ABC电脑分析：库存管理基础【外文翻译】.doc

1、 外文翻译 原文 COMPUTERIZED ABC ANALYSIS: THE BASIS FOR INVENTORY MANAGEMENT Material Source: http:/ Author: Chao-Hsian Chu, Ying-Chan Chu ABSTRACT This paper presents a microcomputer- based ABC analysis for inventory management. The conceptual framework and technical issues involved in the design of the

2、system are discussed. The program is designed to be user-friendly and is full of many informative functions, such as, pause for reaction, full screen, menu selection, error checking, warning, correction, and graphic display. INTRODUCTION ABC analysis, also known as Pareto principle or management by

3、exception tool, has long been used in industries for various IE applications (quality control), cost reduction, work measurement, method improvement, inventory management etc., for instance. The use of ABC analysis in inventory management started from the early 1950s and has become the basis for the

4、 management and control of inventory systems. Three problems associated with the traditional ABC analysis: (1) how to select a suitable measuring criterion, (2) What is the most appropriate numbers of category, and (3) how to classify items into classes. In this paper our focus will be on the classi

5、fying rules with assumptions that annual dollar usage is the criterion and the suitable numbers of category is three. The principles and techniques presented however can be applied to other measuring criteria with different number of grouping. Although 20-80 rules provides an approximate guideline f

6、or the classification, people using this rule always encounter difficulty, due to its ambiguity and subjectiveness. The laborious work involved in the analysis also prevents its broader applications. A computerized system with Japaneses classifying algorithm not only can largely simplify the analysi

7、s but also make the task of classification more objectively. ABC PHENOMENA ABC principle has been used in the field of economics for many years, and is often called praetor principle or Lorenz law. The principle states that a small fraction of items accounts for a large amount of the total value or

8、activity. Many of our real life cases have this type of phenomenon. Some examples from different areas are given in Table 1. A few components have extremely long lead time. A few percent of the orders accounts for the bulk of the dollars spent. A few days have most of the outgoing or incoming orders

9、. A few vendors cause most of the delays. A few Items are holding up most of the backorders. A few customers give a company most of its orders. A few salespersons sell most of the products. A few percent of customers accounts for the bulk of the credit losses and the bulk of unjustified returns. A f

10、ew products generate most of the profit. A few products go through the service department. A few operations have most of the quality problems. A few percent of quality characteristics accounts for the bulk of the customer complaints, scraps, and reworks. A few cities have most of the population. PRO

11、CEDURE FOR ABC ANALYSIS Selecting a suitable measuring criterion and classification rules forms the basis of an ABC analysis. In practice, most of the companies used annual dollar usage, i.e., unit price times annual demand as criterion, and the so called 20-80 rule as an approximate guideline for i

12、nventory classification. Several steps are required for an ABC analysis: 1. Select a suitable measuring criterion. The criterion selected normally depends on the purpose of the study. For example, defective rate is often used for quality control purpose; 70% of total sales is used for marketing stat

13、istics; and the annual usage value is widely used for inventory management. 2. Collect and validate the required data. All of the data collected must be validated and the units of the data must be consistent. 3. Perform the necessary computations. For inventory management application these include t

14、he following: Calculate annual usage value A, where: Annual usage value A = Unit price (p) Annual Demand (D) Arrange the items in descending order of A. Compute the cumulative values of A and their corresponding percentages. 4. Determine the number of categories to be grouped and the related break p

15、oint, i.e., classification rule, for each class. 5. Classify items into groups according to the established rule. 6. Make adjustment according to some other considerations. This step is very important for practical consideration. In most cases four additional factors: annual volume, unit cost, space

16、 utilized, and leads time, are involved in the analyses for inventory management applications. According to the procedure, we can easily conclude that the classifying efficiency and effectiveness depend on the accuracy of the computation and the classification algorithm used in the grouping. In the

17、following sections, we will review the rules for the classification and the research Issues involving in designing a computerized system. All of the discussions will be based on an example from inventory management. APPROACHES TO ABC CLASSIFICATION There are three basic rules.(1) 20-80 rule, (2) log

18、-normal distribution approximation, and (3) 1/3 rule can be used for classifying the items into A, B, C categories. Typically, ABC curves show that 20% of the ranked items account for 80% or more of the annual usage value, from whence the well-known “20-80“ rule derives. However, there is no fixed c

19、onvention as to what constitutes the A, B, or C category .The choice of classifying boundaries can be determined either according to the 20% of items or based on the cumulative 80% of annual usage value, therefore, it is arbitrary and is based on the nature of the business, the judgment and experien

20、ce of the analyst, and the cause of actions that may be taken. Because of the ambiguity, subjectiveness, and laborious work involved in using the 20-80 rules, people often encounter difficulty in classification. One way to resolve the problems and to enhance its applications is to approximate the AB

21、C curves with a log normal distribution. Through the approximation, there is no need to rank the items in descending order of activity or to calculate the summations or percentages of items and activities, thus, manual computations can be reduced. Another alternative is to use the 1/3 rule: a Japane

22、se approach - for the classification. The 1/3 rule uses K values instead of the annual usage value A as the measuring criterion. Where K is the square root of A. It then uses 1/3 of cumulative percentage of K as the break point for groups A and B, and 2/3 of the value, i.e., 66.7% as the cutting poi

23、nt for categories B and C. The main advantages of the method are its objectiveness and ease-of-use. Meanwhile, the rule can be easily extended to use in different number of categories. For example, if a user want to classify the items into five categories, he can use 1/5, 2/5, and so on as the break

24、 points. The laborious work in computation and sorting however remains. COMPUTERIZED ABC ANALYSIS Using the Japanese approach, we have developed a microcomputer-based system to perform the analysis. The program was written in Microsoft BASICA, compiled by Quick BASIC, version 2.0, and tested in an I

25、BM PC/AT. Depicts the conceptual framework used in building the system. The technical issues involved in the system design are discussed below, where explanations are according to a hypothetical example given. System Compatibility The first problem faced by designers in building a micro-based system

26、 is the machine compatibility. Incompatible problem may occur at either hardware or software level. At hardware level, the selection of a target machine and the I/O interfaces are essential. The IBM PC was used to design the system due to its popularity and ease of access. On the software part, the

27、selection of an operating system, a programming language, a file structure, and system utilities must be considered. PC DOS and BASICA were selected because they are the default combinations for most of the IBM compatible machines. The use of Microsoft Quick Basic in compiling the program can furthe

28、r reduce the incompatible problems to a minimum. User/Machine Interfaces The design of user/computer interfaces is a major factor in the ease of learning, ease-of-use, and the reduction of errors. Different types of interfaces such as commands, menus, forms, icons, functional keys, and question/answ

29、er have been popularly used in the microcomputers. Among which menus with detailed question/answer Q/A) inter- faces were used in the ABC Analysis system. To be user friendly and informative, the system has incorporated much error prevention, checking, and correction functions in the design. It alwa

30、ys checks input contents and ranges and if inconsistent data are detected, the computer will sound a short beep to draw users attention and ask for correction. After all of the required data are entered, the computer also provides users an opportunity to save the data for later use. SYSTEM MENU (0).

31、 EXIT ABC Analysis ;(1). MANAGE Data Bases ;( 2).PERFORM ABC Analysis ;( 3). REVIEW ABC Analysis ;( 4). PRINT ABC Reports Enter Selection = ? 2 REPORT MENU (0) Return to System Menu ;( 1) Summary Report ;( 2) Detailed Report ;( 3) ABC Analysis Chart Enter Selection = ? 2 Data Management The data man

32、agement menu as shown offers users a convenient facility to managing and manipulating the database. For easier retrieval, the required data: part number, unit price, and annual demand - was stored in the database (file) follows a random access structure. Each set of data can be created, updated, dis

33、played, printed, and deleted through the menu. Files contained in the database can also be catalogued on the screen. Refer to sample session (given later) for a better understanding of this function. DATA MANAOENT (0). Exit ABC Analysis ;(1). Show Directory ;( 2). Create a Data Base ;( 3). List a Da

34、ta Base ;( 4). Print a Data Base ;( 5). Erase a Data Base ;( 6). Update a Data Base ;( 7). Perform ABC Analysis Enter Selection = : ? 1 Figure 4: An Example of Data Management Menu Report Generation The system could generate two types of reports: detailed and summary reports. Detailed report (Figure

35、 5), is useful for many different inventory management applications (to be discussed later); while, the summary report, as shown in Figure 6, is a useful tool for deciding the class of new items without repeating the analysis. By computing the annual usage value of a new item and comparing it with t

36、he minimum annual usage value of each category, a user can easily decide the class of the new item. Both reports can be displayed at screen in a full-screen mode. Each time the screen will display information for fourteen items, then pause and wait for action. Both also can be printed from the attac

37、hed printer. Graphic Capability In addition to the colored-screen design, the system can also display an ABC analysis chart on the screen (see Figure 7). This is especially useful for pictorial presentation and managerial decision supports. The graphics, however, can only be shown on the machine wit

38、h a graphic adapter card. Sample Session In this section a sample session of data management menu is presented in the sequence of options. Please note that the words underlined indicate where users input is requested by the system. INVENTORY MANAGEMENT APPLICATIONS The ABC principle has been recogni

39、zed by todays business as one of the most effective management control tools. It has had influences on most of the planning and control systems, and particularly has had great impacts on inventory management for the following purposes: Inventory records validation and control Priority and lead time

40、control Inventory cycle counting Ordering policy selection Storage policy selection Safety stock decision Delivery schedule decision ABC analysis is based on the rationale that the efforts, time, and money to be spent or used in the control of inventory should be allocated in proportion to their rel

41、ative importance. According to this, an item will be given the tightest control and C items, sometimes, may be treated without any control at all. 译文 ABC 电脑分析：库存管理基础 资料来源 : http:/ 作者： Chao-Hsian Chu ， Ying-Chan Chu 本文介绍了以库存管理微机为基础的 ABC 分析的概念框架和对系统的设计涉及的技术问题进行了讨论。该方案的设计是为了方便用户，而且拥有众多信息的功能，比如，可以快速反应，全

42、屏，菜单选择，错误检查，警告，纠正，和图形显示。 介绍 ABC 分析法，也称为帕累托原则或例外工具管理，众所周知，长期以来被用于各种工业应用，例如 IE 浏览器（ 质量控制），成本降低，工作量化，方法改进，库存管理等。对 ABC 分析在库存管理中的应用始于 50 年代初期，并已成为管理和库存系统控制的基础。 传统的 ABC 分析有三个问题： （ 1） 如何选择一个合适的测量标准， （ 2）什么是最合适的类别数，及 （ 3） 如何分成类项目。在本文中我们的重点将是分类规则，假设每年美元的使用量是固定的，并且合适的分类是三类。但提出的原则和技巧也可以适用不同数量的分组与其他测量标准。 虽然 20-

43、80 规则规定一个大致的分类指导，但由于其模糊性和主观性，人们使用这个法则总会遇到困难。分析中涉及的高强度的 工作量也防止其更广泛的应用。日本的分类算法计算机系统不仅可以在很大程度上简化了分析，而且使分类工作更加客观。 ABC 的现象 ABC 分类原则已在经济领域使用了很多年，通常被称为帕累托原则或洛伦茨法律。该原则指出，一个项目的小部分占了总价值或活动的大部分。我们的现实生活中，许多案件都有这种现象。来自不同领域的一些例子载于图表 1。 表 1： ABC 现象的例子 几个组件却有极长的前置时间。 小部分的订单却占了大部分的美元。 仅仅几天但是传出或传入的订单却最多。 少数厂商却造成了大部分的

44、延误。 一些项目持有注册 的缺货最多。 几个客户给了一家公司的订单最多。 少数营业员销售了大部分产品。 小部分的客户账户却占了大部分的信贷损失和不合理的收益。 少数产品产生利润的绝大部分。 几种商品却占了整个服务部的服务。 小部分的操作却有大部分的质量问题。 几个品质特性占了大部分客户的投诉 ,产品报废 ,返工生产。 少数城市拥有大部分的人口。 ABC 分析的过程 选择一个合适的测量标准和分类规则，形成 ABC 分析的基础。在实践中，以最常用的公司年度使用为标准，即单位价格乘以每年的需求，以及所谓的20-80 作为一个近似准则库 存分类规则。 ABC 分析需要以下几个步骤： 1.选择合适的测量

45、标准。选定的标准通常由研究的目的而定。例如，不良率常常被用于质量控制的目的。总销售额的 70%用作推广数据 ;以及每年的使用价值广泛用于库存管理使用。 2.收集和验证所需的数据。所有收集到的数据必须验证和数据的单位必须一致。 3.执行必要的计算。库存管理中的应用包括以下内容： 计算年度使用值 A，其中： 年度使用值 A =单位价格（ P）全年需求（ d） 对项目 A 的降序排列顺序 计算出 A 及其相应的累计值的百分比。 4.确定若干类别的数量，进行分组，即每 个类的分类规则。 5.按照既定的规则组分类项目。 6.根据其他一些考虑进行调整。对于实践考虑，这一步是非常重要的。在大多数情况下，另外

46、四个因素是年销量，单位成本，空间效用，和前置时间，这些都参与库存管理应用的分析。 根据程序，我们可以很容易得出这样的结论：分级效率和有效性取决于计算和分类算法在分组中使用的准确性。在下面的章节中，我们将审查的分类和研究的问题用于设计一个电脑系统所涉及的规则。所有的讨论将基于一个库存管理的例子。 ABC 分类法途径研究 ABC 分类法有三个基本规则。 （ 1） 20-80 规则， （ 2） 对数 正态分布近似，以及 （ 3） 1/ 3 规则：可划分为 A， B， C 三个类别的项目使用。 通常情况下， ABC 曲线 表明， 20%的排名项目占 80%或者更多的年度使用价值，这就是由著名的“ 20

47、-80”规则派生的。然而，并没有固定的惯例，通常是看是什么构成的 A， B 或 C 类。选择分类界限按项目 20 或根据年度使用值的累计 80 进行确定，因此，它是任意的，是根据企业的性质，根据判决和经验为基础的，并且根据可能采取的行动为基础。 由于模糊，主体性，又费力的工作规则涉及使用 20-80 规则，人们在分类中经常会遇到困难。一种解决问题和提高其应用程序的方法是近似的 ABC 与数正态分布曲线。通过近似，没有必要排名顺序递减的活动项目或求和计算或项目和活动的百分比，因此，可以减少手工计算。 另一种方法是使用 1 / 3 规则 ：一种日本的分类方法。 1 / 3 规则使用 k 价值代替年

48、度使用价值 A，其中 K 是 A 的平方根。然后，它采用 1 / 3 的 K 累积百分比作为 A， B 组的突破点， 2 / 3 的值即 66.7%作为 B 类和 C 类的切割点。 该方法的主要优点是它具有客观性并且易于使用。同时，该规则可以很容易地扩展到不同数量的 类别的使用。例如，如果用户想把货物分成 5 大类，他可以用 1 / 5， 2 / 5， .，等等作为突破点。但是计算和分类整理中的工作量还是存在的。 电脑应用 ABC 分析 采用日本的方法，我们已经开发出一种以微型计算机为基础的系统来执行ABC 分析。该方案是编写在微软 BASICA 上的，通过快速基础，在版本 2.0 上编译，并

49、在 IBM PC / AT 中进行测试。图描述了在建设系统中使用的概念框架。以下讨论系统设计所涉及的技术问题，实例表给出了解释。 系统兼容性 设计人员面临的建立一个微观基础的系统的第一个问题是机器的兼容性 。不兼容的问题可能发生在任何硬件或软件层面上。在硬件层面上，选择一个目标机和 I / O 接口是必不可少的。 由于其知名度和四通八达的交通网络， IBM 的 PC 被用来设计系统。软件的部分，操作系统的选择，编程语言，文件结构和系统实用程序必须加以考虑。电脑 DOS 和 BASICA 被选中，因为它们是 IBM 兼容机的大部分默认组合。编译程序中 Microsoft 快速基本的使用可以使不兼容的问题减少到最低限度。 用户 /人机界面 用户 /人机界面的设计计算机接口的一个重要因素是为了轻松的学习