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Design for excellence (DFX) and design for Six Sigma (DFSS) have been two of the most popular concepts in quality management in recent years, but very little has been written comparing DFX and DFSS. This article aims to clarify the differences between them in concept and application and further identify how to integrate them effectively by using quality function deployment (QFD).
It is a good starting point to understand the roots of the words "excellence," "Six Sigma" and "quality." Aristotle might have been the first person to talk on the subject of quality in any systematic way.1 In his book Metaphysics, he gave four definitions of quality and later summarized them with two basic meanings: "differences of real substance" and "mode of a subject in motion, of itself." Good (excellence) and bad (inferiority) are parts of the latter mode.
Simply speaking, there are two aspects of quality, according to Aristotle: different quality and good quality. Discussions of quality have revolved around these two aspects since Aristotle's time.2
Whether you're creating different quality or trying to achieve good quality, you must build quality into a product when it is planned and designed. Quality built in at this stage has the maximum return in terms of cost benefits and customer satisfaction. It far surpasses the improvements brought about by relying separately on promotional efforts in selling or detection and modification in manufacturing after a product is released. DFX and DFSS both help build quality into the design stage.
Design for Excellence
DFX has evolved and is still evolving from design for manufacturability. By manufacturability, we mean the ease with which a product or component can be produced. Historically, designers have overlooked manufacturability and have concentrated their efforts on function, features and appearance of their products. However, concentrating on manufacturability during product design has great cost benefits.3
Today, a limited series of design objectives-function, features and appearance-even when manufacturability is added, is not enough to provide the most competitive, economical and beneficial design to customers and society over the long run.4
DFX is intended to provide designers with an objective deployment framework and a means to achieve all desirable dimensions of quality. DFX can be viewed as a design approach that deals with Aristotle's different quality while focusing...