Variation in a milling process. A milling process was used to obtain the correct width of a metal part. Both the width and the microfinish

(smoothness) of the part were important quality characteristics. The process was run by two operators, each responsible for two mills.

Each mill had two spindles and there were two part positions (left and right) for each spindle. Thus, each machine could mill four parts at a time (two spindles with two positions each).

To study the important sources of variation in this process, the process supervisor selected two parts from each position during a one-hour period. The pairs of parts were labeled by location and then randomly ordered for measurement of width (inches) and microfinish (micro units). The following data were obtained:

Develop a design matrix for this study. Show the results of the study on the design matrix. Analyze the data for each quality characteristic with run charts and dot-frequency diagrams. For each characteristic, list the factors in order of contribution to variation.
What action is needed to reduce variation in this process?

Transcribed Image Text:

Width Microfinish Order Operator Mill Spindle Position Part 1 Part 2 Part 1 Part 2 1 A 101 1 L 2.003 1.998 110 122 2 A 123 1 L 2.011 2.007 112 115 3 B 220 2 L 1.991 1.989 123 113 4 A 123 2 R 2.009 2.008 130 126 5 B 220 1 L 2.001 1.998 138 130 6 B 285 1 R 2.015 2.012 155 120 7 B 285 1 L 2.001 1.999 148 125 8 A 101 2 L 1.996 2.001 160 146 9 B 220 2 R 1.990 1.988 158 136 10 A 123 1 R 2.012 2.010 171 155 11 A 101 2 R 2.001 2.004 182 164 12 B 285 2 L 2.003 1.999 168 160 13 B 220 1 R 1.999 2.000 180 172 14 A 123 2 L 2.009 2.007 182 166 15 A 101 1 R 1.997 1.999 198 183 16 B 285 2 R 2.000 2.002 186 192