ABC电脑分析：库存管理基础【外文翻译】

外文翻译原文COMPUTERIZED ABC ANALYSIS: THE BASIS FOR INVENTORYMANAGEMENTMaterial Source: Author: Chao-Hsian Chu, Ying-Chan Chu ABSTRACTThis paper presents a microcomputer- based ABC analysis for inventory management. The conceptual framework and technical issues involved in the design of the 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.INTRODUCTIONABC analysis, also known as Pareto principle or management by 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 1950's and has become the basis for the 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 classifying 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 for 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 Japanese's classifying algorithm not only can largely simplify the analysis but also make the task of classification more objectively.ABC PHENOMENAABC principle has been used in the field of economics for many years, and isoften 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 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.•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 few 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.PROCEDURE FOR ABC ANALYSISSelecting 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 time’s annual demand as criterion, and the so called 20-80 rule as an approximate guideline for inventory 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 statistics; 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 the following:• Calculate annual usage value A, where:Annual usage value A = Unit price (p) Annual ⅹ 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 point, 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 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 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 CLASSIFICATIONThere are three basic rules.(1) 20-80 rule, (2) log-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 convention 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 experience 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 ABC 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 Japanese 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 cumulativepercentage of K as the break point for groups A and B, and 2/3 of the value, i.e., 66.7% as the cutting point 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 points. The laborious work in computation and sorting however remains.COMPUTERIZED ABC ANALYSISUsing 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 IBM 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 CompatibilityThe first problem faced by designers in building a micro-based system 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 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 further reduce the incompatible problems to a minimum.User/Machine InterfacesThe 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/answer 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 always checks input contents and ranges and if inconsistent data are detected, the computer will sound a short beep to draw user's attention and ask for correction. After all of the requireddata are entered, the computer also provides users an opportunity to save the data for later use.SYSTEM MENU(0). EXIT ABC Analysis ;(1). MANAGE Data Bases ;( 2).PERFORM ABC Analysis ;( 3). REVIEW ABC Analysis ;( 4). PRINT ABC ReportsEnter Selection == >? 2REPORT MENU(0) Return to System Menu ;( 1) Summary Report ;( 2) Detailed Report ;( 3) ABC Analysis ChartEnter Selection =~ >? 2Data ManagementThe data management 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, displayed, 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 MANAOE~NT(0). Exit ABC Analysis ;(1). Show Directory ;( 2). Create a Data Base ;( 3). Lista Data Base ;( 4). Print a Data Base ;( 5). Erase a Data Base ;( 6). Update a Data Base ;( 7). Perform ABC AnalysisEnter Selection = : >? 1Figure 4: An Example of Data Management MenuReport GenerationThe system could generate two types of reports: detailed and summary reports. Detailed report (Figure 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 the 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 attached printer.Graphic CapabilityIn 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 with a graphic adapter card.Sample SessionIn 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 APPLICATIONSThe ABC principle has been recognized by today's 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:• Inventor y records validation and control• Priority and lead time control• Inventory cycle counting• Ordering policy selection• Storage policy selection• Safety stock decision• Delivery schedule decisionABC 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 relative 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: / 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。