Manufacturing Technology (ME461) Lecture28

8/12/2019 Manufacturing Technology (ME461) Lecture28

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Manufacturing Technology

(ME461)

Instructor: Shantanu Bhattacharya



Review of revious !ecture

• "ust in ti#e techni$ue of

Manufacturing%

• &o#'onents of Toyota

rouction Syste#%

• ush ase syste#s%



ull versus ush Syste#

rocess 1 rocess * rocess +Raw

Materials

,inishe

rouct

ush

Syste#

•- 'ush syste# is asically a MR ase 'rouction 'lanning an inventory control

syste#% In MR the #aster 'rouction scheule of en 'roucts is transfor#e into'arts re$uire#ents%•.or/ orers are then launche to uil the 'arts in lot si0es using the lot si0ing logic

of MR%•The wor/ orers 'ush #aterials to the #anufacturing floor to 'rouce the 'arts

re$uire%

•The lot si0es are nor#ally large an conse$uently 'rouction lea ti#es are long%•The 'arts are 'ushe to the successive stages as soon as the wor/ is co#'lete at a

'articular stage%•- 'role# is create when so#e 'arts are not co#'lete an re$uire at successive

stages causing shortages% This 'heno#ena is also referre to as starving the

successive stage%

•2n the other han there will e too #uch inventory of so#e co#'onents causing aloc/ing of the 'receing stage%



rocess 1 rocess * rocess +Raw

Materials

,inishe

rouct

ull

Syste#

ull 3ersus ush Syste#s

• The trans#ittal of infor#ation istinguishes a 'ull syste# fro# a 'ush

syste#%

•In a 'ull syste# there is always feeac/ fro# the suse$uent to'receing stages%•The MS is only use to give a roa outline of the re$uire#ents for

resources at ifferent wor/ centers%•The #aor ifference in a 'ull syste# is that although the MS is use for

the 'ur'ose of eciing a''ro5i#ate resource re$uire#ents of wor/stations it is not use to eter#ine the 'rouction rate of each

station%•In a 'ull syste# the #aterials #ove in the sa#e irection as in the 'ush

syste# ut the infor#ation concerning 'rocessing of 'arts is given y the

suse$uent 'rocess%

•Therefore the uil scheule travel in the irection o''osite to the



Ty'es of anan

•anan (in "a'anese) #eans visile recor% Toyota evelo'e the anan

syste#% The syste# consists of a set of cars that travel etween 'receeing an

suceeing 'rocesses co##unicating what 'arts are neee at the suse$uent'rocesses%

•The #ost co##only use anans are the withrawal /anan an the 'rouction

/anan%

Withdrawal Kanban:•The 'ri#ary function of a withrawal /anan is to 'ass the authori0ation for

#ove#ent of 'arts fro# one wor/ center to another%•2nce it fetches the 'arts fro# the 'receing 'rocess an #oves the# to

suse$uent 'rocess it re#ains with the# till the last 'art has een consu#e y

the suse$uent 'rocess%•Then the withrawal /anan travels ac/ to the 'receing 'rocess to fetch 'arts

an the cycle continues%•The withrawal /anan shoul have infor#ation such as the 'art nu#er an 'art

na#e lot si0e an routing 'rocess to fetch 'arts an cycle continues%



.ithrawal an rouction

anans

art 7u#er

&ontainer ca'acity

(7u#er of 'arts)

Raw #aterials an

other 'art ty'es use

in #anufacturing at

the wor/ center

receing wor/ center no%

Stoc/ !ocation no%

art 7u#er

&ontainer ca'acity(7u#er of 'arts)

Suse$uent wor/

center nu#er

receing wor/

center no%

Stoc/ !ocation no%

Stoc/ !ocationnu#er

7u#er of

/anans

release

rouction anan

.ithrawal anan



rouction anan•The #ain function of a 'rouction /anan is to release an orer to the 'receing

'rocess to uil 'arts e$ual to the lot si0e s'ecifie on the car%

•Therefore the 'rouction /anan car shoul have infor#ation on the #aterials an'arts re$uire as in'uts at the 'receing 'rocess in aition to what is 'resent on a

withrawal /anan

,low of .ithrawal an rouction anans an their

interactions

,

E

,

,

,

E

E

,

,

*

receing Stage (S1)

Stac/ing -rea (S-)

Suse$uent Stage

(SS*)

1

+



Flow of withdrawal and production Kanbansand their interaction

•!et us unerstan the flow of withrawal an 'rouction /anans as well as the flow 'aths of

containers%•&onsier a si#'le e5a#'le of controlling wor/ flow etween two 'receeing an succeeing

'rocessing stages S1 an SS* se'arate y a stac/ing area (S-)%•The se$uence of #ove#ents of /anans (oth withrawal an 'rouction) are escrie as

follows:

1%Su''ose you start at 'oint 1 in the stac/ing area% Move the full 'arts container to the

suse$uent 'rocessing stage SS*%

*%8etach the attache withrawal car an sen it to /anan collection o5 at 'oint *%Meanwhile the 'arts in the container are eing use y the suse$uent stage%

+%2nce all 'arts in the container are consu#e at SS* attach a withrawal /anan fro# the

/anan collection o5 to the e#'ty container an #ove it fro# SS* to location + in the

stac/ing area S-%

4%7ow at the + location:•8etach the withrawal /anan fro# the e#'ty container%

•-ttach it to a full 'arts container%•Re#ove a 'rouction /anan fro# the container to e sent to suse$uent stage SS*%•Sen it to 'rocessing stage S1 to trigger the 'rouction of a full container%

9% ut all the 'arts 'rouce in the e#'ty container an sen to stac/ing area S- with the

'rouction /anan attache to it%



Preconditions for operating Kanbans•anan is essentially a tool create to #anage the wor/'lace effectively% The following are

the 'reconitions for effectively o'erating the /anan:

1%Rule 1: No withdrawal of parts without a kanban: .e now /now that a /anan is a

#echanis# that controls 'rouction on a ust in ti#e asis 'roucing necessary 'arts in theright $uantities at the right ti#e%

*%Rule *: The subsequent process comes to withdraw only what is needed: Mua of all

ty'es as iscusse woul occur if the 'receeing 'rocess su''lie #ore 'arts than are

actually neee% This can e avoie only if the succeeing 'rocess co#es to the

'receeing 'rocess to withraw the re$uire nu#er of 'arts at the ti#e neee%

+%Rule +: Do not send the defective parts to the succeeding process: The $uality of 'arts#ove y the /anan is the #aor concern for this rule% ,urther#ore efective 'arts woul

necessitate wor/ in 'rocess inventories esies re$uiring e5tra resources of #aterial

e$ui'#ent an laor%

4%Rule 4: The preceeding process should produce only the exact quantity of parts

withdrawn by the subsequent process: The asic 're#ise ehin this rule is to restrict the

inventory at the 'receeing 'rocess to the asolute #ini#u#%

9%Rule 9: Smoothing of production: revious rules i#'ly that the suse$uent 'rocessco#es to the 'receeing 'rocess to withraw the necessary 'arts in the necessary

$uantities at the necessary ti#e%

6%Rule 6: Fine tuning of production using kanban: S#all variations in 'rouction

re$uire#ents are auste y (a) sto''ing the 'rocess if the 'rouction re$uire#ents

ecrease an () sing overti#e an i#'rove#ents in the 'rocesses if the 'rouction

re$uire#ents increase%



anan lanning an &ontrol Moels

•anan is the heart of the "IT syste#% The nu#er of /anans 'lays the #ost

i#'ortant role in 'lanning controlling an reucing the wor/ in 'rocess inventories%

There are eter#inistic an 'roailistic analytical #oels for eter#ining the

o'ti#al nu#er of /anans%

•8eter#inistic Moel:

!et u first unerstan how the nu#er of /anans is eter#ine at a wor/ center in

Toyota Motors &o#'any%

7u#er of /anans



8eter#inistic Moel for anan•; is a 'olicy variale which is use as a #eans of #anaging e5ternal

isturances such as changes in e#an an variaility in 'rocessing an elivery

ti#es%

•8 is eter#ine as a s#oothe e#an%•y is nor#ally fi5e even if there are variations in e#an%•In that case when <8= increases the value of the lea ti#e #ust e reuce

accoringly%

E5a#'le:

&onsier the 'rouction of a certain ite# #anufacture in >?@ co#'any% Itsre$uire#ents are 1AAAA units 'er #onth% Su''ose the co#'any has ust starte

i#'le#enting the "IT syste#% -ccoringly the 'olicy variale is set at ; A%4A% The

container ca'acity is fi5e at 9A ite#s an the 'rouction lea ti#e is A%9A ays%

1%8eter#ine the no% of 'rouction /anans%

*%Su''ose the co#'any has stale 'rouction environ#ent an the 'olicy variale

can e fi5e at ; A%AA% 8eter#ine the nu#er of /anans an the resulting i#'acton wor/ in 'rocess inventory%

+%.hat ha''ens if the lea ti#e is increase to 1 ay ecause of laor shortages

an failure of #achinesC

4% .hat ha''ens if the lea ti#e is reuce to %*9 ays ecause of 'rocess

i#'rove#entsC The value of ; is A%+A as a result of these 'rocess i#'rove#ents%



In the following e5a#'le we analy0e a two stage syste# involving #anufacturing at

the 'receing stage an asse#ly at the suse$uent stage%

E5a#'le:

&onsier the #anufacture of 'rouct @ in a co#'any% rouct @ is asse#le fro#

two 'arts > an ? that are #anufacture in the co#'any% - sche#atic layout

e'icting 'receing stage staging area suse$uent stage an the flow of 'rouction

an withrawal /anans is given in the ne5t figure

i i i h / i



8eter#inistic a''roach to /anan si0e

.or/

&enter >

.or/

&enter ?

-sse#ly

&enter @

S-D

>

S-D

?

D>

D?

.D>

.D?

receeing

rocesses

Succeeing

rocesses

D> 'rouction /anan for 'art >

D? 'rouction /anan for 'art ?

.D> withrawal /anan for 'art >

.D? withrawal /anan for 'art ?

S-D> staging area for 'art >

S-D? staging area for 'art ?

1% 8eter#ine the 'rouction an withrawal

/anans%

*% 7ow su''ose the asse#ly 'rocess is shifte

to Me5ico as a 'art of a reorgani0ation% The

lea ti#e to travel etween the new location

in Me5ico an the 'resent 'lant location is 4

ays each for > an ?% 8eter#ine the no% of

'rouction an withrawal /anans an the

i#'act of this 'olicy on the wor/ in 'rocessinventory%

Th f h l i i l



The ata for the 'role# is given elow%

part Demand(units/da y)

Lead time(days)

α Containercapacity

-sse#lyStage

> *AAA 1%A A%AA 1AA

? AA A%9 A%*9 9A

ManufacturingStage

> *AAA A%9A A%*A 1AA

? AA 1%AA A%AA 9A



E5a#'le

role#"ohnson an "ohnson a 'rivate co#'any su''lies 'arts to a s'ar/ 'lug

#anufacturing co#'any "" is now 'lanning to introuce "IT 'rouction conce'ts

for their shell #anufacturing section% The following ata are avialale: The

re$uire#ents are *9AAAAAA units 'er #onth% Since the co#'any has ust startei#'le#enting the "IT syste# the 'olicy variale is set at ; A%*A% The container

ca'acity is fi5e at 9AA shells an the 'rouction lea ti#e is A%1A ays%

(a)Since it is the first ti#e that "" is i#'le#enting "IT avise "" in evelo'ing a

/anan o'erating syste#% Fow #any /anans will e neeeC

() Su''ose the co#'any has stale 'rouction environ#ent an the 'olicy

variale can e fi5e at ; A%1A% 8eter#ine the no% of anans an the resulting

i#'act on wor/DinD'rocess inventory%

(c) .hat ha''ens if the lea ti#e is reuce to A%A ays ecause of 'rocess

i#'rove#entsC



Probabilistic cost model for determining optimal number of Kanban:

•Ty'ically in a "IT o'eration the #aster 'rouction scheule is fro0en for 1 #onth

an the no% of anans in each wor/ing center is set ase on average e#an for

the 'erio%•In this section we evelo' a cost #oel consiering the e5'ecte cost of holing

an shortages%•It is assu#e that the 'roaility #ass function (M,) of the nu#er of /anans

re$uire is /nown%•!et us assu#e the following notations:

1%(5) 'roaility #ass function for the nu#er of /anans re$uire

*%&h holing cost 'er container 'er unit ti#e at a wor/ center

+%&s cost of a shortage 'er container 'er unit ti#e at a wor/ center

Su''ose there are <n= /anans circulating in the syste#%



Case 1:The actual requirement for the kanbans, , is less than !n"# $n that case holding costwill be incurred# %ccordingl&,

'pected holding cost ( Ch )*n+ p*

Case -:The actual requirement for the kanbans, is more than n# $n that case shortagecosts will be incurred# %ccordingl&,

'pected shortage cost ( Cs )*+n p*

Therefore, the total epected cost, TC *n is gi.en b&:

TC *n ( Ch )*n+ p* / Cs )*+n p*

The optimal .alue of n that gi.es the minimum .alue of TC *n is the smallest integersatisf&ing the following:



Probability

000 0!0 0"0 0"# 0$0 00#

7o% of/anans

A 1 * + 4 9

Relationship between JIT manufacturing, setup time, and cost:

6$T manufacturing is often understood to mean a manufacturing s&stem with lotsi5e approaching unit&# $t is important to understand the conditions under whichthis goal ma& be achie.ed# The answer ma& come directl& from the classicaleconomic production quantit& in.entor& model#$n a 6$T manufacturing en.ironment the intent is not to permit shortages# %ccordingl&, the total .ariable cost consisting of setup and holding as a function ofeconomic production quantit& 7, is gi.en b&

Manufacturing Technology (ME461) Lecture28

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