system定期订购系统

CHAPTER9InventoryManagement-1FiveLearningObjectivesTodetermine(計算)thecostsofholdinginventoryToidentifythecostsassociatedwithastockoutTounderstandtheEOQconcept2TodifferentiatethevariousinventoryflowpatternsToappreciatetheroleofscannersininventorycontrol317KeyTermsABCanalysisEconomicorderquantity(EOQ)Fixedorderintervalsystem定期訂購系統Fixedorderquantitysystem定量訂購系統HandlingcostsInsurancecostsInventorycarrying(holding)costs存貨(持有)成本Inventoryshrinkage存貨損耗4Marginalanalysis邊際效益分析ObsolescenceOpportunitycostReorderpoint(ROP)SafetystocksStockoutsStoragecosts儲存成本TaxesVendor-managedinventory(VMI)供應商庫存管理5content9.1InventoryClassifications9.2Inventory-RelatedCosts9.3WhentoOrder9.4HowMuchtoReorder9.5InventoryFlows9.6Contemporary(當代)ApproachestoManagingInventory9.7InventoryManagement:SpecialConcerns6InventoryManagementInventoriesarestocksofgoodsandmaterialsthataremaintainedtosatisfynormaldemandpatternsInventorymanagementDecisionsdriveotherlogisticsactivitiesDifferentfunctionalareashavedifferentinventoryobjectivesEx:financevs.marketingdept.7InventorycostsareimportanttoconsiderInventoryturnover:costofgoodssolddividedbyaverageinventoryatcost

costofgoodssold=inventoryturnover averageinventoryEx: $200,000=inventoryissold4timesperyear…愈大愈好 $50,000Comparewithcompetitorsorbenchmarkedcompanies8Lowinventoryturnover=highinventorycarryingcosts,little(orno)stockoutcostsHighinventoryturnover=lowinventorycarryingcosts,highstockoutcostsManagingthetradeoffisimportanttomaintainservicelevels99.1InventoryClassificationsPsychicstock精神庫存(stimulatesdemand!):如零售店架上存貨、看到會想買！Cycleorbasestock週期/基礎庫存：為一般需求之採買Safetyorbufferstock安全/緩衝庫存：週期存貨外、應付不確定需求之存貨Pipelineorin-transitstock管線/過渡庫存：供應鏈上不同倉庫間之存貨Speculativestock推測庫存：應付季節性需求、漲價預期等之存貨109.2Inventory-RelatedCostsInventorycarrying(holding)costs：包含下列因素Obsolescence過時Inventoryshrinkage：入庫數大於出庫數Storagecosts：如空間成本HandlingcostsInsurancecostsTaxes………通常當天的存貨要壓低Interestcharges利息成本Opportunitycost＝備料錯誤之成本Stockouts(costs)…asshownintable9-111Table9-1:DeterminationoftheAverageCostofaStockoutAlternative(種類)LossProbabilityAverageCost1.Brand-loyalcustomer$00.00.10

$00.002.Switches(向別家買)andcomesback$37.00.65

$24.053.Lostcustomer(損失顧客)$1,200.25

$

300.00Averagecostofastockout1.00$324.05Thesearehypotheticalfigures(假設數字)forillustration.12由前表可知，Stockouts(costs)愈高之品、需要準備愈多之safetystock13Trade-offsexistbetweencarryingandstockoutcostsMarginalanalysis：找出讓存貨持有成本與缺貨成本相同之(安全)存貨水準!Asshownintable9-214Table9-2:DeterminationofSafetyStockLevelNumberofUnitsofSafetyStockTotalValueofSafetyStock($480perUnit)25%AnnualCarryingCostCarryingCostofIncrementalSafetyStockNumberofAdditionalOrders(Filled)AdditionalStockoutCostsAvoided(節省)10$4,800$1,200$1,20020$6,481.0020

9,600

2,400

1,20016

5,184.803014,400

3,600

1,20012

3,888.604019,200

4,800

1,2008

2,592.405024,000

6,000

1,2006

1,944.306028,800

7,200

1,2004

1,296.207033,600

8,400

1,2003

972.15159.3WhentoOrderFixedorderquantitysystemFixedorderintervalsystemReorderpoint(ROP)ROP=DDxRCundercertaintyROP=(DDxRC)+SSunderuncertaintyWhereDD=dailydemand RC=lengthofreplenishmentcycle SS=safetystock169.4HowMuchtoReorderEconomicorderquantity(EOQ)indollars

EOQ=√(2AB/C) Where EOQ=themosteconomicordersize,in dollars A=annualusage(用量),indollars B=administrativecostsperorderof placingtheorder C=carryingcostsoftheinventory(%：每年存貨成本之百分比)17Economicorderquantity(EOQ)inunits

EOQ=√(2DB/IC) Where EOQ=themosteconomicordersize,inunits A=annualdemand,inunits B=administrativecostsperorderofplacingthe order C=carryingcostsoftheinventory(%) I=dollarvalueoftheinventory,perunit18Figure9-2:DeterminingEOQbyUseofaGraph19Table9-3:EOQCostCalculationsNumberoforders(訂購)peryearOrdersize($)Orderingcost($)Carryingcost($)Totalcost(sumoforderingandcarryingcost)($)11,000

251001252

500

50

501003

333

75

331084

250

100

251255

200

125

2014520簡單的EOQ公式無考慮購量大之下的折扣因素EOQ中假設需求是連續、不受時間影響的（確定的需求模式！）219.5InventoryFlowsSafetystockcanpreventagainsttwoproblemareasIncreasedrateofdemandLonger-than-normalreplenishment(補貨延誤)如後圖22Figure9-3:InventoryFlowDiagram23由前圖可知，若原本在第十四天會到的貨延至第十五天才到，因此第十四天的30單位貨由安全存貨支應（M點），隨後EOQ到貨24WhenfixedorderquantitysystemlikeEOQisused,timebetweenordersmayvaryWhenreorderpointisreached,fixedorderquantityisordered……電腦化設定reorderpoint!259.6Contemporary(當代)ApproachestoManagingInventoryABCAnalysis有些企業會加入D等級貨、像是dogs（看門狗）或deadinventory（呆貨）之意味：表已無需求之存貨、只增加存貨持有成本！使用ABCAnalysis需謹記：A等級之品不可過多！否則分類管理之技巧便無意義26Just-inTime(JIT)Approach：將存貨視為浪費(注重原物料流動！),ex:supplierparkJust-in-case(JIC)：將存貨視為應變突發需求之保障Leaninventory（臨界存貨、精敏存貨）：著重製造商與零售商間產品、存貨流動。如ECR（用於飲料業、零售業）與QR（用於成衣業）27Vendor-ManagedInventory(VMI):供應商決定下單的時