The Dean Door Corporation (DDC) manufactures steel and aluminum exterior doors for commercial and residential applications. DDC landed a major contract as a supplier to Walker Homes, a builder of residential communities in several major cities throughout the south western United States. Because of the large volume of demand, DDC expanded its manufacturing operations to three shifts and hired additional workers. Not long after DDC began shipping windows to Walker Homes, it received some complaints about excessive gaps between the door and frame. This was somewhat alarming to DDC, because its reputation as a high-quality manufacturer was the principal reason that it was selected as a supplier to Walker Homes. DDC placed a great deal of confidence in its manufacturing capability because of its well-trained and dedicated employees, and it never felt the need to consider formal process control approaches. In view of the recent complaints, however, Jim Dean, the company president, suspected that the expansion to a three-shift operation, the pressures to produce higher volumes, and the push to meet just-in-time delivery requests were causing a breakdown in quality. On the recommendation of the plant manager, Dean hired a quality consultant to train the shift supervisors and selected line workers in statistical process control methods. As a trial project, the plant manager wants to evaluate the capability of a critical cutting operation that he suspects might be the source of the gap problem. The target specification for this cutting operation is 30.000 inches with a tolerance of 0.125 inch. Thus, the upper and lower specifications are LSL =29.875 inches and USL = 30.125 inches. The consultant suggested inspecting five consecutive door panels in the middle of each shift over a 10-day period and recording the dimension of the cut. The Excel file Dean Door Corporation Case Data.xlsx (shown in Exhibit 17.8) shows 10 days’ data collected for each shift, by operator.

Case Questions for Discussion:

1.Construct control charts for the case data using the appropriate Excel template.

2.What do the initial control charts tell you? Do any out-of-control conditions exist?

3.If the process is not in control, what might be the likely causes, based on the information that is available?

4.What is the process capability? What do the process capability indexes tell the company?

5.Is DDC facing a serious problem that it needs to address? How might the company eliminate the problems found by Walker Homes?

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EXHIBIT 17.8 Dean Door Corporation Case Data Observation Shift Operator Sample 2 3 5 1 Terry 30.046 29.978 30,026 29.986 29.961 2 Jordan 2 29.972 29.966 29.964 29942 30.025 3 Dana 3 30.046 30.004 30.028 29.986 30.027 1 Terry 4 29.997 29.997 29.980 30.000 30.034 2 Jordan 5 30.018 29.922 29.992 30,008 30.053 3 Dana 6 29.973 29.990 29985 29.991 30.004 T Terry 29.989 29.952 29.941 30.012 29.984 2 Jordan 29.969 30.000 29.968 29.976 29973 3 1 Cameron Terry 2 Jordan 3 Dana 1 Terry 2 Jordan 3 Dana Terry 2 Jordan 3 Dana 1 Terry 2 Jordan 3 Cameron 123 Terry Jordan Cameron 123123 Terry Jordan Dana Terry Jordan Dana 9222 AR 29.852 29.978 29.964 29.896 29.876 30.042 29.976 30.021 29.996 30.042 30.028 29.999 30.022 29.942 29.998 29.955 29.984 29.977 30.008 30033 30.040 29.965 30.001 29975 29.970 30.007 30.024 29.987 29.951 29.994 29.979 30.007 30.000 30.042 30.000 30.073 29.998 30.027 29.986 30.011 29995 29.966 29.996 30.039 29.976 18 29994 29.982 29.998 30040 30.017 29.977 30.013 30.042 30.001 29.962 20 30021 30.048 30.037 29.985 30.005 29.879 29.882 29.990 29.971 29.953 22 30043 30,021 29.963 29.993 30.006 23 30.065 30.012 30.021 30.024 30.037 24 29.899 29.875 29.980 29.878 29.877 25 30.029 30.011 30.017 30.000 30.000 26 30.046 30.006 30.039 29.991 29970 27 29.993 29.991 29984 30.022 30010 30.057 30.032 29.979 30.027 30.033 29 30.004 30.049 29.980 30.000 29986 29.995 30.000 29.922 29.984 29.968