Limitations of Traditional Quality Control Systems

Quality assurance practice has traditionally focused on downstream activities such as production and testing (see Figures 2.1 and 2.2). Such an approach may not result in an optimal design, even with a large number of repetitive design-prototype-test cycles that may essentially be a trial-and-error approach. This has consequent impact on cost, cycle time, and customer quality if the product is released for production without adequate performance characteristics. Very often this is the case because product managers run out of time and budget and have to release the design for production. Further downstream, products are inspected and screened to identify units that are not within specifications. Such units are repaired, recycled, or rejected. Such quality control systems are based on two basic premises:

• Customer requirements are met as long as the product is within the agreed-upon specification limits.

• Business implications of the product performance or quality being "barely within specification limits" and those of "right on target" are the same.

As you will see, none of these is a valid assumption. W. Edwards Deming^[7] was among the first management thinkers to realize the inadequacy of a quality system depending on inspection. But it was the Japanese industrial engineer Genichi Taguchi who came up with an alternative quality management system known as Taguchi Methods. It emphasizes the value of "right on target" and the need to address quality effectively upstream at R&D, design, and engineering phases of the product development cycle, rather than depending on inspection to detect and correct faults.