chapter 13 planifikimi dhe kontrolimi i rezerves
TRANSCRIPT
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Chapter 13 -Chapter 13 -
Planifikimi dhe Planifikimi dhe kontrolli i kontrolli i rezervësrezervës
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Objectives
• Describe the cost and service trade-offs involved in inventory decisions.
• Distinguish between the different types of inventory and know how to manage their quantities.
• Compute the economic order quantity and apply it in various situations.
• Develop policies for both the continuous review and the periodic review inventory control systems.
• Identify ways to maintain accurate inventory records.
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Përse mbahen rezervat ? Rezervat shërbejnë për disa funksione që
rrisin fleksibilitetin e operacioneve të firmës. 1) Për të rritur efiçencën e operacionit (për të
shpërndarë koston fikse të blerjes apo të pregaditjes, prodhimin,dhe për të niveluar dhe stabilizuar prodhimin)
2) Për ti dhënë një përgjigje të shpejtë klientit (Duke mbajtur rezerva të produktit përfundimtarë,Rezervat në lëndë të para dhe prodhim në proçes)
3) Për të dhene siguri kundrejtë pasigurive normale të biznesit, (Pasiguritë në sistemin e furnizimit,Ngritjet e
paparashikuara në kërkesë) dhe 4) Për të përfituar nga mundësitë për çmimet jo të
zakonshme apo për tu mbrojtur risqeve të binesit (Rezerva spekulative)
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Eficenca ekonomike
• Duke e shpërndarë koston fikse të blerjes apo të pregaditjes
• Për të ndarë prodhimin
• Për të niveluar dhe stabilizuar prodhimin
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Përgjigje e shpejtë për klientin
• Duke mbajtur rezerva të produktit përfundimtarë
• Rezervat në lëndë të para dhe prodhim në proçes
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Reduktimin e riskut dhe rritjen e sigurisë
• Pasiguritë në sistemin e furnizimit
• Ngritjet e paparashikuara në kërkesë
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Mbrojtja ndaj ngjarjeve jo të zakonshme
• Rezerva spekulative
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Shpenzimet që lidhen me rezervat
KOSTOT KRYESORE
• Kosto e mbajtjes - associated with holding or “carrying” inventory over time
• Kosto e porositjes ose e pregaditjes - associated with costs of placing order and receiving goods
• Kosto e mungesës apo e mbarimit të rezervës - cost to prepare a machine or process for manufacturing an order
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Kostoja e mbajtjesKostoja e mbajtjes
Kosto oportune e kapitalit Kosto e ruajtjes (magazinimi) Taksat dhe siguracionet Prishjet,vjedhjet,dëmtimet dhe
mungesat dhe Kostoja e transportimit
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Kosto e porositjes ose pergaditjes
• Numri i njesive per tu porositur ose prodhuar ne nje kohe eshte funksion I kostosfikse te blerjes.
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Llojet e rezervësLlojet e rezervës• Balancimi ndërmjet sasisë së furnizimit dhe
kërkesës në momente të ndryshme për çdo operacion në llojë të ndryshme të rezervës.
1.Rezerva e sigurisë(të kompensoje pasigurite qe ndodhin ne furnizim dhe kerkese)
2.Rezerva periodike(per shkake se nje ose me teper faza te operacionit nuk munde te furnizoje te gjithe artikujte qe prodhohen njekohesisht)
3.Rezerva parashikuara (per te konpensuar mdryshimet ne
kohen ndermjet furnizimit dhe kerkeses )dhe 4.Rezerva në transit(ekzistone per shkake se materiali
nuk munde te transportohet menjehere ndermjet momentit te furnizimit dhe atije te kerkeses
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Llojet e rezervësLlojet e rezervës
Cycle inventory = Q/2= 280/2= 140 drills
Pipeline inventory = DL = dL= (70 drills/week)(3 weeks)= 210 drills
Example 13.1
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Llojet e rezervësLlojet e rezervës
Figure 13.1
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Analiza ABC• Kjo analiza ndan rezervat ne dispozicion ne tre
klasifikime A class, B class, C class
• Bazën e volumit vjetore në vlerë– $ volume = Kerkesën vjetore (per cdo art..rez) x
koston per njesi• Politikat që mundë të bazohen në analizen ABC
- Burimet e blerjes per zhvillimin e furnitorit duhet te jene shume me te larta per artikujt individual A
- Artikujt A duhet te kene kontrolle me te shpeshta fizike
– Parashikimi i artikujve A munde te argumentotohet më me kujdesë.
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% of Inventory Items
Classifying Items as ABC
0
20
40
60
80
100
0 50 100
% Annual $ Usage
AABB CC
Class % $ Vol % ItemsA 80 15B 15 30C 5 55
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• Ndermarrja mundë të ketë bërë përpekje të konsiderueshme për të regjistruar me saktësi rezervën këto regjistirime duhet të verifikohen nëpërmjet një auditimi të vazhdueshëm.
• Used often with ABC classification– A duhet te numrohen shpesh (e.g.,muaj) – B duhet te numrohen jo shumë shpesh (e.g.,3 muaj) – C duhet te numrohen ndoshta një herë (e.g.,6 muaj)
Numërimi Periodik
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Numërimi periodik ka keto avantazhe
• Eliminon mbylljen dhe nderprerjen e prodhimit që është e nevojshme për inventarizmet fizike vjetore
• Eliminon rregulimet vjetore te rezervës
• Personeli I trajnuar auditon saktësine e rezervës.
• Lejon që të identifikohet shkaku I gabimeve dhe veprimet regulluese te ndermeren.
• Mban regjistrime te sakta te rezerves.
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Teknikat që aplikohen përfshijnë• Zgjedhja,trajnimi dhe diciplina e mirë
personelit
• Kontrolli i shtrënguar i ngarkesave që hyjne duke e krahasuar ato me porositë e blerjes
• Kontrolli efektiv i gjithë mallrave që dalin nga njësia
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Analiza ABCAnaliza ABC
10 20 30 40 50 60 70 80 90 100
Percentage of items
Per
cen
tag
e o
f d
oll
ar v
alu
e
100 —
90 —
80 —
70 —
60 —
50 —
40 —
30 —
20 —
10 —
0 —
Figure 13.2
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Analiza ABCAnaliza ABC
10 20 30 40 50 60 70 80 90 100
Percentage of items
Per
cen
tag
e o
f d
oll
ar v
alu
e
100 —
90 —
80 —
70 —
60 —
50 —
40 —
30 —
20 —
10 —
0 —
Figure 13.2
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Analiza ABCAnaliza ABC
10 20 30 40 50 60 70 80 90 100
Percentage of items
Per
cen
tag
e o
f d
oll
ar v
alu
e
100 —
90 —
80 —
70 —
60 —
50 —
40 —
30 —
20 —
10 —
0 —
Class C
Class A
Class B
Figure 13.2
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Analiza ABCAnaliza ABC
10 20 30 40 50 60 70 80 90 100
Percentage of items
Per
cen
tag
e o
f d
oll
ar v
alu
e
100 —
90 —
80 —
70 —
60 —
50 —
40 —
30 —
20 —
10 —
0 —
Class C
Class A
Class B
Figure 13.2
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Analiza ABCAnaliza ABC
10 20 30 40 50 60 70 80 90 100
Percentage of items
Per
cen
tag
e o
f d
oll
ar v
alu
e
100 —
90 —
80 —
70 —
60 —
50 —
40 —
30 —
20 —
10 —
0 —
Class C
Class A
Class B
Figure 13.2
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Analiza ABCAnaliza ABC
10 20 30 40 50 60 70 80 90 100
Percentage of items
Per
cen
tag
e o
f d
oll
ar v
alu
e
100 —
90 —
80 —
70 —
60 —
50 —
40 —
30 —
20 —
10 —
0 —
Class C
Class A
Class B
Figure 13.2
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Kërkesa e panvarur kundrejt asaj të varur
• Kërkese e pamvarur – kerkesa ose perdorimi i artikujve nuk munde te lidhet me ate te nje produkt tjetër
• Kërkese e varur - kerkesa per nje artikull shoqërohet direkt me kerkesen për nje artikull tjetër.
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MODELI I SASISË EKONOMIKE TË POROSISË
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Kur të bëhet porosiaKur të bëhet porosia Sa duhet të porositetSa duhet të porositet
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Sasia ekonomike e porosisSasia ekonomike e porosisë(EOQ)ë(EOQ)
KKa një aplikim mjaft të gjerë dhe a një aplikim mjaft të gjerë dhe mundë të përdoret per planifikim e mundë të përdoret per planifikim e blerjen të lëndëve të para dhe në blerjen të lëndëve të para dhe në planifikimin e blerjeve të shitësit me planifikimin e blerjeve të shitësit me shumicë dhe pakicë të cilët rishesin shumicë dhe pakicë të cilët rishesin produktet.produktet.
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Sasia ekonomike e porosisSasia ekonomike e porosisëë
1. Kërkesa ose përdorimi i artikullit është relativisht konstant gjatë kohës me nje tregues D njësi për njësi kohe
2. Çmimi i artikullit p është i pamvarur nga sasia e porositur(pra nuk do të kemi diskaunte për sasie blerje.
3. Ekziston një kosto fikse kf për kryerjen e porosisë që është e pamvarur nga sasia e porositur Q
4. Kosto e mbajtjes së rezervave është proporcionale me sasinë që ruhet, pra kosto e mbajtjes për njësi kohe,kh është e pamvarur nga niveli i rezervës.
5. Nuk lejohen mungesat,e gjithë kërkesa duhet të kënaqet kur kërkohet.
6. Koha e levrimit (LT) për shpërndarjet 7. Gjithë artikujt e porositur shpërndahen në të njejtën kohë
Supozimet e modelit bazë EOQ janë
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Sasia ekonomike e porosisSasia ekonomike e porosisëëkostoja e mbajtjes vjetore=(average cycle inventory)(unit holding cost)kostoja e mbajtjes vjetore=(average cycle inventory)(unit holding cost)
On
-han
d i
nve
nto
ry (
un
its)
Koha
Averagecycleinventory
Q
Q—2
1 cycle
Receive order
Inventory depletion (demand rate)
Figure 13.3
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• Kosto e mbajtjes = Q/2*(H)
• Kost e porosotijes = D/Q *(S)
• Kosto totale = Q/2*(H) +D/Q*(S)
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Economic Order QuantityEconomic Order QuantitySasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
os
t (d
olla
rs)
Sasia porosisë (Q)
Kosto e porositjes (OC)
Kosto e mbatjes (HC)
Kosto totale = HC + OC
Figure 13.4
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Sasia e porosisë (Q)
3000 —
2000 —
1000 —
0 —
Kosto totale = (H) + (S)DQ
Q2
Kosto e mbajtjes = (H)Q2
Kost e porosotijes = (S)DQ
An
nu
al c
ost
(d
oll
ars)
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
ost
(d
oll
ars)
| | | | | | | |50 100 150 200 250 300 350 400
3000 —
2000 —
1000 —
0 —
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Lot Size (Q)
Birdfeeder costs
C = (H) + (S)Q2
DQ
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 390 units
Example 13.2
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
ost
(d
oll
ars)
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
C = (H) + (S)Q2
DQ
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 390 units
C = $2925 + $108 = $3033
Example 13.2
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
ost
(d
oll
ars)
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
C = (H) + (S)Q2
DQ
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 390 units
C = $2925 + $108 = $3033
Example 13.2
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
ost
(d
oll
ars)
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
C = (H) + (S)Q2
DQ
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 390 units
C = $2925 + $108 = $3033
Example 13.2
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
ost
(d
oll
ars)
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
C = (H) + (S)Q2
DQ
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 468468 units
Example 13.2
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
An
nu
al c
ost
(d
oll
ars)
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
C = (H) + (S)Q2
DQ
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 468468 units
C = $3510 + $90 = $3600
Example 13.2
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Figure 13.4
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = EOQ
C = (H) + (S)Q2
DQEOQ =
2DSH
Example 13.3
An
nu
al c
ost
(d
oll
ars)
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
C = (H) + (S)Q2
DQEOQ =
2DSH
Example 13.3
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
C = $562 + $562 = $1124
C = (H) + (S)Q2
DQEOQ =
2DSH
Example 13.3
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
C = $562 + $562 = $1124
C = (H) + (S)Q2
DQEOQ =
2DSH
Example 13.3
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Bird feeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
C = $562 + $562 = $1124
C = (H) + (S)Q2
DQEOQ =
2DSH
Lowestcost
Best Q(EOQ)
Example 13.3
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Lowestcost
Best Q(EOQ)
Example 13.3
An
nu
al c
ost
(d
oll
ars)
Bird feeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
C = $562 + $562 = $1124
C = (H) + (S)DQ
Q2EOQ =
2DSH
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Birdfeeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
C = $562 + $562 = $1124
C = (H) + (S)DQ
Q2EOQ =
2DSH
Lowestcost
Best Q(EOQ)
Example 13.3
DQ
Time between orders
TBOEOQ = = 75/936 = 0.080 yearEOQ
D
An
nu
al c
ost
(d
oll
ars)
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Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
CurrentQ
Total cost = (H) + (S)DQ
Q2
Birdfeeder costs
D = (18 /week)(52 weeks) = 936 unitsH = 0.25 ($60/unit) = $15S = $45 Q = 75 units
Lowestcost
Best Q(EOQ)
Time between orders
TBOEOQ = = 75/936 = 0.080 year
TBOEOQ = (75/936)(12) = 0.96 months
TBOEOQ = (75/936)(52) = 4.17 weeks
TBOEOQ = (75/936)(365) = 29.25 days
EOQD
Example 13.3
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Economic Order Quantity Economic Order Quantity Sasia ekonomike e porosisSasia ekonomike e porosisëë
| | | | | | | |50 100 150 200 250 300 350 400
Lot Size (Q)
3000 —
2000 —
1000 —
0 —
Currentcost
Lowestcost
Best Q(EOQ)
CurrentQ
Total cost = (H) + (S)DQ
Q2
Holding cost = (H)Q2
Ordering cost = (S)DQ
Figure 13.5
An
nu
al c
ost
(d
oll
ars)
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Ushtrim
• Nje firme perdore rreth 1500 njesi te nenelementi ne vite me nje kosto mbajtje 45$ per njesi.Bërja e cdo porosie kushtone 150$.Firama vepron 300 dite ne vit dhe ka percaktuar qe nje porosi duhet te bëhet me furnitorin e saj 6 dite përpara se ajo parashikon qe te marre atë porosi.Gjeni per kete element.
a) Sasine ekonomikeb) Koston vjetore të mbajtjesc) Koston vjetore të porositjesd) Momentin e riporositjes
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zgjedhje
a)EOQ=√2DS/H= √2*1500*150/45=100 nje
b)Q/2*H=100/2=2250$
c)D/Q*S=1500/100=2250$
d) RP=D*LT=d*l =1500/300*6=30 njesi
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How How Much?Much? When!When!
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Continuous ReviewContinuous Review So
up Sou
pS
ou
p
Time
Figure 13.7
On
-han
d i
nve
nto
ry
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Continuous ReviewContinuous Review So
up Sou
pS
ou
p
Time
R
Orderreceived
Q
OH
Figure 13.7
On
-han
d i
nve
nto
ry
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Continuous ReviewContinuous Review So
up Sou
pS
ou
p
Orderreceived
Q
OH
Orderplaced
IP
TBO
L
R
Figure 13.7
On
-han
d i
nve
nto
ry
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Continuous ReviewContinuous Review So
up Sou
pS
ou
p
Time
Orderreceived
Orderreceived
Q Q
OH OH
Orderplaced
Orderplaced
IP IP
TBO
L
TBO
L
TBO
L
R
Orderreceived
Q
OH
Orderplaced
IP
Orderreceived
Figure 13.7
On
-han
d i
nve
nto
ry
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Continuous ReviewContinuous Review So
up Sou
pS
ou
p
On
-han
d i
nve
nto
ry
Time
Orderreceived
Orderreceived
Q Q
OH OH
Orderplaced
Orderplaced
IP IP
TBO
L
TBO
L
TBO
L
R
Orderreceived
Q
OH
Orderplaced
IP
Orderreceived
Example 13.4
Chicken Soup
R = Average demand during lead time
= (25)(4) = 100 cases
IP = OH + SR – BO= 10 + 200 – 0 = 210 cases
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Uncertain DemandUncertain Demand
Time
On
-han
d i
nve
nto
ry
Orderreceived
Q
OH
Orderplaced
Orderplaced
Orderreceived
IPIP
R
TBO1 TBO2 TBO3
L1 L2 L3
Q
Orderplaced
Q
Orderreceived
Orderreceived
Figure 13.6
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
ushtrim• Në nje ``bar restorant``sherbehet birre. Kerkesa
ditore për birrë zakonisht shperndahet me nje mesatare prej 18 fuÇi me nje mungese 4 fuci.Koha e levrimit që kërkohet per te mare nje porosi birrë nga distributori lokal është 3 dite.Percaktoni rezervën e sigurisë dhe momentin e riporositjes nëse lokali kërkonë qe te ruaje një nivel shebimi 90%.Sa do te jete rritja ne rezervën e sigurisë, nese deshirohet një nivel shebimi 95%.
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Lead Time Distribution sld =90%
δt = 4 d = 18 L = 3 dite
L = t L = 4 3 = 6.93
Rezerva e sigurisë = zL = 1.28*6,93= 8.86njesi ose 9 njesi
Momentin e riporositjes = dL + rezerva e sigurisë = 3(18) + 9 = 63 njesi
dL=kerkesa mesatare gjate kohes se levrimit
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• SLd= niveli I sherbimit te kerkuar
SLd =(kerkesa vjetore- numrin mesatar te njesive te munguara ne vite)/kerkesa vjetore*100%
SLd=95% nga tabela z=1.64
Rezerva e sigurisë= zsL= 1.64*6,93= 11.3 ose 11njesi
Momentin e riporositjes = dL + rezerva e sigurisë = 3(18) + 11 = 65 njesi
Sa here rezervat bie ne nivelin 65 njesi,bejme nje porosi
Shohim qe kure sld=95% ss dhe RP jane me te larta.
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Probability of stockout(1.0 - 0.85 = 0.15)
Cycle-service level = 90%
Average demand
during lead time
zL
R
Reorder Point / Safety StockReorder Point / Safety Stock
Probability of stockout
(1.0 – 0.90 =0.10)
Example 13.5
Safety Stock/R
Safety stock = zL
= 1.28*6,93 = 8.86= 9 njesi
Reorder point = ADDLT + SS= 54 + 9= 63 njesi
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Probability of stockout(1.0 - 0.85 = 0.15)
Cycle-service level = 95%
Average demand
during lead time
zL
R
Reorder Point / Safety StockReorder Point / Safety Stock
Probability of stockout
(1.0 – 0.95 =0.05)
Example 13.5
Safety Stock/R
Safety stock = zL
= 1.64*6,93= 11.3
ose 11njesi
Reorder point = ADDLT + SS= 3(18) + 11
= 65 njesi
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Lead Time DistributionsLead Time Distributions
Figure 13.10
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
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Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Bird feeder Lead Time Distribution
To Accompany Krajewski & Ritzman Operations Management: Strategy and Analysis, Sixth Edition © 2002 Prentice Hall, Inc. All rights reserved.
Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Bird feeder Lead Time Distribution
t = 1 week d = 18 L = 2
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Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Bird feeder Lead Time Distribution
t = 1 week d = 18 L = 2
L = t L = 5 2 = 7.1
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Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Bird feeder Lead Time Distribution
t = 1 week d = 18 L = 2
L = t L = 5 2 = 7.1
Safety stock = zL = 1.28(7.1) = 9.1 or 9 units
Reorder point = dL + Safety stock= 2(18) + 9 = 45 units
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Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Bird feeder Lead Time Distribution
t = 1 week d = 18 L = 2Reorder point = 2(18) + 9 = 45 units
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Lead Time DistributionsLead Time Distributions
Example 13.6
t = 15
=
+
+75
Demand for week 1
75Demand for week 2
75Demand for week 3
t = 26
225Demand for
three-week lead time
t = 15
t = 15
Bird feeder Lead Time Distribution
t = 1 week d = 18 L = 2Reorder point = 2(18) + 9 = 45 units
C = ($15) + ($45) + 9($15)75
2
936
75
C = $562.50 + $561.60 + $135 = $1259.10
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Periodic Review SystemsPeriodic Review Systems
Time
On
-han
d i
nve
nto
ry
IP1
IP3
IP2
Orderreceived
Orderreceived
IP IP
OH OH
Orderplaced
Orderplaced
Q1Q2
Q3
L L LP P
Protection interval
T
Orderreceived
IP
Figure 13.11
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Time
On
-han
d i
nve
nto
ry
IP1
IP3
IP2
Orderreceived
Orderreceived
IP IP
OH OH
Orderplaced
Orderplaced
Q1Q2
Q3
L L LP P
Protection interval
T
Orderreceived
IP
Periodic Review SystemsPeriodic Review Systems
Orderreceived
IPTV Set - P System
IP = OH + SR – BO
Qt = T - IPt
T = 400 BO = 5OH = 0 SR = 0
IP = 0 + 0 – 5 = –5 sets
Q = 400 – (–5) = 405 sets
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Periodic Review SystemsPeriodic Review Systems
Example 13.7
Time
On
-han
d i
nve
nto
ry
IP1
IP3
IP2
Orderreceived
Orderreceived
IP IP
OH OH
Orderplaced
Orderplaced
Q1Q2
Q3
L L LP P
Protection interval
T
Orderreceived
IP
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Time
On
-han
d i
nve
nto
ry
IP1
IP3
IP2
Orderreceived
Orderreceived
IP IP
OH OH
Orderplaced
Orderplaced
Q1Q2
Q3
L L LP P
Protection interval
T
Orderreceived
IP
Periodic Review SystemsPeriodic Review Systems
Example 13.8
T = Average demand during the protection interval + Safety stock
= d (P + L) + zP + L
= (18 units/week)(16 weeks) + 1.28(12 units) = 123 units
EOQ = 75 units D = (18 units/week)(52 weeks) = 936 units
t = 18 units L = 2 weeks cycle/service level = 90%
Bird feeder—Calculating P and T
P = (52) = (52) = 4.2 or 4 weeksEOQ
D75
936
P+L = P + L = 5 6 = 12 units
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Time
On
-han
d i
nve
nto
ry
IP1
IP3
IP2
Orderreceived
Orderreceived
IP IP
OH OH
Orderplaced
Orderplaced
Q1Q2
Q3
L L LP P
Protection interval
T
Orderreceived
IP
Periodic Review SystemsPeriodic Review Systems
Example 13.8
EOQ = 75 units D = (18 units/week)(52 weeks) = 936 units
t = 18 units L = 2 weeks cycle/service level = 90%
Bird feeder—Calculating P and T
P = 4 weeks T = 123 units
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Time
On
-han
d i
nve
nto
ry
IP1
IP3
IP2
Orderreceived
Orderreceived
IP IP
OH OH
Orderplaced
Orderplaced
Q1Q2
Q3
L L LP P
Protection interval
T
Orderreceived
IP
Periodic Review SystemsPeriodic Review Systems
Example 13.8
EOQ = 75 units D = (18 units/week)(52 weeks) = 936 units
t = 18 units L = 2 weeks cycle/service level = 90%
Bird feeder—Calculating P and T
C = ($15) + ($45) + 15($15)4(18)
2936
4(18)
C = $540 + $585 + $225 = $1350
P = 4 weeks T = 123 units
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Analiza ABC — Solved Problem 2Analiza ABC — Solved Problem 2