2925B.骏泽电梯公司库存管理合理化建设探讨 文献及翻译.doc

本科毕业设计（论文）外文参考文献译文及原文 学 院 经济管理学院 专 业 工商管理 年级班别 学 号 学生姓名 指导教师 年 月 日目 录1 什么是库存管理.12 What is the inventory management.53 库存控制 .104 Inventory control.155 60天库存精度管理 .216 Inventory Accuracy in 60 Days.241 什么是库存管理Dr. Hermann Gruenwald公司过去常常用库存的规模来测量他们的实力，认为越大越好。仓库中巨大的贮存量能够有效地保证装配线和产品在面对任何困难下都不会停顿，谁会去关心储存成本？它们会在增长的销售中被抵消。但现在这种平衡被改变了。降低库存量是最快降低工作资金需求量的一种方法。工作状况的测定，比如以前的ROA（资产收益率）和新的EVA（经济效益增值），以及其他测量方法都可以作为标准来确定使用多少的资金是最有效率的，这些都越来越普遍地被企业使用。实际上，很多时候对一个工作的奖励至少在一方面取决于怎样有效率地使用资金，建设高效的资金使用率能迅速满足变化的客户需求，使得订货出货周期越来越短，这些都是你挑战很多其他企业所需要的。倾斜经济及其意义在大范围下，美国的商业成功之处在于它所寻求的倾斜式运作，但几乎所有的公司从1981-1991年期间都在增加库存，且在过去的10年里看不到什么经济效益上提高，库存在1992到2000年间保持在占GDP的3.8，从制造商到顶层供应者再到底层供应者，库存在供应链中被降低，但好过被消灭。举例来说，通用公司，改进库存周期，用平均库存来测量销售商品的总库存，以得到一个有价值的指标，在1996-2001年间，公司售出占其总库存55.2的产品所获得的效果是最好的，然而，该公司供应轮胎，旺盛的年度，在同期它的库存降至21，换句话说，下层供应商不希望留着像通用和沃尔玛这样的大麻烦给自己。库存管理理论：库存及其管理理论每一个公司都有但是没有人承认它们，库存管理理论是真正意义上的跨学科和跨区间理论，包括财务，管理会计，运筹学和物流，以下是对库存控制和理论的一些看法：库存动机：l 库存维持供给与需求的平衡；l 库存是供应临界点的缓冲器；¡ 供应者获取；¡ 获取产品¡ 产品销售¡ 销售分配¡ 分配中间商¡ 中间商消费者l 库存允许规模经济¡ 购买¡ 运输¡ 制造企业都有着不同的原因持有库存，库存在供给与需求波动中和消除供应链系统错误方面扮演着缓冲器的角色，理顺你的供应链运作和使你更好地去预测你需要维持的最低库存，除非你是通过规模经济的购买，运输，制造来获利的。库存的范围：l 原材料库存l 在制品库存l 完成品库存有三种类型的库存，过多的库存对你来说没有好处除非你因为季节性、生产正常运作，防止缺货或改进客户满意度这些原因来持有库存。库存的种类：l 周期性库存；l 在运库存；l 安全（缓冲）库存；l 投机性库存；l 季节性库存；l 呆滞库存；如果需求量和订货时间不变，单周期库存是必须的。在运库存通常是指正在船上运输而未能在目的地使用，在运库存能够通过提高运输模式的速度来减少。安全（缓冲）库存是为了满足不确定需求和延迟时间的库存，维持投机性库存的的原因不同于满足确定的需求，常常用来获得规模经济效益或满足季节性库存需求，呆滞库存包括市场对其没有需求或者是已经变坏的物品。库存管理状态：l 确定性；l 不确定性；如经济学的课本和个案研究中所描述的，通过经济定购批量（EOQ）模型这一方法来使得库存总成本和定货成本最小化是最好的方法：P订货成本 （$/次）D年需求量 （数量单位）C年库存成本 （产品成本的百分比）V单位库存成本 （$/件）这一公式能够调整总额折扣和需要增加的补给量，在任何条件下都适用。大多数情况下我们都不在一个理想的环境下工作，经常会面对不确定性，生命也是经常会因一些微不足道的事情而结束，因此，你应当热衷于看一些运作管理的书和找方法计算补货周期、安全库存和背离周期的标准偏差。低效库存管理的表现：l 不断增加的事后命令l 不断增加的取消命令l 不断增加的返品数量l 高的顾客流转率l 大量的报废商品l 期性缺乏库存空间如果你的事后命令在不断增加以及有时你不得不去取消命令你就知道你有问题了，你的返品数量增加就是逆向物流增加，以及你将会失去顾客，积聚的废弃物品会占用其他物品的空间使得库存空间不足，你必须面对这些库存信号，但他们可能是由大范围中的一部分造成的。降低库存水平的方法：l 前置时间分析；l 交货时间分析；l 消除低周转产品；l 消除报废品l 包装规模分析；l 分析结构折扣；l 检查退货商品程序；l 应单位维持库存（SKU）测量补货频率；l 分析消费者需求；l 10、提高库存预测；l 11、改进买卖双方的电子数据交换。以上将的库存水平的建议是提高库存管理理论方法的一部分库存管理系统/分析：l ABC分析法；l 库存预测；l 订单处理系统；l 企业资源计划；l 电子数据交换；l 知识管理系统；l 供应商库存管理；ABC分析法是根据物品的重要性/收益率来对其进行分类的工具（A类物资比B类物资重要，依此类推），以价值为依据来分类是ABC分类法的基本方法，把良好的销售预测和先进的订货处理系统作为市场计划的一部分可以降低库存，企业资源规划( ERP )系统和企业知识管理( KM )系统，如SAP将消除库存积压及资讯滞留和促进信息共享。高层管理人员可以看到供应商管理库存( VMI )作为一种外在的库存问题。但都必须非常小心,因为它需要合伙人之间有高度的透明度和一体化。就像婚姻一样在蜜月期有很多好处，但是背后也隐藏着昂贵的离婚危险。库存是相对现金来说一种低效的投资，但也必须达到一定的服务水平，保持适当数量和种类的库存是必要的,以为你的顾客提供高质量的产品,及时的服务和产品。防止缺货,需要一个严格的过程和信息系统,以动态地维持这一平衡，优化库存量的两个关键是改进客户可靠性和满足顾客需求来使得成本有效，以使库存刚好到达准时和足量水平。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 assembly 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 measurements, 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 executive's bonus depends, at least in part, on how efficiently 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 business 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 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 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 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. 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¡ marketing 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 failures.  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 Finished 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 stock 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 faster 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 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 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 volume 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 and 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 items 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 accumulating 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 items 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 reduce 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 Systems 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 and 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 management 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 costly 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-outs 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 customer's demand while being cost effective. To order just in time and just enough. 3 库存控制J. E. Beasley库存的基本功能就是使生产过程远离环境变化造成的影响，如下图3.1所示：完成品库存原材料库存制造在制品库存成本收入原材料到货（补充库存）销售产品（减少库存）图3.1 库存功能在此说明，虽然本文我们只涉及到制造业的库存，而其他企业也有着库存，比如银行里可用的库存现金分配给客户，一个区域的警察储备等等。有一点值得注意的是，从上图看出大多数活动都是一种成本只是它在最终点（销售最终产品）时我们用来抵消我们的成本和希望以此获得利润（收入成本）。因此如果我们计算成本总价值，我们就需要涉及到库存的有效性，效率性和经济形式（我习惯称之为3Es）随后产生的问题是：我们应该持有多少库存？库存控制理论就是试图回答这样一个简单的问题。 对这个问题有两个极端的回答：1、大量库存确保我们生产不会中断；这是一种管理库存的简单方法；这样会是昂贵的库存成本，低廉的管理成本。2、没有/非常少库存像准时制（JIT）一样有效率；是一种困难的管理库存方法；这样会是低廉的库存成本和高昂的管理成本；决定完成品库存；决定一个生产过程中产品的规模 。我们应该考虑的是定购原材料的问题，但是相同的基本理论也能够应用在以下问题上：我们需要考虑成本是为了我们能够通过如下的库存维持成本和订货（收货）成本来决定库存数量。在这里指出，习惯地，管理成本是可以忽略的。1、维持成本随着库存的增加而增加储存成本租借费/折旧劳动力费用一般管理费用（比如保温、照明、安全管理费）资金占用（机会成本损失）无形损耗费（如果再生产末期还剩下库存）库存老化（如果库存物资在保存时老化而损耗的资金）防盗/保险费2、订货成本随着订货和收货次数增加而增加定货过程中的记录/人工成本检查和返修低质量产品运输成本订货手续费在这里指出当我们的存货不足以供应给客户时就会发生存货短缺现象，通常库存短缺发生在订货的前置时间，这个时间是指作出订货指令至到货这一段时间。发生缺货时可能会完全失去客户或者客户会选择退定，也就是说，我们要准备充足的库存来满足客户的订货要求。在这里指出，虽然在理念上我们知道成本与这些因素有关，但是却很难得到一个适当合理的库存指数（举例来说，如果产品存储在一幢有多种使用目的的大楼里，我们应当怎样去合理安置保温/照明/保安成本）通过考虑以下简单的模型来决定我们的库存水平：基本模型：在这个基本模型我们设想处于以下情形：1、我们的公司从一个外部供应商那里订货；2、外部供应商刚好能够提供我们所需的定货数量；3、我们的库存产品流通到客户（无论是在一个相同公司的外部客户还是内部客户（例如定购在生长过程中使用的原材料）。假想：1、库存以一个持续的速率消耗；2、每次订货的成本固定为co 常常称之为订货成本；3、从发出订货命令到货物到达没有前置时间；4、每单位每年的储存可变成本为ch；5、然后我们必须确定每次订货的数量Q，常常称之为定购批量。在这些假设条件下随着时间的推移可以得到如图3.2的库存水平：Q0库存水平时间注意：允许库存降低到0而不需要时间来补充库存图3.2 单周期库存模型考虑在上图Q/2处划一条线，如果你划这条线就能清楚地表示当库存量在Q/2附近波动时，此时的库存量是均衡的，换句话说，我们同样可以认为上图表示随着时间的推移库存量持续维持在Q/2的水平上。因此我们可以得到：年库存成本ch(Q/2)Q/2是平均库存水平年定货成本co(R/Q) （R：年总需求量，Q：定购量）R/Q是指每年的订货次数所以 年库存总成本ch(Q/2) + co(R/Q)我们可以通过选择一个最合适的Q值来实现年库存总成本最小在这里指出，显然地，进货成本与R单位每年有关，然而R是一个持续不变的固定值，所以我们在这里可以忽略它。图3.3 库存成本曲线上图举例说明了两个部分（年维持成本和年订货成本）的改变对Q，订货数量的改变，随着Q的增加，维持成本在增加，但是订货成本却在下降，因此总成本曲线如图2.3所示，曲线上的一个Q值能够实现最小总成本。我们能够视Q为0时来区分总成本以准确地计算出哪一个Q值能够实现最小总成本，成本最小化公式：d(总成本)/dQ = ch/2 - coR/Q² = 0使得Q² = 2coR/ch因此最优定购量Q（总定购量总库存量）如下所示：Q =(2Rco/ch)0.5这个就成为经济定购批量（EOQ）注释：1、EOQ公式被认为是起源与十二十世纪初的大规模的装配线生产时期。2、从年库存总成本与EOQ有关我们可以把公式Q =(2Rco/ch)0.5代入年总库存成本ch(Q/2) + co(R/Q)中，从而得到以下年总成本公式：ch(2Rco/ch)0.5/2) + co(R/(2Rco/ch)0.5) = (Rcoch/2)0.5 + (Rcoch/2)0.5 = (2Rcoch)0.5 因此年库存总成本是(2Rcoch)0.5 就意味着当定购最佳数量（EOQ），其总成本就与一些有关因素(R, co and ch)的乘积的平方根成比例。比如，如果我们降低四个因素中的其中一个因素co，我们就能降低总成本中一个因素的两倍，（EOQ也是同样道理），实际上准时制生产（JIT）的基本原理也是在于（不断地）减少co和ch 以致于降低整个成本。3、回到管理成本被忽略这一问题，如果我们考虑上图的总成本曲线可知其基本理由是假如我们不推行政策使得Q非常低（JIT）或Q非常高我们可以说管理成本整合在一个固定的广义上的Q值里面，如果是这样的话,那么这些费用将不影响决定采用什么订货量q最合适，此外，如果我们需要数量上更加接近，我们需要一些能力来确定由此招致的管理成本和定购批量Q之间的关系估计这是一个不可能的任务。4 Inventory controlJ 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 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 have cost associated with stock we need to deal with that stock in an Effective, Efficient and Economic manner (the 3E's 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 extr