Process Capability Analysis

Problem 1 (10 points):

A medical device manufacturer uses a molding process to make oxygenator housings. The quality engineers want to assess the process capability. They collect 25 subgroups of 5 housings and measure the diameters (Total of 125 data points). The specification limits for the housing diameter are 74.0 mm ± 0.05 mm.

Use the raw data contained in the Housing Diameter Data.xls file (assume that the data was taken in chronological order) and assess the capability of the process using the techniques you learned in class.

1. Assess process capability on the diameter of the oxygenator housing data:

a. Use techniques that you learned in class to determine if the process is in statistical control. Based on your results, what do you recommend at this point. Is the process consistent and predictable? Use Minitab and make sure to use all tests as discussed in class (see below). Show your results including the graph and the session window.

b. Construct a histogram using the data with specification limits added. Use Minitab. Show your results including the graph and the session window. Copy and Paste into a word document.

c. Calculate Cp and Cpk using the pooled standard deviation method. Calculate using excel. Turn in excel file with your homework so that we can verify your calculations.

d. Calculate Pp and Ppk using the overall standard deviation. Calculate using excel. Turn in excel file with your homework so that we can verify your calculations.

e. Now, use Minitab to calculate Cp, Cpk, Pp, and Ppk. Compare your answers in 3 and 4 to the results in Minitab. Do they differ? Or are they the same? Show your work including the Minitab graphs and session window outputs. Copy and Paste into a word document.

f. Using the information above, what can you conclude and recommend about the process. What recommendations do you have moving forward?

Problem 2 (10 points):

A medical device manufacturer uses a machining process to make worm screws for their motor drivetrain. Some products have been coming back from the field for failure. So the manufacturing engineers collect 20 subgroups of 5 data points and measure the lengths of each worm screw (Total of 100 data points). The specification limits for the worm screw length are 600.0 mm ± 2.0 mm.

Use the raw data contained in the worm screw length.xls file and assess the capability of the process using the techniques you learned in class.

1. Assess process capability on this data set. Based on the data, what do you find? You may use excel or Minitab to conduct capability analysis. What are your recommendations for moving forward based on the data you have collected so far.