17-18 Managing Inventory
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Transcript of 17-18 Managing Inventory
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Learning Objectives
Conuct an !"C analysis#
$%plain an use the $O& moel#
Compute a reorer point an e%plainsa'ety stoc(#
!pply the prouction orer )uantity
moel# $%plain an use the )uantity iscount
moel#
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To ,ecouple, or separate various parts o'
the prouction process To provie a stoc( o' goos that -ill
provie a .selection, 'or customers
To ta(e avantage o' )uantity iscounts
To hege against in/ation an up-arprice changes
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The unctions o' Inventory
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Types o' Inventory
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5a- material
+or(6in6progress Maintenance7repair7operating supply
inishe goos
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8igher costs
Item cost 9i' purchase
Orering 9or setup cost Costs o' 'orms; cler(s< -ages etc#
8oling 9or carrying cost "uiling lease; insurance; ta%es
etc#
=i>cult to control
8ies prouction problems
=isavantages o' Inventory
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=ivies on6han inventory into 3 classes
! class; " class; C class
"asis is usually annual @ volume @ volume A !nnual eman % nit cost
Bolicies base on !"C analysis
=evelop class ! suppliers more
ive tighter physical control o' ! items
orecast ! items more care'ully
ABC Analysis
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Control o' Fervice Inventories
oo personnel selection; training; aniscipline
Tight control o' incoming shipments
$Gective control o' all goos leaving the'acility
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Independent versus DependentDemand
Independent demand6 eman 'or item
is inepenent o' eman 'or any otheritem
Dependent demand6 eman 'or item isepenent upon the eman 'or some
other item
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Inventory Costs
Holding costs6 associate -ithholing or carryinginventory over time
Ordering costs6 associate -ith costso' placing orer an receiving goos
Setup costs6 cost to prepare amachine or process 'or manu'acturingan orer
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Orering Costs
Fupplies
orms
Orer processing
Clerical support
$tc#
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Fetup Costs
Clean6up costs
5e6tooling costs
!justment costs
$tc#
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i%e orer6)uantity moels
$conomic orer )uantity
Brouction orer )uantity
&uantity iscount
Brobabilistic moels
i%e orer6perio moels
Inventory Moels
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no-n an constant demand
no-n an constant lead time
Instantaneous receipto' material No)uantity discounts
Only orer 9setup cost an holing
cost o stockouts
$O& !ssumptions
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$O& Moel
8o- Much to OrerJ
-rer /,a!tt#
A!!,al Cost
-rer &et,p* Cost C,r"e
-ptmal-rer ',a!tt# &'(*
+!m,m totalost
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$O& Moel $)uations
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Optimal Order Quantity
Expected Number of Orders
Expected Time et!een Orders "or#ing ays &ear
"or#ing ays &ear
' '( (
' '
' '
'
' (
Q* D S
H
N D
Q*
TN
d D
ROP d L
)
D' emand per year
S' *etup +order, cost perorder
H' -olding +carrying, cost
d' emand per day
L' .ead time in days
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'(
-&!ts*
lope ,!ts)a# d
ea tme
Tme &a#s*
I!
"e!tor#
le"el
&,
!ts*
The 5eorer Boint 95OB Curve
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!ns-ers ho- much to orer an -hen toorer
!llo-s partial receipt o' material
Other $O& assumptions apply
Fuite 'or prouction environment
Material prouce; use immeiately Brovies prouction lot si*e
Lo-er holing cost than $O& moel
Production Order Quantity Model
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Tme
I!
"e!tor#
$e"el
Bot7pro,to!a! ,saetae plae
sae o!l#taes plae+am,
m!"e!tor#
le"el
$O&BO&Moel +hen To Orer
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eorer
o!t&-*
Tme
I!"e!tor# e"el
A"eraeI!"e!tor#
ea Tme
-ptmal
-rer',a!tt#&'(*
$O&BO&Moel +hen To Orer
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Optimal Order Quantity
*etup /ost
-olding /ost
' '0
(
1
Q
H*d
p
Q
D
Q
S
p1
2
&
345 1 - 1 Q 0 d
p2
*0 dp2
& *
)11*
& *6aximum inventory level
D Demand peryear
S !etup cost H "oldin# cost
d Demand perday
p Productionper day
BO& Moel $)uations
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&uantity =iscount Fcheule
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$%$&CI!$!
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