbar Chart UGME 740 74.00 1.400 Sections ESE 729 Two .00 USE 719 7177 13 20 R Chart Normal Prob Plot AD: 0.193, P.0892 UCO 002 HA LOG 400 C. 233 7. 14.00 74 Last 25 Subgroups Capability Plot Overall W Dev 0.01005 7402 GA MTT Owl we RO 160 Com PM Within 71 Spea Figure 31. Process Capability Assessment - Six Pack for Piston Rings. Source: Olivares, L. (2018) The average of this process is known to be 74.0 mm True False The target value for this process is: 74.0 mm 0.05 mm 74.0 mm + standard deviation 74.0 mm + 0.05 mm 74.0 mm The upper specification limit is 74.05 mm + 0.05 mm 74.05 mm + standard deviation 74.05 mm 73.95 mm This process is operating lower than at the 6Sigma level True False The data is not normal since the P-value for the normal probability plot is > 0.05 True False The short-term capability standard deviation is 0.01005 True False The average of this process is not known until the data is analyzed True False The sub-group inspection size can be extracted from the individual sub-group graph as five every time the LSS investigated the process True False This process is can be considered capable at the Cp near Cpk> 1.33 True False The average is the same as the target value True False