A production system specializes in sheet metal fabrication. A wide variety of parts are

fabricated for assembly. One simple part involves shearing a small flat blank from coil

stock. The material is fed to a stop and then the shear is engaged to cut the length

dimension. Next, the sheared strip is moved to a second shear and placed against the stop,

the second shear is engaged, and the cut to width is produced. The sheared-off metal is

recycled. The part is then moved to the next operation, a break operation for a bend. The

sheet metal part specifications and targets are as follows:

Length specifications: 6+ 0.04 inches.

Width specifications: 4+ 0.05 inches.

Length target: 6.001 inches.

Width target: 3.990 inches.

Data were collected in sub-groups of four parts, where each part is measured for both

length and width (see Tables 2 and 3).

(A)Construct appropriate control charts for the measured characteristics, assume

assignable causes can be eliminated and revise the limits.

(B) Calculate the process capability indices: Cp, Cpk and Cpm. Any suggestions for

process improvement?

(C) If a 5% reduction in the variability of the width or the length are possible under

current budget, which one would you recommend?

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