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 How QFD integrates DFSS and DFX
 How QFD integrates DFSS and DFX
 How QFD integrates DFSS and DFX
 How QFD integrates DFSS and DFX
 How QFD integrates DFSS and DFX
 How QFD integrates DFSS and DFX
 How QFD integrates DFSS and DFX
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How QFD integrates DFSS and DFX

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Quality Function Deployment provides an architecture that can effectively position and combine Design for Excellence (DFX) and Design for Six Sigma (DFSS). …

Quality Function Deployment provides an architecture that can effectively position and combine Design for Excellence (DFX) and Design for Six Sigma (DFSS).

By combining these methods, manufacturers can differentiate a product in terms of quality prior to the actual production process.

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  1. QUALITY FUNCTION DEPLOYMENTDFX and DFSS:How QFDIntegrates Themby Jui-Chin Jiang, Ming-Li Shiu and Mao-Hsiung TuD esign for excellence (DFX) and design for to integrate them effectively by using quality func- Six Sigma (DFSS) have been two of the tion deployment (QFD). most popular concepts in quality man- It is a good starting point to understand theagement in recent years, but very little has been roots of the words “excellence,” “Six Sigma” andwritten comparing DFX and DFSS. This article “quality.” Aristotle might have been the first per-aims to clarify the differences between them in son to talk on the subject of quality in any system-concept and application and further identify how atic way.1 In his book Metaphysics, he gave four definitions of quality and later summarized them with two basic meanings: “differences of real sub- stance” and “mode of a subject in motion, of itself.”In 50 Words Good (excellence) and bad (inferiority) are parts of Or Less the latter mode. Simply speaking, there are two aspects of quali-• Quality function deployment provides an ty, according to Aristotle: different quality and good quality. Discussions of quality have revolved architecture that can effectively position around these two aspects since Aristotle’s time.2 and combine design for excellence and Whether you’re creating different quality or try- ing to achieve good quality, you must build quality design for Six Sigma. into a product when it is planned and designed. Quality built in at this stage has the maximum• By combining these methods, manufactur- return in terms of cost benefits and customer satis- ers can differentiate a product in terms of faction. It far surpasses the improvements brought about by relying separately on promotional efforts quality prior to the actual production in selling or detection and modification in manu- process. facturing after a product is released. DFX and DFSS both help build quality into the design stage. QUALITY PROGRESS I OCTOBER 2007 I 45
  2. QUALITY FUNCTION DEPLOYMENT Design for Excellence 8. Environmental friendliness: The product’s DFX has evolved and is still evolving from manufacturing process, use and disposal are design for manufacturability. By manufacturability, free of environmental pollution and hazards. we mean the ease with which a product or compo- 9. Psychological characteristics: Product aesthet- nent can be produced. Historically, designers have ics as perceived by the user’s five senses and overlooked manufacturability and have concen- the sensibility that relates to the user’s think- trated their efforts on function, features and ing, feeling and discerning about a product. appearance of their products. However, concentrat- It should be pointed out that DFX objectives are ing on manufacturability during product design all the desirable factors a product should theoreti- has great cost benefits.3 cally have. In practice, DFX objectives are met by a Today, a limited series of design objectives— company’s selective quality characteristics. function, features and appearance—even when manufacturability is added, is not enough to pro- Design for Six Sigma vide the most competitive, economical and benefi- Six Sigma is a disciplined and highly quantita- cial design to customers and society over the long tive approach to improving product or process run.4 quality. The goal is to reduce defects to no more DFX is intended to provide designers with an than 3.4 per million opportunities. Six Sigma was objective deployment framework and a means to introduced at Motorola and has been adopted and achieve all desirable dimensions of quality. DFX generalized by numerous companies, such as can be viewed as a design approach that deals with Allied Signal and General Electric. Aristotle’s different quality while focusing on the Companies that have adopted Six Sigma have right thing to design. realized that once they have hit a “five sigma wall” When we look at research in this field, two and progress has come to a standstill, the only way renowned examples are the eight quality dimen- to surpass this wall is to apply DFSS. DFSS is a rigor- sions David Garvin proposed5 and the internal ous approach to designing products from the begin- structure of quality Noriaki Kano proposed.6 Based ning to ensure customer requirements are met.7 on these ideas, we propose nine dimensions of DFSS can be viewed as a design approach that quality, or DFX objectives: deals with Aristotle’s good quality and a focus on 1. Higher functional performance: Higher effect how to design the right thing right. DFSS follows levels of a product’s main operating character- the define, measure, analyze, design and verify istics. (DMADV) phases during design projects. The core 2. Physical performance: Dimension, volume concept of DMADV implementation is to gradual- and weight of a product. ly flow down new products’ critical-to-quality 3. User friendliness: How easily a product is characteristics to functional design, detailed design used. and process control variables, and then flow up 4. Reliability and durability: Reliability refers to capability to meet these requirements.8 how free of failure a product is during a peri- od of time. Durability refers to a product’s Quality Function Deployment lifespan. QFD is a method of new product development 5. Maintainability and serviceability: How easy under the umbrella of total quality management. It it is to restore a product’s usability after a fail- is a process for systematically converting cus- ure. tomers’ demands into design quality, and it 6. Safety: How free of injury and hazard the pro- deploys quality over design targets and major duct’s user is. quality assurance (QA) points, or milestones, used 7. Compatibility and upgradeability: Compati- throughout the product development process. bility refers to the ease of combining a product QFD was conceived in Japan in the late 1960s with another product. Upgradeability refers to while Japanese industries were departing from the ease of incorporating improved or addi- their postwar mode of product development, tional features into a product. which had essentially involved imitation and copy-46 I OCTOBER 2007 I www.asq.org
  3. FIGURE 1 Comprehensive Quality Function Deployment System Finished product quality characteristics Market evaluation Demanded quality items • Competitive analysis 3 • Complaints/claims 2 3 • Planned quality 1 1. Primary 2 3 • Selling points 2. Secondary 3 • Kano’s attractive quality survey 3. Tertiary • Competitive analysis • Design target setting Setting • Specification tolerance design target • Key quality characteristic list • Bottleneck engineering list Cost deployment Parts • Component unit specifications • Bottleneck engineering list • FTA/FMEA Subsystems • Key component/part list • Supplier feasibility and capability survey • Production specifications • Bottleneck engineering list • FTA/FMEA Processes • Key control item list • Quality assurance process sheet • Shopfloor management system design FTA = fault tree analysis FMEA = failure mode effects analysising, and were moving toward original product simultaneously.11 The objective of each deploymentdevelopment. At that time, there was recognition is as follows:of the importance of designing quality into new • Quality deployment is to systematically de-products, but there was a lack of guidance on how ploy customers’ demanded quality over theto achieve it. design targets and major QA milestones used Companies were already inspecting for quality, throughout the product development process.but it was happening at the manufacturing site • Technology deployment is to extract any bot-after new products had been produced.9 tleneck engineering (BNE) that hinders quality Yoji Akao first presented the QFD concept and and solve it at the earliest possible time.method to solve these problems, and QFD has con- • Cost deployment is to achieve the target costtinued to spread since Shigeru Mizuno and Akao while keeping a balance with quality.published their first book on the topic in 1978.10 • Reliability deployment is to prevent failures To ensure smooth product development, Akao and their effects through early prediction.constructed a comprehensive QFD system that Figure 1 shows the concept in an integrated way.considers quality, technology, cost and reliability The first step for QFD implementation is to QUALITY PROGRESS I OCTOBER 2007 I 47
  4. QUALITY FUNCTION DEPLOYMENT decide on a target market and formulate a product R&D personnel view the subsystem or component portfolio strategy. Then, a survey is conducted unit (also known as a building block) of the inter- with the market’s customers, and a demanded- mediate layer of the product architecture as the quality deployment chart is made. design unit. As a result, a subsystem’s deployment According to market evaluation information is necessary to allocate the specification tolerance such as competitive analysis and claims analysis, of the finished product’s quality characteristics to the company might conduct quality planning and relevant component units. determine the new product’s individuality or sell- In the design stage, the product must effectively ing points. Kano’s attractive quality survey helps prevent a recurrence of the existing product’s design to conduct product planning for creating attractive problems as well as the new product’s potential quality.12 design problems. To that end, a fault tree analysis Customers express demanded qualities by (FTA) and failure mode effects analysis (FMEA) can be employed. With respect to parts and materials needed for constructing subsystems, deployment is required, and an evaluation of the supplier’s feasi- bility and capability should be conducted.Like product design, process Products are made through processes and com- pleted by assembling semifinished products.design must effectively prevent Therefore, a semifinished product and its specifica- tions defined by the subsystem’s deployment area recurrence of the existing made using process deployment and design and by deciding specifications of process conditionsprocess’s design problems and (also known as production specifications). Like product design, process design must effec-the potential design problems tively prevent a recurrence of the existing process’s design problems and the potential design problemsof the new process. of the new process. This can be done by drawing on equipment FTA and process FMEA. Based on process deployment and FMEA infor- mation, a QA process sheet (also known as control plan) can be created to provide an overview of information needed for process control. The design directly describing and perceiving what product of the shop floor management system needed to quality is. However, demanded qualities must be execute the QA process sheet, which is part of the converted to quality characteristics—that is, the process design, ensures that before a product technical language a company’s R&D personnel enters mass production, adequate preparations are use to understand how to technically achieve the already in place to achieve manufacturing QA. demanded qualities. Only in this way is it possible The foregoing quality deployment, which to materialize them through development technol- includes technology and reliability, can realize cus- ogy. tomers’ demanded qualities and failure free quali- Therefore, it is necessary to carry out a quality ties, yet it might increase the cost as a result. By characteristics deployment of the finished product using market evaluation information to decide the to transform product quality from the world of the target cost of the finished product, and by corre- customer into the world of technology. The compa- sponding to quality deployment flows to set up ny can choose design specification values accord- cost targets for materials and labor, a balance ing to competitive analysis and extract the BNE, between QA and cost reduction can be achieved. which hinders the realization of the design quality. When a product is designed and developed, Integrating DFX and DFSS rather than directly designing the entire product, QFD’s structural integrity when dealing with48 I OCTOBER 2007 I www.asq.org
  5. FIGURE 2 QFD Toward DFX and DFSS Positioning and Integration All desirable dimensions of quality Finished product quality characteristics Market evaluation DFX Demanded quality Product target cost identification items • Competitive analysis • Value proposition 3 • Complaints/claims development/positioning 2 3 • Planned quality • Design characterization 1 1. Primary 2 3 • Selling points and differentiation 2. Secondary 3 • Kano’s attractive quality survey 3. Tertiary • Competitive analysis • Design target setting Setting • Specification tolerance design target • Key quality characteristic list • Bottleneck engineering list Cost deployment Parts DFSS • Optimal (Six Sigma) product • Component unit specifications specifications development • Bottleneck engineering list and tolerance allocation • FTA/FMEA • Product specificationsSubsystems • Key component/part list design verification • Supplier feasibility and capability survey • Optimal process conditions design and verification • Shopfloor management system design and verification • Production specifications • Bottleneck engineering list • FTA/FMEA Processes • Key control item list • Quality assurance process sheet • Shopfloor management system design DFX = design for excellence FTA = fault tree analysis FMEA = failure mode effects analysis critical issues (quality, technology, cost and reliabil- developed based on the selection of quality ity) of new product development helps position niches (one X or several Xs). and integrate DFX and DFSS, as illustrated in • In the design stage of demanded quality char- Figure 2. acterization, the design targets that can sup- DFX is a design method that deals with port the value proposition are set. Aristotle’s different quality. It can integrate with • Product design for the DFX and its verifica- QFD in converting demanded qualities into quality tion can then be conducted downstream. characteristics. In other words, it ensures that: DFSS can integrate with QFD in tolerance design • In planning all desirable dimensions of and process design of a product. That is, after set- demanded quality, a value proposition is ting the design targets (also known as nominal val- QUALITY PROGRESS I OCTOBER 2007 I 49
  6. QUALITY FUNCTION DEPLOYMENT ues) of quality characteristics, reference is made to In this example, a chart is used to deploy all specification values, actual performance and demanded qualities of the headlamp. All the process capability of similar products developed in columns in the quality planning section are used to the past. This is done to develop a product specifi- prioritize the demanded qualities that can support cation tolerance with Six Sigma design quality and the company’s market positioning and that are con- allocate the tolerance to related subsystems, com- sidered selling points. When demanded qualities ponent units, parts and materials. are converted into substitute quality characteristics, Moreover, DFSS also includes the design and R&D personnel must base the differentiation on tech- verification of optimal process conditions and shop nical measures that can achieve the selling points. floor management systems to ensure the manufac- For instance, to make sure the demanded quality turing of semifinished products can achieve Six “lamp shines brightly” becomes a quality charac- Sigma design quality. teristic, R&D personnel must determine a target Using the quality deployment of a headlamp as value for the technical measure, transmissivity, an example,13 Figure 3 shows QFD integrated with with a great difference from that of competitors’ the DFX and DFSS in Figure 2 (p. 49). headlamps and make it have significant brightness. FIGURE 3 QFD Integrated With DFX and DFSS Quality Flux distribution value Flux of light Efficiency Quality planning characteristics Flux Low Bright- Deman- distri- beam/ ness of Reflec- Color Air Competi- Abso- ded bution Lens high Aiming light Trans- tion temper- Electric tight- Filament Impor- tive Planned Level- Selling lute quality Demanded quality value size beam angle source missivity factor ature power Voltage ness strength tance analysis quality up rate points weight weight Bright enough to see wellQuality chart (two-dimensional matrix of demanded-quality deployment Can see distant objects Lamp shines brightly chart and quality characteristics deployment chart) Broad beam Quality planning for the Shines with directional stability Light does not scatter company’s market positioning Can see close objects well and sales proposition Low beam is bright enough Broad beam Shines with directional stability Can see well even under adverse conditions Can see well in poor weather conditions Coordinates with steering wheel Design target setting for Can see well even when vehicle bounces technical differentiation that Direction of beam correct under can communicate the no-load condition company’s positioning JIS ±4º require- 160 7.5 Specification nominal value ment ϕ 1º (up/down, left/rigt) cd/mm2 0.9 min 0.9 min 3000ºK 37.5/ 50W 12.8 V 0.2 a. p. impact 95º min Tolerance design for Six Sigma Specification tolerance quality by analyzing historical process control data and Headlamp capability studies Unit holding mechanism Left retaining ring Right retaining ringdeployment chart Tolerance allocation to Subsystems Left mounting ring Right mounting ring lower level characteristics Bolt Unit Lens Reflector Product and process detail Bulb design and verification = Low corresponding strength = Moderate corresponding strength = High corresponding strength JIS = Japanese industry standard SAE = Society of Automotive Engineers50 I OCTOBER 2007 I www.asq.org
  7. Assume we set the transmissivity value to be 0.9 Society for Quality Control), Vol. 13, No. 1, 1983, pp. 61-70.minimum. As for the decision of the specification 12. Kano, “Attractive Quality and Must-be Quality,” seetolerance for making 0.9 minimum, the nominal reference 1.value, we can use the data on variance and process 13. Mizuno, Quality Function Deployment: A Company- Wide Quality Approach, see reference 10.capability obtained from the analysis of historicalprocess control data to calculate the tolerancewidth required for Six Sigma quality. This toler- JUI-CHIN JIANG is an associate pro-ance is then allocated to lower level characteristics fessor in the department of industrialby simultaneously using the subsystems deploy- engineering at Chung Yuan Christianment chart. University (CYCU) in Taiwan. He is The development of the headlamp follows the also the chair of the university’s quali-remaining product and process development. ty research center. Jiang has a doctor-Meanwhile, other quality deployment charts areused, and the Six Sigma target values are flowed ate in industrial engineering fromdown to accomplish the detail designs and their Cleveland State University in Ohio.verifications. DFX and DFSS are two design methods thathave been used in recent years for effective newproduct development. But, more and more, new MING-LI SHIU earned a doctorate inproduct development requires combining the two. industrial engineering at CYCU.QFD offers a structure for linking and integratingthem. It uses the resultant synergy to create anadvantage for product development.REFERENCES 1. Noriaki Kano, Nobuhiko Seraku, FumioTakahashi and MAO-HSIUNG TU is the president ofShimichi Tsuji, “Attractive Quality and Must-be Quality,”Quality (Journal of the Japanese Society for Quality Control), Vol. D&N Business Consulting Co. in14, No. 2, 1984, pp. 147-156. Hsin-Chu City, Taiwan. He received his 2. Ibid. MBA from City University of Seattle. 3. James Bralla, Design for Excellence, McGraw-Hill, 1996. He was formerly the chief corporate 4. Ibid. consultant of the companywide quality 5. David Garvin, “Competing on the Eight Dimensions of improvement office of Philips Taiwan and won the DemingQuality,” Harvard Business Review, November-December1987, pp. 101-109. Application Prize in 1991 and the Japan Quality Medal 6. Noriaki Kano, “Quality Management in Management (Nihon Quality Control Prize) in 1997.Engineering,” Quality, Vol. 17, No. 1, 1987, pp. 23-39. 7. Jiju Antony and Ricardo Banuelas, “Design for SixSigma,” Manufacturing Engineer, February 2002, pp. 24-26. 8. Gerald Hahn, Necip Doganaksoy and Roger Hoerl,“The Evolution of Six Sigma,” Quality Engineering, Vol. 12,No. 3, 2000, pp. 317-326. 9. Yoji Akao and Glenn Mazur, “The Leading Edge in QFD:Past, Present and Future,” International Journal of Quality & PleaseReliability Management, Vol. 20, No. 1, 2003, pp. 20-35. comment 10. Shigeru Mizuno and Yoji Akao (eds.), Quality Function If you would like to comment on this article,Deployment: A Company-Wide Quality Approach, JUSE Press, please post your remarks on the Quality Progress1978. 11. Yoji Akao, Tadatoshi Ono, Akira Harada, Hideharu Discussion Board at www.asq.org, or e-mailTanaka and Kazuo Iwasawa, “Quality Deployment Includ- them to editor@asq.org.ing Cost, Reliability and Technology (part one)—Design ofQuality, Cost and Reliability,” Quality (Journal of the Japanese QUALITY PROGRESS I OCTOBER 2007 I 51

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