The Delaware 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 upper Midwest. Because of the large volume of demand, DDC had to expand its manufacturing operations to three shifts and hire additional workers.

Not long after DDC began shipping doors to Walker Homes, it began receiving some complaints about excessive gaps between the door and frame. This problem 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, Jim Dean, the company president, suspected that the expansion to a three-shift operation and the pressures to produce higher volumes and meet just-in-time delivery requests was causing a breakdown in their quality. On the recommendation of the plant manager, DDC 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 nominal specification for this cutting operation is 30 inches with a tolerance of 0.125 inch.

A.

The consultant suggested inspecting five consecutive door panels in the middle of each shift over a 10-day period and recording the length of each cut. The cutting is done on a highly specialized machine operated by a trained operator. Table 1 shows the data collected over 10 days for each shift.

Shift	Operator	Sample	1	2	3	4	5
1	Terry	1	29.989	29.952	29.941	30.012	29.984
2	Jordan	2	29.972	29.966	29.964	29.942	30.025
3	Dana	3	30.046	30.004	30.028	29.986	30.027
1	Terry	4	29.997	29.997	29.98	30	30.034
2	Jordan	5	29.969	30	29.968	29.976	29.973
3	Dana	6	29.973	29.99	29.985	29.991	30.004
1	Terry	7	30.046	29.978	30.026	29.986	29.961
2	Jordan	8	30.018	29.922	29.992	30.008	30.053
3	Cameron	9	29.852	29.978	29.864	29.896	29.676
1	Terry	10	30.042	29.976	30.021	29.996	30.042
2	Jordan	11	30.028	29.999	30.022	29.942	29.998
3	Dana	12	29.955	29.984	29.977	30.008	30.033
1	Terry	13	30.04	29.994	30.001	29.975	29.97
2	Jordan	14	30.007	30.024	29.987	29.951	29.994
3	Dana	15	29.979	30.007	30	30.042	30
1	Terry	16	30.073	29.998	30.027	29.986	30.011
2	Jordan	17	29.995	29.966	29.996	30.039	29.976
3	Dana	18	29.994	29.982	29.998	30.04	30.017
1	Terry	19	29.977	30.013	30.042	30.001	29.962
2	Jordan	20	30.021	30.048	30.037	29.985	30.005
3	Cameron	21	29.879	29.682	29.79	29.971	29.953
1	Terry	22	30.043	30.021	29.963	29.993	30.006
2	Jordan	23	30.065	30.012	30.021	30.024	30.037
3	Cameron	24	29.899	29.875	29.98	29.878	29.777
1	Terry	25	30.029	30.011	30.017	30	30
2	Jordan	26	30.046	30.006	30.039	29.991	29.97
3	Dana	27	29.693	29.991	29.784	30.022	30.01
1	Terry	28	30.057	30.032	29.979	30.027	30.033
2	Jordan	29	30.004	30.049	29.98	30	29.986
3	Dana	30	29.995	30	29.922	29.984	29.968

QUESTION:

1. Interpret the data in Table 1....... is the cutting process in control? Is the highly specialized cutting tool capable of meeting the strict product specifications?
2. If the process is not in control, what might be the likely causes based on the available information.
3. Establish a state of statistical control and evaluate the capability of the process to meet specifications.
4. How might the company ensure that the problems that Walker Homes found be eliminated? What do you recommend?