Lect12_ Kanban Systems

7/23/2019 Lect12_ Kanban Systems

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KANBAN SYSTEMS

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21. Kanban (kahn-bahn)is a Japanese word that means

card or visible record.

2. In general context, it refers to a signal of some ind.

!. "h#s, in the man#fact#ring environment, anbans are

signals #sed to replenish the inventor$ of items #sed

repetitivel$ within a facilit$.

%. "he anban s$stem is based on a c#stomer of a partp#lling the part from the s#pplier of that part.

&. "he c#stomer of the part can be an act#al cons#mer of a

finished prod#ct (external' or the prod#ction personnel at

the s#cceeding station in a man#fact#ring facilit$

(internal'.. )iewise, the s#pplier co#ld be the person at the

preceding station in a man#fact#ring facilit$.

*. "he premise of anbans is that material will not be

prod#ced or moved #ntil a c#stomer sends the signal to

do so.

INTRODUCTION


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WORKING OF KANBAN SYSTEMS

1. Kanbanis a production control system

2. Communication takes place when a successor (upstream)workstation issues a request for parts to the output buer of apredecessor (downstream) work station.

!. "hen the desired le#el of stock of completed parts (in the buer) isdepleted$ the work center reacts to replace the remo#ed parts and tomaintain a balanced$ tar%et le#el of &nished parts.

4. Kanban includes information on: (a) part type (b) number of units (c)location of materials needed to produce them.

'. ach type of part produced by a work center has its own Kanban$ eachKanban authories a particular number of units of that part type.

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KANBAN AUTHORIZATION CONCEPT

1. ach work center is responsible to keep a full container ofparts for each kanban allocated to that work center.

2. If the container is not full for a kanban, then thekanban authorizes production of the decient units.

!. "hen a de&cient item is to be produced$ aterial handlerproceeds to the predecessor (down stream) to requisition therequired parts* material.

+. ,s these parts are deli#ered$ this workstation automaticallybe%ins to replace this stock.

'. ,ll this action takes place -ust because of the appearance ofthe material handler at output buer to remo#e a container ofparts.

. /o other production schedulin% information is supplied to thework center.

0. y usin% this simple authoriation procedure$ kanban systemsa#oid the need to maintain a direct information link betweenthe lon% ran%e production plan and operational schedule.

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Operation of SINGE KANBAN SYSTEM

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1. "ork center at sta%e i attempts tomaintain one full container of partsin the output buer for each kanban.

2. "hen workstation i1 requires parts$ the operator or aterial handler

transports a container of parts from the output buer of sta%e i to sta%e i1!. The operator rst "ust# reo$es the production

orderin% kanban "&O'# at sta%e i and place thekanban on the sta%e i collection bo(.

+. 34K kanbans are arran%ed into a production sequenceand mo#ed to a schedulin% board.

'. 5he worker at sta%e i checks the schedule board onwhich the cards are arran%ed into the productionschedule.

. 5his type of a sin%le kanban system is used when

workstations are close to%ether.


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0. )ssentiall*, the output bu+er at sta%e i is the input bu+er at sta%e i-.

6. 5he consecuti#e sta%es are linked by this intermediate buer of parts.

7. ach part type can be assi%ned a dedicated stora%e space. 5he sie of the space corresponds to the

space required to store the number of parts de&ned by the set ofkanbans for that part. 5he need for the actual kanban is eliminatedbecause ept* space is sae as a kanban in the collection

bo(

(called kanban squares)

18. ach sta%e can either be a workstation or an entire department.

--. ead tie in kanban e9tends from the time a kanban is remo#edfrom a container until that kanban re:enters the output buer with a

full container of parts.


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K,/,/ ;


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Operation of !UA KANBAN SYSTEM

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1. >ual kanban systems are usedwhen lar%e distances between workstations dictate the need for /input bu+ers0 at 1orkstations to

store ra1 aterialsin addition to the output buers used in the

sin%le kanban system.2. "e continue to use the production orderin% kanban (34K) of the sin%le

system$ but add 1ithdra1al orderin% kanbans "O'# for each parttype.

!. 5he system has two loops?a) 5he production orderin% kanbans (34K) follow the same loop as

before : between the output buer$ the collection bo9$ the scheduleboard$ the workstations and back to the output buer.

b) 5he withdrawal orderin% kanbans ("4K)$ also calledtransportation

kanbans$ ser#e as material requisitions. 5hey loop between theinput buer at sta%e i1$ their own collection bo9 at sta%e i1$

the output buer at sta%e i and &nally back to the input buer atsta e i1.

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+. 5he material handler periodicallychecks the withdrawal kanban ("4K)collection bo9. =f kanbans are

present the material handler mo#esfrom sta%e i1 to the output buer

at sta%e i to obtain the parts requisitioned by the withdrawal orderin% kanbans.

'. ,t sta%e i$ the handler remo#es the production orderin% kanban(34K) and places them on the schedule board. 5he withdrawalorderin% kanban ("4K) is added to each container and thenthey are mo#ed to input at buer at sta%e i1.

. 5he withdrawal orderin% kanbans ("4K) are remo#ed from thecontainer only when that containerBs &rst part is placed intoproduction at sta%e i1.

0. 5he two loops therefore control the production andtransportation.

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HYBRI! SINGE KANBAN SYSTEM

1. ybrid Din%le Kanban Dystem uses push for order

releases and pull for part con$e*ance.2. 3roduction schedule is prepared (from demand forecasts)

which lists the quantity of each item to be produced eachday.

!. 5he work:center is made responsible for meetin% this

schedule o#er the course of the day.

3. &roduction authorization is pro$ided b* theschedule, and production orderin% kanbans "&O'#are eliinated.

'. "ithdrawal orderin% kanbans ("4K) are still used to controlthe con#eyance of parts between work centers.

. "4Ks are used in the same manner as in the dual kanbansystem to control input buers.

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RUES FOR SCHE!UING KANBAN PRO!UCTION

1. Common rules for schedulin% production are?

a) Din%le:Kanban 3riority Aule?

i. =f setup time is brief$ then production quantities can be set equal to sie

of the container. 5he work center produces a batch sie equal to thequantity speci&ed on a sin%le kanban.

ii. ,ny method of assi%nin% priority to the kanbans pendin% production canbe adopted

iii. ;C;D (&rst come &rst ser#e) rules can be followed.

i#. 4r D35 (shortest possible time &rst) can also be followed.

b) ;amily Aules?

i. =n some work areas$ parts can be di#ided into families based on setuprequirements

ii. , family of part may share same &9ture or other toolin% with quick

chan%e o#ers bein% possible between parts in the same family.iii. =n this case$ we &ll all the kanban orders for parts in the same family at

the same time.

i#. ;amilies can be scheduled on the basis that which family has beenwaitin% the lon%est.

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c) Einimum conomic 4rder Fuantity?

5o -ustify a set:up from an economic point of #iew$ the operatormay

need to wait until a minimum number of kanbans of a particular

type are on the schedule board.

d) Di%nal Kanbans?

i. Used 1hen iniu econoic order 4uantit* ")O5# isused.

ii. 4F may result from lar%e set:up cost or time.

iii. , si%nal that authories production of the 4F is used.

i#. 5he re:order point is determined$ usin% standard in#entorymodels$ i.e. lead time demand safety stock point.

#. Di%nal kanban is placed on the re:order point le#el

$i. hen the in$entor* le$el drops to this le$el, the si%nalkanban is reo$ed and used to initiate replenishentorder.

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e) Cyclical 3roduction G Continuous 5ime?

i. =f achine set6ups are dependent on the se4uence of

part t*pes produced$ parts may be produced in &9ed$repeatin% sequence$ i.e. part ,$ then $ then C and so on.

ii. The se4uence is specied to iniize chan%e o$ertie.

iii. ach time a part type completes processin%$ kanban on theschedule board for the ne9t part type in the sequence arecounted and production is set to this amount.

f) Cyclical 3roduction G 3eriodic Ae#iew?

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7&)CI89IN: &;R;iand load sie of ni$ we mo#e loads per year.

18. Ioad Die? =s the number of items that can be transported by the aterialhandler at one time while deli#erin% parts from one work center to the other.>epends on the method of transportation$ i.e.$ technolo%y used.

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;=)R;:) IN=)NTOR9 )=)

1. 5he in#entory in a kanban system takes two forms?

a) "=3 in the form of parts passin% throu%h intermediate work

stations in the cell$ and the cell safety stock.b) 5he number of parts in the output buer of the workstation.

2. =n#entory costs are associated with a#era%e in#entory le#els ina kanban system.

!. =n a %enuine -ust:in:time system with no randomness$ we would

schedule our container replenishments to complete processin%and arri#e at the output buer -ust as the request for a containerof parts arri#ed from the successor work:center. =n this case$ theoutput buer would always be empty.

+. "=3 are created from the Wow of each unit throu%h the system

durin% processin%. ,lthou%h we can put bounds on this le#el of"=3$ but it is diUcult to eliminate or reduce it beyond a certainlimit.

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D)8ININ: T@) 797T)< CONTRO&OINT7

1. 5he container sie and the number of kanbans re%ulate the in#entory

le#el at each sta%e of production system

2. In soe cases, the sta%es "1ork centers# are easil* dened bya natural set of production acti#ities (if the components are

fabricated in one area and then stored$ that forms a sta%e.)

!. 4n the other hand$ if part fabrication requires parts to #isit se#eral

%eo%raphically dispersed machinin% centers$ with heat treatments

and inspections followed by paintin%$ etc.$ de&nin% sta%es of workmay not be easy. ere we mi%ht prefer to establish interediate

control points.

+. y addin% control points$ we can bifurcate work center into more

sta%es.

'. 5he two sta%e approach adds a second control sta%e point. =ne9chan%e for the e9tra "=3 in#entory point$ we %ain a reduction in

cycle time.

(, %eneral depiction of one work center #ersus two work centers

is shown in the ne9t slide.)

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D)8ININ: T@) 797T)< CONTRO&OINT7

. , choice of control points and stora%e de&nition

depends on product #ariety$ stora%e costs andcycle time requirements.

0. , common approach sets control points

immediately before the bottleneck operation andalso as far down the operation sequence as we an%o before the product dierentiates into manymodels.

E. This allo1s stora%e of fe1er in6pro%ressproducts but still allo1s rapid custoizationto replenish deand for nished products.

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5he end of this lecture

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Lect12_ Kanban Systems

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