1、BRITISH STANDARD BS 5192-3: 1993 Guide to production control Part 3: Ordering methodsBS5192-3:1993 This British Standard, having been prepared under the directionof the Quality, Management and Statistics Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into
2、 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 responsible for this British Standard The preparation of this British Standard was entrusted by the Quality, Man
3、agement and Statistics Standards Policy Committee (QMS/-) to Technical Committee QMS/33, upon which the following bodies were represented: British Computer Society British Production and Inventory Control Society Chartered Institute of Management Accountants EEA (the Association of Electronics, Tele
4、communications and Business Equipment Industries) Institute of Logistics and Distribution Management Ministry of Defence Nottingham University PERA International (Production Engineering Research Association) University of Bradford University of Manchester Institute of Science and Technology Amendmen
5、ts issued since publication Amd. No. Date CommentsBS5192-3:1993 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii Introduction 1 1 Scope 1 2 References 1 3 Definitions 1 4 The order 1 5 Ordering systems 7 6 Stock control systems 10 7 Period batch control (PBC) 23 8 Ma
6、terial requirements planning (MRP) 28 9 Just-in-time (JIT) 32 Figure 1 Stages of production control 2 Figure 2 Bill of material 4 Figure 3 Example of when to order 5 Figure 4 A feedback system 8 Figure 5 Single- and multi-cycle ordering 9 Figure 6 Fixed order quantity system 13 Figure 7 Service leve
7、l 13 Figure 8 Fixed interval re-order system 15 Figure 9 ABC analysis 16 Figure 10 Fixed order quantity with allocations 18 Figure 11 Min-max re-order system 20 Figure 12 Deficiencies of stock control 21 Figure 13 Variations in stocks due to multi-cycle ordering 22 Figure 14 PBC as an extension of f
8、lexible programming 23 Figure 15 The PBC process 25 Figure 16 Bought items and PBC 26 Figure 17 The PBC system 27 Figure 18 MRP logic flow diagram 29 Figure 19 MRP scrap and yield calculation 31 Figure 20 The kanban system 34 Figure 21 Kanban types 35 Table 1 Standard ordering system classifications
9、 10 Table 2 Common stock categories 11 Table 3 Stock control applications 12 Table 4 Typical ABC analysis of stock using computer calculations 17 Table 5 Uses of stock control systems 23 List of references Inside back coverBS5192-3:1993 ii BSI 08-1999 Foreword This Part of BS5192 has been prepared u
10、nder the direction 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 satisfyin
11、g sales demand, achieving 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 traine
12、d and dedicated staff. BS5192 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, cho
13、osing the system to 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 o
14、f each for particular 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
15、 flows in the organization, 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 B
16、ritish Standard does 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 f
17、ront cover, an inside front cover, pages i and ii, pages1 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 theinside front cover.BS5192-3:1993 BSI 08-1999 1 Int
18、roduction This Part of BS5192 describes the second stage of production control (seeFigure 1). It covers the methods used to order the manufacture of components to be made in the companys workshops and to instruct the companys buyer concerning the deliveries of purchased parts and materials that are
19、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 BS5192 gives guidance on ordering in all types of production industry ranging from the simplest to the most
20、 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 ordering systems are described together with their applicability. The level of detail is sufficien
21、t 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 BS5192 incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in
22、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 BS5192 only when incorporated in it by updating or revision. 2.2 Informative references This Part of BS5192 refers to other publications that
23、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 Definitions For the purposes of this Part of BS5192, the definitions given in BS3138:1992, BS5191:
24、1975 and BS5192-1:1993 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 BS5192-2. An order is an instruction to make or purchase an item contained in a product. 4.2 Push and pull ordering systems There are two w
25、ays 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 former method is described as a push system because it pushes material into the manufacturing process to mee
26、t 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 those that treat demand as dependent and those that treat demand as independent. Manufactured products with
27、 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 each item is dependent. In non-manufacturing situations, for example in a finished goods warehouse, dem
28、and 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 explanation of their application to particular industries. Different situations require different solutions
29、 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 are not over-complex yet are sufficiently resilient and comprehensive to meet all conditions of the par
30、ticular 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 deliver; e) whether to make or buy. These decisions are considered in 4.5.2 to 4.5.6.BS5192-3:1993 2 BS
31、I 08-1999 Figure 1 Stages of production controlBS5192-3:1993 BSI 08-1999 3 4.5.2 What to order As explained in BS5192-2, 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 item as it is sometimes
32、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 the finished product.
33、 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 and it is presented
34、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 order The bill of mater
35、ial 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 order quantities. a) Dis
36、crete order quantity. The order quantity can be exactly that required to meet the immediate programme, i.e. if the programme calls for 10of item A per week/day/hour, then the order for item X will be 60per week/day/hour. This is called a discrete or lot-for-lot order quantity. Should the item be com
37、mon 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 be further adjusted by
38、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 purchase quantity discoun
39、ts. 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 relationship known as the
40、 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 accuratevalues for the cost factors used in the formula. Many businesses use instead simple rule-of-thumb methods for calculating
41、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, a situation can arise
42、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 overstocking. Further explanati
43、ons 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 not easily quantified. How
44、ever, 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 are now widely recogniz
45、ed 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.BS5192-3:1993 4 BSI 08-1999 4.5.4 When to order The latest date by which an order for an it
46、em 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 the bill of material as well as the lead time of the item itself (seeFigure 3). See clause6 for when to order in a stock control sys
47、tem. 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
48、 93% of their manufacturing lead time queuing between operations, there is considerable scope for lead time reduction. In practice this often takes the form of expediting to achieve earlier delivery, but this can also delay other items. The emphasis should be on reduction of lead times by reducing q
49、ueueing time for all items. An order may be issued earlier than the latest date though this may cause delivery to be made earlier than required, especially with purchase orders, unless there are control procedures to prevent this happening. 4.5.5 When to deliver Delivery date is the latest order date for the item plus the lead time of the order (seeFigure 3). 4.5.6 Whether to make or buy Make-or-buy decisions can broadly be divided into long term and short term. Long term decisions are generally dictated by ma
