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TO PULL OR NOT TO PULL:WHAT IS THE QUESTION?

Wallace J. Hoppand Mark L. Spearman

epar!men! o" Ind#$!r%al En&%neer%n& and Mana&emen! Sc%ence$Nor!'(e$!ern Un%)er$%!*E)an$!on+ Ill%no%$ ,--/'opp0nor!'(e$!ern.ed#

1ac!or* P'*$%c$+Inc.23-4 La#rel 5alle* 6o#r!+ S#%!e --

6olle&e S!a!%on+Te7a$44/82(((."ac!or*p'*$%c$.com

A#$! 32+ --Re)%$edJ#l* 9+ --9

c Hopp and Spearman+ ----9

mailto:hopp@northwestern.edumailto:hopp@northwestern.edumailto:hopp@northwestern.eduhttp://www.factoryphysics.com/http://www.factoryphysics.com/http://www.factoryphysics.com/http://www.factoryphysics.com/mailto:hopp@northwestern.edu

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1

A;$!rac!

T'e !erm$ p#ll and lean prod#c!%on 'a)e ;ecome corner$!one$ o" modern man#"ac!#r%n&prac!%ce.

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A

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%n$p%ra!%on "or kan;an a$ com%n& "rom a )%$%! !o !'e U.S. d#r%n& !'e 3@2-$ %n ('%c' 'e (a$more %mpre$$ed (%!' Amer%can $#permarke!$ !'an (%!' Amer%can man#"ac!#r%n&. T'e %dea o"'a)%n& all &ood$ a)a%la;le a! all !%me$ (a$+ !o O'no+ no)el and re)ol#!%onar*. He $a%d:

1rom !'e $#permarke! (e &o! !'e %dea o" )%e(%n& !'e earl%er proce$$ %n a pro?d#c!%on l%ne a$ a k%nd o" $!ore. T'e la!er proce$$ c#$!omerF &oe$ !o !'e earl%erproce$$ $#permarke!F !o aG#%re !'e needed par!$ commod%!%e$F a! !'e !%me and %n !'eG#an!%!* needed. T'e earl%er proce$$ %mmed%a!el* prod#ce$ !'e G#an!%!* B#$! !aken re?$!ock%n& !'e $'el)e$F. C9,+ p. ,D

To do !'%$+ O'no 'ad !o make $ome maBor $*$!em c'an&e$. I" !'e $#permarke! (a$ !o

replen%$' onl* ('a! (a$ B#$! !aken %n a !%mel* manner+ lo! $%>e$ 'ad !o ;e dra$!%call* red#ced.Toac'%e)e !'e e c%enc%e$ffi needed+ O'no and '%$ To*o!a colleae$ "o#nd man* crea!%)e (a*$ !o red#cec'an&eo)er !%me$. Al!'o#&' c'an&e d%d no! 'appen o)ern%&'! !'e JIT re)ol#!%on (a$ reall* ane)ol#!%onF+ !'e re$#l!$ (ere $#;$!an!%al. In 3@82 $e!#p$ on lar&e pre$$e$ !ook ?9 'o#r$.

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%n !'e $pec% cfi appl%ca!%on$. O" co#r$e+ ERP (a$ m#c' more comple7 !'an MRP II+ con!a%n%n&mod#le$ "or e)er* ;#$%ne$$ "#nc!%on %ma&%na;le+ "rom acco#n!%n& and nanc%alfi "#nc!%on$ !o'#man re$o#rce$. And %! (a$ corre$pond%n&l* more e7pen$%)e+ (%!' %mplemen!a!%on co$!$ a! $omecompan%e$ $oar%n& a$ '%&' a$ 2- m%ll%on C@D. In $p%!e o" !'e pr%ce !a& and !'e &ro(%n& n#m;er o"%mplemen!a!%on 'orror $!or%e$+ ERP con!%n#ed !o &ro( %n pop#lar%!*. A$ !'e 3@@-$ dre( !o aclo$e and "ear o" !'e M%llenn%#m ed %n !'e ISO@--- 6er!% ca!%onfi proce$$.T'e "oc#$ onTQM %n !'e 3@/-$ al$o $p#rred Mo!orola !o e$!a;l%$'an am;%!%o#$ G#al%!* &oal and !o de)elop a $e! o" $!a!%$!%cal !ec'n%G#e$ "or mea$#r%n& and ac'%e)%n&%!. T'%$ approac' ;ecame kno(n a$ S%7 S%&ma and (a$ e)en!#all* adop!ed ;* compan%e$ $#c'a$ All%ed S%&nal and !'en Keneral Elec!r%c. S%7 S%&ma en!ered !'e ma%n$!ream mana&emen! le7%con('en Jack Welc'+ !'e c'ar%$ma!%c 6EO o" KE+ declared !'a! %! pla*ed a maBor role %n '%$compan*$ nanc%alfi $#cce$$.Toda*+ S%7 S%&ma carr%e$ on !'e le&ac*o"TQMB#$! l%keleancarr%e$on !'e le&ac*o"JIT.e$p%!e !ra)el%n& $epara!e pa!'$ $%nce emer&%n& "rom JIT+ %! no( appear$ !'a! !'e Lean

Man#"ac!#r%n& and S%7 S%&ma mo)emen!$ are a;o#! !o mer&e+ a$ $#&&e$!ed ;* !'e recen! ;e$!$ell%n& mana&emen! ;ook+ Lean S%7S%&maC-D. A! !'e $ame !%me+ !'e comp#!er approac' c'arac!er%>ed ;* MRP=ERP %$ al$o #nder&o%n& con$ol%da!%on. A"!er pro)ed !o ;e a none)en!+ERP ;ecame pa$$e a$ a !erm ;#! (a$ G#%ckl* replaced ;* S6M S#ppl* 6'a%n Mana&emen!F.Remarka;l*+ SAP+!'e (orld$ lar&e$!pro)%der o" ERP $o"!(are+ c'an&ed %!$ en!%re prod#c! l%ne%n a ma!!er o" mon!'$ or $o %! (o#ld appear ('en a $earc' o" !'e%r (e;$%!e re)ealed !'a!all re"erence$ !o ERP (ere &one and 'ad ;een replaced (%!' !'e ne( S6M acron*mF. S%nce

;o!' ERP and S6M !race !'e%r roo!$ ;ack !o G#an!%!a!%)e prod#c!%on and %n)en!or* con!rol+%! %$ per'ap$ no! $#rpr%$%n& !'a! !'e* (o#ld (%nd #p em;od%ed %n !'e $ame $o"!(are prod#c!$.Ho(e)er+ all !'%$ lead$one !o (onder ('en !'e Lean S%7 S%&ma S#ppl* 6'a%n Mana&emen!mo)emen! (%ll ;e&%n.

9 P#ll Re$earc'

W'%le corpora!e Amer%ca !r%ed !o na)%&a!e !'%$ $ea o" ;#>> (ord$ and !o compre'end !'e To*o!aProd#c!%on S*$!em alon& (%!' !'e m*$!er%o#$ concep! o" p#ll+ !'o$e %n !'e academ* (ere ;#$* a$(ell. A$ (%!' an* ne( mana&emen! !rend+ academ%c re$earc'er$ (ere G#%ck !o &e! on !'eJIT;and(a&on. Hall and Sc'on;er&er (ere ;o!' academ%c$ ('o (en! !oJapan !o $!#d*B#$!

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%n!%me r$!'and.fi Monden+ o" !'e Un%)er$%!* o" T$#k#;a+ d%d no! 'a)e !o !ra)el a$ "ar. I!appear$ !'e r$!fi academ%c paper de$cr%;%n& kan;an (a$ p#;l%$'ed ;*Japane$ere$earc'er$ %n3@44. T'e !%!le o" !'e paper ;* S#&%mor%+ e! al. C84D %$ !ell%n&: To*o!a Prod#c!%on S*$!emand an;an S*$!em: Ma!er%al%>a!%on o" J#$!InT%me and Re$pec!1orH#man S*$!em. L%keOrl%ck*$ Ne( Wa* o" L%"e+ !'e To*o!a Prod#c!%on S*$!em %$ $ome!'%n& ;%& !'a! &oe$ ;e*ondprod#c!%on con!rol. T'e !%!le o" !'%$ r$!fi paper ma* al$o 'a)e con!r%;#!ed !o !'e m%$!akeneG#%)alence ;e!(een !'e To*o!a Prod#c!%on S*$!em and kan;an. I! (a$ "ollo(ed "o#r *ear$la!er ;* ano!'er paper ;* !(o o!'erJapane$ere$earc'er$+ %m#ra and Terada C9-D. e$ !'a! 'andler !o !ake !'e$e par!$ and !ell$ '%m ('ere !'e par!$ are needed.

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1%re 3: A !(o card kan;an $*$!em.

1%re : EG#%)alence o" !'e one and !(o card kan;an $*$!em$.

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3. Red#ced WIP and 6*cle T%me:

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W'en an order %$ placed+ %! %$ lledfi "rom %n)en!or* %" !'e %n)en!or* %$ no! >ero. I"!'e %n)en!or* %$ >ero+ !'e order %$ placed %n a ;ackorder le+fi !o ;e lledfi ('en an%!em arr%)e$. In an* e)en!+ a man#"ac!#r%n& order %$ %mmed%a!el* placed (%!' !'epreced%n& man#"ac!#r%n& opera!%on !o prod#ce an %!em !o replace !'e %!em !'a! 'a$;een con$#med. T'e man#"ac!#r%n& opera!or+ %n !#rn+ %mmed%a!el* place$ an order"or !'e reG#%red ra( ma!er%al$ a&a%n$! !'e preced%n& %n)en!or*+ and a$ $oon a$ !'%$order %$ lledfi C%.e.+ 'e 'a$ !'e needed %n)en!or*D+ proceed$ !o opera!e on %! !oprod#ce !'e reG#%red %!em. In !'%$ (a* an order a&a%n$! !'e la$! %n)en!or* "or a n%$'edfi%!em %$ %mmed%a!el* !ran$m%!!ed all !'e (a* ;ack alon& !'e l%ne !o all !'eman#"ac!#r%n& opera!%on$+ eac' o" ('%c' %$ &al)an%>ed %n!o prod#c!%on.

an%$ C8,D "o#nd !'a! ('%le $pec% cfi en)%ronmen!al%mpro)emen!$ are cer!a%nl* %n #efl n!%al e.&.+ $e!#p red#c!%on+ prod#c!%on $moo!'%n&F+ !'ere are !'reepr%mar* lo&%$!%cal rea$on$ "or !'e %mpro)ed per"ormance o" p#ll $*$!em$:

3. Le$$6on&e$!%on: 6ompar%$on o" a open G#e#e%n& ne!(ork (%!' an eG#%)alen! clo$edone $'o($ !'a! !'e a)era&e WIP %$ lo(er %n !'e clo$ed ne!(ork !'an !'e open ne!(ork&%)en !'e $ame !'ro#&'p#!. T'e e ec!ff %$ rela!%)el* m%nor and %$ d#e !o !'e "ac! !'a!G#e#e len&!'$ 'a)e no correla!%on %n an open $*$!em ;#! are ne&a!%)el* correla!ed %n aclo$ed G#e#e%n& ne!(ork+ an o;$er)a!%on made earl%er ;* W'%!! C28D.. Ea$%er 6on!rol: T'%$ %$ a "#ndamen!al ;ene !+fi ('%c' re$#l!$ "rom $e)eral o;$er)a!%on$:

a. WIP %$ ea$%er !o con!rol !'an !'ro#&'p#! $%nce %! can ;e o;$er)ed d%rec!l*.;. T'ro#&'p#! %$ !*p%call* con!rolled (%!' re$pec! !o capac%!*. a!%on ra!e$.A$a re$#l!+ $*$!em$ !'a! con!rol WIP are $#;$!an!%all* more ro;#$! !ocon!rol error$ !'an are $*$!em$ !'a! con!rol !'ro#&'p#! $ee 6'ap!er 3- o" C3/D "or ama!'ema!%cal %ll#$!ra!%on o" !'%$ ro;#$!ne$$ e ec!F.ff

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9. WIP 6ap: T'e ;ene !$fi o" a p#ll en)%ronmen! o(e more !o !'e "ac! !'a! WIP %$ ;o#nded !'an!o !'e prac!%ce o" p#ll%n& e)er*('ere. T'%$ (a$ ared ;* o;$er)%n& !'a! a $%mpleo)erall ;o#nd on !'e WIP %.e.+ a$ %n a clo$ed G#e#e%n& ne!(ork (%!'o#! ;lock%n&F (%llpromo!e !'e $ame ;ene !$fi a$ !'o$e c%!ed "or kan;an and ;* $'o(%n& !'a! !'e !'ro#&'p#! o" aclo$ed G#e#e%n& ne!(ork (%!'o#! ;lock%n& %$ &rea!er !'an !'a! o" a clo$ed G#e#e%n& ne!(ork(%!' ;lock%n& %.e.+ a kan;an $*$!emF.

a!%on$

#r%n& !'e la!e 3@/-$ and earl* 3@@-$ a n#m;er o" re$earc'er$ compared d% ereff n! )er$%on$ o"kan;an+ 6ONWIP and o!'er $*$!em$. A &ood o)er)%e( o" !'e (ork ;e"ore 3@@, can ;e "o#nd %nC9D.A$ more )ar%an!$ o" kan;an and rela!ed $*$!em$ (ere propo$ed+ re$earc'er$ ;e&an !o $eek (a*$!o #n%"* !'em. 1or e7ample+ aco!! de$cr%;ed a &eneral%>ed kan;an pol%c* %n C4D and%n!rod#ced !'e concep! o" prod#c!%on a#!'or%>a!%on card$. T'%$ concep! (a$ de)eloped"#r!'er %n C/D ('ere %! (a$ $'o(n !o repre$en! MRP+kan;an+ 6ONWIP+a$ (ell a$ man* '*? ;r%d$*$!em$. U$%n& !'%$ "rame(ork and $ample pa!' armen!$+ aco!! and S'an!'%k#mar $'o(ed!'a! 6ONWIP %$ !'e op!%mal $!r#c!#re "or ma7%m%>%n& !'ro#&'p#! "or an* WIP l%m%!%n& $*$!em.Ta*#r C8@D al$o con$%dered !'e G#e$!%on o" !'e op!%mal p#ll $!r#c!#re+ )%e(%n& $*$!em$ a$ acon!%n##m "rom kan;an !o 6ONWIP depend%n& on 'o( !'e* are par!%!%oned %n!o WIPcon!rolled $e&men!$ and con$%dered 'o( !o op!%m%>e !'e alloca!%on o" card$ %n $#c' $*$!em$ $o a$!o ma7%m%>e !'ro#&'p#!.In ano!'er #n% ca!%onfi paper+A7$a!erand Ro$l%n& CD $'o(ed !'a! kan;an %$ a $pec%al !*pe o"%n$!alla!%on $!ock pol%c* %.e.+ one %n ('%c' !'e reorder po%n! %$ an %n!e&er m#l!%ple o" !'ereorder G#an!%!* and ('ere ;acklo&$ are no! $#;!rac!ed "rom !'e %n)en!or* po$%!%onF. T'e* al$ode nedfi an Hec'elon $!ock pol%c* %n ('%c' !'e %n)en!or* po$%!%on %$ !'e $#m o" !'e %n$!alla!%on %n)en!or* po$%!%on$ "or !'e %n$!alla!%on and all do(n$!ream %n$!alla!%on$. T'e* !'endemon$!ra!ed !'a! ec'elon $!ock pol%c%e$ (%ll al(a*$ dom%na!e %n$!alla!%on $!ock pol%c%e$ and $okan;an (%ll ;e dom%na!ed ;* a ec'elon $!ock pol%c*. In la!er (ork+ A7$a!er and Ro$l%n& C9+ 8D$'o(ed !'a! a kan;an $*$!em can ;e reprod#ced (%!'%n MRP (%!' a $#%!a;le $elec!%on o"parame!er$ %.e.+ >ero lead !%me+ and !'e $a"e!* $!ock le$$ one %$ a m#l!%ple o" !'e order G#an !%!*F.T'e re$#l! %$ comple!el* &eneral e7cep! !'a! MRP %$ a per%od%c re)%e( $*$!em ('%le !'e kan;an$*$!em %$ a con!%n#o#$ re)%e( $*$!em al!'o#&' !'ere %$ no rea$on ('* !'e re)%e( %n

*They termed this a hybrid system because the first station in the line re/uires a pull si!nal 0anban card1

but the other stations in the line do not. $o, all operators except the one at the first stationbehave the same as

they would in a conventionalpush system2 they 3ust process 3obs when theyhave them.

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MRP co#ld no! ;e done con!%n#o#$l*F. T'%$ ma!!er$ $%nce %" kan;an %$ a $#;$e! o" MRP+!'en %!%$ clearl* dom%na!ed ;* MRP. Ho(e)er+ !'%$ dom%nance (%ll ;e l%m%!ed !o !'e e7per%men!alcond%!%on$ $%nce !'e A7$a!er and Ro$l%n& model doe$ no! con$%der ro;#$!ne$$ %$$#e$+ $#c' a$!'o$e ar%$%n& "rom m%$!akenl* relea$%n& !oo m#c' (ork %n!o !'e l%ne.O!'er &eneral%>a!%on$ o" kan;an %ncl#de !'o$e o" Kla$$erman and ao C3D and ao and6'en& C3D. T'e$epaper$ %n!rod#ce a ;lockand'oldkcard !'a! de!erm%ne$ 'o( m#c' (ork%n proce$$ $'o#ld ;e kep! ;e"ore mo)%n&. Ho(e)er+ ;eca#$e B#$!% ca!%onfi o" !'%$ approac' rel%e$ on!'e e7%$!ence o" $epara!e mo)e card$+ !'e ;ene !$ d%$apfi pear ('en (e con$%der !'e eG#%)alen! onecard kan;an $*$!em.S#r% C8/D %n!rod#ced a &eneral%>a!%on o" kan;an called Pa%red?cell O)erlapp%n& Loop$ o"

6ard$ (%!' A#!'or%>a!%on or POL6A. POL6A %$ d% ereff n! "rom kan;an %n !'a! card$ are

a$$%&ned !o pa%r$ o" cell$ ra!'er !'an par!%c#lar par!$ (%!'%n a cell. T'e re$#l! %$ a more &eneralcon$!r#c! !'an kan;an !'a! can ;e appl%ed !o make!oorder $%!#a!%on$. a!%on %$ "rom an MRP $*$!em+ ;#! card$ are #$ed !o l%m%! WIP (%!'%n pa%r$ o" cell$+POL6A po$$e$$e$ ;o!' p#$' and p#ll c'arac!er%$!%c$. One dra(;ack+ 'o(e)er+ %$ !'a! one m#$!$e! a card co#n! "or e)er* $e! o" con$ec#!%)e cell$. None!'ele$$+ S#r% de$cr%;e$ $e)eral e7ample$('ere POL6A 'a$ ;een #$ed !o &rea!l* red#ce o)erall c*cle !%me$ and WIP.

More recen!l*+ L%;eropo#lo$ and aller* C99D ;#%ld%n& on C39+3-DF de)eloped ano!'er &eneral%>ed p#ll $*$!em %n !'e "orm o" a make!o$!ock $*$!em (%!' $epara!e l%m%!$ on n%$'edfi &ood$SF and WIP KF !'a! (e (%ll re"er !o a$ a K, SF $*$!em. T'%$ model %ncorpora!e$ cla$$%cal;a$e $!ock K +S < F+6ONWIP K SF+ $%n&le$!a&e re$er)ed$!ock kan;an a$ %n C4DK < SF+ $%n&le$!a&e ;ackordered kan;an pol%c* a$ %n C4D and C39D K > SF and $e)eral o!'er"orm#la!%on$. T'e* de nefi a cr%!%cal WIP+Kc+a$ a m%n%m#m WIP le)el !'a! $#ppl%e$ eno#&'

!'ro#&'p#! "rom !'e prod#c!%on $*$!em $o !'a! "or an*K Kc+ !'e op!%mal ;a$e $!ock le)el %$eG#al !o !'e ;a$e $!ock le)el !'a! (o#ld occ#r (%!'K +no!ed a$ S. T'e* !'en conBec!#re!'a! !'e pol%c* parame!er$ !'a! m%n%m%>e !o!al WIP and n%$'edfi &ood$ (%!' %den!%cal carr*%n&co$!$F areKc and S. I" !'%$ conBec!#re %$ !r#e+ !'en one can ea$%l* %mpro)e on a 6ONWIPmake!o$!ock pol%c* ;* pro)%d%n& $epara!e l%m%!$ on WIP and n%$'edfi &ood$. A !r%)%al ca$e %$!'a!o"a$%n&le$er)erprod#c!%on?%n)en!or*$*$!em+('ere!'eop!%mal)al#e$areclearl*Kc 3and S $e! !o ('a!e)er )al#e %$ reG#%red !o ma%n!a%n !'e llfi ra!e.

8 Mean('%le+ In !'e Real World ...

T'e re$earc' l%!era!#re &a)e a clear de n%!%onfi o" kan;an and a de!a%led $#mmar* o" %!$ ;ene !$.fi I!al$o $'o(ed !'a! kan;an co#ld ;e &eneral%>ed %n a (%de )ar%e!* o" prac!%cal (a*$. Ho(e)er+ all!'e$e )ar%an!$ o" kan;an $#&&e$!ed !'a! p#ll (a$ cer!a%nl* a more &eneral %dea !'an kan;an. So+('a! e7ac!l* %$ %!?Ind#$!r* d%d no! 'a)e a clear an$(er. One rea$on "or !'%$ (a$ !'a! O'no and !'e o!'er

earl* prac!%!%oner$ o"JIT d%$c#$$ed p#ll onl* %n )er* &eneral+ '%&'le)el!erm$.Man#"ac!#rer$ and (orkplace$ can no lon&er ;a$e prod#c!%on on de$k!op plann%n&alone and !'en d%$!r%;#!e+or p#$'+ !'em on!o !'e marke!. I! 'a$ ;ecome a ma!!er o"co#r$e "or c#$!omer$+ or #$er$+ eac' (%!' a d% eff ren! )al#e $*$!em+ !o $!and %n !'e"ron! l%ne o" !'e marke!place and+ $o !o $peak+ p#ll !'e &ood$ !'e* need+ %n !'e amo#n!and a! !'e !%me !'e* need !'em. O'no+ 3@//+ p. 7%)F

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In o!'er (ord$+ one $'o#ld no! $%mpl* make a lar&eamo#n! o" $!ock and !'en !r* !o &o and $ell%!. One need$ !o ;e a(are o" !'e marke! and pa* a!!en!%on !o !'e c#$!omer.W'%le !'%$ m%&'! $o#nd l%ke common $en$e !oda*+ %! (a$ re)ol#!%onar* "or !'e m%d -!'6en!#r*.

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p#;l%c%>ed Alcoa Prod#c!%on S*$!em+ one o" !'e ;a$%c !enan!$ (a$: Prod#ce "or #$e+ no! "or%n)en!or* C3D e)en !'o#&' %!$ pr%nc%ple me!'od o" prod#c!%on con!rol (a$ kan;an.Un"or!#na!el*+ $#c' lean !'%nk%n& 'a$ ;ecome per)a$%)e %n %nd#$!r*.

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2 T'e E$$ence o" P#ll

To remo)e !'%$ con"#$%on+ (e need a de n%!%onfi o" p#ll !'a! cap!#re$ ('a! %$ e$$en!%al "or o;!a%n %n&%!$ ;ene !$+fi ;#! doe$ no! o)erl* re$!r%c! %mplemen!a!%on e.&.+ ;* eG#a!%n& %! (%!' a $pec% cfi $*$!em$#c' a$ kan;anF.A$ (e no!ed a;o)e+ !'e !erm p#ll can ;e appl%ed a! !'e ;o!' $!ra!e&%c and !'e !ac!%cal

le)el$. E$!a;l%$'%n& a !ak! !%me !o $e! !'e o#!p#! o" !'e plan! !o ;e eG#al !o demand %$ a(a* !o e$!a;l%$' $!ra!e&%c or marke!F p#ll. T'%$ (a$ an %mpor!an! par! o" O'no$ or%&%nal)%$%on aro#nd 3@2-F and (a$ adop!ed or+ more l%kel*+ %ndependen!l* d%$co)eredF ;* !'o$e ('ode)eloped comp#!er ;a$ed p#$' $*$!em$. 1or %n$!ance+ %n 3@4- W%&'! de$cr%;ed )er* $%m%larlo&%c %.e.+ Inp#!=O#!p#! 6on!rolF !o ;e #$ed (%!' MRP C22D. Hence+ $!ra!e&%c p#ll can ;e%mplemen!ed e)en %n+ ('a! 'a)e ;een !rad%!%onall* called+ p#$' $*$!em$.

T'ere"ore+ !'e ke* G#e$!%on (e m#$! an$(er !o "#ll* de nefi p#ll %$ ('a! con$!%!#!e$ !ac!%calp#ll+ a$ c'arac!er%>ed ;* kan;an. To ;e mean%n&"#l+ (e m#$! de nefi p#ll $o !'a! %! %ncl#de$!'o$e $*$!em$ !'a! people !end !o !'%nk o" a$ p#ll e.&.+ kan;anF ;#! no! !'o$e !'a! 'a)e ;eencon$%dered a$ p#$' e.&.+ MRPF. Moreo)er+ %" p#ll %$ $ome'o( %n!r%n$%call* ;e!!er+ o#r de n%!%onfi$'o#ld pro)%de a mean$ !o de!erm%ne %" a $*$!em ;elon&$ !o a cla$$ o" $*$!em$ !'a! dom%na!e %nper"ormance. 1%nall*+al!'o#&' adm%!!edl* le$$%mpor!an!+ $#c' a de n%!%onfi $'o#ld $e!!le lon&$!and%n& de;a!e$ amon& academ%c$ a$ !o ('e!'er )ar%o#$ $*$!em$ e.&.+ ;a$e$!ock model$ and

o!'er make!o$!ock )ar%a!%on$F are "#ndamen!all* p#ll or p#$' $*$!em$.2.3 T'e 1#ndamen!al % erenceff

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Make?!o?1oreca$! Make!oOrder Make!oS!ock

P#$' MRP (%!'"oreca$! MRP (%!' rmfiorder$ Q, rF (%!' p#ll"rom 1KI

P#ll kan;an (%!' !ak! kan;an (%!' !ak! kan;an (%!' p#ll!%me V "oreca$! !%me V order$ "rom 1KI

Ta;le 3: E7ample$ o" P#$' and P#ll.

ne!(ork+ (%!' a r%&%dl* $e! l%m%! on !'e n#m;er o" en!%!%e$+ %$ a p#re p#ll $*$!em+ ('%le an openG#e#e%n& $*$!em e.&.+ a KI=K=3 G#e#eF %$ an p#re p#$' $*$!em. T'e "ormer 'a$ a clear l%m%! onWIP ('%le !'e la!!er doe$ no!.

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. 6la$$%c kan;an %$ a p#ll $*$!em. T'e n#m;er o" kan;an card$ e$!a;l%$'e$ a 7edfi l%m%! onWIP.

9. 6la$$%c

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1%re 9:T'e %n)en!or*=order %n!er"ace.

T'%$ correc!%on %n !erm%nolo&* doe$ no! c'an&e !'e "#ndamen!al po%n! !'a! (e and Leeand

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!'a! !'e el%m%na!%on o" o;)%o#$ (a$!e %$ o;)%o#$. Un"or!#na!el*+ !'%$ !end$ !o ;e !'e "oc#$and l%m%! o" mo$! lean %mplemen!a!%on$ !'a! ne)er &e! !o !'e real mea! o" !'e pro;lem.T'e le$$ o;)%o#$ $o#rce o" ;# er%n&ff co$!$ %$ )ar%a;%l%!*. T'%$ can !ake on man* "orm$+%ncl#d%n& )ar%a;%l%!* %n proce$$ !%me$+ del%)er* !%me$+ *%eld ra!e$+ $!a n&ffi le)el$+demand ra!e$+ e!c.An*!'%n& %n !'e $*$!em !'a! %$ no! a;$ol#!el* relar and pred%c!a;le e7'%;%!$ )ar%a;%l%!*. T'eca#$e$ o" )ar%a;%l%!* can ;e cla$$% edfi %n!o %n!ernal "ac!or$+ $#c' a$ $e!#p$+ do(n!%me $c'ed #led and#n$c'ed#ledF+ opera!or %nd#ced #c!#a!%on$fl %n prod#c!%on ra!e$+ *%eld lo$$+ re(ork+ en&%neer%n&c'an&e order$ and man* o!'er$+ and e7!ernal "ac!or$+ %ncl#d%n& %rrelar demand+ prod#c! )ar%e!*!o mee! marke! need$F+ c#$!omer c'an&e order$+ e!c. E7!ernal )ar%a;%l%!* %$ o"!en !'e con$eG#enceo" a rm$fi ;#$%ne$$ $!ra!e&*+ $#c' a$ o er%n&ff '%&' le)el$ o" prod#c! )a r%e!* !o ac'%e)e acompe!%!%)e ad)an!a&e. In $#c' %n$!ance$+ a cer!a%n amo#n! o" )ar%a;%l%!* %$ $%mpl* a co$! o"do%n& ;#$%ne$$.

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('ene)er an opera!or 'a$ a pro;lem. T'%$ add%!%onal $!aff repre$en!$ an e)en lar&ercapac%!* ;# erff !'a! (a$ no! a)a%la;le %n !'e or%&%nal $*$!em. Increa$%n& capac%!* r$!fi and!'en red#c%n& %n)en!or* #$%n& a p#ll $*$!em allo($ one !o red#ce c*cle !%me$ (%!'o#! lo$%n&!'ro#&'p#! or '#r!%n& c#$!omer $er)%ce.

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. Increa$e !'e %n)en!or* ;# erff !o %n$#la!e pro;lem$ %n "a;r%ca!%on. E$$en!%all* (e%$ola!ed "a;r%ca!%on "rom !'e $#;a$$em;l* and nalfi a$$em;l* area$ ;* e$!a;l%$'%n& kan;an$!ore$ "or mo$! o" !'e componen!$. To $e! !'e$e %n)en!or* le)el$ (e #$ed more$op'%$!%ca!ed %n)en!or* model$ !'an !'o$e propo$ed ;* lean !e7!$. In !'%$ (a*+ !'e lead!%me !o !'e c#$!omer (a$ c#! "rom 3,- (eek$ !o le$$!'an 8 (eek$.

9. Red#ce )ar%a;%l%!* %n $#;?a$$em;l* and nalfi a$$em;l*. T'%$ (a$ done ;* $!reaml%n%n& !'e flo( and e$!a;l%$'%n& a 6ONWIP $*$!em. Lead !%me came do(n "rom 9 da*$ !o ,da*$ ('%le $er)%ce (en! "rom le$$!'an 2- !o o)er @2.8. Red#ce %n)en!or* ;# er$.ff

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or!'o&onal !o !'e p#$' )er$#$ p#ll dec%$%on. T'e WIP cap de n%!%onfi o" p#ll &%)en %n !'%$ paper(%ll pre)en! con"#$%on o" !'e$e %mpor!an!+ ;#! $epara!e+ %$$#e$.T'e $%n o" o)er$%mpl% ca!%onfi 'a$ ;een carr%ed o)er "rom p#ll !o lean. Prac!%!%oner l%!era!#re!'a! de$cr%;e$ leanprod#c!%on onl* %n !erm$ o" red#c%n& (a$!e doe$ !'e pro"e$$%on a d%$$er)%ce ;*o)erlook%n& %mpor!an! ;#! %nd%rec! $o#rce$ o" (a$!e. Moreo)er+ !'ere are man* ca#$e$ o")ar%a;l%!* !'a! re$#l! %n a ;# erff !'a! are no! (a$!e. 1or %n$!ance+add%n& )ar%e!* !o a prod#c!m%7 !o accommoda!e c#$!omer$ demand$ %$ 'ardl* con$%dered (a$!e ;#! %! (%ll red#ce e c%enc*ffiand %ncrea$e;# er$.ff Lean %$ ;e!!er de nedfi a$ ;e$! ;# erff prod#c!%on !'an lo( (a$!e or e)enlo( ;# erff prod#c!%on. T'%nk%n& %n !erm$ o" !'e more "#ndamen!al concep!$ o" )ar%a;%l%!* and;# er%n&ff enco#ra&e$ more compre'en$%)e con$%dera!%on o" e c%enc*ffi %mpro)emen! al!erna!%)e$.W'%le !'ere 'a)e ;een plen!* o" ca$e$ ('ere academ%c$ 'a)e con"#$ed or m%$$ed !'e po%n! o" aprac!%cal pro;lem E$ee e.&.+ C38D "or a cr%!%c%$m o" $c'ed#l%n& re$earc'F+ (e "eel !'e p#ll arena %$ one('ere !'e academ%c comm#n%!* 'a$ ;een a )o%ce o" rea$on. T'e G#e$!%on "or #$ no(: %$ an*onel%$!en%n&?

/ Ackno(led&men!$

We (o#ld l%ke!o !'ank Lee Sc'(ar> "or enco#ra&%n& #$ !o (r%!e !'%$ paper. We (o#ld al$o l%ke !o!'ank !'e !r#l* (onder"#l re"eree$+ r. Ro;er! Inman+ r. W%ll%am Jordan+ Pro"e$$or Uda*armarkar+ and Pro"e$$orJo'n aco!!+ ('o pro)%ded m#c' %dance %n !'e prepara!%on o" !'eman#$cr%p!. All o" !'e%r %np#! (a$ e7!remel* )al#a;le %n $'arpen%n& o#r !'%nk%n& and clear%np o#r m%$#nder$!and%n&$. 1%nall*+(e (o#ld l%ke!o !'ank Pro"e$$or Sco!! Mo$e$ ('o po%n!ed o#!an %mpor!an! lo&%cal %ncon$%$!enc* %n o#r e7po$%!%on on p#ll %n o#r ;ook+ 1ac!or* P'*$%c$.

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C@D

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C9-D %m#ra+ O. and H.Terada+ e$%&n and Anal*$%$ o" P#ll S*$!em+ A Me!'od o" M#l!%?S!a&e Prod#c!%on 6on!rol+ In!l.J. o" Prod. Re$. 3@:9+ 8329+ 3@/3.C93D raBe($k%+ L.J.+ man+ and .S. Won&+ an;an+ MRP+ and S'ap%n& !'e Man#"ac!#r%n& En)%ronmen!+ M&m!. Sc%. 99:3 3@/4F+ 9@24.C9D Lee+ H.L.+ and 6. an%$+ P#$' and P#ll Prod#c!%on S*$!em$: I$$#e$ and 6ompar%$on$+Opera!%on$ Re$earc'+ 8- 3@@F+ 2329.

C88D Spearman+ M.L.+ An Anal*!%c 6on&e$!%on Model "or 6lo$ed Prod#c!%on S*$!em$+ Mana&emen!Sc%ence+ 94:/ 3@@3F+ 3-323-@.

C82D Spearman+ M.L.+ 6#$!omer Ser)%ce %n P#ll Prod#c!%on S*$!em$+ Opera!%on$ Re$earc'+ 8- 3@@F+@8/@2/.

C8,D Spearman+ M.L. and M.A. a>an%$+ P#$' and P#ll Prod#c!%on S*$!em$: I$$#e$ and 6ompar%$on$+Opera!%on$ Re$earc'+ 8- 3@@F+ 2329.

C84D S#&%mor%+ .+ .#$#nok%+ 1.6'o and S. Uc'%ka(a+ To*o!a Prod#c!%on S*$!em and an;an

S*$!em: Ma!er%al%>a!%on o"J

#$!?In?T%meand Re$pec!1orH#man S*$!em+ In!erna!. J. Prod#c!%on Re$.+32 3@44F:,+ 2292,8.C8/D S#r%+ R. 3@@/. Q#%ck Re$pon$e Man#"ac!#r%n&: A 6ompan*(%de Approac' !o Red#c%n& Lead!%me$.

Por!land+ OR: Prod#c!%)%!* Pre$$.

C8@D Ta*#r+ S.R.+ S!r#c!#ral Proper!%e$ and a He#r%$!%c "or an;an?con!rolled Ser%al L%ne$+ Mana&emen! Sc%ence 9@+ 398439,/+ 3@@9.C2-DT#r;%de+ .A. 1lo( Man#"ac!#r%n&A S!ra!e&* W'%!e Paper+ a!(((.p o( ercer).com=d o (nload$=flo (.p d"+ 3@@@.

http://www.powercerv.com/downloads/%EF%AC%82ow.pdfhttp://www.powercerv.com/downloads/%EF%AC%82ow.pdf

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C23D U>$o*+ R.+ and L.A. Mar!%n?5e&a+ Model%n& an;an