DFSS-6sigma

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Six Sigma Forum Magazine

Volume 1 Issue 1 November 2001

Contents

Six Sigma and the Evolution of Quality in ProductDevelopment

The evolution of Six Sigma parallels that of quality methods. Design for Six Sigma

can help take your organization even farther.

by Larry R. Smith, Ford North meri!an "ru!#

$eor%e &o' had it ri%ht (hen he said, )ll models are (ron% but some are use*ul.+

Nam Suh, !hairman o* the e!hani!al -n%ineerin% e/artment at assa!husettsInstitute *or "e!hnolo%y I", develo/ed a very use*ul model o* rodu!t

evelo/ment as a ma//in% o* elements bet(een various domains !ustomerattributes to *un!tional re3uirements to desi%n /arameters to /ro!ess variables.

eter Sen%e, also o* I", develo/ed a use*ul model !on!ernin% (ays or levels o*thin#in% in terms o* events, /atterns or stru!ture. 4hen these t(o models are

!ombined, a ne( model is !reated that !an be used to understand the history andevolution o* 3uality and the role o* Si' Si%ma and esi%n *or Si' Si%ma FSS in

/rodu!t develo/ment.

5uality in /rodu!t develo/ment be%an (ith attem/ts to ins/e!t 3uality into /rodu!ts

or servi!es either in the /ro!ess domain s!ra/ and re(or#, the desi%n domainveri*i!ation tests and durability *ailures or the !ustomer domain (arranty !osts

and !om/laints. "he evolution o* 3uality involved a si%ni*i!ant mind6set transition

*rom rea!tin% to ins/e!tion events to utili7in% /ro!ess /atterns in en%ineerin% andmanu*a!turin% to build 3uality into the /rodu!t. Re!ent develo/ments in 3ualityen%ineerin% involve the use o* stru!tural tools to lay the /ro/er *oundation *or %ood

desi%n and enable the /ro!ess6level methods to (or# better. Si' Si%ma is used to

rea!t to or *i' un(anted events in the !ustomer, desi%n or /ro!ess domains. FSS isused to /revent /roblems by buildin% 3uality into the desi%n /ro!ess a!ross domains

at the /attern level o* thin#in%. 8se o* ne( stru!tural tools su!h as "RI9 a Russian

a!ronym *or )theory o* inventive /roblem solvin%+ and a'iomati! desi%n /rovide a*oundation *or *uture enhan!ement o* Si' Si%ma methodolo%ies.

Model of Product Development

"he /ro!ess o* desi%n involves understandin% (hat you (ant to a!hieve and thensele!tin% a strate%y that a!hieves that intent. "o better understand the history o*3uality and the role o* Si' Si%ma in /rodu!t develo/ment, !onsider the domain model

o* /rodu!t develo/ment sho(n in Fi%ure 1. Nam Suh, !hairman o* the e!hani!al-n%ineerin% e/artment at I", !reated this model, a//li!able to the develo/ment o*

either /rodu!ts or servi!es, in the late 1:;0s.1

Suh believes the !reation o* %reat /rodu!ts or servi!es involves sele!tin% strate%ies

asso!iated (ith *our /rimary a!tivities or domains< !ustomer domain, *un!tional
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domain, /hysi!al domain and /ro!ess domain. "he !ustomer domain !onsists o*!ustomer attributes=a !hara!teri7ation o* needs, (ants or deli%hts that de*ine a

su!!ess*ul /rodu!t or servi!e *rom a !ustomer /ers/e!tive. "he *un!tional domain!onsists o* *un!tional re3uirements=a !hara!teri7ation o* desi%n %oals or (hat the

/rodu!t or servi!e must a!hieve to meet !ustomer attributes *rom the vie(/oint o*the desi%ner. "he /hysi!al domain !onsists o* desi%n /arameters=the !olle!tion o*

/hysi!al !hara!teristi!s or a!tivities that are sele!ted to meet *un!tional %oals. "he/ro!ess domain !onsists o* /ro!ess variables=the !olle!tion o* /ro!ess

!hara!teristi!s or resour!es that !reate the desi%n /arameters.

"he develo/ment o* /rodu!ts or servi!es is hi%hly iterative and involves sele!tin%

elements in ea!h domain and ma//in% these elements *rom one domain to another.

"he better the ma//in% bet(een these domains, the better the desi%n. Fi%ure 2illustrates the %eneri! nature o* this model, (hi!h is literally a//li!able to any desi%n

a!tivity.

"he evolution o* desi%n is !orrelated (ith the evolution o* our thin#in%. eter Sen%e,a /ro*essor at I">s Sloan ana%ement S!hool, des!ribes three levels o* thin#in%s domain model sho(n in Fi%ure 1. a//in% bet(een domains re/resents ama//in% o* (hats to ho(s. "he /rin!i/le o* inde/enden!e states that in %reat

desi%ns, the ho(s are !hosen in su!h a (ay that the (hats maintain inde/enden!e.For e'am/le, desi%n /arameters must be !hosen in su!h a (ay that *un!tional

re3uirements maintain inde/enden!e. Consider the (ater *au!et desi%ns sho(n inFi%ure ;.

"he *un!tional re3uirements *or a (ater *au!et are t(o< !ontrol the *lo( rate and!ontrol the (ater tem/erature. "he *au!et on the le*t o* Fi%ure ;has t(o desi%n

/arameters< a hot (ater #nob and a !old (ater #nob. 4hat is the relationshi/bet(een these desi%n /arameters and the *un!tional re3uirementsM 4hen the hot

(ater #nob is turned, tem/erature is a**e!ted and so is *lo(. "urnin% the !old (ater#nob also a**e!ts tem/erature and *lo(. "here*ore this desi%n is !ou/led and the

*un!tional re3uirements are not inde/endent. I* a !onsumer has o/timi7ed *lo( rate,then turns one o* the #nobs to o/timi7e tem/erature, the *lo( rate is !han%ed and is

no lon%er o/timal. esi%ns o* this ty/e eventually satis*y !ustomers by iteratin%bet(een the t(o desi%n /arameters.

Consider the desi%n on the ri%ht o* Fi%ure ;. "his *au!et has one handle and thedesi%n /arameters are to li*t the handle to adHust *lo( and move the handle *rom

side to side to adHust tem/erature. In this desi%n, adHustin% tem/erature does nota**e!t *lo( and adHustin% *lo( does not a**e!t tem/erature. From an a'iomati! desi%n

/oint o* vie(, this desi%n is su/erior be!ause the *un!tional re3uirements maintaininde/enden!e.

Ima%ine (hat ha//ens (hen a desi%ner is (or#in% in a situation (ith a do7en ormore *un!tional re3uirements. I* the desi%n is !ou/led, then o/timi7ation o* one

*un!tion may adversely im/a!t several other *un!tions. 4hen these *un!tions are*i'ed, the ori%inal *un!tion no lon%er (or#s (ell. "he desi%ner is al(ays tunin% and

&and6idin% su!h a desi%n, and the !ustomer (ill never be !om/letely ha//y.Ko(ever, i* the desi%n is !reated in su!h a (ay that ea!h o* the *un!tional

re3uirements is handled inde/endently by the desi%n /arameters, then ea!h *un!tiono* the desi%n !an easily be o/timi7ed (ith /attern level tools.

"he /rin!i/le o* inde/enden!e !an be used to evaluate ho( %ood a desi%n (ill be

(hen the desi%n is still on /a/er. &ut su//ose you have t(o desi%n alternatives thatboth *ollo( the inde/enden!e a'iom. No( (hi!h one is betterM "he se!ond /rin!i/le

states that the better desi%n (ill minimi7e the in*ormation !ontent ne!essary *or
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im/lementation.;esi%ns that have a solid a'iomati! *oundation sim/ly (or# betterthan desi%ns that do not.

Su//ose the desi%ner !annot *ind a set o* desi%n /arameters that #ee/ all the*un!tional re3uirements inde/endent. In this situation, im/rovin% one *un!tion

ty/i!ally de%rades another. n e'am/le in automotive steerin% is steerin% road *eel

and /ar#in% e**orts. 4hen the steerin% e**orts are hi%h, the !ustomer e'/erien!es%ood road *eel. Ko(ever, hi%h e**orts !an ma#e it di**i!ult *or !ustomers to /ar#.dHustin% e**orts to ma#e the vehi!le easy to /ar# (ill result in de%raded road *eel.

ty/i!al a//roa!h to resolve this situation is !om/romise=trade o** !ustomer

*un!tionality and ho/e *or the best. "his is (here "RI9 is most hel/*ul. "RI9 is the

result o* more than D years o* resear!h by $enri!h ltshuller and !ollea%ues.ltshuller hated !om/romise. Ke !alled the situation (here *un!tions o//ose ea!h

other !ontradi!tions and develo/ed a methodolo%y in (hi!h desi%n teams !ouldsystemati!ally innovate and *ind desi%n /arameters that resolved !ontradi!tions,

!reatin% (in6(in *un!tional situations. "he methodolo%y be%an by identi*yin% all/ossible !ontradi!tions that e'isted in /atent databases and identi*yin% ho( these

!ontradi!tions (ere resolved. ltshuller *ound that only a *e( /arti!ular /rin!i/les o*resolution have ever been used in the history o* man#ind to resolve !ertain /airs o*

*un!tional !ontradi!tions.

For e'am/le, su//ose the *un!tions o* (ei%ht and reliability !ontradi!t. 4hen the

desi%n is !han%ed to im/rove reliability, (ei%ht in!reases. 4hen (ei%ht is de!reased,reliability de%rades. ltshuller *ound there are only *our /rin!i/les that have ever

been used to resolve this !ontradi!tion.:Ke !reated a matri' o* !ontradi!tions andresolution /rin!i/les and used this in*ormation to %uide desi%n teams so that they

!ould brainstorm in areas that are li#ely to lead to (in6(in solutions. ltshuller alsobelieved in minimi7in% in*ormation !ontent? he !alled this the /rin!i/le o* ideality.

Later, "RI9 (as e'/anded to in!lude an entire al%orithm o* innovation te!hni3ues,in!ludin% the study o* system evolution.

ltshuller *ound that systems tend to evolve alon% s/e!i*i! la(s and lines o*evolution. &y studyin% system evolution *or the /ast and /resent *or the

su/ersystem, system and subsystem, a desi%ner !an identi*y the !urrent sta%e o*system evolution. &y a//lyin% la(s and lines o* evolution, desi%n teams !an /redi!t

(hat the ne't develo/ments o* the system (ill be. "his is a hu%e !om/etitiveadvanta%e. Com/anies that o/erate at the event level obtain in*ormation about the

!ustomer throu%h (arranty data. Com/anies at the /attern level intera!t (ith!ustomers and *ind out (hat !ustomers believe is im/ortant today. No !ustomer !an

tell the desi%ner (hat (ill be im/ortant tomorro(. t the stru!tural level, "RI9dire!ted evolution /redi!ts (hat (ill be im/ortant to !ustomers tomorro(.

So i* "RI9 (or#s at the stru!tural *oundation o* desi%n, (hy does the name im/ly/roblem solvin%M "he ans(er is sim/ly that hi%her level thin#in% !an al(ays be used

as a methodolo%y to solve lo(er level /roblems. "he *a!t that /roblems e'ist in theevent realm means that the ori%inal /ro!ess o* desi%n had serious *la(s=/attern or

stru!tural (or# that should have been done is either missin% or in!om/lete. "hedesi%ner !an al(ays %o ba!# and !om/lete this (or# at anytime.

"his is (hy !om/letin% (or# asso!iated (ith /attern or stru!tural tools !an 3ui!#ly

lead to /roblem resolution. %ood e'am/le o* this is Si' Si%ma. It addresses
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/roblems !reated by event level thin#in%, but the methodolo%y o* Si'Si%ma utili7es /attern level tools su!h as F-.

The Roles of Six Sigma and DSS

"he /rodu!t develo/ment model in Fi%ure is use*ul to illustrate the roles o* Si'

Si%ma and FSS and also /rovides im/li!ations *or ne't ste/s. "he role o* Si' Si%mais to solve /roblems at the event level in the !ustomer domain !ustomer !om/laints

or (arranty, the /rodu!t domain desi%n or servi!e does not /ass tests or the

/ro!ess domain internal s!ra/, re(or# or !a/ability issues. n e**e!tive Si' Si%ma/ro%ram, even thou%h this /ro%ram saves lots o* money, is still an attem/t to ins/e!t

in 3uality by addressin% events a*ter the *a!t. !om/any that o/erates only at this

level (ill never be !om/etitive (ith a !om/any that /revents /roblems in the *irst/la!e usin% FSS.

"he role o* FSS is to build 3uality into the desi%nby im/lementin% /revent thin#in%and tools in the /rodu!t develo/ment /ro!ess. FSS is, in *a!t, an inte%ration o*

/revent methods at the /attern level a!ross all *our domains. "he relative roles o* Si'

Si%ma and FSS in /rodu!t develo/ment are sho(n in Fi%ure .

n e**e!tive FSS /ro%ram must utili7e tools that ma#e a di**eren!e in ea!h desi%ndomain. For e'am/le, a FSS /ro%ram that does not inter*a!e (ith !ustomers or

does not utili7e /o(er*ul methods li#e "a%u!hi>s /arameter desi%n to hit the desi%n(ith noise or un!ontrolled variation and adHust !ontrollable *a!tors in the desi%n to

ma#e the desi%n robust a%ainst noise is a /ro%ram that is %uaranteed to leavesi%ni*i!ant /ortions o* the (or# o* desi%n in!om/lete. "his (ill virtually %uarantee

that the Si' Si%ma /ro%ram (ill have /lenty o* issues to (or# on in the *uture.

&oth Si' Si%ma and FSS !an be made more e**e!tive by in!or/oratin% stru!tural

tools su!h as a'iomati! desi%n and "RI9 into the methodolo%y. &e!ause these toolsaddress desi%n *oundation *la(s, they (ill enhan!e every as/e!t o* Si' Si%ma and

FSS, ma#in% the /ro!ess o* /roblem solvin% and /roblem /revention mu!h moreinsi%ht*ul, /rodu!tive and e**i!ient than /ro%rams that do not utili7e these methods.

Move Past the !ompetition

5uality tools and methods have evolved utili7in% three sta%es o* thin#in% event,

/attern and stru!ture a!ross various domains asso!iated (ith /rodu!t develo/ment."he evolution o* Si' Si%ma /arallels the evolution o* 3uality methods. Si' Si%ma

addresses event level !on!erns that o!!ur in /rodu!t develo/ment a*ter the *a!t.FSS re/resents a hi%her evolution o* the methodolo%y, utili7in% /attern level

thin#in% and tools to build 3uality into the /rodu!t or servi!e.

"he *uture o* Si' Si%ma and FSS involves in!or/oratin% stru!tural thin#in% methodssu!h as a'iomati! desi%n and "RI9. 8se o* these methods (ill ma#e Si' Si%ma and

FSS more e**e!tive and more /rodu!tive (ith less e**ort. Com/anies that (ish to

a!!elerate develo/ment o* their o(n 3uality /ro%rams !an utili7e the evolutionarytrends e'/lained in this /a/er to understand their !urrent level o* evolution and to

im/lement *o!used a!tions that !an 3ui!#ly move them /ast their !om/etition.

REERE"!ES
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1. Nam . Suh, The Principles of DesignNe( Jor#< @'*ord 8niversity ress, 1::0.2. eter . Sen%e, The Fifth DisciplineNe( Jor#< oubleday, 1::0.

. i#el Karry and Ri!hard S!hroeder, Six Sigma: The reakthrough !anagement Strategy "evolutionizingthe #orld$s Top %orporationsNe( Jor#< oubleday, 2000.

D. Ibid.

. Baoru Ishi#a(a, )5uality nalysis,+ 1:;; S5C Con*eren!e "ransa!tions il(au#ee< S5, 1:;;, //.D26D2:.

. i#el Karry and Ri!hard S!hroeder, Six Sigma: The reakthrough !anagement Strategy "evolutionizingthe #orld$s Top %orporationssee re*eren!e .

;. Nam . Suh,&xiomatic Design: &dvances and &pplicationsNe( Jor#< @'*ord 8niversity ress, 2001.. $enri!h ltshuller and Lev Shulya#, '( Principles: T")* +eys to Technical )nnovation4or!hester,

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