Emrecan Yalçın 1002002032Eda Anahtar 10020002017Gizem Tütüncü 10020002045
WHAT IS INVENTORY ?. stock of items kept to meet future demand. purpose of inventory management -how many units to order -when to order
INVENTORY
.definition - a phsysical resource that a firm holds in stock with the intent of selling it or transforming it into a more valuable state. raw materials. work in process. finished goods. maintenance, repair and operating (MRO)
Inventories in the Supply Chain
INVENTORY COST
carrying cost - capital costs - space costs - inventory service costordering cost - order processing costs - shipping costs - handling costsshortage costs
IMPORTANCE OF INVENTORY CONTROL
. ımprove customer service
. economies of purchasing
. economies of production
. transportation savings
. unplanned stocks
. to maintain independence of supply chain
Modeling Inventory in a Supply Chain…
WarehouseRetail
Supplier
. ABC classification is a method for determining level of control and frequency of review of inventory item
.Basis is usually annual $ volume =Annual demand x Unit cost
. A items - typically 20% of the items acounting for 80% of the inventory value use Q system
. B items - typically an additional 30% of the items accounting for 15% of the inventory value use Q or P
. C items - typically the remaining 50% of the items accounting for only 5% of the inventory value use P
12 - 9© 2011 Pearson Education, Inc. publishing as Prentice Hall
ABC Analysis
Item Stock
Number
Percent of Number of
Items Stocked
Annual Volume (units) x
Unit Cost =
Annual Dollar
Volume
Percent of Annual Dollar
Volume Class
#10286 20% 1,000 $ 90.00 $ 90,000 38.8% A
#11526 500 154.00 77,000 33.2% A
#12760 1,550 17.00 26,350 11.3% B
#10867 30% 350 42.86 15,001 6.4% B
#10500 1,000 12.50 12,500 5.4% B
72%
23%
12 - 10© 2011 Pearson Education, Inc. publishing as Prentice Hall
ABC Analysis
Item Stock
Number
Percent of Number of
Items Stocked
Annual Volume (units) x
Unit Cost =
Annual Dollar
Volume
Percent of Annual Dollar
Volume Class
#12572 600 $ 14.17 $ 8,502 3.7% C
#14075 2,000 .60 1,200 .5% C
#01036 50% 100 8.50 850 .4% C
#01307 1,200 .42 504 .2% C
#10572 250 .60 150 .1% C
8,550 $232,057 100.0%
5%
12 - 11© 2011 Pearson Education, Inc. publishing as Prentice Hall
C Items
ABC Analysis
A Items
B Items
Percent of annual dollar usage
80 –70 –60 –50 –40 –30 –20 –10 –
0 – | | | | | | | | | |
10 20 30 40 50 60 70 80 90 100
Percent of inventory itemsFigure 12.2
BENEFITS OF INVENTORY
. Hedge against uncertain demand
. Hedge aganist uncertain supply
. Economize on ordering costs
. SmoothingTo summarize, we build and keep inventory in order to match supply and demand in the most cost effective way.
DISADVANTAGES OF INVENTORY
.higher costs -Item cost (if purchased) -Ordering (or setup) cost -Holding (or carrying) cost . Building lease, insurance, taxes etc.Difficult to control.Hides production problems
Multiperiod model – The Economic Order Quantity
• Demand is known and deterministic: D units/year
• We have a known ordering cost, S, and immediate replenishment
• Annual holding cost of average inventory is H per unit
• Purchasing cost C per unit
Supplier DemandRetailer
Economic Order Quantity - EOQ
Q* = 2SD
H
Example:
Assume a car dealer that faces demand for 5,000 cars per year, and that it costs $15,000 to have the cars shipped to the dealership. Holding cost is estimated at $500 per car per year. How many times should the dealer order, and what should be the order size?
548500
)000,5)(000,15(2* Q
REORDER POINT Level of inventory at which a new order is placedR = dLWhere d = demand rate per period L = lead timeEXAMPLE ; Demand = 10.000 yards / yearStore open 311 days / yearDaily demand = 10.000 / 311 = 32.154 yards / dayLead time = L= 10 daysR = dL = ( 32.154)(10) = 321.54 yards
Independent Versus Dependent Demand
. Independent Demand - the demand for items is independent of the demand for any other items in inventory. Depedent Demand - the demand for items is dependent upon the demand for some other item in the inventory
WHAT IS MRP ?
. Computerized ınventory control
. Production planning system
. Management ınformation system
. Manufacturing control system
WHEN TO USE MRP?Job shop production. Complex products. Assemble to order enverionments. Discrete and dependent demant items
WHAT CAN MRP DO? . Improve customer service. ımprove productivity. reduce inventory levels. reduce manufacturing cost. ımprove plant efficiency. ımprove competition position
• MRP INPUTS • MRP OUTPUTS
. Product structure file
. Master production schedule
. Inventory master file
. Manufacturing orders
. Purchasing orders
. various reports