庫存決策培訓(xùn)教材

1、庫存決策CR (2004) Prentice Hall, Inc.Chapter 9每一個(gè)管理上的失誤最后都會(huì)變成庫存。“Every management mistake ends up in inventory.” Michael C. Bergerac Former Chief Executive Revlon, Inc.1產(chǎn)品計(jì)劃三角形產(chǎn)品計(jì)劃三角形Product in the Planning TriangleCR (2004) Prentice Hall, Inc.PLANNINGORGANIZINGCONTROLLINGTransport Strategy Transport fu

2、ndamentals Transport decisionsCustomer service goals The product Logistics service Ord . proc. & info. sys.Inventory Strategy Forecasting Inventory decisions Purchasing and supply scheduling decisions Storage fundamentals Storage decisionsLocation Strategy Location decisions The network planning

3、 process 計(jì)劃計(jì)劃 組織組織 控制控制Transport Strategy Transport fundamentals Transport decisionsCustomer service goalsThe product Logistics service Ord . proc. & info. sys.Inventory Strategy Forecasting Inventory decisions Purchasing and supply scheduling decisions Storage fundamentals Storage decisionsLoca

4、tion Strategy Location decisions The network planning process 庫存戰(zhàn)略 預(yù)測客戶服務(wù)目標(biāo)采購和供應(yīng)時(shí)間決策存儲(chǔ)基礎(chǔ)知識存儲(chǔ)決策產(chǎn)品物流服務(wù)訂單管理和信息系統(tǒng) 庫存決策 運(yùn)輸戰(zhàn)略 運(yùn)輸基礎(chǔ)知識 運(yùn)輸決策 選址戰(zhàn)略 選址決策 網(wǎng)絡(luò)規(guī)劃流程2Inventory Decisions in StrategyCR (2004) Prentice Hall, Inc.PLANNINGORGANIZINGCONTROLLINGTransport Strategy Transport fundamentals Transport decisionsC

5、ustomer service goals The product Logistics service Ord. proc. & info. sys.Inventory Strategy Forecasting Inventory decisions Purchasing and supply scheduling decisions Storage fundamentals Storage decisionsLocation Strategy Location decisions The network planning processPLANNINGORGANIZINGCONTRO

6、LLINGTransport Strategy Transport fundamentals Transport decisionsCustomer service goals The product Logistics service Ord. proc. & info. sys.Inventory Strategy Forecasting Inventory decisions Purchasing and supply scheduling decisions Storage fundamentals Storage decisionsLocation Strategy Loca

7、tion decisions The network planning process3CR (2004) Prentice Hall, Inc.什么是庫存什么是庫存What are Inventories?庫存就是在企業(yè)生產(chǎn)和物流渠道中各點(diǎn)堆積的原材料、供給品、零部件、半成品和成品。4CR (2004) Prentice Hall, Inc.Where are Inventories?MaterialsourcesInboundtransportationProductionOutboundtransportationFinished goodswarehousingCustomersInv

8、entory locationsFinished goodsShippingInventoriesin-processReceivingProductionmaterials9-4原料來源生產(chǎn)內(nèi)向運(yùn)輸外向運(yùn)輸成品儲(chǔ)存 客戶原材料半成品成品庫存選址5CR (2004) Prentice Hall, Inc.9.1對庫存的評述對庫存的評述9.1.1庫存原因庫存原因Reasons for Inventories1.改善客戶服務(wù)2.降低成本首先，保有庫存可以使生產(chǎn)的批量更大、批次更少，運(yùn)作水平更高，因而產(chǎn)生經(jīng)濟(jì)效益其次，保有庫存有助于實(shí)現(xiàn)采購和運(yùn)輸中的成本節(jié)約第三，先期購買可以在當(dāng)前交易的低價(jià)位購買額

9、外數(shù)量的產(chǎn)品。第四，抵銷生產(chǎn)和運(yùn)輸過程中的不確定性第五，應(yīng)付突發(fā)事件。6CR (2004) Prentice Hall, Inc.9.1對庫存的評述對庫存的評述9.1.1庫存原因庫存原因Reasons for InventoriesImprove customer service-Provides immediacy in product availabilityEncourage production, purchase, and transportation economies-Allows for long production runs-Takes advantage of price

10、-quantity discounts-Allows for transport economies from larger shipment sizesAct as a hedge against price changes-Allows purchasing to take place under most favorable price termsProtect against uncertainties in demand and lead times-Provides a measure of safety to keep operations running when demand

11、 levels and lead times cannot be known for sureAct as a hedge against contingencies-Buffers against such events as strikes, fires, and disruptions in supply7CR (2004) Prentice Hall, Inc.9.1.2反對保有庫存的原因反對保有庫存的原因Reasons Against Inventories第一，庫存被認(rèn)為是一種浪費(fèi)第二，庫存可能掩蓋質(zhì)量問題第三，保有庫存鼓勵(lì)人們以獨(dú)立的觀點(diǎn)來看待物流渠道整體的管理問題8CR (20

12、04) Prentice Hall, Inc.9.1.2反對保有庫存的原因反對保有庫存的原因Reasons Against InventoriesThey consume capital resources that might be put to better use elsewhere in the firmThey too often mask quality problems that would more immediately be solved without their presenceThey divert managements attention away from ca

13、reful planning and control of the supply and distribution channels by promoting an insular attitude about channel management9流通渠道流通渠道Pipeline （Inventories in transit）投機(jī)投機(jī)Speculative-Goods purchased in anticipation of price increases定期性或周期性特征定期性或周期性特征Regular/Cyclical/Seasonal-Inventories held to meet

14、 normal operating needs安全安全Safety-Extra stocks held in anticipation of demand and lead time uncertainties倉耗倉耗Obsolete/Dead Stock-Inventories that are of little or no value due to being out of date, spoiled, damaged, etc.9.2庫存類型庫存類型Types of Inventories10持久性需求持久性需求Perpetual demand-Continues well into

15、the foreseeable future季節(jié)性需求季節(jié)性需求Seasonal demand-Varies with regular peaks and valleys throughout the year尖峰需求尖峰需求Lumpy demand-Highly variable 規(guī)律性需求規(guī)律性需求Regular demand-Not highly variable (3 Mean)終端需求終端需求Terminating demandDemand goes to 0 in foreseeable future派生需求派生需求Derived demandDemand is determine

16、d from the demand of another item of which it is a part9.3庫存管理類型的分類庫存管理類型的分類9.3.1需求特點(diǎn)需求特點(diǎn)Nature of DemandAccurately forecasting demand is singly the most important factor in good inventory management11CR (2004) Prentice Hall, Inc.拉動(dòng)式庫存管理法拉動(dòng)式庫存管理法Pull-基于每個(gè)倉庫的特定需求以一定的訂貨批量補(bǔ)足庫存-每一個(gè)存儲(chǔ)點(diǎn)獨(dú)立Each stocking loc

17、ation is considered independent-最大化控制庫存Maximizes local control of inventories推動(dòng)式庫存管理法推動(dòng)式庫存管理法Push根據(jù)總需求分配產(chǎn)品到庫存點(diǎn)鼓勵(lì)規(guī)模生產(chǎn)準(zhǔn)時(shí)生產(chǎn)制準(zhǔn)時(shí)生產(chǎn)制Just-in-time同步庫存流量以滿足需求Attempts to synchronize stock flows so as to just meet demand as it occurs最小化庫存Minimizes the need for inventory9.3.2管理思想管理思想Inventory Management Philos

18、ophies12CR (2004) Prentice Hall, Inc.拉動(dòng)式庫存管理法拉動(dòng)式庫存管理法Pull-Draws inventory into the stocking location-Each stocking location is considered independent-Maximizes local control of inventories推動(dòng)式庫存管理法推動(dòng)式庫存管理法PushAllocates production to stocking locations based on overall demandEncourages economies of sc

19、ale in production準(zhǔn)時(shí)生產(chǎn)制準(zhǔn)時(shí)生產(chǎn)制Just-in-timeAttempts to synchronize stock flows so as to just meet demand as it occursMinimizes the need for inventory9.3.2管理思想管理思想Inventory Management Philosophies13CR (2004) Prentice Hall, Inc.供給驅(qū)動(dòng)供給驅(qū)動(dòng)Supply-Driven-供應(yīng)量和時(shí)間未知Supply quantities and timing are unknown-所有的供應(yīng)必須

20、接受和處理All supply must be accepted and processed-通過需求控制庫存Inventories are controlled through demand聯(lián)合控制聯(lián)合控制Aggregate Control項(xiàng)目分類項(xiàng)目組根據(jù)基于80-20法則確定的銷售水平為3個(gè)或以上的產(chǎn)品組合允許不同的庫存策略9.3.2管理思想管理思想Inventory Management Philosophies14PlantWarehouse #1Warehouse #2Warehouse #3A1A2A3A = Allocation quantity to each warehou

21、seQ = Requested replenishment quantity by each warehouseQ1Q2Q3DemandforecastDemandforecastDemandforecastPULL - Replenish inventory withorder sizes based on specific needsof each warehousePUSH - Allocate supply to eachwarehouse based on the forecastfor each warehouse拉動(dòng)式或推動(dòng)式庫存管理思想拉動(dòng)式或推動(dòng)式庫存管理思想Pull vs.

22、 Push Inventory PhilosophiesCR (2004) Prentice Hall, Inc.9-11推動(dòng)式基于每個(gè)倉庫的預(yù)測將供給分配給各個(gè)倉庫拉動(dòng)式基于每個(gè)倉庫的特定需求以一定訂貨批量補(bǔ)足庫存A將產(chǎn)品分配到各個(gè)倉庫Q每個(gè)倉庫需要的補(bǔ)貨量159.3.3產(chǎn)品匯總程度n多數(shù)庫存管理是針對每一種產(chǎn)品的庫存進(jìn)行控制。自下而上法n另一種方法是管理一類產(chǎn)品而不是管理單獨(dú)一種產(chǎn)品自上而下法169.3.4多層級庫存n供應(yīng)鏈管理鼓勵(lì)管理者將供應(yīng)渠道中更多的部分包括到計(jì)劃過程中來，供應(yīng)渠道中多個(gè)層級的庫存也成為核心問題。179.3.5虛擬庫存n虛擬庫存即將自己將來所可能需要而又沒有的東西的所

23、有相關(guān)信息建立檔案，包括品名規(guī)格價(jià)格數(shù)量等，在需要時(shí)能使用上。189.4庫存目標(biāo)庫存目標(biāo)Inventory Management ObjectivesGood inventory management is a careful balancing act between stock availability and the cost of holding inventory.Customer Service, i.e., Stock AvailabilityInventory Holding costsService objectives-Setting stocking levels so

24、that there is only a specified probability of running out of stockCost objectives-Balancing conflicting costs to find the most economical replenishment quantities and timingCR (2004) Prentice Hall, Inc.199.4.1產(chǎn)品的現(xiàn)貨供應(yīng)比率n服務(wù)水平n=1-每年產(chǎn)品缺貨件數(shù)的期望值/ 年需求總量 20CR (2004) Prentice Hall, Inc.采購成本采購成本Procurement co

25、sts-準(zhǔn)備訂單的成本Cost of preparing the order-訂單傳輸成本Cost of order transmission-產(chǎn)品安裝成本Cost of production setup if appropriate-接受地物料搬運(yùn)或加工成本Cost of materials handling or processing at the receiving dock-商品價(jià)格Price of the goods9.4.2庫存管理相關(guān)成本庫存管理相關(guān)成本Costs Relevant to Inventory Management21CR (2004) Prentice Hall,

26、 Inc.Relevant Costs (Contd)采購成本采購成本Procurement costs-Cost of preparing the order-Cost of order transmission-Cost of production setup if appropriate-Cost of materials handling or processing at the receiving dock-Price of the goods22CR (2004) Prentice Hall, Inc.庫存持有成本庫存持有成本Carrying costs-空間成本。庫存成本隨時(shí)間推

27、移-Cost for holding the inventory over time-資金成本。-庫存服務(wù)成本-庫存風(fēng)險(xiǎn)成本23CR (2004) Prentice Hall, Inc.9.4.2庫存管理相關(guān)成本庫存管理相關(guān)成本Costs Relevant to Inventory Management庫存持有成本庫存持有成本Carrying costs-Cost for holding the inventory over time-The primary cost is the cost of money tied up in inventory, but also includes ob

28、solescence（報(bào)廢）, insurance, personal property taxes, and storage costs-Typically, costs range from the cost of short term capital to about 40%/year. The average is about 25%/year of the item value in inventory.24CR (2004) Prentice Hall, Inc.Relevant Costs (Contd)缺貨成本缺貨成本Out-of-stock costs-銷售損失成本Lost

29、sales cost利潤損失Profit immediately foregone商譽(yù)損失Future profits foregone through loss of goodwill-缺貨成本Backorder cost額外訂單處理費(fèi)用Costs of extra order handling額外的運(yùn)輸和處理費(fèi)用Additional transportation and handling costs可能的安裝費(fèi)用Possibly additional setup costs25Inventorys Conflicting Cost PatternsCost補(bǔ)給量Replenishment

30、quantity缺貨成本Stockout cost采購成本Procurement cost庫存持有成本Carrying cost總成本Total cost最低訂貨成本最低訂貨成本Minimum costreorder quantityCR (2004) Prentice Hall, Inc.9-1626術(shù)語匯編術(shù)語匯編Glossary of Termssold being units of yprobabilit CPtime lead of deviation standard and average ,demand annual total of percent a as level se

31、rvice $ cost, relevant total units , or stock, safety ondistributi demand compound on mean from deviations standard of number or deviate normal units level, inventory target days e.g., interval, order units quantity, point reorder quantity order system-(P time cycle order plus time lead during or sy

32、stem)-(Q time lead during stock-in being of yprobabilit integral loss normal unit or nexpectatio partial ondistributi demand compound of deviation standardprice purchase unit per $ cost, stock-of-out units (d), demand of deviation standard unit per $ value, product year per % value, product of perce

33、nt a as costs carrying $/order order, per cost tprocuremen units demand, period average units demand, annual average n)(nsLTSLTCz x srzMAXTROPQPEspksCISdDLTzd=279.5推動(dòng)式庫存管理n1.通過預(yù)測或其他手段確定從現(xiàn)在到下一次生產(chǎn)或采購期間的需求量n2.找出每個(gè)存儲(chǔ)點(diǎn)現(xiàn)有的庫存量n3.設(shè)定每個(gè)存儲(chǔ)點(diǎn)庫存的現(xiàn)貨供應(yīng)水平n4.計(jì)算總需求n5.計(jì)算凈需求n6.在平均需求速率的基礎(chǔ)上，將超過總凈需求的部分分配到各存儲(chǔ)點(diǎn)n7.在凈需求加上分配的超量

34、部分得到需分配到每個(gè)存儲(chǔ)點(diǎn)的貨物總量289.6基本的拉動(dòng)式庫存管理n（1）需求是一次性的、高季度性的或持續(xù)性的情況n（2）訂貨程序在某一庫存水平上啟動(dòng)或由庫存盤點(diǎn)程序啟動(dòng)n（3）需求和補(bǔ)貨提前期存在不同程度不確定性的情況29CR (2004) Prentice Hall, Inc.9.6.1一次性訂貨量一次性訂貨量Single Order PurchasingMake a one-time purchase of an item. How much to order?Procedure: 平衡利潤增加額與損失增加額利潤 =單位價(jià)格-單位成本損失 = 單位成本-單位殘值如果考慮一定量產(chǎn)品被售出的

35、概率 CPn，預(yù)期收益和預(yù)期損失在以下點(diǎn)得到平衡 CPn x 損失 = (1 -CPn) x 利潤or CPn = 利潤/(利潤+ 損失)CPn代表至多售出n個(gè)單位產(chǎn)品的累積概率Daily stocking of newspapers in vending machines is a good example9-1830CR (2004) Prentice Hall, Inc.9.6.1一次性訂貨量一次性訂貨量Single Order PurchasingMake a one-time purchase of an item. How much to order?Procedure: Bala

36、nce incremental profit against incremental loss.Profit = Price per unit Cost per unitLoss = Cost per unit Salvage value per unitIf CPn is probability of n units being sold, then CPn x Loss = (1 CPn) x Profitor CPn = Profit/(Profit + Loss)Now, increase order quantity until CPn just matches cumulative

37、 probability of selling additional units.Daily stocking of newspapers in vending machines is a good example9-1831CR (2004) Prentice Hall, Inc.Single Order Purchasing (Contd)Example A clothing item is purchased for a seasonal sale. It costs $35, but it has a sale price of $50. After the season is ove

38、r, it is marked down by 50% to clear the merchandise. The estimated quantities to be sold are:Number ofitems, nProbability ofselling exactly nitemsCumulativeprobability100.150.15150.200.35200.300.65250.200.85300.100.95350.05 1.001.009-1932CR (2004) Prentice Hall, Inc.9.6.1一次性訂貨量一次性訂貨量Single Order Pu

39、rchasing (Contd)SolutionProfit = $50-35 = $15Loss = $35 -(0.5)(50) = $10CPn = 15/(15 + 10) = 0.60CPn is between 15 and 20 items, round up and order 20 items.332ICDS QQTC庫存持有成本采購成本9.6.2重復(fù)訂貨量重復(fù)訂貨量1.即刻補(bǔ)貨即刻補(bǔ)貨TC每年總的相關(guān)成本（美元）Q補(bǔ)充存貨的訂單批量（件）D對庫存產(chǎn)品的年需求量（件）S采購成本（美元/訂單）C庫存產(chǎn)品的價(jià)值（美元/件）I庫存持有成本占產(chǎn)品價(jià)值的比例（%/年）Develop a

40、 simple control system by finding the replenishment quantity (Q) and the reorder point (ROP).The relevant total cost is:總成本=采購成本和庫存成本注注:需求和提前期確定需求和提前期確定周期性的庫存管理周期性的庫存管理9-21342ICDS QQTC庫存持有成本采購成本9.6.2重復(fù)訂貨量重復(fù)訂貨量1.即刻補(bǔ)貨即刻補(bǔ)貨TC每年總的相關(guān)成本（美元）Q補(bǔ)充存貨的訂單批量（件）D對庫存產(chǎn)品的年需求量（件）S采購成本（美元/訂單）C庫存產(chǎn)品的價(jià)值（美元/件）I庫存持有成本占產(chǎn)品價(jià)值的比

41、例（%/年）Develop a simple control system by finding the replenishment quantity (Q) and the reorder point (ROP).The relevant total cost is:總成本=采購成本和庫存成本Note: No uncertainty in demand or lead timemanage regular (cycle) stock only9-2135CR (2004) Prentice Hall, Inc.0TimeLead timeLead timeOrder PlacedOrder

42、PlacedOrder ReceivedOrder ReceivedInventory LevelReorder point, RQReorder Point Method Under Certaintyfor a Single ItemQuantity on-hand plus on-order9-22369.6.2重復(fù)訂貨量重復(fù)訂貨量Given: d = 50 units/week I = 10%/year S = $10/order C = $5/unit LT = 3 weeksNote: No uncertainty in demand or lead timemanage regu

43、lar (cycle) stock only9-212.有提前期的補(bǔ)貨有提前期的補(bǔ)貨37CR (2004) Prentice Hall, Inc.Using differential calculus, the optimal value for Q will be:units 322)0)/(0.10 x52(50 x52)(1= 2DS/ICQ*The reorder point is: ROP = d(LT) = 3(50) = 150 unitsFamous EOQformulaRule When the inventory level drops to 150 units (ROP)

44、 then reorder 322 units (Q*).9-23383.對不準(zhǔn)確數(shù)據(jù)的敏感性n盡管我們不一定總能知道需求和成本的確切水平，經(jīng)濟(jì)訂貨批量的計(jì)算對估計(jì)錯(cuò)誤的數(shù)據(jù)并不敏感。394.非即刻補(bǔ)貨nEOQ模型中有一個(gè)基本假設(shè)，即任何訂貨批量都可以及時(shí)補(bǔ)進(jìn)。在有些制造和再供應(yīng)環(huán)節(jié)中，生產(chǎn)要持續(xù)一定時(shí)間，并且可能和需求同步進(jìn)行。np是生產(chǎn)速率，d是需求速率dppICDSQp=2*40CR (2004) Prentice Hall, Inc.9.7高級拉動(dòng)式庫存管理高級拉動(dòng)式庫存管理9.7.1需求不確定下的再訂貨點(diǎn)模型需求不確定下的再訂貨點(diǎn)模型1.計(jì)算計(jì)算Q*和和ROPIC2DS*QGood

45、method for products:1. Of high value2. That are purchased from one vendor or plant3. Having few economies of scale in production, purchasing, or transportation9-24Find Q* and ROP)(dszLTROPd41CR (2004) Prentice Hall, Inc.9.7高級拉動(dòng)式庫存管理高級拉動(dòng)式庫存管理9.7.1需求不確定下的再訂貨點(diǎn)模型需求不確定下的再訂貨點(diǎn)模型Given: d = 50 units/week C =

46、 $5/unit sd = 10 units/week LT = 3 weeks I = 10%/year P = 99% during lead time S = $10/orderFind Q* and ROPFrom the EOQ formulaunits 3220.10(5)0)2(50 x52)(1=*QGood method for products:1. Of high value2. That are purchased from one vendor or plant3. Having few economies of scale in production, purcha

47、sing, or transportation9-2442CR (2004) Prentice Hall, Inc.Reorder Point Control for a Single ItemROPQuantity on hand0QQReceive orderPlace orderStockoutLTTimeLTDDLTP9-2543CR (2004) Prentice Hall, Inc.ROPQ0Inventory levelLTLTTimeSafety stockReorder Point Control for a Single ItemActual on handQuantity

48、 on hand +on order backordersQuantity for control9-2644Weekly demand is normally distributed with a mean of d = 100 and a standard deviation of sd = 10Lead time is 3 weeksReorder Point Control (Contd)Finding the reorder point requires an understanding of the demand-during-lead-time distributionsd=10

49、d =100sd=10d =100sd=10d =100+=Week 3Week 2Week 1zPDDLTX = 300 ROP17.3310300100(3)=LTssLTdXdS=17.39-2745CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)units 190 )2.33(17.32150 Hence,units 32.17310units 150)3(50)(Now,=rXzsXROPLTssLTdXdwhere 2.33 is the normal deviate at a probability of 0.0

50、1 taken from a normal distribution table.462.平均庫存成本n平均庫存=經(jīng)常性庫存+安全庫存nA/L=Q/2+z(sd)n在前例中，n平均庫存=322/2+2.33*17.32=201(個(gè)）47Reorder Point Control (Contd)3.總相關(guān)成本Total relevant cost The total relevant cost equation is now extended to include the costs of safety stock as well as out-of-stock. The out-of-stoc

51、k cost (k) is $2/unit. The price term is dropped. Hence,20.182$)0034.0)(32.17(322600, 22)40)(5)(1.0(2322)5)(1.0(322)10(600, 22)(=zEsQDkICrQICQDSTCwhere E(z) = 0.0034 from a unit normal loss table at a z value of 2.339-29484.服務(wù)水平n服務(wù)水平n=1-每年產(chǎn)品缺貨件數(shù)的期望值/年需求總量( )( )( / )( ) ()11dzdzD Q sEsESLDQ= -= -49CR

52、 (2004) Prentice Hall, Inc.9.7.2缺貨成本已知情況下的再訂貨成本缺貨成本已知情況下的再訂貨成本W(wǎng)ith known stockout costs k如果缺貨成本已知，就沒必要規(guī)定客戶服務(wù)水平了，可以將服務(wù)和成本的最佳平衡點(diǎn)計(jì)算出來?？捎梅磸?fù)迭代的方法IC2DSQ=1 利用基本EOQ公式得出訂貨量的近似值Solve initially for Q2 通過下式計(jì)算提前期內(nèi)現(xiàn)貨供應(yīng)的概率Using Q, findDkQIC1P=如果缺貨允許If backordering is allowedorQICDkQIC1P=如果銷售出現(xiàn)損失If sales are lost50

53、CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)3 計(jì)算Q的修正值Using P, find revised QIC(z)Edks2DSQ=4 重復(fù)2,3步直到P和Q不再變化Repeat steps 2 and 3 until no further change5 計(jì)算ROP和其他所需的統(tǒng)計(jì)值Compute ROP and other statistics51CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)Example Given: 每月需求預(yù)測, d 11

54、,107 units預(yù)測標(biāo)準(zhǔn)差, sd 3,099 units補(bǔ)貨提前期, LT 1.5 months產(chǎn)品價(jià)值, C $0.11/unit處理訂單的成本, S $10/order庫存持有成本, I 20%/year缺貨成本, k $0.01/unitBackordering is allowed允許缺貨Find optimal Q and P52CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)Example Given: Monthly demand forecast, d 11,107 unitsStd. error of

55、forecast., sd 3,099 unitsReplenishment lead-time, LT 1.5 monthsItem value, C $0.11/unitCost for processing vendor order, S $10/orderCarrying cost, I 20%/yearStockout cost, k $0.01/unitBackordering is allowedFind optimal Q and P53CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)SolutionEstim

56、ate Qunits 11,0080.20(0.11)12)(10)2(11,107)(=IC2DSQEstimate P0.82(0.01)11,107(12)0)(0.11)11,008(0.21=DkQIC1PRevise QFind App A, z0.82=0.92 and from App B, E(0.92)=0.0968For these data, sd was previously calculated as 3,795 units54CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)units 12,872

57、0.20(0.11)(0.068)0.01(3,79512)(102(11,107)(=ICEksS2DQ(z) dRevise P0.79(0.01)11,107(12)0)(0.11)12,872(0.21P=Now, z0.79=0.81 and E(0.81)=0.118155CR (2004) Prentice Hall, Inc.Reorder Point Control (Contd)Revise Qunits 13,2460.20(0.11)(0.1181)0.01(3,79512)102(11,107)(=QContinue to revise Q and P until n

58、o further change occurs. P=78% and Q=13,395 units.Note Although the in-stock probability during the lead time is 78%, the actual service level is SL=96%569.7.3需求和提前期不確定條件下的再訂貨點(diǎn)法需求和提前期不確定條件下的再訂貨點(diǎn)法Reorder point control with demand and lead time uncertainties)()(222LTdsdsLTs=Caution: Can result in very

59、high safety stock levels whenlead-time variability is high9-37在需求和提前期不確定的情況下找到正態(tài)分布的標(biāo)準(zhǔn)差sd。這可以通過將需求波動(dòng)和提前期波動(dòng)累加獲得。由此sd得到修正公式sLT是提前期的標(biāo)準(zhǔn)差57CR (2004) Prentice Hall, Inc.Supply Chain Example (Contd)DistributorOutbound transportInbound transportPool pointSupplier Xspp=10 12,.Xsii=4102,.Xsoo=20 252,.Processin

60、g timeTransport timeTransport time供應(yīng)商內(nèi)向運(yùn)輸集散地加工時(shí)間供應(yīng)商58CR (2004) Prentice Hall, Inc.Pull Methods (Contd)Supply chain exampleSuppose that inventory is to be maintained on a distributors shelf for an item whose demand is forecasted to be d = 100 units per day and sd = 10 units per day. A reorder point is the method of