Inventory Management - Safety Stock安全库存.ppt

Inventory Management IV Safety Stock Lecture 7 ESD.260 Fall 2003 Caplice Assumptions: Basic EOQ Model ◆ Demand?? ■ Constant vs Variable?? ■ Known vs Random?? ■ Continuous vs Discrete ◆ Lead time ■ Instantaneous?? ■ Constant or Variable (deterministic/stochastic) ◆ Dependence of items ?? ■ Independent ■ Correlated?? ■ Indentured ?? ◆ Review Time ■ Continuous vs Periodic ◆ Number of Echelons?? ■ One vs Many ◆ Capacity / Resources?? ■ Unlimited vs Limited ◆ Discounts?? ■ None?? ■ All Units or Incremental ◆ Excess Demand?? ■ None?? ■ All orders are backordered?? ■ Lost orders?? ■ Substitution ◆ Perishability?? ■ None?? ■ Uniform with time ◆ Planning Horizon?? ■ Single Period?? ■ Finite Period?? ■ Infinite ◆ Number of Items?? ■ One?? ■ Many Fundamental Purpose of Inventory To buffer uncertainties in: -supply, -demand, and/or -transportation the firm carries safety stocks. To capture scale economies in: -purchasing, -production, and/or -transportation the firm carries cycle stocks. Cycle Stock and Safety Stock Preview: Safety Stock Logic Determining the Reorder Point Define Some Terms Service Level and Stockout Probability Cumulative Normal Distribution Finding SL from a Given K K Factor versus Service Level Safety Stock and Service Level Service Level ◆ What is exactly is Service Level? So, how do I find Item Fill Rate? Expected Units Short Consider both continuous and discrete cases The N[k] Table Item Fill Rate Item Fill Rate Example Find fill rate for R=250, 300, 350, and 500 where, Q = 500