The Dandeo Door Corporation (DDC) manufactures steel and aluminum exterior doors for commercial and residential applications. DDC landed a major
contract as supplier to Berney Homes, a builder of residential communities in several major cities throughout the southwestern 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 Berney 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 principle reason that it was selected as a supplier to
Berney 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 complaint, however, Jeremy Dandeo, 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, Jeremy hired a quality consultant to train the shift supervisors and selected line workers in
statisticalprocess control methods. As a trial project, the plant manager wants to evaluate the capability of 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
0.125inch. 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. Exhibit 16.12 shows 10 days’ data
collected for each shift, by operator.
Case Questions:
1) Interpret the data in the attached Excel Document, establish a state of statistical control, and evaluate the capability of the process to
meet specifications. In other words, produce the appropriate control chart and interpret the results.
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 Berney Homes?
Shift Operator Sample Observation
Sample 1 2 3 4 5
1 Jermey 1 30.046 29.978 30.026 29.986 29.961
2 Dominic 2 29.972 29.966 29.964 29.942 30.025
3 Cobalt 3 30.046 30.004 30.028 29.986 20.027
1 Jermey 4 29.997 29.997 29.980 30.000 20.034
2 Dominic 5 30.018 29.922 29.992 30.008 30.053
3 Cobalt 6 29.973 29.990 29.985 29.991 30.004
1 Jermey 7 29.989 29.952 29.941 30.012 29.984
2 Dominic 8 29.969 30.000 29.968 29.976 29.973
3 Randy 9 29.852 29.978 29.964 29.896 29.876
1 Jermey 10 30.042 29.976 30.021 29.996 30.042
2 Dominic 11 30.028 29.999 30.022 29.942 29.998
3 Cobalt 12 29.955 29.984 29.977 30.008 30.033
1 Jermey 13 30.040 29.965 30.001 29.975 39.970
2 Dominic 14 30.007 30.024 29.987 29.951 29.994
3 Cobalt 15 29.979 30.007 30.000 30.042 30.000
1 Jermey 16 30.073 29.998 30.027 29.986 30.011
2 Dominic 17 29.995 29.966 29.996 30.039 29.976
3 Cobalt 18 29.994 29.982 29.998 30.040 30.017
1 Jermey 19 29.977 30.013 30.042 30.001 29.962
2 Dominic 20 30.021 30.048 30.037 29.985 30.005
3 Randy 21 29.879 29.882 29.990 29.971 29.953
1 Jermey 22 30.043 20.021 29.963 29.993 20.006
2 Dominic 23 30.065 30.012 30.021 30.024 30.037
3 Randy 24 29.899 29.875 29.980 29.878 29.877
1 Jermey 25 30.029 30.011 30.017 30.000 30.000
2 Dominic 26 30.046 30.006 30.039 29.991 29.970
3 Cobalt 27 29.993 29.991 29.984 30.022 30.010
1 Jermey 28 30.057 30.032 29.979 20.027 30.033
2 Dominic 29 30.004 20.049 29.980 30.000 29.986
3 Cobalt 30 29.995 30.000 29.922 29.984 29.968
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