Quality Engineering and Taguchi Methods: A Perspective Robust product design and parameter design-methods to develop prod­ ucts that will perform well regardless of changes in uncontrollable envtron­ mental conditions or that are insensitive to component vanatlon-are key concepts in the work of Or. Taguchi. We should encourage. design ~nd manufacturing engineers to apply these useful ideas. But In deslgnlnQ. exper­ iments and analyzing data - key aspects of the practical Implementation - better and simpler methods are available and should be preferred over Taguchi's less intuitive and more cumbersome approaches. Smen Bisgaard uring the last few years we have In conjunction with the broader by our competitors, we have the Dwitnessed a surge in interest in vision of quality management we foundation for a better strategy. In quality improvement. Quality im­ are also seeing a rapid development an effort to become more competi­ provement, or as it used to be of new quality engineering concepts. tive, it is important to use the best called, quality control, is a field with In particular, we are hearing a lot and simplest tools available. a loog history that continues to about Taguchi methods. The history Quality Improvement and Quality grow. New contributions are made of quality control, engineering statis­ Engineering every year. In the 1960s and 70s tics, and quality engineering is little Concern about quality of manu­ there was a slump in the Western known and few people can put factured goods goes back as far as development partly because of mis­ Taguchi methods in perspective. But ancient Egypt.' In more modern understanding of the enormous eco­ without a proper perspective, man­ times, pioneering industrialists such nomic benefits of quality control. agers and engineers might commit as Joshua Wedgwood and Henry During that period, quality control Ford emphasized the importance of was mostly perceived as a set of Perhaps the most important delivering high-quality products at a techniques for sorting and final in­ low price and made that philosophy spection of products. Thus, quality development is that in some the basis for their business success. control was seen as an added ex­ companies, management is The earliest applications of sta­ pense. coming to the fundamental tistical methods for quality control This view is rapidly changing. conceptual understanding that date back to the 1920s and are due Many companies are now develop­ quality does not necessarily to Dr. Walter A. Shewhart and his ing a much more visionary associates working for Bell Labora­ company-wide quality improvement come at a higher cost. tories and Western Electric. Through strategy. Perhaps the most impor­ Shewhart's efforts, Quality Control tant development is that in some themselves and their companies to became an engineering discipline in companies, management is coming long-term strategies and expensive its own right. His two books',' are as to the fundamental conceptual un­ educational programs that later important today as when they were derstanding that quality does not might turn out to be imprudent. Al­ first published. Blanton Godfrey has necessarily come at a higher cost. though the review of Taguchi's written an interesting article on the By using quality improvement con­ methods provided in this article is early history of statistical quality cepts, quality engineering methods, somewhat critical, the purpose is not control at Bell Laboratories. 4 and quality management principles, to be negative and in particular not Shewhart inspired many people it is possible to develop products to criticize Dr. Taguchi personally. both in the United States and and processes of higher quality at The intent is instead to alert engi­ abroad. Perhaps he found in Great lower overall cost. In fact, quality neers and managers to the fact that Britain the most receptive foreign management is an integrating con­ although many of Taguchi's engi­ audience. At the time, quality control cept for cost-effective, rational, co­ neering ideas are very useful, his was seen as a way of fending off operative manufacturing of high­ statistical inventions are inefficient, the depression, then at its worst. quality products and for delivering and also more cumbersome and Despite the fact that most of the high-quality services. less intuitive than need be. We can fundamental ideas of quality control do better. This really is good news. If we can improve on the methods used I> Fall 1989 13 have been around since World War use of the seven tools for solving all from that country and India in the II, quality improvement today seems kinds of problems, manufacturing as 1940s. They have been applied by to be the most promising avenue for well as service-related, at all organi­ quality professionals in the United American industry to follow in its zational levels of Japanese compa­ States and Great Britain since that current struggle to regain competi­ nies has profoundly increased the time. tive strength. This can be said with quality and reduced the cost of their In the same article, Professor confidence, for it is widely acknowl­ products. It is widely believed that Kusaba supplies an interesting table edged that a major reason for the these tools, despite their simplicity reproduced here as Fig. 1. It is a success of many Japanese compa­ (or perhaps because of it), have sig­ statistical tabuiation of methods nies is the use of the quality im­ nificantly contributed to Japan's suc­ used in case studies presented at provement philosophy they originally cess. the Quality Control Annual Confer­ learned from Shewhart's friend and Lately "Taguchi methods" and ences held each year in Japan. long time associate, Dr. W. Edwards Quality Function Deployment (QFD) From this tabie it is clear that the Deming.s have received attention. Eureka seven toois are in fact the most uti­ writes that "The use of QFD and lized methods and more likely are Always a Better Way of Doing Taguchi Methods has been instru­ key ingredients in Japan's success. Things What is quality improvement? mental in helping Japanese compa­ Note also the use of the generic Without trying to corne up with a nies to improve quality, reduce cost, term "design of experiments." stringent definition, quality improve­ cut product development time in I think Japan's secret weapon is ment is operating on the philosophy half, and achieve major competitive the company-wide, cooperative use that there is always a better way of market advantages.'" of a scientific approach to problem doing things. To find out how to do Taguchi methods undoubtedly solving. In particular, the scientific are applied extensively in selected thing~ better, we use simple scientif­ attitude as characterized by the industries, but data from Japan ic methods of data collection, data Plan-Do-Check-Action (PDCA) cir­ analysis, and experimentation as a provided by Professor Kusaba, cle, also known as the Deming Musashi Institute of Technology, and catalyst for our engineering and Cycle or Deming Wheel. Used the Japanese Union of Scientists other knowledge. An excellent intro­ throughout all organizational levels and Engineers (JUSE) seem to indi­ duction te; the fundamental and per­ and across all functions, in a spirit of cate that Taguchi's personal contri­ haps most powerful tools for quality genuine cooperation, this approach butions to quality engineering have improvement in manufacturing is is extremely powerful. When an Ishikawa's Guide to Quality Control, been applied only on a rather limited overall scientific attitude character­ basis in that country. In evaluating originally written for factory fore­ ized by the PDCA circle is adopted, the roie of statistical methods in men' The late Professor Ishikawa the seven tools and more advanced Japanese quality control, Kusaba describes what has become known statistical methods, such as design as the Seven Tools: check sheets, writes: of experiments, naturally present Pareto diagrams, cause and effect As regards the so-called Taguchi themselves as the tools for particu­ diagrams, histograms, stratification, method, the basic usage of the or­ lar jobs. scatter plots, and graphs. The seven thogonal array has been widely History of Industrial Applications tools and the spirit in which they are adopted since the 1950s as a type of Design of Experiments used by Ishikawa are simple appli­ of the design-of-experiment method. Although the seven tools have cations of a scientific approach to By contrast, its complicated usages played an important role in improv­ probiem solving. represented by the pseudo-factor ing quality in Japan, they are most Every process generates infor­ method, and the concepts of SN­ applicable to ongoing processes. To mation that can be used to improve ratio and on-line QC are the choice be more effective we need to start the process. 7 For example, when a of only a small number of people. the quality improvement effort up­ product fails it also produces infor­ The reasons are: 1) In spite of their stream at product design and proc­ mation (that it faiied and under what originality, these methods have not ess design. circumstances) that can be used to been provided with sufficient logical This need was recognized by find the cause for failure. In turn, explanation; 2) The usage of the the pioneers in quality control. One that information can be used to gain methods requires special skills; 3) of these was L. H. C. Tippett, who understanding of "why" the problem SN-ratio is effective in solving a lim­ worked for the British cotton indus­ occurs and to permanently fix it or ited range of problems, but the use tryon practical problems associated change the system. We therefore of logarithms makes it difficult to get with the manufacture of cotton prod­ need to "listen" to the process.