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Quality Engineering, 11(4), 593-611 (1999) QFD: VALIDATING ROBUSTNESS Kinnar K. Ghiya Intel Corporation 5000 W. Chandler Blvd., CH7-306 Chandler, Arizona 85226 A. Terry Bahill Systems and Industrial Engineering Department University of Arizona Tucson, Arizona 85721-0020 William L, Chapman Raytheon Systems Company Tucson, Arizona 85734 Key Words Quality function deployment (QFD); Concurrent engineering; Sensitivity analysis; Total quality management (TQM). Introduction Quality function deploy
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  Quality Engineering, 11(4), 593-611 (1999) QFD: VALIDATING ROBUSTNESS Kinnar K.Ghiya IntelCorporation 5000 W. Chandler Blvd., CH7-306 Chandler, Arizona 85226 A. Terry Bahill Systems and Industrial Engineering Department University of ArizonaTucson, Arizona 85721-0020 William L, Chapman RaytheonSystems CompanyTucson, Arizona 85734 Key Words Quality function deployment (QFD); Concurrent engi-neering; Sensitivity analysis; Total quality management(TQM). Introduction Quality function deployment (QFD) started in Japan in the late 1960s and is now used by half of Japan's majorcompanies. It was introduced in American automobile manufacturing companies in the early 1980s and is beingused by numerous American corporations (1,2). QFD is a handy tool for interdisciplinary teams. A typical QFD team will have members from marketing, sales, manufacturing,design, quality control, purchasing, and so on. QFD en-hances communication levels within the core team (3). Quality function deployment strives to get the customer's view of quality introduced in the early phases of the designcycle and considered throughout the product's entire life cycle. QFD therefore represents a change from manufac- turing-process quality control to product development qual- ity control (1). In most implementations, QFD uses manymatrixlike charts to discover interrelationships among cus- tomer demands, product characteristics, and manufacturing processes, as shown in Figure 1. For example, the first QFD chart compares the customer's demands to quality charac-teristics. The second chart then investigates the relationshipbetweenthese quality characteristicsandcharacteristicsof the product. The third chart subsequently examines the re-lationships between these product characteristics and manufacturing processes. Finally, these manufacturing pro- cesses are compared to the quality controls that will bemonitored during manufacturing. ToothBrite Inc.: A Heuristic Case Study In order to analyze QFD as a tool, we need an exampletostudy; therefore,wewillnowpresent ToothBrite (4). Assume that you are the Chief Executive Officer of 593 Copyright © 1999 by Marcel Dekker, Inc. www.dekker.com  594 GHIYA, BAHILL, AND CHAPMAN Quality CharacteristicsCustomerDemands Phase I QualityCharacteristics Product CharacteristicsPhase IIManufacturing Processes Product Characteristics Phase III Manufacturing Processes QualityControlsPhase IV Figure L Relationship of the four QFD charts. ToothBrite Inc., a major toothpaste manufacturer, and your market share has suddenly dropped, You suspect that this is a result of your competitor's new innovation. Crest® has developeda newtoothpaste container calledtheNeatSqueeze dispenser and has endowed it with a substantialadvertising budget, (To understand this example better, you might cut open a Crest® Neat Squeeze dispenser or aColgate® Neat and Easy Stand Up dispenser and see how it is produced and what is inside.) To recapture your mar- ket share, you decide to redesign your product; therefore, you decide to use QFD as your analysis tool. We had our marketing department interview all people we thought couldprovide inputs for the system design. In the QFD literature, the aspects deemed important by the customer are calledcustomer demands. Our marketing department derived thefollowing customer demands:Neatness Tidy tip: The tip stays neat and clean.Retains shape:thecontainer retainsitssrcinal shape. Stays put: The container will not roll off the counter. Hygienic: Toothpaste cannot touch the brush and then be drawn back into the container.Squeezable: People want to squeeze the container, notpump.Easy open: The cap opens and closes easily. No waste: Almost all the toothpaste comes out.Small footprint: Container takes little counter space.Reasonable cost: It should cost about the same as presentcontainers. Attractive container: The sales department says that itmust look good. After listing the demands, the customer assigns a weight indicating the relative importance of each demand. Usually,the weights are between 1 and 10, with 10 being most im- portant. Figure 2a shows the customer demands on the left side and the associated weights in the right column.  §. CTQ I I Sa I I 2 1 13 3 10 8 11 4 6 8 7 5 12 i 252315 59 21196100 92 120108100 104 117 70 Alttractive Container ~ UJ ~~ - so ~ o Reasonable Cost U) vO ^ SO so - U) SO 03 mall Footprint _ so ~ OJ Lh ãX o Waste U) NO so SO VO - VOON Easy Open U) \ O-i ^ ^ (Squeezable SOSO so - U) 00 o' so sO ~ U) ^ U) sO J^ Stays Put ^ SO ^ U) ON Retains Shape SOSO so - - u> U) ã£> | Tidy Tip so SO OJ u>u> 0 ?g f| ill «t Suction DeviceDashpot & Air ChamberElastic Walls Rigid Walls&PumpPlastic WallsPaste Viscosity Requirement Fixed Amount DispensedNew Cap Design FlatTop &BottomSqueezable Top & BottomInexpensive MaterialsSimple Manufacturing ProcessesGraphic DesignerTamper Proof PackageImportance (1 to 10) I I 1 1 GO I 3 96 10 8 7 5 4 1 2 i 13772 94 3676 82110126184 144 (Attractive Container U) - U) SO ~ sO <l ja (fD* i « U) NO \ C0 T) » \ - Wi iNo Waste UJ - U) so - ON S 1 ^ I - NO w ^ 00 ?r NO « Ui - oo 1 o* - vO NO ^ Stays Put oooo ON | Retains Shape - - <jj \ - - ^> 1 Tidy Tip SO U> - t^i SO 0 ? o 3 O 1 Is* -* fc AmountofMessAmount of Fullback Amount of PressureAmount of Effort Amount of WasteCounter SpaceAmount of DeformationPleasing AppearanceCost to ProduceSelling PriceImportance (1 to 10) Ui V4D  596 GHIYA, BAHILL, AND CHAPMAN In this example,ourcustomeris thepersonwhobrusheshis or her teeth with the toothpaste. However, the cus- tomer should also include all people who should provideinputsfor the system design. This includes buyers, storemanagers, mothers, the manufacturer's sales force, the de- sign team, and the production facility. See Chapter 5 of Ref.5 for a fuller exposition of this matter.Next, we asked our Systems Engineering Department toderive measures to assure that these customer demands arebeing satisfied. In the QFD literature, these measures arecalled figures of merit, quality characteristics, or, some-times, measures of effectiveness. Quality characteristicsshouldbe quantitative and measurable. The following arethe quality characteristics we used for the ToothBriteproject.Mess: amount of toothpaste scraped off the tip when halfemptyPull-back: amount of toothpaste pulled back when donedispensingPressure: amount of pressure needed to squeeze out thetoothpaste Effort: numberofturns,ortime,or effort neededto re-move capWaste: amountoftoothpaste left in thecontainerat end of life cycleCounter space: amountofcounter space occupiedbycontainerDeformation: amountofchangeinshapeofcontainer when half emptyCostofmaterials: costof rawmaterials usedtomakethecontainerPleasing appearance: based on results of customer survey In general, QFD charts have a desire that needs to be satis- fied listed along the side, and measures or approaches for satisfying the desires across the top, as shown in Figure 2a.The items listed on the left are called Whats and items listedalongthe top arecalled Hows.Tohelp determinetheHowswe ask, This is What the customer wants, now How can we measure it? Wewill often associate optimalortargetvalues with these measures. These measures become thedesires on the next chart, The next stepin QFD analysis is determining the strength of the relationships (or the degree of correlation) betweenthe Whats and the Hows. This is done by filling in the cen- ter matrix on a column-by-column basis as shown in Fig- ure 2a. Each What is compared to each How. Four classifi-cations are given: If they are strongly related, a value of 9,or a black disk with a white dot inside, is recorded in theappropriate cell. Moderate relationshipsaregivena 3, or acircle; weak relationships are given a 1, or a triangle; andno relationship is given a 0, or thecellis left blank. Depend- ing on thecustomers, symbolsandnumbercan bemixed.The next step is multiplying each cell's value by theweight of the customer demand and totaling the column for each quality characteristic. This is shown in the row across the bottom labeled Score in Figure 2a. The total score foreach column is an indication of the importance of that char-acteristic in measuring the customer's satisfaction. Typi-cally, measures with low scores receive little consideration.However, this does not necessarily mean that these measureswill not be used in the product design: They still may benecessary for contractual or other reasons. To satisfy thecustomer, we must pay strict attention to the measures withthe highest scores. Focusing attention on the customer is the main purpose of the QFD chart. The chart and its results arenot as important as the process of concentrating on the Voice of the Customer rather than the Voice of the Manufacturer. For the ToothBrite project, the Cost to Pro- duce (with a score of 184) and Selling Price (with a score of 144) were the most important measures, Subsequent QFD Charts To continue our QFD analysis, we will relate the qual-ity characteristics of Figure 2a to characteristics of the prod-uct. One of the purposes of a QFD analysis is to investigate many alternative designs. However,as theanalysisprogresses, we must limit the number of alternatives underconsideration. The characteristics of the product will be different for each alternative design. Thus, if we wish to continue investigating alternative designs, thenwemighthave to create a second QFD chart for each alternative. The following product characteristics, providedby theDesignEngineering Department, seem to imply a suction type ofcontainer:Double lead threads on cap andtip—allowingcap re-moval with a half-turnSize of dispensing hole in tipThickness of side wallsType of material for side walls Size of dashpot (the portion of the tube containing air) Viscosity of dashpotTotal weight of the containerSize of the container Printing on label—must be colorful and easy to read These product characteristicsnowbecome Howsin oursecondQFDchart showninFigure3a, The score ofeach
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