2925B.駿澤電梯公司庫(kù)存管理合理化建設(shè)探討 文獻(xiàn)及翻譯

1、本科畢業(yè)設(shè)計(jì)（論文）外文參考文獻(xiàn)譯文及原文 學(xué) 院 經(jīng)濟(jì)管理學(xué)院 專 業(yè) 工商管理 年級(jí)班別 學(xué) 號(hào) 學(xué)生姓名 指導(dǎo)教師 年 月 日目 錄1 什么是庫(kù)存管理.12 what is the inventory management.53 庫(kù)存控制 .104 inventory control.155 60天庫(kù)存精度管理 .216 inventory accuracy in 60 days.241 什么是庫(kù)存管理dr. hermann gruenwald公司過(guò)去常常用庫(kù)存的規(guī)模來(lái)測(cè)量他們的實(shí)力，認(rèn)為越大越好。倉(cāng)庫(kù)中巨大的貯存量能夠有效地保證裝配線和產(chǎn)品在面對(duì)任何困難下都不會(huì)停頓，誰(shuí)會(huì)去關(guān)心儲(chǔ)存成本

2、？它們會(huì)在增長(zhǎng)的銷售中被抵消。但現(xiàn)在這種平衡被改變了。降低庫(kù)存量是最快降低工作資金需求量的一種方法。工作狀況的測(cè)定，比如以前的roa（資產(chǎn)收益率）和新的eva（經(jīng)濟(jì)效益增值），以及其他測(cè)量方法都可以作為標(biāo)準(zhǔn)來(lái)確定使用多少的資金是最有效率的，這些都越來(lái)越普遍地被企業(yè)使用。實(shí)際上，很多時(shí)候?qū)σ粋€(gè)工作的獎(jiǎng)勵(lì)至少在一方面取決于怎樣有效率地使用資金，建設(shè)高效的資金使用率能迅速滿足變化的客戶需求，使得訂貨出貨周期越來(lái)越短，這些都是你挑戰(zhàn)很多其他企業(yè)所需要的。傾斜經(jīng)濟(jì)及其意義在大范圍下，美國(guó)的商業(yè)成功之處在于它所尋求的傾斜式運(yùn)作，但幾乎所有的公司從1981-1991年期間都在增加庫(kù)存，且在過(guò)去的10年里看不

3、到什么經(jīng)濟(jì)效益上提高，庫(kù)存在1992到2000年間保持在占gdp的3.8，從制造商到頂層供應(yīng)者再到底層供應(yīng)者，庫(kù)存在供應(yīng)鏈中被降低，但好過(guò)被消滅。舉例來(lái)說(shuō)，通用公司，改進(jìn)庫(kù)存周期，用平均庫(kù)存來(lái)測(cè)量銷售商品的總庫(kù)存，以得到一個(gè)有價(jià)值的指標(biāo)，在1996-2001年間，公司售出占其總庫(kù)存55.2的產(chǎn)品所獲得的效果是最好的，然而，該公司供應(yīng)輪胎，旺盛的年度，在同期它的庫(kù)存降至21，換句話說(shuō)，下層供應(yīng)商不希望留著像通用和沃爾瑪這樣的大麻煩給自己。庫(kù)存管理理論：庫(kù)存及其管理理論每一個(gè)公司都有但是沒(méi)有人承認(rèn)它們，庫(kù)存管理理論是真正意義上的跨學(xué)科和跨區(qū)間理論，包括財(cái)務(wù)，管理會(huì)計(jì)，運(yùn)籌學(xué)和物流，以下是對(duì)庫(kù)存控制

4、和理論的一些看法：庫(kù)存動(dòng)機(jī)：l 庫(kù)存維持供給與需求的平衡；l 庫(kù)存是供應(yīng)臨界點(diǎn)的緩沖器； 供應(yīng)者獲??； 獲取產(chǎn)品 產(chǎn)品銷售 銷售分配 分配中間商 中間商消費(fèi)者l 庫(kù)存允許規(guī)模經(jīng)濟(jì) 購(gòu)買 運(yùn)輸 制造企業(yè)都有著不同的原因持有庫(kù)存，庫(kù)存在供給與需求波動(dòng)中和消除供應(yīng)鏈系統(tǒng)錯(cuò)誤方面扮演著緩沖器的角色，理順你的供應(yīng)鏈運(yùn)作和使你更好地去預(yù)測(cè)你需要維持的最低庫(kù)存，除非你是通過(guò)規(guī)模經(jīng)濟(jì)的購(gòu)買，運(yùn)輸，制造來(lái)獲利的。庫(kù)存的范圍：l 原材料庫(kù)存l 在制品庫(kù)存l 完成品庫(kù)存有三種類型的庫(kù)存，過(guò)多的庫(kù)存對(duì)你來(lái)說(shuō)沒(méi)有好處除非你因?yàn)榧竟?jié)性、生產(chǎn)正常運(yùn)作，防止缺貨或改進(jìn)客戶滿意度這些原因來(lái)持有庫(kù)存。庫(kù)存的種類：l 周期性庫(kù)存；

5、l 在運(yùn)庫(kù)存；l 安全（緩沖）庫(kù)存；l 投機(jī)性庫(kù)存；l 季節(jié)性庫(kù)存；l 呆滯庫(kù)存；如果需求量和訂貨時(shí)間不變，單周期庫(kù)存是必須的。在運(yùn)庫(kù)存通常是指正在船上運(yùn)輸而未能在目的地使用，在運(yùn)庫(kù)存能夠通過(guò)提高運(yùn)輸模式的速度來(lái)減少。安全（緩沖）庫(kù)存是為了滿足不確定需求和延遲時(shí)間的庫(kù)存，維持投機(jī)性庫(kù)存的的原因不同于滿足確定的需求，常常用來(lái)獲得規(guī)模經(jīng)濟(jì)效益或滿足季節(jié)性庫(kù)存需求，呆滯庫(kù)存包括市場(chǎng)對(duì)其沒(méi)有需求或者是已經(jīng)變壞的物品。庫(kù)存管理狀態(tài)：l 確定性；l 不確定性；如經(jīng)濟(jì)學(xué)的課本和個(gè)案研究中所描述的，通過(guò)經(jīng)濟(jì)定購(gòu)批量（eoq）模型這一方法來(lái)使得庫(kù)存總成本和定貨成本最小化是最好的方法：p訂貨成本 （$/次）d年需

6、求量 （數(shù)量單位）c年庫(kù)存成本 （產(chǎn)品成本的百分比）v單位庫(kù)存成本 （$/件）這一公式能夠調(diào)整總額折扣和需要增加的補(bǔ)給量，在任何條件下都適用。大多數(shù)情況下我們都不在一個(gè)理想的環(huán)境下工作，經(jīng)常會(huì)面對(duì)不確定性，生命也是經(jīng)常會(huì)因一些微不足道的事情而結(jié)束，因此，你應(yīng)當(dāng)熱衷于看一些運(yùn)作管理的書和找方法計(jì)算補(bǔ)貨周期、安全庫(kù)存和背離周期的標(biāo)準(zhǔn)偏差。低效庫(kù)存管理的表現(xiàn)：l 不斷增加的事后命令l 不斷增加的取消命令l 不斷增加的返品數(shù)量l 高的顧客流轉(zhuǎn)率l 大量的報(bào)廢商品l 期性缺乏庫(kù)存空間如果你的事后命令在不斷增加以及有時(shí)你不得不去取消命令你就知道你有問(wèn)題了，你的返品數(shù)量增加就是逆向物流增加，以及你將會(huì)失去顧

7、客，積聚的廢棄物品會(huì)占用其他物品的空間使得庫(kù)存空間不足，你必須面對(duì)這些庫(kù)存信號(hào)，但他們可能是由大范圍中的一部分造成的。降低庫(kù)存水平的方法：l 前置時(shí)間分析；l 交貨時(shí)間分析；l 消除低周轉(zhuǎn)產(chǎn)品；l 消除報(bào)廢品l 包裝規(guī)模分析；l 分析結(jié)構(gòu)折扣；l 檢查退貨商品程序；l 應(yīng)單位維持庫(kù)存（sku）測(cè)量補(bǔ)貨頻率；l 分析消費(fèi)者需求；l 10、提高庫(kù)存預(yù)測(cè)；l 11、改進(jìn)買賣雙方的電子數(shù)據(jù)交換。以上將的庫(kù)存水平的建議是提高庫(kù)存管理理論方法的一部分庫(kù)存管理系統(tǒng)/分析：l abc分析法；l 庫(kù)存預(yù)測(cè)；l 訂單處理系統(tǒng)；l 企業(yè)資源計(jì)劃；l 電子數(shù)據(jù)交換；l 知識(shí)管理系統(tǒng)；l 供應(yīng)商庫(kù)存管理；abc分析法是

8、根據(jù)物品的重要性/收益率來(lái)對(duì)其進(jìn)行分類的工具（a類物資比b類物資重要，依此類推），以價(jià)值為依據(jù)來(lái)分類是abc分類法的基本方法，把良好的銷售預(yù)測(cè)和先進(jìn)的訂貨處理系統(tǒng)作為市場(chǎng)計(jì)劃的一部分可以降低庫(kù)存，企業(yè)資源規(guī)劃( erp )系統(tǒng)和企業(yè)知識(shí)管理( km )系統(tǒng)，如sap將消除庫(kù)存積壓及資訊滯留和促進(jìn)信息共享。高層管理人員可以看到供應(yīng)商管理庫(kù)存( vmi )作為一種外在的庫(kù)存問(wèn)題。但都必須非常小心,因?yàn)樗枰匣锶酥g有高度的透明度和一體化。就像婚姻一樣在蜜月期有很多好處，但是背后也隱藏著昂貴的離婚危險(xiǎn)。庫(kù)存是相對(duì)現(xiàn)金來(lái)說(shuō)一種低效的投資，但也必須達(dá)到一定的服務(wù)水平，保持適當(dāng)數(shù)量和種類的庫(kù)存是必要的,

9、以為你的顧客提供高質(zhì)量的產(chǎn)品,及時(shí)的服務(wù)和產(chǎn)品。防止缺貨,需要一個(gè)嚴(yán)格的過(guò)程和信息系統(tǒng),以動(dòng)態(tài)地維持這一平衡，優(yōu)化庫(kù)存量的兩個(gè)關(guān)鍵是改進(jìn)客戶可靠性和滿足顧客需求來(lái)使得成本有效，以使庫(kù)存剛好到達(dá)準(zhǔn)時(shí)和足量水平。2 what is inventory management?dr. hermann gruenwaldcompanies used to measure their muscle by the size of their inventory. bigger was better. vast warehouses filled to capacity ensured efficient a

10、ssembly lines and guaranteed that, come hell or high water, production would never stop. who cared about carrying costs? they would be erased by increased sales. but now that equation has changed. lowering inventories is one of the quickest ways to decrease working capital needs. performance measure

11、ments, such as the old standby roa (return on assets) and the newer eva (economic value added), as well as other measures that gauge how efficiently capital is used, have become more common organizational drivers. in fact, many times an executives bonus depends, at least in part, on how efficiently

12、capital is used. couple the drive for efficient capital use with the need to respond more quickly to changes in customer demand, with shorter and shorter order-to-delivery cycle times, and you have a problem that is challenging many organizations. leaner and meanerin the big picture, american busine

13、ss has succeeded in its quest to run lean. but almost all these gains in inventory reduction happened from 1981 to 1991, and the past 10 years have not seen much improvement. inventory as a percent of gdp held steady at 3.8 percent from 1992 to 2000. rather than being eliminated, inventory has been

14、pushed down into the lower reaches of the supply chain, from manufacturers to top-tier suppliers to lower-tier suppliers. gm, for example, improved inventory turns, a common metric that measures total cost of goods sold divided by average inventory, and serves as a valuable indication of how often a

15、 company sells out its inventory (the higher the better) - 55.2 percent between 1996 and 2001. however, the company that supplies its tires, goodyear, saw its inventory turns decline 21 percent during that same time. in other words, lower-tier suppliers are left holding the bag for the big boys like

16、 gm and wal-mart. inventory management theoryinventory and the management thereof belong to everyone in the company but nobody wants to own it. inventory management is truly interdisciplinary and spans from financial and managerial accounting, to operations research, material handling to logistics.

17、the following is a quick overview of inventory control/management terminology and theory. reasons for holding inventory: l inventory balances supply and demand.l inventory acts as a buffer between critical supply chain interfaces. supplier procurement procurement production production marketing mark

18、eting distribution distribution intermediary intermediary userl inventory allows for economies of scale in. purchasing transportation manufacturing there are various reasons for holding inventory. inventory acts as a buffer between supply and demand fluctuations and irons out supply chain system fai

19、lures. the smoother your supply chain operates and the better you are able to forecast the less inventory you have to hold, unless you gain some economies of scale in purchasing, transportation and or manufacturing. categories of inventory l raw material inventory l work-in-progress inventory l fini

20、shed goods inventory there are three categories of inventory; too much in either may be a bad thing unless you have reasons for it such as seasonality, production runs, and prevention of stockouts or improvement of customer satisfaction levels. types of inventory/stockl cycle stock l in-transit stoc

21、k l safety or buffer stock l speculative stock l seasonal stockl dead stock if demand and lead time is constant, only cycle stock is necessary. in transit inventory is usually accounted for on the place of shipment as it is not available at the destination. in-transit stock can be reduced through fa

22、ster modes of transportation. safety or buffer stock is a result of uncertainty of demand and lead time. speculative stock is inventory held for reasons other than satisfying current demand, often acquired to reach economies of scale or to generate seasonal stock. dead stock includes items for which

23、 no demand has been registered and may become obsolete. inventory management conditionsl certainty l uncertainty in a perfect world as described in business school text books and case studies one manages in a world of certainty. and the best ordering policy can be determined by minimizing the total

24、of inventory carrying costs and ordering costs using the economic order quantity (eoq) model. p = ordering cost ($/order) d = annual demand (number of units) c = annual inventory carrying cost (% of product cost) v = average cost of one unit of inventory ($/unit) this formula can be adjusted for vol

25、ume discounts and incremental replenishment, as well as other conditions. most of us dont work in a place called perfect, and are facing uncertainties. life ends up throwing monkey wrenches into the production of widgets. for those of you who love math look at the operations management literature an

26、d you will find ways to calculate fill rates, safety stock, and standard deviation of replenishment cycles. symptoms of poor inventory management:l increasing number of backorders l increasing cancelled orders l increasing numbers of returns l high customer turnover rate l large number of obsolete i

27、tems l periodic lack of storage space you know you have a problem if your backorders continue to increase and at the same time you are faced with increasing cancelled orders. reverse logistics may be tasking as well as your number of returns increase, and you end up loosing customers, while accumula

28、ting obsolete items which among other things may lead to lack of storage space. you may face these inventory symptoms, but the causes may be part of the bigger picture. ways to reduce inventory levels:l lead-time analysis l delivery-time analysis l eliminate low turnover itemsl eliminate obsolete it

29、ems l analysis of package size l analysis of discount structure l examine returned goods procedures l measurement of fill rate by stock-keeping unit (sku) l analysis of customer demand l improve forecasting l improve electronic data interchange with vendors/suppliers the above mentioned ways to redu

30、ce inventory levels should be part of a system approach to improving inventory management inventory management systems/analysisl abc analysis l forecasting l advanced order processing systems l enterprise resource planning (erp)l electronic data interchange (edi) l knowledge management (km) l system

31、s vendor-managed inventory (vmi)abc analysis is a tool to classify items according to their relative importance/profitability (category a items are more important than category b items, and so on). a distribution by value report usually forms the basis of an abc analysis. better sales forecasting an

32、d advanced order processing systems as part of a larger marketing plan will reduce inventory. and enterprise resource planning (erp) system such as sap will eliminate stove pipes and information silos and contribute to information sharing along with a company knowledge management (km) system. top ma

33、nagement may see vendor-managed inventory (vmi) as a way to out-source the inventory problem. but one has to be careful as it requires a high degree of transparency and integration between the partners. such a marriage may bring a lot of benefits during the honeymoon period but also may have a costl

34、y divorce lurking in the background. inventory is a poor investment alternative for cash, but imperative to achieve required service levels. maintaining the appropriate levels and types of inventory is essential to providing quality, timely service and products to your customers. preventing stock-ou

35、ts without overstocking products requires a disciplined process and information system that can dynamically manage this balance. two of the keys to optimizing inventories are to improve reliability and reduce variability in the supply chain to meet your customers demand while being cost effective. t

36、o order just in time and just enough. 3 庫(kù)存控制j. e. beasley庫(kù)存的基本功能就是使生產(chǎn)過(guò)程遠(yuǎn)離環(huán)境變化造成的影響，如下圖3.1所示：完成品庫(kù)存原材料庫(kù)存制造在制品庫(kù)存成本收入原材料到貨（補(bǔ)充庫(kù)存）銷售產(chǎn)品（減少庫(kù)存）圖3.1 庫(kù)存功能在此說(shuō)明，雖然本文我們只涉及到制造業(yè)的庫(kù)存，而其他企業(yè)也有著庫(kù)存，比如銀行里可用的庫(kù)存現(xiàn)金分配給客戶，一個(gè)區(qū)域的警察儲(chǔ)備等等。有一點(diǎn)值得注意的是，從上圖看出大多數(shù)活動(dòng)都是一種成本只是它在最終點(diǎn)（銷售最終產(chǎn)品）時(shí)我們用來(lái)抵消我們的成本和希望以此獲得利潤(rùn)（收入成本）。因此如果我們計(jì)算成本總價(jià)值，我們就需要涉及到庫(kù)存的

37、有效性，效率性和經(jīng)濟(jì)形式（我習(xí)慣稱之為3es）隨后產(chǎn)生的問(wèn)題是：我們應(yīng)該持有多少庫(kù)存？庫(kù)存控制理論就是試圖回答這樣一個(gè)簡(jiǎn)單的問(wèn)題。 對(duì)這個(gè)問(wèn)題有兩個(gè)極端的回答：1、大量庫(kù)存確保我們生產(chǎn)不會(huì)中斷；這是一種管理庫(kù)存的簡(jiǎn)單方法；這樣會(huì)是昂貴的庫(kù)存成本，低廉的管理成本。2、沒(méi)有/非常少庫(kù)存像準(zhǔn)時(shí)制（jit）一樣有效率；是一種困難的管理庫(kù)存方法；這樣會(huì)是低廉的庫(kù)存成本和高昂的管理成本；決定完成品庫(kù)存；決定一個(gè)生產(chǎn)過(guò)程中產(chǎn)品的規(guī)模 。我們應(yīng)該考慮的是定購(gòu)原材料的問(wèn)題，但是相同的基本理論也能夠應(yīng)用在以下問(wèn)題上：我們需要考慮成本是為了我們能夠通過(guò)如下的庫(kù)存維持成本和訂貨（收貨）成本來(lái)決定庫(kù)存數(shù)量。在這里指出，

38、習(xí)慣地，管理成本是可以忽略的。1、維持成本隨著庫(kù)存的增加而增加儲(chǔ)存成本租借費(fèi)/折舊勞動(dòng)力費(fèi)用一般管理費(fèi)用（比如保溫、照明、安全管理費(fèi)）資金占用（機(jī)會(huì)成本損失）無(wú)形損耗費(fèi)（如果再生產(chǎn)末期還剩下庫(kù)存）庫(kù)存老化（如果庫(kù)存物資在保存時(shí)老化而損耗的資金）防盜/保險(xiǎn)費(fèi)2、訂貨成本隨著訂貨和收貨次數(shù)增加而增加定貨過(guò)程中的記錄/人工成本檢查和返修低質(zhì)量產(chǎn)品運(yùn)輸成本訂貨手續(xù)費(fèi)在這里指出當(dāng)我們的存貨不足以供應(yīng)給客戶時(shí)就會(huì)發(fā)生存貨短缺現(xiàn)象，通常庫(kù)存短缺發(fā)生在訂貨的前置時(shí)間，這個(gè)時(shí)間是指作出訂貨指令至到貨這一段時(shí)間。發(fā)生缺貨時(shí)可能會(huì)完全失去客戶或者客戶會(huì)選擇退定，也就是說(shuō)，我們要準(zhǔn)備充足的庫(kù)存來(lái)滿足客戶的訂貨要求。在

39、這里指出，雖然在理念上我們知道成本與這些因素有關(guān)，但是卻很難得到一個(gè)適當(dāng)合理的庫(kù)存指數(shù)（舉例來(lái)說(shuō)，如果產(chǎn)品存儲(chǔ)在一幢有多種使用目的的大樓里，我們應(yīng)當(dāng)怎樣去合理安置保溫/照明/保安成本）通過(guò)考慮以下簡(jiǎn)單的模型來(lái)決定我們的庫(kù)存水平：基本模型：在這個(gè)基本模型我們?cè)O(shè)想處于以下情形：1、我們的公司從一個(gè)外部供應(yīng)商那里訂貨；2、外部供應(yīng)商剛好能夠提供我們所需的定貨數(shù)量；3、我們的庫(kù)存產(chǎn)品流通到客戶（無(wú)論是在一個(gè)相同公司的外部客戶還是內(nèi)部客戶（例如定購(gòu)在生長(zhǎng)過(guò)程中使用的原材料）。假想：1、庫(kù)存以一個(gè)持續(xù)的速率消耗；2、每次訂貨的成本固定為co 常常稱之為訂貨成本；3、從發(fā)出訂貨命令到貨物到達(dá)沒(méi)有前置時(shí)間；4

40、、每單位每年的儲(chǔ)存可變成本為ch；5、然后我們必須確定每次訂貨的數(shù)量q，常常稱之為定購(gòu)批量。在這些假設(shè)條件下隨著時(shí)間的推移可以得到如圖3.2的庫(kù)存水平：q0庫(kù)存水平時(shí)間注意：允許庫(kù)存降低到0而不需要時(shí)間來(lái)補(bǔ)充庫(kù)存圖3.2 單周期庫(kù)存模型考慮在上圖q/2處劃一條線，如果你劃這條線就能清楚地表示當(dāng)庫(kù)存量在q/2附近波動(dòng)時(shí)，此時(shí)的庫(kù)存量是均衡的，換句話說(shuō)，我們同樣可以認(rèn)為上圖表示隨著時(shí)間的推移庫(kù)存量持續(xù)維持在q/2的水平上。因此我們可以得到：年庫(kù)存成本ch(q/2)q/2是平均庫(kù)存水平年定貨成本co(r/q) （r：年總需求量，q：定購(gòu)量）r/q是指每年的訂貨次數(shù)所以 年庫(kù)存總成本ch(q/2) +

41、 co(r/q)我們可以通過(guò)選擇一個(gè)最合適的q值來(lái)實(shí)現(xiàn)年庫(kù)存總成本最小在這里指出，顯然地，進(jìn)貨成本與r單位每年有關(guān)，然而r是一個(gè)持續(xù)不變的固定值，所以我們?cè)谶@里可以忽略它。圖3.3 庫(kù)存成本曲線上圖舉例說(shuō)明了兩個(gè)部分（年維持成本和年訂貨成本）的改變對(duì)q，訂貨數(shù)量的改變，隨著q的增加，維持成本在增加，但是訂貨成本卻在下降，因此總成本曲線如圖2.3所示，曲線上的一個(gè)q值能夠?qū)崿F(xiàn)最小總成本。我們能夠視q為0時(shí)來(lái)區(qū)分總成本以準(zhǔn)確地計(jì)算出哪一個(gè)q值能夠?qū)崿F(xiàn)最小總成本，成本最小化公式：d(總成本)/dq = ch/2 - cor/q = 0使得q = 2cor/ch因此最優(yōu)定購(gòu)量q（總定購(gòu)量總庫(kù)存量）如下

42、所示：q =(2rco/ch)0.5這個(gè)就成為經(jīng)濟(jì)定購(gòu)批量（eoq）注釋：1、eoq公式被認(rèn)為是起源與十二十世紀(jì)初的大規(guī)模的裝配線生產(chǎn)時(shí)期。2、從年庫(kù)存總成本與eoq有關(guān)我們可以把公式q =(2rco/ch)0.5代入年總庫(kù)存成本ch(q/2) + co(r/q)中，從而得到以下年總成本公式：ch(2rco/ch)0.5/2) + co(r/(2rco/ch)0.5) = (rcoch/2)0.5 + (rcoch/2)0.5 = (2rcoch)0.5 因此年庫(kù)存總成本是(2rcoch)0.5 就意味著當(dāng)定購(gòu)最佳數(shù)量（eoq），其總成本就與一些有關(guān)因素(r, co and ch)的乘積的平方

43、根成比例。比如，如果我們降低四個(gè)因素中的其中一個(gè)因素co，我們就能降低總成本中一個(gè)因素的兩倍，（eoq也是同樣道理），實(shí)際上準(zhǔn)時(shí)制生產(chǎn)（jit）的基本原理也是在于（不斷地）減少co和ch 以致于降低整個(gè)成本。3、回到管理成本被忽略這一問(wèn)題，如果我們考慮上圖的總成本曲線可知其基本理由是假如我們不推行政策使得q非常低（jit）或q非常高我們可以說(shuō)管理成本整合在一個(gè)固定的廣義上的q值里面，如果是這樣的話,那么這些費(fèi)用將不影響決定采用什么訂貨量q最合適，此外，如果我們需要數(shù)量上更加接近，我們需要一些能力來(lái)確定由此招致的管理成本和定購(gòu)批量q之間的關(guān)系估計(jì)這是一個(gè)不可能的任務(wù)。4 inventory co

44、ntrolj e beasleythe basic function of stock (inventory) is to insulate the production process from changes in the environment as shown below.note here that although we refer in this note to manufacturing, other industries also have stock e.g. the stock of money in a bank available to be distributed

45、to customers, the stock of policemen in an area, etc. one point to note from the above diagram is that most of the activities are a cost. it is only at the final point (sales of finished goods) that we get revenue to set against our costs and hopefully make a profit (= revenue - cost). hence if we h

46、ave cost associated with stock we need to deal with that stock in an effective, efficient and economic manner (the 3es as i tend to term it). the question then arises: how much stock should we have? it is this simple question that inventory control theory attempts to answer. there are two extreme an

47、swers to this question: a lot this ensures that we never run out is an easy way of managing stock is expensive in stock costs, cheap in management costs none/very little this is known (effectively) as just-in-time (jit) is a difficult way of managing stock is cheap in stock costs, expensive in manag

48、ement costs we shall consider the problem of ordering raw material stock but the same basic theory can be applied to the problem of: deciding the finished goods stock; and deciding the size of a batch in a batch production process.the costs that we need to consider so that we can decide the amount o

49、f stock to have can be divided into stock holding costs and stock ordering (and receiving) costs as below. note here that, conventionally, management costs are ignored here. holding costs - associated with keeping stock over timestorage costs rent/depreciation labour overheads (e.g. heating, lightin

50、g, security) money tied up (loss of interest, opportunity cost) obsolescence costs (if left with stock at end of product life) stock deterioration (lose money if product deteriorates whilst held) theft/insuranceordering costs - associated with ordering and receiving an orderclerical/labour costs of

51、processing orders inspection and return of poor quality products transport costshandling costs note here that a stockout occurs when we have insufficient stock to supply customers. usually stockouts occur in the order lead time, the time between placing an order and the arrival of that order. given

52、a stockout the order may be lost completely or the customer may choose to backorder, i.e. to be prepared to wait until we have sufficient stock to supply their order. note here that whilst conceptually we can see that these cost elements are relevant it can often be difficult to arrive at an appropr

53、iate numeric figure (e.g. if the stock is stored in a building used for many other purposes, how then shall we decide an appropriate allocation of heating/lighting/security costs).to see how we can decide the stock level to adopt consider the very simple model below. basic modelin this basic model w

54、e have the situation where:our company orders from an outside supplier; that outside supplier delivers to us precisely the quantity we ask for; and we pass that stock onto our customers (either external customers, or an internal customer within the same company (e.g. if ordering raw materials for us

55、e in the production process). assume: stock used up at a constant rate (r units per year) fixed set-up cost co for each order - often called the order cost no lead time between placing an order and arrival of the order variable stock holding cost ch per unit per year then we need to decide q, the amount to order each time, often called the batch (or lot) size. consider drawing a horizontal line at q/2 in the above diagram. if you were to draw this line then it is clear that the times when stock exceeds q/2 are exactly balanced by the times whe