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1、BRITISH STANDARD BS 5192-3: 1993 Guide to production control Part 3: Ordering methods Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:44:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 This British Standard, having been prepared under the direction of the Quality, Management a
2、nd Statistics Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 May 1993 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference QMS/33 Draft for comment 90/97589 DC ISBN 0 580 21581 4 Committees
3、 responsible for this British Standard The preparation of this British Standard was entrusted by the Quality, Management and Statistics Standards Policy Committee (QMS/-) to Technical Committee QMS/33, upon which the following bodies were represented: British Computer Society British Production and
4、Inventory Control Society Chartered Institute of Management Accountants EEA (the Association of Electronics, Telecommunications and Business Equipment Industries) Institute of Logistics and Distribution Management Ministry of Defence Nottingham University PERA International (Production Engineering R
5、esearch Association) University of Bradford University of Manchester Institute of Science and Technology Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:44:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 BSI 08-1999i Con
6、tents Page Committees responsibleInside front cover Forewordii Introduction1 1Scope1 2References1 3Definitions1 4The order1 5Ordering systems7 6Stock control systems10 7Period batch control (PBC)23 8Material requirements planning (MRP)28 9Just-in-time (JIT)32 Figure 1 Stages of production control2 F
7、igure 2 Bill of material4 Figure 3 Example of when to order5 Figure 4 A feedback system8 Figure 5 Single- and multi-cycle ordering9 Figure 6 Fixed order quantity system13 Figure 7 Service level13 Figure 8 Fixed interval re-order system15 Figure 9 ABC analysis16 Figure 10 Fixed order quantity with al
8、locations18 Figure 11 Min-max re-order system20 Figure 12 Deficiencies of stock control21 Figure 13 Variations in stocks due to multi-cycle ordering22 Figure 14 PBC as an extension of flexible programming23 Figure 15 The PBC process25 Figure 16 Bought items and PBC26 Figure 17 The PBC system27 Figur
9、e 18 MRP logic flow diagram29 Figure 19 MRP scrap and yield calculation31 Figure 20 The kanban system34 Figure 21 Kanban types35 Table 1 Standard ordering system classifications10 Table 2 Common stock categories11 Table 3 Stock control applications12 Table 4 Typical ABC analysis of stock using compu
10、ter calculations17 Table 5 Uses of stock control systems23 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:44:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 ii BSI 08-1999 Foreword This Part of BS 5192 has been prepared under the direction
11、of the Quality, Management and Statistics Standards Committee. The prime objective of production control is to help a company become more competitive and profitable. An effective production control function endeavours to fulfil this objective by keeping a balance between satisfying sales demand, ach
12、ieving high plant utilization and maintaining low investment in stocks and work-in-progress. An optimum balance between these often conflicting objectives will only be achieved by a production control system designed to meet the specific needs of the company and run by well trained and dedicated sta
13、ff. BS 5192 is published in six Parts and gives comprehensive guidance in those areas that are considered essential for effective production control. Part 1: Introduction: Scope of the guide, purpose of production control, relationship to other functions, technological changes, choosing the system t
14、o fit the business; Part 2: Production programming: Relationship to corporate and business programmes, planning techniques, master production scheduling, capacity planning; Part 3: Ordering methods: The various types of ordering and stock control systems, comparing the advantages of each for particu
15、lar applications; Part 4: Dispatching (shop-floor control): The methods of shop-floor production control and documentation involved and the increasing influence of computers; Part 5: The relationship between control and other management functions: The production control information flows in the orga
16、nization, their generation, presentation, use and maintenance; Part 6: Computer aided production control: The application of computer software to the production control function; Throughout this standard use of the pronouns he, him and his is intended to be non-gender-specific. A British Standard do
17、es not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an ins
18、ide front cover, pages i and ii, pages 1 to 36, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fr
19、i Dec 01 13:44:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 BSI 08-19991 Introduction This Part of BS 5192 describes the second stage of production control (see Figure 1). It covers the methods used to order the manufacture of components to be made in the companys workshops and to in
20、struct the companys buyer concerning the deliveries of purchased parts and materials that are required from suppliers. An effective ordering system should avoid the pitfalls of excessive stock holding at one extreme or stock shortages at the other end of the scale. 1 Scope This Part of BS 5192 gives
21、 guidance on ordering in all types of production industry ranging from the simplest to the most complicated case of engineering multi-product batch production. It describes the decisions to be made and the systems and methods that can ensure that these decisions are made efficiently. A number of ord
22、ering systems are described together with their applicability. The level of detail is sufficient to guide the readers on the choice of a system or systems appropriate to their industry. 2 References 2.1 Normative references This Part of BS 5192 incorporates, by reference, provisions from specific ed
23、itions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, any of these publications apply to this Part of BS 5192 only when incorporated in it by updati
24、ng or revision. 2.2 Informative references This Part of BS 5192 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3
25、Definitions For the purposes of this Part of BS 5192, the definitions given in BS 3138:1992, BS 5191:1975 and BS 5192-1:1993 apply. 4 The order 4.1 Purpose of an order Ordering is the first stage in the process of executing the production programmes described in BS 5192-2. An order is an instruction
26、 to make or purchase an item contained in a product. 4.2 Push and pull ordering systems There are two ways in which order action can be generated: either directly from a production programme or indirectly from a stock control system (to replenish stock as a result of stock being consumed). The forme
27、r method is described as a push system because it pushes material into the manufacturing process to meet a demand and the latter is known as a pull system because material is pulled through the factory by demand. 4.3 Dependent and independent demand Ordering systems can be further classified as thos
28、e that treat demand as dependent and those that treat demand as independent. Manufactured products with some exceptions consist of two or more items. Manufacture depends upon bringing together all the items required to make the product in the right amounts and at the right time, i.e. the demand for
29、each item is dependent. In non-manufacturing situations, for example in a finished goods warehouse, demand for each item is usually independent of the demand for every other item. 4.4 Choosing the right ordering system for the business Ordering systems are described in clause 5 together with an expl
30、anation of their application to particular industries. Different situations require different solutions and it is quite common for businesses to use more than one system or a combination of systems. The latter are sometimes known as hybrid systems. It is essential that the user selects systems that
31、are not over-complex yet are sufficiently resilient and comprehensive to meet all conditions of the particular operation. 4.5 Ordering decisions 4.5.1 General Before an order can be placed the following decisions need to be taken: a) what to order; b) how much to order; c) when to order; d) when to
32、deliver; e) whether to make or buy. These decisions are considered in 4.5.2 to 4.5.6. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:44:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 2 BSI 08-1999 Figure 1 Stages of production control Licensed Copy: sheffieldun sheffieldun,
33、na, Fri Dec 01 13:44:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 BSI 08-19993 4.5.2 What to order As explained in BS 5192-2, a production programme is a statement of what finished products are to be made, how many are needed and when they are required. A finished product, or end ite
34、m as it is sometimes called, is a product that is offered for sale. It can be either a complete product, a service part or a byproduct. To translate the programme into action, an order should be raised for the finished product itself. This in turn will trigger demand for all the items that comprise
35、the finished product. A product may comprise a single item of raw material, e.g. steel used to make a forging, or many thousands of items as in an aeroplane. It is therefore necessary to know the content of the finished product and the way it is structured. Content defines the items and their amount
36、 and it is presented in a parts list, formula or specification. Structure defines the hierarchy in which the items are put together or assembled. A parts list that arranges the items in structured form is known as a bill of material. Figure 2 is an example of a bill of material. 4.5.3 How much to or
37、der The bill of material shows the quantity of each item needed to make the next level up in the bill. For example in Figure 2, three of item X are needed to make item C; two of item C which are needed to make item A. Therefore, six of item X are needed to make item A. The following are types of ord
38、er quantities. a) Discrete order quantity. The order quantity can be exactly that required to meet the immediate programme, i.e. if the programme calls for 10 of item A per week/day/hour, then the order for item X will be 60 per week/day/hour. This is called a discrete or lot-for-lot order quantity.
39、 Should the item be common to more than one product, the quantity may be increased to aggregate concurrent requirements from several products. If there is surplus stock of the item arising from past orders, the quantity may be reduced by the amount surplus. b) Batch quantity. The order quantity may
40、be further adjusted by aggregating quantities from several time periods to take account of batching rules or policies set by production management. The purpose of batching is to reduce the cost of administration and of setting up machines or, in the case of purchased items, to gain the benefit of pu
41、rchase quantity discounts. However, the larger the batch size relative to immediate requirements, the greater the cost of holding stock. The most economic quantity is in theory the one for which the cost saving in the production process balances or equals the cost of holding stock. A mathematical re
42、lationship known as the economic order quantity formula can be used to calculate economic batch quantity. The formula is difficult to apply in practice because of the difficulty of determining accurate values for the cost factors used in the formula. Many businesses use instead simple rule-of-thumb
43、methods for calculating batch size. Examples of such rules are “the batch quantity is not to exceed one months estimated usage” and “the operation time for a batch is not to exceed one week”. Similar rules apply for deciding whether or not to accept a quantity discount from a supplier. In purchasing
44、, a situation can arise where it is expedient to order more than the immediate programme requires in order to take advantage of pending price increases or to avoid shortages arising from breakdowns in the source of supply. Such decisions should be made with great care as they can cause gross oversto
45、cking. Further explanations of the way batch size may be calculated are given in clauses 6 to 9 which cover individual ordering systems. Conventional cost accounting systems favour large batch sizes since set-up costs and purchase discounts are readily identifiable whereas stock holding costs are no
46、t easily quantified. However, large stock holdings impose severe penalties on the business in terms of high interest charges on capital tied up in stock, loss of flexibility, slow response to customer demand, increased risk from stock obsolescence and unproductive use of floor space. These penalties
47、 are now widely recognized with the result that there is a move towards reducing batch sizes. This move has been helped by advances in production engineering which have made possible very significant reductions in plant set-up times. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:44:40 GM
48、T+00:00 2006, Uncontrolled Copy, (c) BSI BS 5192-3:1993 4 BSI 08-1999 4.5.4 When to order The latest date by which an order for an item has to be issued to meet a programme demand is obtained by back scheduling from the completion date in the programme through the lead times of higher level items in
49、 the bill of material as well as the lead time of the item itself (see Figure 3). See clause 6 for when to order in a stock control system. Lead time is often difficult to estimate since it can vary from order to order depending on a number of circumstances: supply source, factory load, batch size, season, etc. Experience will help to determine a reasonable lead time under normal conditions. In many factories parts spend on average 93 % of their manufacturing lead time queuing between operations, there is cons