文档介绍：Prof. Y. Peter Chiu
3 / 2003
Material Management
Class note # 3a ( In review )
~ Inventory control, analysis, and management ~
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§ I1 : Types of Inventories
(A) Row Materials (B) Components (C) Work in process (D) Finished goods
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§ I2 : Inventory Relevant Costs
(A) Holding Cost (B) Order Cost (C) Penalty Cost (D) Outdate Cost
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§ I3 : Motivation for Holding Inventories
Economies of Scale
Uncertainties . Excess demand
Speculation
Transportation
Smoothing
Logistics . safety stock . minimum purchasing quantity
Control Costs . record keeping &
. management costs
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§ I4 : Characteristics of Inventory System
(A) Demand
. Constant versus Variable
. Known versus Random
(B) Lead Time
. Zero, Constant, Variable, Random
(C) Review Time
. Continuous, Periodic
(D) Excess Demand
. Backordered, Lost
(E) Ordering Policy
. (r,Q), (s,S), etc.
(F) Issuing Policy
. FIFO, LIFO, etc.
(G) Changing Inventory
. Shelf life (expired), obsolete
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§ I5: EOQ(Economic Order Quantity)
K : setup (ordering) cost (per cycle)
c : unit cost (per item)
h : holding cost ( per item per year )
λ: demand per unit time (eg. year )
Q
T
I(t)
t
where T = Q / (cycle length)
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§ : EOQ
EOQ model :
Balances order cost and holding cost
The basic model:
1. The demand rate is known and
is constant λ items per unit time
2. Shortages are not permitted
3. No order lead time
4. Costs include
◆ setup (ordering) cost K per order
◆ holding cost h per item held per unit time
◆ unit cost c per item ordered.
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§ I6 : Sensitivity
How cost increases if not using Q*
recall []
Drop λC for now
if we use Q rather than Q*, then
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§ I6 : Sensitivity
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§ I7 : Order Lead Time : τ
To order “τ” time in advance.
or to consider a reorder point
(. level of inventory = “R”)
(A) For τ< T
4 month
R=1040
Q*=3870
t
I(t)
T = year
◇
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Let τ= 4 months = year
R= λτ= 3120() = 1040
When τ> T
(1) From the