Sven Axsäter. Inventory Control. Third Edition. Springer

Transcription

1 Sven Axsäter Inventory Control Third Edition Springer

2 Contents 1 Introduction Importance and Objectives of Inventory Control Overview and Purpose of the Book Framework 4 2 Forecasting Objectives and Approaches Demand Models Constant Model Trend Model Trend-seasonal Model Choosing Demand Model Moving Average Exponential Smoothing Updating Procedure Comparing Exponential Smoothing to a Moving Average Practical Considerations and an Example Exponential Smoothing with Trend Updating Procedure Practical Considerations and an Example Winters'Trend-seasonal Method Updating Procedure Practical Considerations and an Example Using Regression Analysis Forecasting Demand for a Trend Model Practical Considerations and an Example Forecasts Based on Other Factors More General Regression Models Sporadic Demand Box-Jenkins Techniques Forecast Errors Common Error Measures Updating MAD or a 2 26 vii

3 viii Contents Determining the Standard Deviation as a Function of Demand Forecast Errors for Other Time Periods Sales Data Instead of Demand Data Monitoring forecasts Checking Demand Checking that the Forecast Represents the Mean Manual forecasts 31 Problems 32 3 Costs and Concepts Considered Costs and Other Assumptions Holding Costs Ordering or Setup Costs Shortage Costs or Service Constraints Other Costs and Assumptions Different Ordering Systems Inventory Position Continuous or Periodic Review Different Ordering Policies {R, Q) Policy (s, S) Policy 42 4 Single-Echelon Systems: Deterministic Lot Sizing The Classical Economic Order Quantity Model Optimal Order Quantity Sensitivity Analysis Reorder Point Finite Production Rate Quantity Discounts Backorders Allowed Time-Varying Demand The Wagner-Whitin Algorithm The Silver-Meal Heuristic A Heuristic that Balances Holding and Ordering Costs Exact or Approximate Solution 60 Problems 60 5 Single-Echelon Systems: Reorder Points Discrete Stochastic Demand Compound Poisson Demand Logarithmic Compounding Distribution Geometrie Compounding Distribution Smooth Demand Fitting Discrete Demand Distributions in Practice 71

4 Contents ix 5.2 Continuous Stochastic Demand Normally Distributed Demand Gamma Distributed Demand Continuous Review (R, Q) Policy Inventory Level Distribution Distribution of the Inventory Position An Important Relationship Compound Poisson Demand Normally Distributed Demand Service Levels Shortage Costs Determining the Safety Stock for Given Si Fill Rate and Ready Rate Constraints Compound Poisson Demand Normally Distributed Demand Fill Rate-a Different Approach Shortage Cost per Unit and Time Unit Compound Poisson Demand Normally Distributed Demand Shortage Cost per Unit Continuous Review (s, S) Policy Periodic Review-Fill Rate Basic Assumptions Compound Poisson Demand-(/?, Q) Policy Compound Poisson Demand-(s, S) Policy Normally Distributed Demand-(R, Q) Policy The Newsboy Model A Model with Lost Sales Stochastic Lead-times Two Types of Stochastic Lead-times Handling Sequential Deliveries Independent of the Lead-time Demand Handling Independent Lead-Times Comparison of the Two Types of Stochastic Lead-Times 102 Problems Single-Echelon Systems: Integration-Optimality Joint Optimization of Order Quantity and Reorder Point Discrete Demand (R,Q) Policy (s, S) Policy An Iterative Technique Fill Rate Constraint: A Simple Approach Optimality of Ordering Policies Optimality of (R, Q) Policies When Ordering in Batches Optimality of (s, S) Policies Updating Order Quantities and Reorder Points in Practice 116 Problems 119

5 x Contents 7 Coordinated Ordering Powers-of-Two Policies Production Smoothing The Economic Lot Scheduling Problem (ELSP) Problem Formulation The Independent Solution Common Cycle Time Bomberger's Approach A Simple Heuristic Other Problem Formulations Time-Varying Demand A Generalization of the Classical Dynamic Lot Size Problem Application of Mathematical Programming Approaches Production Smoothing and Batch Quantities Joint Replenishments A Deterministic Model Approach 1. An Iterative Technique Approach 2. Roundy's 98 % Approximation A Stochastic Model 143 Problems Multi-Echelon Systems: Structures and Ordering Policies Inventory Systems in Distribution and Production Distribution Inventory Systems Production Inventory Systems Repairable Items Lateral Transshipments in Inventory Systems Inventory Models with Remanufacturing Different Ordering Systems Installation Stock Reorder Point Policies and KANBAN Policies Echelon Stock Reorder Point Policies Comparison of Installation Stock and Echelon Stock Policies Material Requirements Flanning Ordering System Dynamics 167 Problems Multi-Echelon Systems: Lot Sizing Identical Order Quantities Infinite Production Rates Finite Production Rates 172

6 Contents xi 9.2 Constant Demand A. Simple Serial System with Constant Demand Roundy's 98 % Approximation Time-Varying Demand Sequential Lot Sizing Sequential Lot Sizing with Modified Parameters Other Approaches Concluding Remarks 187 Problems Multi-Echelon Systems: Reorder Points The Clark-Scarf Model Serial System The Clark-Scarf Approach for a Distribution System The METRIC Approach for Distribution Systems Two Exact Techniques Disaggregation of Warehouse Backorders A Recursive Procedure Optimization of Ordering Policies Batch-Ordering Policies Serial System Distribution System Some Basic Results METRIC Type Approximations Disaggregation of Warehouse Backorders Following Supply Units through the System Practical Considerations Other Assumptions Guaranteed Service Model Approach Coordination and Contracts The Newsboy Problem with Two Firms Wholesale-Price Contract Buyback Contract 221 Problems Implementation Preconditions for Inventory Control Inventory Records Updating Inventory Records Auditing and Correcting Inventory Records Performance Evaluation Development and Adjustments Determine the Needs Selective Inventory Control Model and Reality 229

7 xii Contents Step-by-Step Implementation Simulation Short-Run Consequences of Adjustments Education 232 Appendix Appendix References 253 Index 265