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  1. 1. inventory management CHAPTER 9
  2. 2. Introduction Inventory is material that the firm obtains in advance of need, holds until it is needed, and then used, consumes, incorporates into a product, sells, or otherwise disposes it of. A business inventory is temporary in nature. Inventories are stock of any kind like fuel and lubricants, spare parts and semi- processed materials to be stored for future use mainly in the process of production or it can be known as the ideal resource of any kind having some economic values. Meaning A stock of items held to meet future demand. Inventory is a list for goods and materials, or those goods and materials themselves, held available in stock by a business.
  3. 3. Objectives/Importance of Inventory Management 1.To supply the required materials continuously: There should be a continuous available of materials in the factory or finished goods for trade. The main objective of inventory management in to maintain required inventory so that production and sales process run smoothly. 2. To minimize the risk of under and over stocking of material: If a company keeps inventory without proper analysis, there will be a chance of overstocking, which will increase the cost of carrying the inventory or under stocking of inventory that create problem in smooth operation of a business. So one of the main objectives of the inventory management is to minimize the risk caused due to under and over stocking of inventory. 3. To maintain systematic record of inventory: Management needs different information regarding inventory for planning and decision-making. A systematic recodes of inventory helps provides such information to the management. It also assists to evaluate the current inventory management policy.
  4. 4. 4. To reduce losses, damages and misappropriation of materials: Inventory management aims to reduce or remove the losses and misappropriate of materials. This is done by maintaining the proper stocks of materials with utmost care. 5. To minimize the cost associated with inventory: The proper maintenance of the information regarding inventory helps to make decisions like whether to take discounts or not, the size of order to be placed, when to order etc. the total cost associated with inventory may be minimized by analyzing the lot size to be acquired, the offer of discount on variable lot size and the timing of order. Such analysis helps to reduce the unnecessary inventory in inventories. 6. To make stability in price: An effective inventory management system minimizes the effects of regular price fluctuation. This is turn helps to gain the stability is selling price. 7. Other Objectives Protection against fluctuating demand.  Protection against fluctuations in output.  Minimization of risk and uncertainty.  Risk of obsolescence. Minimization of material cost
  5. 5. 5 Types/ Nature of Inventory Work in process Work in process Work in process Finished goods Raw Materials Vendors Customer
  6. 6. Raw Materials – Basic inputs that are converted into finished product through the manufacturing process Work-in-progress – Semi-manufactured products need some more works before they become finished goods for sale Finished Goods – Completely manufactured products ready for sale Supplies – Office and plant cleaning materials not directly enter production but are necessary for production process and do not involve significant investment.
  7. 7. Reasons or motives of holding inventory The main reason or motives of holding inventory is to supply the required of inventory to different department as needed so that production/ sales process does not get hampered. The motives or reason of holding inventory are: 1.Transaction motive: The manufacturing concerns need inventories of raw material and work in progress so as to maintain regular production activities. Similarly, the trading organization need the inventories of finish goods for supplying the goods and services to the customers regularly, in this way, holding of inventories helps to have regular transactions. 2. Precautionary motive: due to different reasons, like shortage of inventory with the suppliers, week relation with the supplier, disturbance in transaction, delay in inventory supply etc. might take place. It is also importance objective of holding the inventory to take precaution from take the above. 3. Speculative motive: generally the price of inventories rise, so the companies may keep additional amount of inventory to get benefit by selling the surplus inventory at higher price than purchase price. It crates risk when the price of inventory falls.
  8. 8. Inventory Functionality 1) Geographical Specialization : Inventory allows geographical specialization for individual operating units. The need for geographical specialization arises because various factors of production like power, materials, water, labour etc. are located at a considerable distance from the major markets. Hence, for economical gains, manufacturing operations are usually located close to the sources of these factors ofproduction.Such geographical separations will require internal inventory transfer to completely integrate components into a final product. Thus, the manufactured goods from various locations are collected at a single warehouse to assemble into final product. For example, Procter & Gamble uses distribution centres to combine products from its laundry, food and health care divisions to offer the customer a single integrated shipment. When geographical specialisation is utilised, inventory in the form of materials, semi-finished goods, components and finished goods is introduced to the logistical system. Economies gained through geographical specialisation will invariably offset increased inventory and transportation cost.
  9. 9. 2) Decoupling: The economic lot size of manufacturing (or transportation) may be different from the market requirements. Decoupling process permit each product to be manufactured & distributed in economic lot sizes that are greater than market demands. For example, let us consider a tyre manufacturing unit. This unit, once the production operations begin, will continue top roduce a certain type of tyre till an economic lot size is produced. There may not be market demand for the entire lot of production. But the production of the lot was carried out keeping in mind the future demand as well as the economies of production. This is sent to the market in large shipments with full load capacity to achieve economies of transportation. This results in the need to hold excess inventory. 3) Balancing Demand and Supply : There is a time gap between the demand and supply for the products. Some products areproduced throughout the year but are sold only during a short market period. e.g. Woollen clothes. Similarly, some products are produced only during a short period butare consumed throughout the year. e.g. Agricultural products. In both cases, holding inventory is very important.
  10. 10. 4) Buffer uncertainties : Safety stock is also known as Buffer uncertainties .The purpose of safety stock is to facilitate continuity in operations. Holding inventory as safety stock protect against two types of uncertainties: a. Demand in excess of forecast during the performance cycle. For example: customer request for more or less units than planned. b. Delays in the performance cycle length itself. for example: Delay in order receipt, order processing or transportation.
  11. 11. Classification of inventory (Selective Inventory Control Techniques/Traditional Technique) 1. ABC Classification 2. HML Classification 3. XYZ Classification 4. VED Classification 5. FSN Classification 6. SDF Classification 7. GOLF Classification/GNGLF Analysis 8. SOS Classification 11
  12. 12. ABC Classification •In most of the cases 10 to 20 % of the inventory account for 70 to 80% of the annual activity. •A typical manufacturing operation shows that the top 15% of the line items, in terms of annual rupees usage, represent 80% of total annual rupees usage. •Next 15% of items reflect 15% of annual rupees •Next 70% accounts only for 5% usage A B C 12
  13. 13. A-B-C analysis states that when a large number of items are involved, relatively a few item account for a major part of activity, based on annual value of consumption of items. According to A-B-C analysis, inventories are reported in percent averages and classified as follows :- A-items :- 15% of the items are of the highest value and their inventory accounts for 70% of the total. B-Items :- 20% of the items are of the intermediate value and their inventory accounts for 20% of the total C-Items :-65% of the items are of the lowest value and their inventory accounts for the relatively small balance i.e., 10%
  14. 14. XYZ Classification On the basis of value of inventory stored Whereas ABC was on the basis of value of consumption to value. X – High Value Y – Medium value Z – Least value Aimed to identify items which are extensively stocked. 14
  15. 15. HML Classification On the basis of unit value of item There is 1000 unit of Q @ Rs. 10 and 10,000 units of W @ Rs. 5. Aimed to control the purchase of raw materials. H – High, M- Medium, L - Low 16
  16. 16. VED Classification •Mainly for spare parts because their consumption pattern is different from raw materials. •Raw materials on market demand •Spare parts on performance of plant and machinery. •V – Vital, E – Essential, D – Desirable Therefore V items has to be stocked more and D Items has to be less stocked 18
  17. 17. FSN Classification According to the consumption pattern To combat obsolete items F – Fast moving S – Slow moving N – Non Moving 20 SDE Classification  Based on source of procurement  S – Scarce, D- Difficult, E- Easy
  18. 18. GOLF Classification G – Government, O – Ordinary, L – Local, F – Foreign. Also known as GNGLF analysis. 22 SOS Classification  Raw materials especially for agriculture units  S – Seasonal  OS – Off seasonal
  19. 19. Modern Inventory Control Techniques JIT I JIT II Vendor Managed Inventory/ Continuous Replenish Strategies/ CR Quick Response Automatic/ Profile Replenishment/ AR
  21. 21. Founder of JIT Founded by Taiichi Ohno A vice president of Toyota Basically implemented in Toyota plant 1950, well established after 1970 Well known as Toyota Production System
  22. 22. Emergence of JIT Evolved in Japan after World War II, as a result of their diminishing market share in the auto industry. Toyota Motor Company- first to implement fully functioning and successful JIT system, in 1970’s. Japanese Manufacturers looked for a way to gain the most efficient use of limited resources. They worked on "optimal cost/quality relationship.
  24. 24.  Involves keeping stock levels to a minimum  Stock arrives just in time to be used in production  Works best where there is a close relationship between manufacturer and suppliers  Goods not produced unless firm has an order from a customer  Aims to get highest volume of output at the lowest unit cost. Functioning of JIT
  25. 25. Functioning of JIT  A method of production control.  No demand - no production!  Anticipated/planned consumer demand triggers production  Finished goods assembled just in time to be sold to customer  Component parts assembled just in time to become finished goods  Materials purchased just in time to make component parts.
  26. 26. Companies adopted JIT
  27. 27. Advantages of JIT  Capital not tied up in stocks  Less space required for stock  Closer relationships with suppliers  Reduction in stockholding costs  Transportation, warehousing, Material handling cost gets reduced  Processing time get reduced Disadvantages of JIT  Danger of disrupted production due to non-arrival of supplies  High dependence on suppliers  Less time for quality control on arrival of materials  May lose bulk-buying discounts
  28. 28. •JIT II is a customer-supplier partnership concept pioneered at the Bose Corporation & now practiced by many companies & their suppliers. •Designed to create harmony and efficiencies for both sides. •It relies heavily on trust. •It is a customer-supplier relationship where suppliers have been given authority in customer’s operations. •The employee of the supplier works in-house with the customer. •The employee of the supplier takes all the responsibilities of inventory management. •Though he works full time in the customer’s firm, he is being paid by the supplier. JUST IN TIME II
  29. 29. 35 Benefits of JIT 2 Inventory level of firm gets reduced. Inventory level of suppliers also gets reduced. Improved relationship with the suppliers. JIT II reduces administrative costs for both the customer & supplier.
  30. 30. 36 Vendor Managed Inventory/ Continuous Replenish Strategies/ CR Traditionally the customer has to place order before the supplier for the goods. But in this revised model, the customer no longer places order but instead shares information with the vendors. This information relates to the actual usage of their products, current stock on hand & anticipated demand. On the basis of this information, the supplier takes responsibility for replenishment of customer’s inventory. No order is received but an indication is given by the customer on maximum & minimum limits of stocks that they wish to keep in stock. It is the responsibility of the supplier to maintain customer’s inventory within the stipulated stock level.
  31. 31. 37 Quick Response When a retailer places an order for replenishment, the supplier with the help of EDI (Electronic Data Interchange) finalizes the delivery details & communicates them to the customer in advance. It helps to increase turnover & improved availability. It is a technology driven cooperative efforts from suppliers & retailers to increase the inventory velocity.
  32. 32. 38 Automatic/ Profile Replenishment/ AR AR enables the supplier to anticipate the customer’s requirement in advance to make replenishment. The responsibility for inventory management is placed directly on the supplier. There should be information flow between customer & supplier that makes inventory available visible.
  33. 33. Material Requirement Planning (MRP) & Distribution Requirement Planning (DRP)
  34. 34. Introduction of MRP in 1960’s by Dr Joseph Orlicky. Definition : MRP is a software based production, planning and inventory control system used to manage the manufacturing process. It is a computer based system in which the given Master Schedule is exploded with Bills Of Material, into the required amount of raw material, parts and subassemblies needed top produce the final products in each tome period of say a week or month (called as “Buckets”)
  35. 35. MRP stands for Material requirement planning. Basic definition: It is a planning technique which converts master production schedule of end products into detailed schedule for raw materials and parts used in those end products. MRP is a means for determining the number of parts, components, and materials needed to produce a product MRP
  36. 36. MRP 1 - Functions Forecasting Order, Planning and Control Priority Planning and Control Planning Capacity Requirement and Development of Broad Business Plans
  37. 37. Objectives Ensure The Availability of Material Components and Products For Planned Production and Customer Delivery. Maintain The Lowest Possible Inventory Level. Plan Manufacturing Activities, Delivery Schedules and Purchasing Activities.
  38. 38. Inputs to MRP system
  39. 39. Master Production Schedule (MPS):- MPS is a series of time phased quantities for each item that a company manufactures. It gives the details of the products to be manufactured over the given space of time. Bills Of Material (BOM):- BOM is the document generated at design stage. It gives the details of the structure of the product by dividing the final assembly into major assemblies and sub-assemblies. BOM provides details such as part name, part no., description, quantity required material, etc. Inventory Status File (ISF):- ISF reports the inventory on hand. It allows the company to subtract existing inventory from gross requirements, so net requirements can be ordered. The ISF also reports on safety stock needs and lead times for each item. Outputs And Reports:- The MRP 1 package generates many reports such as action notices, priority reports, inventory status information.
  40. 40. Material Requirements Planning MRP1 Master Production Schedule MRP Material requirement planning Material plans Customer orders Bill of materials Purchase orders Demand forecast Inventory records Works orders
  41. 41. Keep inventory levels to a minimum. Keeps track of inventory that is used. Tracks the amount of material that is required. Set safety stock levels for emergencies. Set up production times among the separate manufacturing stages. Plan for future needs of raw materials or components. Benefits
  42. 42. Inaccurate information can result in mis-planning , overstock, under-stock, or lack of appropriate resources. The inaccurate master schedule will provide wrong lengths of time for production . Hence affecting planning. MRP systems can be costly and time-consuming to set up Drawbacks
  43. 43. In the 1980,MRP technology was expanded to create a new approach called manufacturing resources planning MRP II . It expanded included financial ,marketing and logistic elements . Manufacturing resource planning (MRPII) is defined as a method for the effective planning of all resources of a manufacturing company. MRP II serves as an extension of MRP(closed loop manufacturing resource planning, also abbreviated as CLMRP). Manufacturing resource planning (MRP- II)
  44. 44. More efficient use of resources Reduced inventories Less idle time Fewer bottlenecks ( a stage in a process that causes the entire process to slow down or stop) Better priority planning Quicker production starts Schedule flexibility Improved customer service Meet delivery dates Improved quality Lower price possibility Improved employee moral Better management information Benefits
  45. 45. Error Due To Poor OR incorrect Information Can be used only manufacturing operations of firm. Drawbacks
  46. 46. DRP is the application of MRP principles to the distribution environment. It integrates the, special needs of distribution. It is a dynamic model which looks at a time-phased plan of events that affect inventory. DRP provides the basis for integrating supply chain inventory information and physical distribution activities with the Manufacturing Planning and Control system. Managing the flow of materials between firms, warehouses, distribution centers. DRP helps manage these material flows. Just like MRP did in Manufacturing. Links firms in the supply chain by providing planning records that carry demand information from receiving points to supply points and vice versa.
  47. 47. Marketing Benefits Increases service level and decrease customer complaints. Improve inventory coordination. Enhances ability to offer customer a coordinated inventory management service.
  48. 48. Logistical Benefits Reduces freight costs. Reduces inventory level. Decreases warehousing space. Reduces customer freight cost. Enhances budgeting capitability.
  49. 49. Constraints of DRP Inventory planning systems require accurate and coordinated forecasts for each distribution center. Integrated planning is subject to system nervousness and frequent rescheduling, because of production breakdowns and delivery delays. DRP is not the universal solution for inventory management.
  50. 50. Distribution Resource planning II Distribution resource planning [DRP II] is an extension of DRP I.Distribution resource planning applies the time phased logic of DRP I to replenish inventories in multi echelon warehousing systems.Distribution resources planning extends DRP I to include the planning of key resources in a distribution system – warehouse space, equipments, labors, transport capacity [e.g trucks,rail cars] and financial flows
  51. 51. Objectives Of DRP II The objective of Distribution Resource Planning are, To improve customer service levels by anticipating customer demand at distribution centers and providing finished products at the correct location when customer needs arise. To provide an accurate requirements plan for manufacturing. To optimize the distribution of available stock in the distribution network using the deployment function.
  52. 52. Difference between DRP and MRP MRP DRP Scope Inbound logistics Outbound logistics Guiding factor Guided by production schedules Guided by customer demand Control of the firm Under control of the firm Not under control of the firm Demand situation Operates in dependant demand situation Operates in independent demand situation Area of operation & coordination Coordinates scheduling & integration of materials into finished goods Coordinates demand between outlets & supply sources Stage of functioning Controls inventory until manufacturing & assembly is complete Controls inventory after manufacturing & assembly of finished goods Planning availability of stock at? Market[retailers] & warehouses Raw materials store, conversion process & finished goods store
  53. 53. 63 EOQ & Re-order point EOQ – gives answer to question “How much to Order” Re-order point – gives answer to question “when to order”
  54. 54. ROP = LxD Receive order Time Inventory Order Quantity Q Place order Lead Time Reorder Point (ROP) If demand is known exactly, place an order when inventory equals demand during lead time. D: demand per period L: Lead time in periods Q: When shall we order? A: When inventory = ROP Q: How much shall we order? A: Q = EOQ
  55. 55. 65 Economic Order Quantity It is also known as standard order quantity , optimum quantity or economic lot size. By definition economic order quantity that size of order for which the total cost is minimum.
  56. 56. Economic Order Quantity (EOQ) EOQ or Fixed Order Quantity system is the technique of ordering materials whenever stock reaches the reorder point. Economic order quality deals when the cost of procurement and handling of inventory are at optimum level and total cost is minimum. In this technique, the order quantity is larger than a single period’s ne requirement so that ordering costs & holding costs balance out. 66
  57. 57. Basic EOQ Model Assumption •Seasonal fluctuation in demand are ruled out •Zero lead time – Time lapsed between purchase order and inventory usage •Cost of placing an order and receiving are same and independent of the units ordered •Annual cost of carrying the inventory is constant •Total inventory cost = Ordering cost + carrying cost 67
  58. 58. Assumptions of EOQ Demand for the product is constant Lead time is constant Price per unit is constant Inventory carrying cost is based on average inventory Ordering costs are constant per order All demands for the product will be satisfied (no back orders) 68
  59. 59. Weaknesses of EOQ formula Erratic usages Faulty basic information Costly calculations No formula is substitute for commonsense EOQ ordering must be tempered with judgment 69
  60. 60. 70 Computation of EOQ The widely used formula is EOQ =√{2*AD* OC} CPU * ICC AD= Annual demand OC= Ordering cost per order ICC = Inventory Carrying cost CPU= Cost per unit
  61. 61. Re-Order Level It is the level of stock at which to storekeeper initiates the purchase requisition for fresh supplies of material. The fresh order must be made before the actual touches the minimum level. This level should be fixed by taking into account as abnormal usages of material; unexpected delay in procuring the material etc. the following factors should be taken into consideration while fixing re-ordering level. a. Minimum quantity of the item to be maintained. b. Rate of consumption c. Lead time
  62. 62. The re-order point, order quantity and procurement time may be show by diagram as given above. Re ordering level can be computed by using one of the following formula's based on information available. Re-order level = maximum consumption x maximum Re-ordering period Re-order level = safety stock + daily consumption x lead time Re-order level = safety stock + normal consumption x normal re-ordering period If no information has been given, the minimum stock level should be assumed to be the safety stock lead time. Delivery period and re-order period refer to the total time taken to receive the material after the order has been placed. Consumption, usage and need refer to the need of material for a certain period of time, say per day, week month etc.
  63. 63. Maximum Level: It is a peak level of the material in stock. It is also called as 'maximum limit' or maximum stock'. It represents the maximum quantity of an item of material, which may be held in stock. The stock should not exceed his quantity. The purpose of fixing this quantity is to avoid overstocking. Overstocking unnecessarily blocks working capital, which can be utilized in some profitable activities. Similarly, overstocking also increase the cost due to the requirement of more space in go down. There may be more chances of having obsolescent and deterioration of quality when the actual stock exceeds the maximum stock level. The following points are to be considered while determining the maximum stock level. a. Working capital: sufficient amount of working capital should be kept for maintaining the maximum level of stock. b. Go down space: for putting the material safely, there is a need to have sufficient space in go down requirement may arise at any time. c. Maximum requirement: there is a need to keep maximum stock of material since maximum requirement may arise at any time.
  64. 64. d. Time lag: the lead-time should be determined. e. Rate of consumption: while fixing maximum level of material, the rate of consumption of material during the lead-time should be determined. f. Cost of managing the store: it is another importance factor, which should be kept in mind while fixing maximum level of material. g. Loss of managing the store: the maximum quantity of material will be fixed at a lower level in as of store, which deteriorates in quantity if they are stored over a lag period. h. Seasonal nature of material: Some materials are available only during specific season in a year. Such materials should be stored beyond the maximum level during the season.
  65. 65. i. Change is fashion and habit: possibility of change in fashion and habit, which may necessitate changes in the requirement of materials, should also be considered. j. Fluctuation in price: the fluctuation in the price of material may have effect on the fixation of maximum stock level. For instance, if it is anticipated that the price of the material will increase in future, a possible of decreasing the price of the material on the near future, maximum stock level may be fixed at a comparatively lower level.
  66. 66. Minimum Level It is also known as 'buffer stock', ' safety stock', minimum limit' or ' minimum stock', this represents the minimum quantity of the material which must be kept in hand at all the times. Such level of material is fixed so that production may not be held up due to shortage of material. The following points should be considered to determine the minimum stock level: a. Lead time: it is a time lag between the points of placing an order and receiving the material. b. Consumption rate: the consumption rate of material during the lead time should also be considered. c. Re-order level: the level at which initiation to purchase requisition for new purchase of materials is taken by the store in-charge is the re-order level. It should also be considered. d. Disruption of supply: the possibility of any disruptions in supply of material in near future should be taken into mind. e. Nature of material: it is another factor, which should be considered while fixing minimum level. Minimum level is not need in the case of the material that is required against customer's specific order.
  67. 67. Average stock level Average stock level refers the normal or moderate stock level. It is calculated as under. Average stock level= minimum stock level + Average of recorder quantity (EOQ) Average Stock Level = Minimum Level + Maximum level/2
  68. 68. Danger level This is the level of material at which issue of material is temporarily stopped. From this level material are issued for some abnormal situations only. The issue of material can be made against the special order from the level. Since it is a danger level, some serious actions should be taken to acquire materials. Danger level = normal consumption x maximum re-order period for emergency purchase
  69. 69. Formulas: 1) a)Re-order level = Maximum consumption x Maximum Re-order period b) Re-order level = Safety stock + Daily consumption x Lead time c)Re-order level = Safety stock + Normal consumption x Normal Re-order period 2) Maximum Level = Re-Order Level + Re-Order Qty – (Minimum Rate of Consumption X Minimum Re-Order Period) 3) Minimum Level= Re-Order level – (Normal Rate of Consumption X Normal Re-Order Period) 4) a)Average stock level= Minimum level + EOQ or Re-order Qty /2 b) Average Stock Level = Minimum Level + Maximum level 2 5) Danger level = Normal consumption x Maximum Re-order period for Emergency purchase
  70. 70. Thank you