Achieving Robust Designs through Quality Engineering: Taguchi Method V Shuji Takeshita V Tetsuo Hosokawa (Manuscript received June 1, 2006) Development processes must be constantly reviewed to quickly provide superior products that meet the complex demands of the marketplace. Quality engineering (also known as the Taguchi Method) is a systematized methodology for technology development that is attracting much attention. Quality engineering focuses on the functionality (generic functions) of products and separates the components of systems into three function categories: signal factors, control factors, and error factors. Although quality engineering may be difficult to understand for engineers used to conventional methods, it should be actively promoted to change their mindset as well as that of the divisions to which they belong. This will help ensure innovation in manufacturing. This paper outlines efforts made to promote quality engineering and analytical tools such as WebSTAT and ParaNAVI that are used to support it. It also gives examples of its application in simulation, the development of process materials, and software evaluation. 1. Introduction design (parameter design) and has since been Robust designs are those that make products expanded to include the Mahalanobis-Taguchi resistant to variations in production processes and System (MTS) and function evaluation procedures. enable them to withstand influences in the In a method-ranking survey recently environments in which they are used. However, conducted by NIKKEI BizTec magazine,3) quality this does not just mean making designs that are engineering was ranked top for recognition as a resilient, it also means attaining maximum development and production support tool and for stability under limited design conditions, and an adoption rate, showing that its introduction is important means of achieving this is quality proceeding in various types of companies. engineering (also called the Taguchi Method1)). Quality engineering focuses on the function- Quality engineering is a technology develop- ality of a system (generic functions) and then ment methodology created and systematized by makes an evaluation of the system’s components Dr. Genichi Taguchi and was widely adopted in according to three function categories — signal the US as the Taguchi Method in the 1980s, prin- factors, control factors, and error factors — with cipally in the automobile industry. It was first a view to system optimization. Quality engineer- introduced in Japanese companies in the 1990s. ing aims, as far as possible, to streamline The Quality Engineering Forum was established development by evaluating the good and bad in 1993 and was later renamed the Quality Engi- points of various technologies in the upstream neering Society2) when the Taguchi Method stages of the product commercialization process. became known as quality engineering. Initially, Although quality engineering is not a pana- quality engineering was used for optimizing cea for all problems, the practice of early and FUJITSU Sci. Tech. J., 43,1,p.105-112(January 2007) 105 S. Takeshita et al.: Achieving Robust Designs through Quality Engineering: Taguchi Method accurate evaluation is an effective means of avoid- ened development times for process design and ing product recalls and customer complaints, and control, feature upgrades for mechanical devices, as a methodology for innovation, it occupies an and elemental technology development, the important position in product creation. following problems arose: In this paper, we consider efforts at the 1) Most engineers went no further than just organizational level to expand the use of quality receiving the training. engineering, the tools used to support this expan- 2) When engineers applied quality engineering, sion, and some examples of quality engineering there were problems in the way it was done application. and benefits were not always realized. As a result, the engineers tended to stop using 2. Fujitsu’s response to quality quality engineering. engineering 3) There were not enough engineers in Fujitsu Fujitsu is among the Japanese companies divisions who could become key persons in that have been introducing quality engineering. quality engineering. Initially, it was only included in Fujitsu as part of training, but the extent of its adoption has steadily 2.2 Renewed efforts towards quality increased. engineering (fiscal 2004 onwards) In view of this situation, in fiscal 2004, 2.1 Efforts in the 1990s Fujitsu embarked on projects aimed at providing In the 1990s, Fujitsu began company-wide an environment in which engineers could training on quality engineering as part of its train- properly apply quality engineering and enhance ing program for engineers, and so far, more than their skills in order to reinforce their develop- 4000 people have undergone this training. The ment capability (Figure 1). The basic goals of training was stepped up in 1997 with the start of these projects were to: case-study meetings. Although the training short- 1) Focus more on problem-solving than on <<Initial response to quality engineering>> <<New response >> Part of training for engineers Implemented as strategy for enhancing performance of business divisions Lectures on quality engineering Training conducted by external consultants Quality Quality engineering engineering lectures Simulation Test piece Application of IT, promotion of prototype-less development Everyone independent of each other Inauguration of study meetings Formation of mutually (groups) ⇒expanded application Case study meetings dependent networks Absorption of application know-how of knowledge Extensive successful applications Cultivation of skilled personnel - Training to improve individual skills - Instruction given by outside consultants begun in 1990. - Activities of in-house study groups - Application of knowledge gained in - Form systems for mutual enhancement, networks of engineers training did not go well. - Raise skills at organizational unit level, train engineers to perform key - Theory understood, but engineers roles did not know how to put knowledge into practice. Figure 1 Activity scheme. 106 FUJITSU Sci. Tech. J., 43,1,(January 2007) S. Takeshita et al.: Achieving Robust Designs through Quality Engineering: Taguchi Method training, and ParaNAVI is provided mainly for intermedi- 2) obtain better results by listening to lectur- ate-level users and can be run in Excel. This tool ers from outside the company who have can handle large volumes of data that would be abundant experience of quality engineering difficult to achieve under WebSTAT. (to accumulate knowledge of successful 3) CAOS4) applications) This is a simulator linkage tool having Therefore, in fiscal 2004, we strengthened functions for automatic parameter insertion and our secretariat for promoting quality engineering, results collection. formed a group of in-house experts, and began addressing the major issues concerning quality 4. Application to design of engineering in Fujitsu’s business divisions. Then, magnetic recording heads in fiscal 2005, we began holding in-house study In this section, we will look at the applica- meetings to share information and study ways of tion of quality engineering to magnetic recording solving common problems, with the most experi- head design as an example of optimization using enced persons from each division acting as the key simulation.5) participants. Furthermore, we expanded the base 1) Problem of activities by restructuring the training Figure 3 shows the structure of a magnetic system to include e-learning and introduced a recording head, and Figure 4 shows the distri- skills-recognition system. bution of the head’s write magnetic field. For optimum function, the magnetic field must be 3. Support tools concentrated where it is required and suppressed In the application of quality engineering, sta- in other areas. It must also have characteristics tistical calculations are needed to obtain the SN that are not easily affected by manufacturing ratio, which is an indicator of the effect of varia- variations. tion, and sensitivity, which is a measure of the 2) Solution influence of parameters. Although there are Conventionally, several representative points various types of software for this purpose on the are selected and the best design is sought through market, it is not instantly available to engineers trial and error by monitoring changes in their when they need it. For this reason, Fujitsu has values. However, for this head, we quickly opti- developed the following three software applica- tions and made them available on our in-house Website (Figure 2). This Website also provides case studies and Website for dissemination of information about upcoming events. information and WebSTAT 1) WebSTAT distribution of WebSTAT is provided as an entry-level soft- support tools ware tool. It can be used from any computer in the company that has a Web browser. In addition to quality engineering functions, WebSTAT provides a function for testing signifi- ParaNAVI CAOS cance and other much-used statistical functions. Overall, WebSTAT is used more than 10 000 times a year. Figure 2 2) ParaNAVI Support tools. FUJITSU Sci. Tech. J., 43,1,(January 2007) 107 S. Takeshita et al.: Achieving Robust Designs through Quality Engineering: Taguchi Method 1.70 Coil Read terminal Conventional method 1.30 Tuning by trial and error using representative points 0.90 Write lower magnetic pole 0.50 Quality engineering Write upper Read element