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Transcript of Inventory Control Models Part II Applied Management Science for Decision Making, 1e © 2012 Pearson...
![Page 1: Inventory Control Models Part II Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro, PhD.](https://reader035.fdocuments.us/reader035/viewer/2022081504/56649cb95503460f94980ec9/html5/thumbnails/1.jpg)
Inventory Control ModelsInventory Control Models
Part IIPart II
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
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The Production Order Quantity ModelThe Production Order Quantity Model
USED WHENEVER THE VENDORCANNOT DELIVER THE ORDER
( Q* ) ALL IN ONE DAY
USED WHENEVER THE FACTORYCANNOT PRODUCE THE ORDER
( Q* ) ALL IN ONE DAY
OR
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Service SectorService Sector
Variable InterpretationsVariable Interpretations
P or p
The delivery rateThe delivery rateofof
purchased itemspurchased items
P or p
The production rateThe production rateofof
manufactured itemsmanufactured items
ManufacturingManufacturing
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Service SectorService Sector
Variable InterpretationsVariable Interpretations
The optimal The optimal EOQEOQ whenwhen
purchased items purchased items areare
received in partialreceived in partialshipmentsshipments
The optimal The optimal EOQEOQwhen when
manufactured itemsmanufactured itemscannot cannot
all be producedall be producedin a single dayin a single day
ManufacturingManufacturing
Qp* Qp*
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Production Order Quantity ModelProduction Order Quantity Model Cycle ChartCycle Chart
Maximum Inventory Level Maximum Inventory Level ( ( IMAXIMAX ) )Replenishment Rate Replenishment Rate ( ( PP ) )Consumption Rate Consumption Rate ( ( DD ) )
TimeTime Cycle Chartsenhance
understandingof basic
inventoryconcepts
Graphically depicts the relationship betweenGraphically depicts the relationship between
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SAW TOOTH VERSIONSAW TOOTH VERSION
Production Order Quantity ModelProduction Order Quantity ModelCycle ChartCycle Chart
MAXIMUM INVENTORY LEVELMAXIMUM INVENTORY LEVEL
AVERAGE INVENTORY LEVELAVERAGE INVENTORY LEVEL
PP PPDD DD
CONSUMPTIONCONSUMPTIONRATE ONLYRATE ONLY
REPLENISHMENTREPLENISHMENTRATERATE
UN
ITS
ELAPSED TIME
CONSUMPTION OCCURSEVEN AS
REPLENISHMENTIS TAKING PLACE
0
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Production Order Quantity ModelProduction Order Quantity ModelCycle ChartCycle Chart
MAXIMUM INVENTORY LEVELMAXIMUM INVENTORY LEVEL
AVERAGE INVENTORY LEVELAVERAGE INVENTORY LEVEL
PP PPDD DD
CONSUMPTIONCONSUMPTIONRATE ONLYRATE ONLY
REPLENISHMENTREPLENISHMENTRATERATE
0
ELAPSED TIME
An EOQ of 100 unitsis delivered at the rate of20 units per week over
five weeks
INVENTORYLEVEL PEAKSAT THIS POINT
INVENTORYFALLS TO ZERO OR
REORDER POINT
UN
ITS
SAW TOOTH VERSIONSAW TOOTH VERSION
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CYCLE CHART DISCUSSIONCYCLE CHART DISCUSSION
The replenishment rate ( PP or pp ) is diminished by the consumption rate ( DD or dd ).
Average inventory will always be less than [ Q* / 2 ] .
Average inventory is essentially [ IMAX / 2IMAX / 2 ] .
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Production Order Quantity Production Order Quantity FormulaFormula
2DS
H [ 1 – d / p ]
THE CONSUMPTION OR THE CONSUMPTION OR USAGE RATE ( D )USAGE RATE ( D )
THE REPLENISHMENT OR THE REPLENISHMENT OR PRODUCTION RATE ( P )PRODUCTION RATE ( P )
THE THE FINITE CORRECTION FACTORFINITE CORRECTION FACTOR PRODUCES A LARGER PRODUCES A LARGERVALUE OF Q* IN ORDER TO COMPENSATE FOR PIECEMEALVALUE OF Q* IN ORDER TO COMPENSATE FOR PIECEMEAL
REPLENISHMENT AND CONSUMER DEMANDREPLENISHMENT AND CONSUMER DEMAND
Qp* = √
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Production Order Quantity ModelProduction Order Quantity ModelEXAMPLEEXAMPLE
DA = 1000 units ( annual demand ) S = $10.00 ( cost per order ) H = $.50 ( annual unit carry cost ) P = 8 units ( daily supply rate ) D = 6 units ( daily usage rate )
How manyunits shouldbe ordered at a time?
How long to receivethe entire
order?
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Production Order Quantity ModelProduction Order Quantity ModelSOLUTIONSOLUTION
2(1000)(10.00)
.50 [ 1 – 6 / 8 ]
20,000 .50 [ .25 ]
Qp* = √=√ = 160,000 = 400 units√
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The Basic EOQ ModelThe Basic EOQ ModelSOLUTIONSOLUTION
2(1000)(10.00)
.50
20,000 .50
Q* = √= √ = 40,000 = 200 units√
Q* IS ONLYHALF OF WHAT
IT WAS UNDER THEPRODUCTION ORDER
QUANTITY MODEL
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Production Order Quantity ModelProduction Order Quantity ModelEXAMPLEEXAMPLE
Qp* 400 P 8
ORDER RECEIPT TIME PERIOD ( t )
t = = = 50 days
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Production Order Quantity ModelProduction Order Quantity ModelEXAMPLEEXAMPLE
TOTAL VARIABLE COSTS ( TVC )
TVC =Q*p
2X 1 - D
PX H +
D
Q*pX S
= 400
2X 1 - 6
8 X .50 + 1,000
400X 10.00
= [ 200 x (.25)(.50) ] + [ 2.5 x 10.00 ] = [ 25.00 ] + [ 25.00 ] = $50.00
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Post Solution Comments
The Qp* must be larger than Q* since it is being drawn down even as it arrives on a piecemeal basis. The larger Qp* produces no increase in carry costs.
Annual carry costs are actually less than they are
under the basic EOQ model ( Q* ) .
““P” and “D” can be expressed asP” and “D” can be expressed asdaily, weekly, monthly, and annualdaily, weekly, monthly, and annualfigures without changing the valuefigures without changing the valueof the finite correction factor [1-d/p]of the finite correction factor [1-d/p]
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ProductionOrder
QuantityModel
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WE SELECT THE“INVENTORY”
MODULE
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WE SELECT THE“PRODUCTION ORDER
QUANTITY MODEL”
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THE DIALOGUE BOXALLOWS US TOINSERT A TITLE
FOR THIS PROBLEM
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THE DATA INPUTTABLE
APPEARS
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ANNUAL DEMAND = 1,000 UNITS
ORDER COST = $10.00
UNIT CARRY COST = $.50
DAILY REPLENISHMENT RATE = 8 UNITS
DAILY CONSUMPTION RATE = 6 UNITS
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Optimal Order Quantity
Total Variable Costs
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Total Variable Cost
Annual Carry Cost
Annual Order Cost
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ProductionOrder
QuantityModel
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Templateand
Sample Data
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Sensitivity Analysisalso shows the
optimal solution
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The The Backorder Inventory Backorder Inventory ModelModel
USED WHENEVER THEFIRM IS APPEALING TO ITS CUSTOMERS TO BUY AND THEN
WAIT FOR THEIR PURCHASES UNTILA NEW SHIPMENT
( Q* ) IS ORDERED AND RECEIVED
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Backorder ModelBackorder Model Variables Variables
Backorder cost – BB
Optimal number of backorders – S*S*
Optimal order quantity under a backordering
scenario – QQbb**
Number of units going into stock after all
backorders have been filled – bb or [ QQbb* - S** - S* ]
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Backorder Model Cycle ChartBackorder Model Cycle Chart
Optimal Order Quantity,Optimal Order Quantity,
Optimal Number of Backorders,Optimal Number of Backorders,
Remaining Units Going IntoRemaining Units Going Into
Stock after Backorders Stock after Backorders
Have Been FilledHave Been Filled
Graphically depicts the relationship betweenGraphically depicts the relationship between
Cycle chartsenhance
understandingof basic inventory
concepts
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Backorder Model Cycle ChartBackorder Model Cycle ChartPICKET FENCE VERSIONPICKET FENCE VERSION
Q* or EOQ Q* or EOQ b = Q*- S* b = Q*- S*
S*
0
INITIALCYCLE
CYCLE2
CYCLE3
CYCLE4
PO
SIT
IVE
INV
EN
TO
RY
NEGATIVENEGATIVEINVENTORYINVENTORY
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Backorder Model Cycle ChartBackorder Model Cycle ChartPICKET FENCE VERSIONPICKET FENCE VERSION
Q* or EOQ = 92 unitsQ* or EOQ = 92 units b = Q*- S* = 88 unitsb = Q*- S* = 88 units
S* = 4 UNITS
0
INITIALCYCLE
CYCLE2
CYCLE3
CYCLE4
PO
SIT
IVE
INV
EN
TO
RY
NEGATIVENEGATIVEINVENTORYINVENTORY
ASSUME ANEOQ OF92 UNITS
88 UNITS GO INTO INVENTORYAFTER THE FOUR
STOCKOUTS HAVE BEEN
FILLED
THE FIRMALLOWS
BACKORDERSTO REACH
4 UNITS
THIS MODELASSUMESTHAT THE
NEW EOQ ISORDERED WHEN
BACKORDERSEQUAL FOUR
UNITS
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Backorder Model FormulaBackorder Model Formula
B
HBDSQb 2*
OPTIMAL ORDER QUANTITYIN BACKORDER-TOLERATED
SITUATIONS
UNIT BACKORDERCOST
HH
ANNUAL CARRY COSTPER UNIT
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Backorder Model FormulaBackorder Model Formula
BH
HQbS **
OPTIMAL ORDERQUANTITY UNDERBACKORDERING
UNIT BACKORDERCOST
THE OPTIMALNUMBER
OFBACKORDERS
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The Backorder ModelThe Backorder ModelEXAMPLEEXAMPLE
DA = 500 units ( annual demand ) S = $4.00 ( order cost ) H = $ .50 ( annual unit carry cost ) B = $10.00 ( unit backorder cost )
How many units shouldbe ordered?
What are the number of
backorders?
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The Backorder ModelThe Backorder ModelSOLUTIONSOLUTION
2(500)(4.00) (10.00 + .50) .50 10.00
= 8000 x 1.05
= 8400
≈ 92 units
Qb* =√√
√
X
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The Backorder ExampleThe Backorder ExampleSOLUTIONSOLUTION
.50
.50 + 10.00S* = 91.65 x
= ( 91.65 x .0476 )
≈ 4 units
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Relationship Between ROP and S*Relationship Between ROP and S*
IF LEADTIME IS ZERO, THE REORDER POINT OCCURS WHEN THE OPTIMAL NUMBER OF BACKORDERS IS REACHED
If leadtime ( L ) = 0 , then ROP = S*
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Relationship Between ROP and S*Relationship Between ROP and S*
IF LEADTIME IS NOT ZERO, THE REORDER POINT OCCURS BEFORE THE OPTIMAL NUMBER OF
BACKORDERS IS REACHED
If leadtime ( L ) > 0, then ROP > S*
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Backorder Reorder PointBackorder Reorder PointEXAMPLEEXAMPLE
Given: L = 0 days Qb* = 92 units S* = 4 units
Order 92 units when the number of backorders
accumulate to 4
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Backorder Reorder PointBackorder Reorder PointEXAMPLEEXAMPLE
Given: d = 2 units, L = 6 days, Qb* = 92 units, S* = 4 units
Order 92 units when there are 8 units still left in the
account balance.
THE INITIAL ROP = d x L = [ 2 units x 6 days ] = 12 units12 units
THE FINAL ROP = Initial ROP – S* = [ 12 units – 4 units ] = 8 units8 units
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ROP under BackorderingROP under BackorderingEXAMPLE WHERE L IS POSITIVEEXAMPLE WHERE L IS POSITIVE
S* = 4 units ( - 4 )
NEGATIVENEGATIVEINVENTORYINVENTORY
REGIONREGION
POSITIVEINVENTORY
REGION
Qb* Qb*
00
FINAL ROP FINAL ROP
12 – 4 = +8 12 – 4 = +8IN
ITIAL R
OP = 12 U
NITS
INITIAL ROP = 12 UNITS
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THE BACKORDER MODELMAY OR MAY NOT BE AVAILABLE ONYOUR PARTICULAR
SOFTWARE
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Inventory ControlInventory Control
Part IIPart II
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
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The The ABC ABC Classification SystemClassification System
Its purpose is to assist inventory specialistsin establishing policies that focus their limited resources on the relatively few
critical materials, components, and products...and not the many trivial ones.
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
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ABC Classification SystemABC Classification System
Purchasing personnel are relatively few in number in the firm.
There are thousands of components, materials, and finished good inventory accounts in medium and large firms.
There needs to be a priority system for establishing and updating inventory control doctrines ( Q* / R ).
RATIONALE
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Class “A” Class “A” Inventory ItemsInventory Items
LARGE APPLIANCESLARGE APPLIANCES AUTOMOBILESAUTOMOBILES FURNITUREFURNITURE DIAMONDSDIAMONDS
Comprise only 15% of thetotal items in stock yetrepresent 70% - 80% ofthe total dollar volume.
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Class “B” Class “B” Inventory ItemsInventory Items
MID-SIZED APPLIANCESMID-SIZED APPLIANCES LAWN MOWERSLAWN MOWERS MOST SUITS & COATSMOST SUITS & COATS
Comprise 30% of thetotal items in stock and represent 15% - 25% ofthe total dollar volume
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Class “C”Class “C” Inventory Items Inventory Items
TOASTERS / BLENDERSTOASTERS / BLENDERS NUTS, BOLTS, SCREWSNUTS, BOLTS, SCREWS STATIONERY SUPPLIESSTATIONERY SUPPLIES MOST ACCESSORIESMOST ACCESSORIES
Comprise 55% of the total items in stock yet
represent only 5% ofthe total dollar volume
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Policies Based On ABCPolicies Based On ABC
“A” items would be inventoried in a more secure areaitems would be inventoried in a more secure area
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Policies Based On ABCPolicies Based On ABC
“A” items would be inventoried in a more secure areaitems would be inventoried in a more secure area
“ “A” items would warrant more care in forecastingA” items would warrant more care in forecasting
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Policies Based On ABCPolicies Based On ABC
“A” items would be inventoried in a more secure areaitems would be inventoried in a more secure area
“ “A” items would warrant more care in forecastingA” items would warrant more care in forecasting
“ “A” item records would be verified more frequentlyA” item records would be verified more frequently
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Policies Based On ABCPolicies Based On ABC
“A” items would be inventoried in a more secure areaitems would be inventoried in a more secure area
“ “A” items would warrant more care in forecastingA” items would warrant more care in forecasting
“ “A” item records would be verified more frequentlyA” item records would be verified more frequently
“ “A” items would justify closer attention to customerA” items would justify closer attention to customer service levelsservice levels
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Policies Based On ABCPolicies Based On ABC
“A” items would be inventoried in a more secure area
“A” items would warrant more care in forecasting
“A” item records would be verified more frequently
“A” items would justify closer attention to customer service levels
“A” items would qualify for real-time inventory tracking systems and more sophisticated ordering rules
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Additional Criteria for ABCAdditional Criteria for ABC
Anticipated engineering changesAnticipated engineering changes
Delivery problemsDelivery problems
Quality problemsQuality problems
High unit production costsHigh unit production costs
WE FOCUS ON THE RELATIVELY FEW ITEMS WITH MAJOR PROBLEMSWE FOCUS ON THE RELATIVELY FEW ITEMS WITH MAJOR PROBLEMS
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ABCAnalysis
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WE FIRST SCROLLWE FIRST SCROLLTOTO
““INVENTORY”INVENTORY”
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WE THEN SELECT THEWE THEN SELECT THESUB MENUSUB MENU
““ABC Analysis”ABC Analysis”
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THE DIALOG BOXTHE DIALOG BOXAPPEARSAPPEARS
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WE HAVE FIVE ( 5 )WE HAVE FIVE ( 5 )ITEMS THAT NEEDITEMS THAT NEEDTO BE CLASSIFIEDTO BE CLASSIFIED
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THE DATA INPUT TABLETHE DATA INPUT TABLE
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FIVE ITEMS, TOGETHER WITHFIVE ITEMS, TOGETHER WITHTHEIR ANNUAL DEMANDS, THEIR ANNUAL DEMANDS,
AND UNIT VALUESAND UNIT VALUES
WE DESIRE WE DESIRE 20% OF ALL20% OF ALLITEMS BE ITEMS BE
““A” CATEGORYA” CATEGORY
WE DESIRE WE DESIRE 30% OF ALL30% OF ALLITEMS BE ITEMS BE
““B” CATEGORYB” CATEGORY
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One “A” ItemOne “A” ItemOne “B” ItemOne “B” Item
Three “C” ItemsThree “C” Items
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ABCAnalysis
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Templateand
Sample Data
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ABC Classification ABC Classification SystemSystem
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
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Reorder Point ModelsReorder Point Models
Known Stockout Cost Model
Service Level Model
Variable Demand / Constant Lead Time Model
Constant Demand / Variable Lead Time Model
Variable Demand / Variable Lead Time Model
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
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Reorder Point Models
The original reorder point formula
ROP = d x L
computes the mean demandduring lead time, that is, theaverage demand during thewaiting period for the item.
Where d = daily demandWhere d = daily demand L = lead timeL = lead time ( in days )( in days )
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Reorder Point Models
However, actual demand duringlead time can be much higher
than the mean (average) demand.
For this reason, the reorder pointshould contain a built-in safety stock ( SS or B ) that will meetunexpectedly higher demands
and consequently reduce stockout costs.
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Reorder Point Models
The reorder point formulanow becomes
ROP = d x L + SS
But larger safety stocksinvolve higher carry costs.
We must find a safetyWe must find a safetystock that minimizesstock that minimizesboth carry costs andboth carry costs andexpected stockoutexpected stockout
costs annuallycosts annually
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Reorder Point Reorder Point Cost TradeoffCost Tradeoff
ANNUALANNUALSAFETYSAFETY
( BUFFER ) ( BUFFER ) STOCKSTOCKCARRY CARRY COSTSCOSTS
ANNUALANNUALEXPECTEDEXPECTEDSTOCKOUTSTOCKOUT
COSTSCOSTS
REORDERREORDERPOINTPOINTTOTALTOTALCOSTSCOSTS
00 Safety ( Buffer ) Stock in Units
Co
stKNOWN STOCKOUT COST MODEL
∞
THESELECTED
SAFETY( BUFFER )
STOCKLEVEL
( SS or B )
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Known Stockout Cost ModelKnown Stockout Cost Model
Stockout cost per unit is known.
Lead time is known and constant.
Lead time demand is variable.
IT IS ALSO ASSUMED THAT THE ANNUAL NUMBERIT IS ALSO ASSUMED THAT THE ANNUAL NUMBER OF ORDERING PERIODS IS KNOWN ( n )OF ORDERING PERIODS IS KNOWN ( n )
ASSUMPTIONS
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Demand During Lead TimeDemand During Lead Time ( D ( DL L ))
15% 25% 30% 20% 10%
30 40 50 60 70
DEMAND IN UNITS
Probability
LEAD TIME DEMAND IS APPROXIMATELY NORMALLY DISTRIBUTED AND RANGES BETWEEN THIRTY AND SEVENTY UNITS
EXAMPLEEXAMPLE
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Demand During Lead TimeDemand During Lead Time ( D ( DL L ))
15% 25% 30%30% 20% 10%
30 40 50 60 70
DEMAND IN UNITS
Probability
SINCE THERE IS A 30% CHANCE THAT LEAD TIME DEMAND WILL BE FIFTY ( 50 ) UNITS WE WOULD AT LEAST SET THE REORDER POINT AT 50 UNITS. OTHERWISE, WE ARE EXTREMELY VULNERABLE TO
LARGE AND RECURRING STOCKOUTS.
THE HIGHESTPROBABILITY
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Demand During Lead TimeDemand During Lead Time ( D ( DL L ))
15% 25% 30% 20% 10%
30 40 50 60 70
DEMAND IN UNITS
Probability
THE SAFETY OR BUFFER STOCK LEVEL AT THE MINIMUM REORDER POINT IS ZERO BY DEFINITION
SAFETYSTOCK
IS ZEROHERE
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Reorder Point Carry CostReorder Point Carry Cost
X
=
ANNUAL UNITCARRY COST
SAFETY OR BUFFERSTOCK in units
ANNUAL SAFETY STOCKCARRY COSTS
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Reorder Point of 50 UnitsReorder Point of 50 UnitsANNUAL SAFETY STOCK CARRY COSTS
‘0’ Safety Stock x $5.00 per unit = $0.00 per year carry cost
( BUFFER STOCK )
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Reorder Point of 50 UnitsReorder Point of 50 Units
15% 25% 30%30% 20% 10%
30 40 5050 60 70
ReorderReorderPointPoint
Probability
ActualDemand
10 Stockouts
20 Stockouts
A DEMAND OF 60 UNITS WOULDCREATE A STOCKOUT OF 10 UNITS
WITH A 20% PROBABILITY
A DEMAND OF 70 UNITS WOULDCREATE A STOCKOUT OF 20 UNITS
WITH A 10% PROBABILITY
EXPECTED STOCKOUTS PER ORDER PERIOD
EXPECTED STOCKOUTS
2 + 2
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Reorder Point Stockout CostReorder Point Stockout Cost
X
X
=
Lead Time ExpectedStockouts in units
Annual Number of Lead Time Periods
( ordering periods )
Stockout Cost per unitAnnual ExpectedStockout Costs
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Reorder Point of 50 UnitsReorder Point of 50 UnitsANNUAL EXPECTED STOCKOUT COSTS
NUMBEROF
STOCKOUTS
EXPECTEDSTOCKOUTS
STOCKOUT
COST ( per unit )
NUMBER OFORDER PERIODS
( per year )
10 2 $40.00 6
COST
$480.00
20 2 $40.00 6 $480.00
Σ = $960.00
Lead TimeDemand
of 60
Lead TimeDemand
of 70
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Reorder Point Total CostReorder Point Total Cost
ANNUAL SAFETY STOCKCARRY COSTS
+
ANNUAL EXPECTED STOCKOUT COSTS
THE REORDER POINT THAT HAS THE LOWEST TOTAL COST IS SELECTED
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Reorder Point Score BoardReorder Point Score Board
REORDERREORDER
POINTPOINT
ANNUAL CARRY ANNUAL CARRY COSTSCOSTS
ANNUAL STOCKOUT ANNUAL STOCKOUT COSTSCOSTS
TOTAL COSTSTOTAL COSTS
5050 $0.00$0.00 $960.00$960.00 $960.00$960.00
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Reorder Point of 60 UnitsReorder Point of 60 UnitsANNUAL SAFETY STOCK CARRY COSTS
‘10’ Safety Stock x $5.00 per unit = $50.00 per year carry cost
( BUFFER STOCK )
RAISING THE REORDER POINTTO 60 UNITS AUTOMATICALLYCREATES A SAFETY STOCK
OF TEN UNITS
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Reorder Point of 60 UnitsReorder Point of 60 Units
15% 25% 30% 20%20% 10%
30 40 50 6060 70
ReorderReorderPointPoint
Probability
ActualDemand
10 Stockouts
A DEMAND OF 70 UNITS WOULDCREATE A STOCKOUT OF 10 UNITS
WITH A 10% PROBABILITY
EXPECTED STOCKOUT
1
EXPECTED STOCKOUTS PER ORDER PERIOD
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Reorder Point of 60 UnitsReorder Point of 60 UnitsANNUAL EXPECTED STOCKOUT COSTS
NUMBEROF
STOCKOUTS
EXPECTEDSTOCKOUTS
STOCKOUT
COST ( per unit )
NUMBER OFORDER PERIODS
( per year )
1010 1 $40.00 6
COST
$240.00
Σ = $240.00LEAD TIMEDEMAND
of 70
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Reorder Point Score BoardReorder Point Score Board
REORDERREORDER
POINTPOINT
ANNUALANNUAL
CARRY COSTSCARRY COSTS
ANNUALANNUAL
STOCKOUT COSTSSTOCKOUT COSTS TOTAL COSTSTOTAL COSTS
50 Units $0.00 $960.00 $960.00
60 Units $50.00 $240.00 $290.00
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Reorder Point of 70 UnitsANNUAL CARRY COSTS
‘20’ Safety Stock x $5.00 per unit = $100.00 per year carry cost
( BUFFER STOCK )
RAISING THE REORDER POINTTO 70 UNITS AUTOMATICALLY
CREATES A SAFETY STOCKOF 20 UNITS
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Reorder Point of 70 UnitsReorder Point of 70 Units
15% 25% 30% 20% 10%
30 40 50 60 7070
ReorderReorderPointPoint
Probability
0Stockouts
BASED ON HISTORICAL DEMAND DATA,NO DEMAND SHOULD OCCUR THAT
CREATES A STOCKOUT
EXPECTEDSTOCKOUTS
ZERO
EXPECTED STOCKOUTS PER ORDER PERIOD
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Reorder Point of 70 UnitsReorder Point of 70 UnitsANNUAL EXPECTED STOCKOUT COSTS
NUMBEROF
STOCKOUTS
EXPECTEDSTOCKOUTS
STOCKOUT
COST ( per unit )
NUMBER OFORDER PERIODS
( per year )
0 0 $40.00 6
COST
$0.00
Σ = $0.00LEAD TIMEDEMAND
of 70
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Reorder Point Score BoardReorder Point Score Board
REORDERREORDER
POINTPOINT
ANNUALANNUAL
CARRY COSTSCARRY COSTS
ANNUALANNUAL
STOCKOUT COSTSSTOCKOUT COSTS TOTAL COSTSTOTAL COSTS
50 Units $0.00 $960.00 $960.00
60 Units $50.00 $240.00 $290.00
70 Units $100.00 $0.00 $100.00
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The ConclusionThe Conclusion
The lowest cost option:
ROP = 70 units
SS = 20 units
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KnownStockout
CostModel
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WE SCROLL TOWE SCROLL TO““INVENTORY”INVENTORY”TO FIND THETO FIND THE
KNOWN STOCKOUT COSTKNOWN STOCKOUT COSTREORDER POINT MODELREORDER POINT MODEL
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WE SELECT THEWE SELECT THE“Reorder Point / Safety Stock”“Reorder Point / Safety Stock”
( Discrete Distribution )( Discrete Distribution )SUB MENUSUB MENU
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THE DIALOG BOXTHE DIALOG BOXAPPEARSAPPEARS
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WE HAVE FIVE ( 5 )WE HAVE FIVE ( 5 )DISCRETE DEMANDSDISCRETE DEMANDSDURING LEAD TIMEDURING LEAD TIME
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THE DATA INPUT TABLETHE DATA INPUT TABLE
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THE COMPLETEDTHE COMPLETEDDATA INPUT TABLEDATA INPUT TABLE
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THE KNOWN STOCKOUT COSTTHE KNOWN STOCKOUT COSTREORDER POINT MODELREORDER POINT MODEL
Reorder Point = 70 UNITSReorder Point = 70 UNITS
Safety Stock = 20 UNITSSafety Stock = 20 UNITS
Reorder Point = 50 UNITSReorder Point = 50 UNITS
Reorder Point = 60 UNITSReorder Point = 60 UNITS
Reorder Point = 70 UNITSReorder Point = 70 UNITS
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KnownStockout
CostModel
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Templateand
Sample DataInsert Selected
Reorder Point, etc.
This is the conditional payoff matrix for this problem. The strategiesare the safety stocks, the events are the five possible demands, and
the conditional payoffs are the cost consequences (expectedstockouts + carry costs) of selecting a particular safety stock
and a certain demand materializing.
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Selected Reorder Point
5 discrete demand possibilities during any given lead time ( with probabilities )
Safety stocks associatedwith all 5 discrete demands
For ROP = 50 , total cost = $960.00 , H = $ 0.00For ROP = 60 , total cost = $290.00 , H = $ 50.00For ROP = 70 , total cost = $100.00 , H = $100.00
Conditional Payoffs
EMV Criterion Maxi-Min Criterion
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Service Level ModelService Level Model
FOR EXAMPLE, THE FIRM MAY DESIRE A SERVICE LEVELTHAT MEETS 95% OF THE DEMAND, OR CONVERSELY,
RESULTS IN STOCKOUTS ONLY 5% OF THE TIME.
REORDER POINT DETERMINATION
When the stockout cost per unit ( Cs ) isdifficult or impossible to determine, thefirm may elect to establish a policy of
keeping enough safety stock on hand tosatisfy a prescribed level of customer
service.
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Service Level ModelService Level ModelREORDER POINT DETERMINATION
SALES DATA ARE USUALLY ADEQUATE FOR COMPUTINGTHE MEAN AND STANDARD DEVIATION
Assuming that the demand during lead time( DL ) follows a normal distribution, only themean ( µ ) and standard deviation ( σ ) arerequired to define the reorder point as wellas the safety stock ( SS or B ) for any given
service level.
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Service Level ModelService Level ModelREORDER POINT DETERMINATION EXAMPLE
A firm stocks an item that has a normally-distributed demand during the lead time period. The average or mean demand during the lead time period is 400 units and the standard deviation is 15 units. The firm wants a reordering policy that limits stockouts to only 5% of the time.
Requirement: 1. How much safety stock should the firm maintain? 2. What should be the reorder point?
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Service Level ModelService Level Model
.03.03 .04.04 .05 .06.06 .07.07
1.4 .92364.92364 .92507.92507 .92647.92647 .92785.92785 .92922.92922
1.5 .93699.93699 .93822.93822 .93943.93943 .94062.94062 .94179.94179
1.6 .94845.94845 .94950.94950 .95053 .95154.95154 .95254.95254
1.7 .95818.95818 .95907.95907 .95994.95994 .96080.96080 .96164.96164
AREAS UNDER THE STANDARD NORMAL CURVE
Z
95% SERVICE LEVEL IS REPRESENTED BY z = 1.65 standard normal deviates
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Service Level ModelService Level Model
ROPROP
95% STOCKAGE PROBABILITY5%
STOCKOUTPROBABILITY
SAFETY STOCK
Z = + 1.65
μ LEAD TIME MEAN DEMAND = 400 UNITS
0 units0 units
REORDER POINT AND SAFETY STOCK FOR 95% SERVICE LEVEL
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Service Level ModelService Level ModelFORMULAE
Reorder Point ( R ) = μ + ( z )( σ )
Safety Stock ( SS ) = ( z )( σ )
μ = MEAN DEMAND DURING LEAD TIME
z = NUMBER OF STANDARD NORMAL DEVIATES
σ = STANDARD DEVIATION OF LEAD TIME DEMAND
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Service Level ModelService Level ModelEXAMPLE – 95% SERVICE LEVEL
Reorder Point ( R ) = 400 + ( 1.65 )( 15 ) = 425 units
Safety Stock ( SS ) = ( 1.65 )( 15 ) = 25 units
μ = 400 units
z = 1.65 ( 95% service level )
σ = 15 units
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Service Level ModelService Level ModelEXAMPLE – 99% SERVICE LEVEL
Reorder Point ( R ) = 400 + ( 2.33 )( 15 ) = 435 units
Safety Stock ( SS ) = ( 2.33 )( 15 ) = 35 units
μ = 400 units
z = 2.33 ( 99% service level )
σ = 15 units 2.3 .99010
.03Z
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ServiceLevel
ReorderPointModel
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TO FIND THE SERVICE LEVELTO FIND THE SERVICE LEVELREORDER POINT, SCROLL TOREORDER POINT, SCROLL TO
“ “ INVENTORY “INVENTORY “
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SELECT THE SUB MENUSELECT THE SUB MENUENTITLEDENTITLED
“ “ Reorder Point / Safety Stock “Reorder Point / Safety Stock “( Normal Distribution )( Normal Distribution )
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THE DIALOG BOXTHE DIALOG BOXAPPEARSAPPEARS
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THE DATA INPUT TABLE REQUIRESTHE DATA INPUT TABLE REQUIRES
- DAILY DEMAND DURING LEAD TIMEDAILY DEMAND DURING LEAD TIME
- THE STANDARD DEVIATION OF DAILYTHE STANDARD DEVIATION OF DAILY DEMAND DURING LEAD TIMEDEMAND DURING LEAD TIME
- THE SERVICE LEVEL DESIRED ( i.e. 95% )THE SERVICE LEVEL DESIRED ( i.e. 95% )
- LEAD TIME IN DAYSLEAD TIME IN DAYS
- THE STANDARD DEVIATION OF LEAD TIMETHE STANDARD DEVIATION OF LEAD TIME
IF THE DAILY DEMAND IF THE DAILY DEMAND AND/ORAND/OR
LEADTIME ARE CONSTANT,LEADTIME ARE CONSTANT,THEN THEIR STANDARDTHEN THEIR STANDARD
DEVIATION(S) = 0DEVIATION(S) = 0
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The mean demand during lead time was given as 400 units.
Since this model requires both daily demand during thelead time, and the lead time ( in days ), we will assume
here that daily demand = 50 units, and lead time = 8 days.
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THE 95% “SERVICE LEVEL”THE 95% “SERVICE LEVEL”REORDER POINT = 423 UNITSREORDER POINT = 423 UNITS
THE 95% “SERVICE LEVEL” THE 95% “SERVICE LEVEL” SAFETY STOCK = 23 UNITSSAFETY STOCK = 23 UNITS
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ServiceLevel
ReorderPointModel
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Templates for three ( 3 ) differentreorder point models.
( we choose the first model )
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The Reorder Point = 400 + 25 = 425 !
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Stochastic Reorder Point ModelsStochastic Reorder Point Models
These models generally assume that any variability in either the demand rate or lead time can be adequately described by a normal distribution. This, however, is not a strict requirement.
These models will provide approximate reorder points even in cases where the actual probability distributions depart substantially from normal.
In all models shown, stockout costs are assumed to be unknown.
WHEN DEMAND AND / OR LEAD TIME ARE VARIABLE
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Stochastic Reorder Point ModelsStochastic Reorder Point Models MODELS CONSIDERED IN THIS PRESENTATION
I. variable demand rate / constant lead time
II. constant demand rate / variable lead time
III. variable demand rate / variable lead time
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Stochastic Reorder Point ModelsStochastic Reorder Point Models THE VARIABLES
d = constant demand rate
d = average demand rate
L = constant lead time
L = average lead time
σD = standard deviation of demand rate
σL = standard deviation of lead time
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Stochastic ReorderStochastic Reorder Point Models Point Models
Jack’s Pizza Parlor uses 1,000 cans of tomatoes per month at an average rate of 40 per day for each of 25 days per month. Usage can be approximated by a normal distribution with a standard de- viation of 3 cans per day. Lead time is constant at 4 days. Jack desires a service level of 99% , that is, a stockout risk of only 1%
Requirement:
1. Determine the reorder point ( ROP )
2. Determine the safety or buffer stock ( SS or B )
LEAD TIME IS CONSTANT
DEMAND RATE IS VARIABLE
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Reorder Point SolutionReorder Point Solution
Given:Given:
d = 40 cans dailyd = 40 cans daily
σσDD = 3 cans daily = 3 cans daily
L = 4 daysL = 4 days
__
ROP = ( d x L ) + ( z ) ( L ) ( σD )_
= ( 40 x 4 ) + 2.33 ( 4 ) ( 3 )
= 160 + 2.33 ( 6 )
= 160 + 13.98
= 174 cans
PIZZA PARLOR
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Safety Stock SolutionSafety Stock Solution
SS or B = ( z ) ( L ) ( σD )
= 2.33 ( 4 ) ( 3 )
= 2.33 ( 6 )
≈ 14 cans
PIZZA PARLOR
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ReorderPoint
WhereLead Time
IsConstant
Demand RateIs
Variable
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Templatefor
pizza parlorreorder point
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Reorder point = 174Safety stock = 14
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Stochastic ReorderStochastic Reorder Point Models Point Models
An oil-driven generator uses 2.1 gallons per day. Lead time is normally distributed with a mean of 6 days. The standard deviation of lead time is 2 days. The service level is 98%, that is, the stockout risk is 2%
Requirement:
1. Determine the reorder point ( ROP )
2. Determine the safety or buffer stock ( SS or B )
LEAD TIME IS VARIABLE
DEMAND RATE IS CONSTANT
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Reorder Point SolutionReorder Point Solution
Given:Given:
d = 2.1 gallons dailyd = 2.1 gallons daily
σσLL = 2 days = 2 days
L = 6 daysL = 6 days
ROP = ( d x L ) + ( z ) ( d ) ( σL )_
= ( 2.1 x 6 ) + 2.055 ( 2.1 ) ( 2 )
= 12.6 + 2.055 ( 4.2 )
= 12.6 + 8.631
= 21.23 gallons
__
THE GENERATOR
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Safety Stock SolutionSafety Stock Solution
SS or B = ( z ) ( d ) ( σL )
= 2.055 ( 2.1 ) ( 2 )
= 2.055 ( 4.2 )
= 8.63 gallons
THE GENERATOR
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ReorderPoint
WhereLead Time
IsVariable
Demand RateIs
Constant
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Stochastic Reorder Point ModelsStochastic Reorder Point Models
Beer consumption at a local tavern is known to be normally distributed with a mean of 150 bottles daily and a standard deviation of 10 bottles daily. Delivery time is also normally distributed with a mean of 6 days and a standard deviation of 1 day. The service level is 90%
Requirement:
1. Determine the reorder point ( ROP )
2. Determine the safety or buffer stock ( SS or B )
LEAD TIME IS VARIABLE
DEMAND RATE IS VARIABLE
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Reorder Point SolutionReorder Point Solution
Given: d = 150 bottles daily
σD = 10 bottles daily
L = 6 days
σL = 1 day
_
TAVERN EXAMPLE
_
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Reorder Point SolutionReorder Point Solution
ROP = ( d x L ) + ( z ) ( L )( σD ) + ( d ) ( σL )_ _ _ _2 22
= ( 150 x 6 ) + ( 1.28 ) (6)(10) + (150) (1)2 2 2
= 900 + 1.28 600 + 22,500
= 900 + 1.28 ( 151.986 ) ≈ 1,095 bottles
TAVERN EXAMPLE
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Safety Stock SoluSafety Stock Solutiontion
SS or B = ( z ) ( L )( σD ) + ( d ) ( σL )
_ _2 22
= (1.28 ) (6)(10) + (150) (1)2 2 2
= 1.28 600 + 22,500
= 1.28 ( 151.986 ) ≈ 195 bottles
TAVERN EXAMPLE
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StochasticReorder
PointModel
Demandand
Lead TimeVariable
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TO SOLVE A STOCHASTICTO SOLVE A STOCHASTICREORDER POINTREORDER POINT
AND AND SAFETY STOCKSAFETY STOCK
PROBLEMPROBLEM
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THE DIALOG BOXTHE DIALOG BOXAPPEARSAPPEARS
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THE DATA INPUT TABLETHE DATA INPUT TABLEREQUIRES DAILY DEMANDREQUIRES DAILY DEMAND
AND STANDARD DEVIATIONAND STANDARD DEVIATION( if any )( if any )
LEAD TIME ( DAYS ) LEAD TIME ( DAYS ) AND STANDARD DEVIATIONAND STANDARD DEVIATION
( if any )( if any )
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STOCHASTIC MODELSTOCHASTIC MODEL
REORDER POINT = 1,095 UNITSREORDER POINT = 1,095 UNITS
SAFETY STOCK = 195 UNITSSAFETY STOCK = 195 UNITS
THE LOCAL TAVERNTHE LOCAL TAVERN
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StochasticReorder Point
Model
DemandVariable
Lead TimeVariable
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Reorder Point ModelsReorder Point Models
Inventory ControlInventory Control
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
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Solved Problem
Quantity Discount Model
Ivonne CallenIvonne Callen
Computer-BasedComputer-Based
ManualManual
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Ivonne Callen ProblemIvonne Callen Problem
Ivonne Callen sells beauty supplies. Her annual demand for a particular skin lotion is 1,000 units.The cost of placing an order is $20.00, while the holdingcost per unit per year is 10 percent of the cost.The item currently costs $10.00 if the order quantity isless than 300. For orders of 300 units or more, the costfalls to $9.80.To minimize total cost, how many units should Ivonneorder each time she places an order?What is the minimum total cost?
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Ivonne Callen Problem
D = 1,000 units
S = $20.00
I = 10%
P = $10.00 if Q < 300 units
P = $ 9.80 if Q > 300 units
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Ivonne Callen Problem
To minimize total costs, how many units should Ivonne order each time she places an order ?
What is the minimum total cost ?
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EOQ at $10.00 Item Cost
Q*1 =
2 x D x S
I x P√2 (1,000 ) ( 20 )
( .10 ) ( 10.00 )√=
= √40,000
1.00= 200 units
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Total Cost at $10.00 Item Cost
TC = [ Q* / 2 ] (I)(P) + [ D / Q* ] (S) + [ D x P ]
= [ 200 / 2 ] (.10)(10.00) + [ 1,000 / 200 ] (20.00) + [1,000 x 10.00]
= $100.00 + $100.00 + $10,000.00
= $10,200.00
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Total Cost at $9.80 Item Cost
TC = [ Q* / 2 ] (I)(P) + [ D / Q* ] (S) + [ D x P ]
= [ 300 / 2 ] (.10)(9.80) + [ 1,000 / 300 ] (20.00) + [1,000 x 9.80]
= $147.00 + $66.67 + $9,800.00
= $10,013.67
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Ivonne Callen Problem
Therefore, she should order 300 units.
CONCLUSIONCONCLUSION
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Solved Problem
Serial Rate Production Model
The Handy Manufacturing CompanyThe Handy Manufacturing Company
Computer-BasedComputer-Based
ManualManual
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The Handy Mfg. Company
The Handy Manufacturing Company manufactures smallair conditioner compressors. The estimated demand forthe year is 12,000 units. The setup cost for the productionprocess is $200.00 per run, and the carrying cost is $10.00per unit per year. The daily production rate is 100 units perday, and demand has been 50 units per day.
Determine the number of units to produce in each batch, the number of batches that should be run each year, andthe time interval, in days, between each batch.( Assume 240 operating days. )
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The Data
D = 12,000 units
S = $200.00
H = $10.00 / unit / year
p = 100 units / day
d = 50 units / day
240 working days / yearUse
Production OrderQuantity Model
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Production Run Model
Qp* = √ 2 (D)(S)
H ( 1 - d / p )
=√ 2 (12,000)(200.00)
(10.00)( 1 - 50 / 100 )
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Production Run Model
Qp* = √ 4,800,000
(10.00)(.5)
=√ 4,800,000
5=√960,000 = 979.8
units
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Batches Run Annually
n = D / Q*p
n = 12,000 / 980
n ≈ 12 production runs
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Time Between Runs
t = 240 days / n
= 240 days / 12
= every 20 days
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Solved Problem
Reorder Point Model
Mr. Beautiful Mr. Beautiful
Computer-BasedComputer-Based
ManualManual
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Mr. Beautiful ProblemMr. Beautiful ProblemMr. Beautiful, an organization that sells weight training sets, has an ordering cost of $40.00 for the BB-1 set. The carry cost for theBB-1 set is $5.00 per set per year. To meet demand, Mr. Beautiful orders large quantities of BB-1 (7)seven times a year. The stockout cost for BB-1 is estimated to be$50.00 per set. Over the past several years, Mr. Beautiful has ob-served the following demand during lead time for BB-1:
Lead Time Demand Probability 40 .10 50 .20 60 .20 70 .20 80 .20 90 .10
Starting with a ROP of 60 units, what level of safety stockshould be maintained for BB-1?
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Mr. Beautiful ProblemMr. Beautiful Problem
40 50 60 70 80 90
.10 .20 .20 .20 .20 .10
ROP
Expected Stockouts
[.20 x 10] + [.20 x 20] + [.10 x 30] = 9 sets
10 sets
20 sets
30 sets
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Mr. Beautiful ProblemMr. Beautiful Problem
Carry Cost / Set / Year = $5.00 Stockout Cost / Set = $50.00 Order Periods / Year = 7At ROP = 60 sets , SS = 0 sets
Stockout Cost:
[.20 x 10 sets + .20 x 20 sets + .10 x 30 sets] x 7 orders x $50.00 [ 2 + 4 + 3 ] x 7 x $50.00 = $3,150.00
Carrying Cost:
SS = 0 sets x $5.00 / set / year = $0.00
TOTAL COST = $3,150.00
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Mr. Beautiful ProblemMr. Beautiful Problem
40 50 60 70 80 90
.10 .20 .20 .20 .20 .10
ROP
Expected Stockouts
[.20 x 10] + [.10 x 20] = 4 sets
10 sets
20 sets
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Mr. Beautiful ProblemMr. Beautiful Problem
Carry Cost / Set / Year = $5.00 Stockout Cost / Set = $50.00 Order Periods / Year = 7At ROP = 70 sets , SS = 10 sets
Stockout Cost:
[.20 x 10 sets + .10 x 20 sets] x 7 orders x $50.00 [ 2 + 2 ] x 7 x $50.00 = $1,400.00
Carrying Cost:
SS = 10 sets x $5.00 / set / year = $50.00
TOTAL COST = $1,450.00
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Mr. Beautiful ProblemMr. Beautiful Problem
40 50 60 70 80 90
.10 .20 .20 .20 .20 .10
ROP
Expected Stockouts
[.10 x 10] = 1 set
10 sets
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Mr. Beautiful ProblemMr. Beautiful Problem Carry Cost / Set / Year = $5.00 Stockout Cost / Set = $50.00 Order Periods / Year = 7
At ROP = 80 sets , SS = 20 sets
Stockout Cost:
[.10 x 10 sets] x 7 orders x $50.00 [ 1 ] x 7 x $50.00 = $350.00
Carrying Cost:
SS = 20 sets x $5.00 / set / year = $100.00
TOTAL COST = $450.00
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Mr. Beautiful ProblemMr. Beautiful Problem
40 50 60 70 80 90
.10 .20 .20 .20 .20 .10
ROP
Expected Stockouts
[ .00 x 0 ] = 0 sets
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Mr. Beautiful ProblemMr. Beautiful Problem Carry Cost / Set / Year = $5.00 Stockout Cost / Set = $50.00 Order Periods / Year = 7
At ROP = 90 sets , SS = 30 sets
Stockout Cost:
[.0 x 0 sets] x 7 orders x $50.00 [ 0 ] x 7 x $50.00 = $0.00
Carrying Cost:
SS = 30 sets x $5.00 / set / year = $150.00
TOTAL COST = $150.00
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Mr. Beautiful ProblemMr. Beautiful Problem
Reorder
Point
Stockout
Cost
Carry
Cost
Total
Cost
60 sets $3,150.00 $0.00 $3,150.00
70 sets $1,400.00 $50.00 $1,450.00
80 sets $350.00 $100.00 $450.00
90 sets $0.00 $150.00 $150.00
Mr. Beautiful should select a ROP = 90 sets with a SS = 30 sets
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We Scroll Down ToINVENTORY
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WE SELECT THE SUB MENUWE SELECT THE SUB MENU““Reorder Point / Safety Stock”Reorder Point / Safety Stock”
( Discrete Distribution )( Discrete Distribution )
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THE DIALOG BOXTHE DIALOG BOXAPPEARSAPPEARS
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THERE ARE SIX ( 6 ) DEMANDSTHERE ARE SIX ( 6 ) DEMANDSTHAT CAN OCCUR THAT CAN OCCUR DURING LEADTIMEDURING LEADTIME
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THE DATA INPUT TABLE REQUIRES:THE DATA INPUT TABLE REQUIRES:
- STARTING REORDER POINT WHERESTARTING REORDER POINT WHERE THE SAFETY STOCK IS ZERO ( 0 )THE SAFETY STOCK IS ZERO ( 0 )
- CARRY COST PER UNIT PER YEARCARRY COST PER UNIT PER YEAR
- STOCKOUT COST PER UNIT PER YRSTOCKOUT COST PER UNIT PER YR
- NUMBER OF ORDERS PER YEAR ( 7 )NUMBER OF ORDERS PER YEAR ( 7 )
THE DISCRETE THE DISCRETE PROBABILITYPROBABILITY
DISTRIBUTION OF DISTRIBUTION OF LEAD TIME DEMANDLEAD TIME DEMAND
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THE ROP = 90 SETSTHE ROP = 90 SETSTHE SS = 30 SETSTHE SS = 30 SETS
Expected Stockout Cost = $0.00Expected Stockout Cost = $0.00
Carry ( Holding ) Costs = $150.00Carry ( Holding ) Costs = $150.00