The effect of the independent evaluation of quality characteristic variance on computed process loss

This study explores the effect of the relaxation of the assumption--quality characteristic variance and squared difference from quality characteristic target are of equal importance--on computed process loss. Industrial experimentation methods were applied to a coil spring manufacturing process to derive alternative manufacturing processes. The loss of each manufacturing process was computed under two loss functions--one which held the above assumption as true, the other which relaxed the above assumption. Manufacturing process loss was compared across the two loss functions. This study found that the relaxation of the assumption substantially changed the computed relative loss of the alternative manufacturing processes, especially for the very high loss manufacturing processes. This study indicates that companies should be most concerned in determining the importance of quality characteristic variance when factors I beyond the industrial experiment must be considered in selecting a manufacturing process and/or when the firm needs accurate estimates of loss for very high loss manufacturing process alternatives.